Podcasts about pdgfr

BUFFALO, NY- September 20, 2023 – A new editorial paper was published in Oncotarget's Volume 14 on September 15, 2023, entitled, “Potential repurposing of DPP4 inhibitors for target therapy resistance in renal cell carcinoma.” In their new editorial, researchers Kuniko Horie and Satoshi Inoue from Saitama Medical University and Tokyo Metropolitan Institute for Geriatrics and Gerontology discuss renal cell carcinoma (RCC) — a major adult kidney cancer, which is often incidentally discovered as an asymptomatic disease on imaging in the developed countries. RCC has the most fatal disease among urological cancers, as a recent 5-year relative survival rate in the U.S. (2009–2015) is less than 80%. While RCC is known as a cancer resistant to chemo- and radio-therapies, the prognosis of RCC has been remarkably improved after the clinical application of tyrosine kinase inhibitors (TKIs) and immunotherapy. The rationale for the efficacy of TKIs in RCC is mainly based on the angiogenetic status, particularly in clear cell RCC (ccRCC) that is the most common type of RCC (70–75% of RCC), in which the loss of function mutation of Von Hippel-Lindau (VHL) tumor suppressor gene activates hypoxia inducible factor (HIF) and vascular endothelial growth factor (VEGF) pathways. The first-line TKIs that predominantly target VEGF receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR) (e.g., sunitinib and sorafenib) have been clinically used since late 2000s, and the second-line TKIs such as cabozantinib, which targets more receptor tyrosine kinases including MET and TAM kinases as well as VEGFR, have been further applied to the treatment of advanced RCC since early 2010s in which the first-line TKIs are ineffective. “In our recent study, we established a panel of patient-derived ccRCC spheroid cultures with the enhancement of cancer stemness gene signature including DPP4 [9]. Focusing on TKI sunitinib sensitivity, we demonstrated that DPP4 inhibition increased sunitinib efficacy in DPP4-high RCC spheroids and DPP4 was upregulated in sunitinib-resistant RCC cells.” DOI - https://doi.org/10.18632/oncotarget.28463 Correspondence to - Satoshi Inoue - sinoue07@gmail.com Sign up for free Altmetric alerts about this article - https://oncotarget.altmetric.com/details/email_updates?id=10.18632%2Foncotarget.28463 Subscribe for free publication alerts from Oncotarget - https://www.oncotarget.com/subscribe/ Keywords - cancer, renal cell carcinoma (RCC), tyrosine kinase inhibitor (TKI), Dipeptidyl peptidase IV (DPP4), drug resistance, drug repurposing About Oncotarget Oncotarget (a primarily oncology-focused, peer-reviewed, open access journal) aims to maximize research impact through insightful peer-review; eliminate borders between specialties by linking different fields of oncology, cancer research and biomedical sciences; and foster application of basic and clinical science. To learn more about Oncotarget, please visit https://www.oncotarget.com and connect with us: SoundCloud - https://soundcloud.com/oncotarget Facebook - https://www.facebook.com/Oncotarget/ X - https://twitter.com/oncotarget Instagram - https://www.instagram.com/oncotargetjrnl/ YouTube - https://www.youtube.com/@OncotargetJournal LinkedIn - https://www.linkedin.com/company/oncotarget Pinterest - https://www.pinterest.com/oncotarget/ Reddit - https://www.reddit.com/user/Oncotarget/ Media Contact MEDIA@IMPACTJOURNALS.COM 18009220957

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.23.550235v1?rss=1 Authors: Tsutsumi, R., Ueberheide, B., Liang, F.-X., Neel, B. G., Sakai, R., Saito, Y. Abstract: Glycolysis is a fundamental cellular process, yet its regulatory mechanisms remain incompletely understood. Here, we show that a subset of glucose transporter 1 (GLUT1/SLC2A1) co-endocytoses with platelet-derived growth factor (PDGF) receptor (PDGFR) upon PDGF-stimulation. Furthermore, multiple glycolytic enzymes localize to these endocytosed PDGFR/GLUT1-containing vesicles adjacent to mitochondria. Contrary to current models, which emphasize the importance of glucose transporters on the cell surface, we find that PDGF-stimulated glucose uptake depends on receptor/transporter endocytosis. Our results suggest that growth factors generate glucose-loaded endocytic vesicles that deliver glucose to the glycolytic machinery in proximity to mitochondria, and argue for a new layer of regulation for glycolytic control governed by cellular membrane dynamics. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.09.531751v1?rss=1 Authors: Altrieth, A. L., O'Keefe, K. J., Gellatly, V. A., Tavarez, J. R., Feminella, S. M., Moskwa, N. L., Cordi, C. V., Turrieta, J. C., Nelson, D. A., Larsen, M. Abstract: Fibrosis results from excess extracellular matrix accumulation, which alters normal tissue architecture and impedes function. In the salivary gland, fibrosis can be induced by irradiation treatment for cancer therapy, Sjogrens Disease, and other causes; however, it is unclear which stromal cells and signals participate in injury responses and disease progression. As hedgehog signaling has been implicated in fibrosis of the salivary gland and other organs, we examined contributions of the hedgehog effector, Gli1, to fibrotic responses in salivary glands. To experimentally induce a fibrotic response in female murine submandibular salivary glands, we performed ductal ligation surgery. We detected a progressive fibrotic response where both extracellular matrix accumulation and actively remodeled collagen trended upwards at 7 days and significantly increased at 14 days post- ligation. Macrophages, which participate in extracellular matrix remodeling, Gli1+ and PDGFR+ stromal cells, which may deposit extracellular matrix, both increased with injury. Using single-cell RNA-sequencing, we found that a majority of Gli1+ cells at embryonic day 16 also express Pdgfra and/or Pdgfrb. However, in adult mice, only a small subset of Gli1+ cells express PDGFR and/or PDGFR{beta} at the protein level. Using lineage-tracing mice, we found that Gli1-derived cells expand with ductal ligation injury. Although some of the Gli1 lineage-traced tdTomato+ cells expressed vimentin and PDGFR{beta} following injury, there was no increase in the classic myofibroblast marker, smooth muscle alpha-actin. Additionally, there was little change in extracellular matrix area, remodeled collagen area, PDGFR, PDGFR{beta}, endothelial cells, neurons, or macrophages in Gli1 null salivary glands following injury when compared with controls, suggesting that Gli1 signaling and Gli1+ cells have only a minor contribution to mechanical injury-induced fibrotic changes in the salivary gland. We used scRNA-seq to examine cell populations that expand with ligation and/or showed increased expression of matrisome genes. Pdgfra+/Pdgfrb+ stromal cell subpopulations both expanded in response to ligation, showed increased expression and a greater diversity of matrisome genes expressed, consistent with these cells being fibrogenic. Defining the signaling pathways driving fibrotic responses in stromal cell sub-types could reveal future therapeutic targets. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.02.530787v1?rss=1 Authors: Opiełka, M., Caratis, F., Haussmann, M., Velasco-Estevez, M., de Valliere, C., Seuwen, K., Rogler, G., Karaszewski, B., Rutkowska, A. Abstract: Acidosis is one of the hallmarks of demyelinating central nervous system (CNS) lesions in multiple sclerosis (MS). Response to acidic pH is primarily mediated by a family of G protein-coupled proton-sensing receptors: OGR1, GPR4, and TDAG8. These receptors are inactive at alkaline pH, while at acidic pH they are maximally activated. Genome-wide association studies identified a locus within the TDAG8 gene to be associated with several autoimmune diseases including MS. Notably, we here found that TDAG8 expression is upregulated in MS plaques which prompted us to explore the expression and function of TDAG8 in the CNS in human MO3.13 oligodendrocytes in vitro and in vivo in the lipopolysaccharide-induced neuroinflammation model. We found that TDAG8 is upregulated in maturing oligodendrocytes and temporarily under acidic conditions. Acidic pH also induces oligodendrocyte branching, inhibits chemotaxis and affects the expression of oligodendrocyte maturation markers, PDGFR and MBP in vitro. Even though myelination was not affected in the adult TDAG8-deficient mice, the expression of human and murine TDAG8 was strongly regulated upon inflammation in vivo in the brain and in vitro in lipopolysaccharide and pro-inflammatory cytokine-treated oligodendrocytes. Together these findings point toward a potential role of TDAG8 in oligodendrocyte biology, neuroinflammation and pathophysiology of MS and provide new directions for further scientific enquiry. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

A new research paper was published in Oncotarget's Volume 13 on October 19, 2022, entitled, “Platelet-derived growth factor (PDGF) cross-signaling via non-corresponding receptors indicates bypassed signaling in colorectal cancer.” Platelet-derived growth factor (PDGF) signaling, besides other growth factor-mediated signaling pathways like vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF), seems to play a crucial role in tumor development and progression. Previously, researchers Romana Moench, Martin Gasser, Karol Nawalaniec, Tanja Grimmig, Amrendra K. Ajay, Larissa Camila Ribeiro de Souza, Minghua Cao, Yueming Luo, Petra Hoegger, Carmen M. Ribas, Jurandir M. Ribas-Filho, Osvaldo Malafaia, Reinhard Lissner, Li-Li Hsiao, and Ana Maria Waaga-Gasser, from Harvard Medical School, Shenzhen Traditional Chinese Medicine Hospital, University of Wuerzburg, and Mackenzie Evangelical Faculty of Paraná, recently provided evidence for upregulation of PDGF expression in UICC stage I–IV primary colorectal cancer (CRC) and demonstrated PDGF-mediated induction of PI3K/Akt/mTOR signaling in CRC cell lines. In their new study, the researchers sought to follow up on our previous findings and explore the alternative receptor cross-binding potential of PDGF in CRC. “Our analysis of primary human colon tumor samples demonstrated upregulation of the PDGFRβ, VEGFR1, and VEGFR2 genes in UICC stage I-III tumors.” Immunohistological analysis revealed co-expression of PDGF and its putative cross-binding partners, VEGFR2 and EGFR. The team then analyzed several CRC cell lines for PDGFRα, PDGFRβ, VEGFR1, and VEGFR2 protein expression. They found these receptors to be variably expressed amongst the investigated cell lines. Interestingly, whereas Caco-2 and SW480 cells showed expression of all analyzed receptors, HT29 cells expressed only VEGFR1 and VEGFR2. However, stimulation of HT29 cells with PDGF resulted in upregulation of VEGFR1 and VEGFR2 expression despite the absence of PDGFR expression and mimicked the effect of VEGF stimulation. Moreover, PDGF recovered HT29 cell proliferation under simultaneous treatment with a VEGFR or EGFR inhibitor. “Our results provide some of the first evidence for PDGF cross-signaling through alternative receptors in colorectal cancer and support anti-PDGF therapy as a combination strategy alongside VEGF and EGF targeting even in tumors lacking PDGFR expression.” DOI: https://doi.org/10.18632/oncotarget.28281 Correspondence to: Ana Maria Waaga-Gasser - awaaga@bwh.harvard.edu Keywords: PDGF, VEGFR, EGFR, bypassed signaling, colorectal cancer About Oncotarget: Oncotarget (a primarily oncology-focused, peer-reviewed, open access journal) aims to maximize research impact through insightful peer-review; eliminate borders between specialties by linking different fields of oncology, cancer research and biomedical sciences; and foster application of basic and clinical science. To learn more about Oncotarget, visit Oncotarget.com and connect with us on social media: Twitter - https://twitter.com/Oncotarget Facebook - https://www.facebook.com/Oncotarget YouTube – www.youtube.com/c/OncotargetYouTube Instagram - https://www.instagram.com/oncotargetjrnl/ LinkedIn - https://www.linkedin.com/company/oncotarget/ Pinterest - https://www.pinterest.com/oncotarget/ LabTube - https://www.labtube.tv/channel/MTY5OA SoundCloud - https://soundcloud.com/oncotarget For media inquiries, please contact: media@impactjournals.com. Oncotarget Journal Office 6666 East Quaker Str., Suite 1A Orchard Park, NY 14127 Phone: 1-800-922-0957 (option 2)

Antaros Medical's Chief Scientific Officer Lars Johansson joins Stephen Harrison, Louise Campbell, and Roger Green to reprise the key points of his recent Paris NASH talk. In this conversation, Lars and Stephen discuss the value of assessing the balance of fibrogenesis and fibrosis in healthy and unhealthy livers.Introducing our guest surfer, Stephen Harrison describes Lars Johansson's Paris NASH talk as "remarkable and intriguing." Lars begins his comments by discussing the use of PET tracers to target fibrosis through Collagen Type I cells as well as hepatic stellate cell activation through PDGFR beta. He and Stephen go on to discuss two critical ways the resulting insights can change drug development: first by identifying the correct circulating blood biomarkers to include in different trials or pieces of research, and second by optimizing combination therapies based on the specific effects each agent has on the fibrosis and fibrogenesis processes. On the latter issue, Stephen suggests this approach might have benefit not only in NASH but also a broader range of metabolic diseases Lars concurs.

Go online to PeerView.com/MER860 to view the activity, download slides and practice aids, and complete the post-test to earn credit. Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Our understanding of the pathogenesis of GISTs was revolutionized by the discovery of KIT and PDGFRα mutations, which provided a diagnostic criteria and expanded treatment options. Tyrosine kinase inhibitors (TKIs), imatinib, sunitinib, and regorafenib are the recommended first three lines of therapy for most patients; however, tumor responses remain suboptimal, in part, because of resistance mutations associated with TKI therapy. With the goal to overcome treatment resistance and prolong life, research on modern TKIs has led to the approvals of avapritinib and ripretinib. Modern TKIs are also transforming the therapeutic algorithm for patients with unresectable/metastatic GISTs. In this video-based activity, leading experts on GISTs will dive into the pathobiology of this malignancy and discuss the latest data for newly approved and emerging agents to offer guidance on adopting modern targeted strategies to improve outcomes across multiple lines of therapy. Case vignettes and patient stories will help illustrate the practical aspects of multidisciplinary care throughout the treatment journey. Upon completion of this activity, participants should be better able to: Describe the pathobiology, including recurrence patterns and molecular/mutational features, of unresectable/metastatic GIST, Assess emerging and newly validated evidence on targeted TKI options for patients with GIST along multiple lines of treatment, Develop safe and effective therapeutic algorithms with modern TKIs based on molecular status, prior treatment history, and patient-centered factors, Plan management strategies associated with the use of modern TKIs in the GIST setting.

Go online to PeerView.com/MER860 to view the activity, download slides and practice aids, and complete the post-test to earn credit. Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Our understanding of the pathogenesis of GISTs was revolutionized by the discovery of KIT and PDGFRα mutations, which provided a diagnostic criteria and expanded treatment options. Tyrosine kinase inhibitors (TKIs), imatinib, sunitinib, and regorafenib are the recommended first three lines of therapy for most patients; however, tumor responses remain suboptimal, in part, because of resistance mutations associated with TKI therapy. With the goal to overcome treatment resistance and prolong life, research on modern TKIs has led to the approvals of avapritinib and ripretinib. Modern TKIs are also transforming the therapeutic algorithm for patients with unresectable/metastatic GISTs. In this video-based activity, leading experts on GISTs will dive into the pathobiology of this malignancy and discuss the latest data for newly approved and emerging agents to offer guidance on adopting modern targeted strategies to improve outcomes across multiple lines of therapy. Case vignettes and patient stories will help illustrate the practical aspects of multidisciplinary care throughout the treatment journey. Upon completion of this activity, participants should be better able to: Describe the pathobiology, including recurrence patterns and molecular/mutational features, of unresectable/metastatic GIST, Assess emerging and newly validated evidence on targeted TKI options for patients with GIST along multiple lines of treatment, Develop safe and effective therapeutic algorithms with modern TKIs based on molecular status, prior treatment history, and patient-centered factors, Plan management strategies associated with the use of modern TKIs in the GIST setting.

Go online to PeerView.com/MER860 to view the activity, download slides and practice aids, and complete the post-test to earn credit. Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Our understanding of the pathogenesis of GISTs was revolutionized by the discovery of KIT and PDGFRα mutations, which provided a diagnostic criteria and expanded treatment options. Tyrosine kinase inhibitors (TKIs), imatinib, sunitinib, and regorafenib are the recommended first three lines of therapy for most patients; however, tumor responses remain suboptimal, in part, because of resistance mutations associated with TKI therapy. With the goal to overcome treatment resistance and prolong life, research on modern TKIs has led to the approvals of avapritinib and ripretinib. Modern TKIs are also transforming the therapeutic algorithm for patients with unresectable/metastatic GISTs. In this video-based activity, leading experts on GISTs will dive into the pathobiology of this malignancy and discuss the latest data for newly approved and emerging agents to offer guidance on adopting modern targeted strategies to improve outcomes across multiple lines of therapy. Case vignettes and patient stories will help illustrate the practical aspects of multidisciplinary care throughout the treatment journey. Upon completion of this activity, participants should be better able to: Describe the pathobiology, including recurrence patterns and molecular/mutational features, of unresectable/metastatic GIST, Assess emerging and newly validated evidence on targeted TKI options for patients with GIST along multiple lines of treatment, Develop safe and effective therapeutic algorithms with modern TKIs based on molecular status, prior treatment history, and patient-centered factors, Plan management strategies associated with the use of modern TKIs in the GIST setting.

Go online to PeerView.com/MER860 to view the activity, download slides and practice aids, and complete the post-test to earn credit. Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Our understanding of the pathogenesis of GISTs was revolutionized by the discovery of KIT and PDGFRα mutations, which provided a diagnostic criteria and expanded treatment options. Tyrosine kinase inhibitors (TKIs), imatinib, sunitinib, and regorafenib are the recommended first three lines of therapy for most patients; however, tumor responses remain suboptimal, in part, because of resistance mutations associated with TKI therapy. With the goal to overcome treatment resistance and prolong life, research on modern TKIs has led to the approvals of avapritinib and ripretinib. Modern TKIs are also transforming the therapeutic algorithm for patients with unresectable/metastatic GISTs. In this video-based activity, leading experts on GISTs will dive into the pathobiology of this malignancy and discuss the latest data for newly approved and emerging agents to offer guidance on adopting modern targeted strategies to improve outcomes across multiple lines of therapy. Case vignettes and patient stories will help illustrate the practical aspects of multidisciplinary care throughout the treatment journey. Upon completion of this activity, participants should be better able to: Describe the pathobiology, including recurrence patterns and molecular/mutational features, of unresectable/metastatic GIST, Assess emerging and newly validated evidence on targeted TKI options for patients with GIST along multiple lines of treatment, Develop safe and effective therapeutic algorithms with modern TKIs based on molecular status, prior treatment history, and patient-centered factors, Plan management strategies associated with the use of modern TKIs in the GIST setting.

FDA连续批准2个治疗胃肠道间质瘤的靶向药 Nature Review 肠易激综合征的中饮食疗法的循证医学证据和机制的见解Science子刊 生活方式和遗传因素使亚洲人易患胃癌阿伐普替尼（Avapritinib）胃肠道间质瘤（GIST）是胃肠道最常见的间叶细胞肿瘤，目前普遍认为是是由编码酪氨酸激酶受体蛋白基因（KIT）突变、或血小板源性生长因子受体 α（PDGFRα）基因激活突变所诱发。其中以KIT突变最常见，占80%；PDGFRα突变占10%，PDGFRα外显子18 D842V是最常见突变，与伊马替尼耐药相关；还有10%的患者缺少KIT或PDGFRα突变，称为野生型胃肠道间质瘤。阿伐普替尼（Avapritinib）是一种高效、选择性、口服生活性的KIT和PDGFRα抑制剂。2020年1月9日，FDA批准Avapritinib用于治疗经过基因检测确认的PDGFRα18外显子突变的不可切除（无法通过手术切除）或转移性（癌细胞扩散至身体其他部位）胃肠道间质瘤患者。《NAVIGATOR研究：阿伐普替尼治疗PDGFRα D842V基因突变的、晚期胃肠道间质瘤的研究》Lancet Oncology，2020年7月 (1)NAVIGATOR研究是一项两部分、开放标签、剂量递增和剂量扩大的1阶段研究。这篇文章对PDGFRA D842V突变的患者进行单独分析，并报道了研究结果。研究纳入无法手术切除的、胃肠道间质瘤患者，其中56人携带PDGFRα D842V突变，其中20位患者进入剂量递增组（即从30mg qd逐渐加量至最大耐受剂量），36位患者进入剂量扩大组（即使用最大耐受剂量）。最大耐受剂量为400mg qd，推荐剂量为300mg qd。中位随访15·9个月，在PDGFRα D842V突变的56名患者中，9%完全缓解，79%部分缓解。治疗相关严重不良反应最常见的是贫血。在30-400mg qd的剂量下，没有观察到药物毒性；600mg qd时，两名患者出现剂量相关的不良反应。结论：阿伐普替尼在晚期PDGFRα D842V突变的胃肠道间质肿瘤患者中具有初步的抗肿瘤活性。瑞普替尼（ripretinib） 瑞普替尼（ripretinib）是一种对广泛的KIT和PDGFRA基因突变激酶抑制剂。2020年5月，FDA批准瑞普替尼（ripretinib）用于晚期胃肠道间质瘤的四线治疗。《INVICTUS研究：瑞普替尼治疗晚期胃肠间质肿瘤的3期试验》Lancet Oncology，2020年7月 (2)这项双盲、随机、安慰剂对照的第三期研究中，纳入晚期、进展性胃肠间质肿瘤患者129人，既往均使用过伊马替尼、舒尼替尼和瑞格拉非尼在内的治疗。患者随机分入瑞普替尼 150mg qd或安慰剂组，随机分配到安慰剂组的患者在疾病进展时允许转到瑞普替尼组。双盲期，瑞普替尼组和安慰剂组的中位无进展生存期分别为6.3个月和1.0个月（风险比0.15，p < 0.0001）。最常见的严重不良反应包括脂肪酶升高、高血压、疲劳和低磷血症，两组发生率相似。结论：瑞普替尼显著提高晚期胃肠道间质瘤患者的无进展生存期。乙型肝炎急性和慢性乙型肝炎感染均刻有不同的临床表现。急性期，临床表现可从亚临床、或无黄疸型肝炎至黄疸型肝炎，有时还会出现爆发性肝炎（

FDA连续批准2个治疗胃肠道间质瘤的靶向药 Nature Review 肠易激综合征的中饮食疗法的循证医学证据和机制的见解Science子刊 生活方式和遗传因素使亚洲人易患胃癌阿伐普替尼（Avapritinib）胃肠道间质瘤（GIST）是胃肠道最常见的间叶细胞肿瘤，目前普遍认为是是由编码酪氨酸激酶受体蛋白基因（KIT）突变、或血小板源性生长因子受体 α（PDGFRα）基因激活突变所诱发。其中以KIT突变最常见，占80%；PDGFRα突变占10%，PDGFRα外显子18 D842V是最常见突变，与伊马替尼耐药相关；还有10%的患者缺少KIT或PDGFRα突变，称为野生型胃肠道间质瘤。阿伐普替尼（Avapritinib）是一种高效、选择性、口服生活性的KIT和PDGFRα抑制剂。2020年1月9日，FDA批准Avapritinib用于治疗经过基因检测确认的PDGFRα18外显子突变的不可切除（无法通过手术切除）或转移性（癌细胞扩散至身体其他部位）胃肠道间质瘤患者。《NAVIGATOR研究：阿伐普替尼治疗PDGFRα D842V基因突变的、晚期胃肠道间质瘤的研究》Lancet Oncology，2020年7月 (1)NAVIGATOR研究是一项两部分、开放标签、剂量递增和剂量扩大的1阶段研究。这篇文章对PDGFRA D842V突变的患者进行单独分析，并报道了研究结果。研究纳入无法手术切除的、胃肠道间质瘤患者，其中56人携带PDGFRα D842V突变，其中20位患者进入剂量递增组（即从30mg qd逐渐加量至最大耐受剂量），36位患者进入剂量扩大组（即使用最大耐受剂量）。最大耐受剂量为400mg qd，推荐剂量为300mg qd。中位随访15·9个月，在PDGFRα D842V突变的56名患者中，9%完全缓解，79%部分缓解。治疗相关严重不良反应最常见的是贫血。在30-400mg qd的剂量下，没有观察到药物毒性；600mg qd时，两名患者出现剂量相关的不良反应。结论：阿伐普替尼在晚期PDGFRα D842V突变的胃肠道间质肿瘤患者中具有初步的抗肿瘤活性。瑞普替尼（ripretinib） 瑞普替尼（ripretinib）是一种对广泛的KIT和PDGFRA基因突变激酶抑制剂。2020年5月，FDA批准瑞普替尼（ripretinib）用于晚期胃肠道间质瘤的四线治疗。《INVICTUS研究：瑞普替尼治疗晚期胃肠间质肿瘤的3期试验》Lancet Oncology，2020年7月 (2)这项双盲、随机、安慰剂对照的第三期研究中，纳入晚期、进展性胃肠间质肿瘤患者129人，既往均使用过伊马替尼、舒尼替尼和瑞格拉非尼在内的治疗。患者随机分入瑞普替尼 150mg qd或安慰剂组，随机分配到安慰剂组的患者在疾病进展时允许转到瑞普替尼组。双盲期，瑞普替尼组和安慰剂组的中位无进展生存期分别为6.3个月和1.0个月（风险比0.15，p < 0.0001）。最常见的严重不良反应包括脂肪酶升高、高血压、疲劳和低磷血症，两组发生率相似。结论：瑞普替尼显著提高晚期胃肠道间质瘤患者的无进展生存期。乙型肝炎急性和慢性乙型肝炎感染均刻有不同的临床表现。急性期，临床表现可从亚临床、或无黄疸型肝炎至黄疸型肝炎，有时还会出现爆发性肝炎（

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.07.328971v1?rss=1 Authors: Chamling, X., Kallman, A., Berlinicke, C., Devkota, P., Mertz, J. L., Chang, C., Kaushik, A., Chen, L., Calabresi, P., Mao, H.-Q., Wang, J. T.-H., Zack, D. Abstract: Injury and loss of oligodendrocytes can cause demyelinating diseases such as multiple sclerosis. To improve our understanding of oligodendrocyte development, which could facilitate development of remyelination-based treatment strategies, we performed single-cell- transcriptomic-analysis of developing human oligodendrocyte-precursor-cells (hOPCs). We engineered knock-in hESC-reporter lines in which an Identification-and-Purification tag is expressed under control of the endogenous, OPC-specific, PDGFR promoter, and performed time-course single-cell-RNA-sequencing of purified hOPCs. Our analysis uncovered marked transcriptional heterogeneity of PDGFR+ hOPCs and identified regulatory genes and networks that control their differentiation and myelination competence. Pseudotime trajectory analysis revealed two distinct trajectories for the development of oligodendrocytes vs astrocytes from hOPCs. We also identified novel transcription factors and other genes that developing hOPCs potentially use to choose between oligodendrocyte vs astrocyte lineages. In addition, pathway enrichment analysis followed by pharmacological intervention of those pathways confirm that mTOR and cholesterol biosynthesis signaling pathways are involved in maturation of oligodendrocytes from hOPCs. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.16.207076v1?rss=1 Authors: Glück, C., Ferrari, K. D., Keller, A., Saab, A. S., Stobart, J. L., Weber, B. Abstract: Even though pericytes have been implicated in various neurological disorders, little is known about their function and signaling pathways in the healthy brain. Here, we characterized cortical pericyte calcium dynamics using two-photon imaging of Pdgfr{beta}-CreERT2;GCaMP6s mice under anesthesia in vivo and in brain slices ex vivo. We found distinct differences between pericyte subtypes in vivo: Ensheathing pericytes exhibited smooth muscle cell-like calcium dynamics, while calcium signals in capillary pericytes were irregular, higher in frequency and occurred in cellular microdomains. In contrast to ensheathing pericytes, capillary pericytes retained their spontaneous calcium signals during prolonged anesthesia and in the absence of blood flow ex vivo. Chemogenetic activation of neurons in vivo and acute increase of extracellular potassium in brain slices strongly decreased calcium activity in capillary pericytes. We propose that neuronal activity-induced elevations in extracellular potassium suppress calcium activity in capillary pericytes, likely mediated by Kir2.2 and KATP channel activation. Copy rights belong to original authors. Visit the link for more info

Plenary Coverage: ASCO Chief Medical Officer Dr. Richard L. Schilsky Discusses LBA3 with Dr. William Tap. Welcome to the ASCO Daily News podcast. I'm Dr. Richard Schilsky, senior vice president and chief medical officer of ASCO. I'm pleased to be joined today by Dr. William Tap, a medical oncologist and chief of the sarcoma medical oncology service at Memorial Sloan Kettering Cancer Center. He presented abstract LBA3 at the plenary session reporting results of the ANNOUNCE trial, a randomized placebo controlled double blind phase three trial of doxorubicin plus olaratumab versus doxorubicin plus placebo in patients with advanced soft tissue sarcomas. Dr. Tap, welcome to the podcast. Thank you so much, Dr. Schilsky. I really appreciate the opportunity to talk to you today and also to have had the opportunity to present these data at ASCO during the plenary session. Olaratumab, a PDGFR alpha antagonist, in combination with doxorubicin was approved by the FDA in 2016 for patients with advanced soft tissue sarcomas who are not candidates for curative radiotherapy or surgery. A phase two trial showed a significant improvement in overall survival for olaratumab plus doxorubicin versus doxorubicin monotherapy. The ANNOUNCE study was designed as a phase three trial to confirm overall survival of this treatment combination. However, the study did not meet its primary endpoint. What are some possible explanations for the difference in outcomes in the phase two and phase three trials? I think that's such an important question. The results of the ANNOUNCE study have really only become available within the last few months. So therefore, at this time, there is a really large and concerted effort that is ongoing to really understand them, not only as they stand alone, but as you mentioned in the context of the phase 1B two result that led to accelerated approval. First of all, we have not found any noted discrepancies in study conduct or data integrity which could explain these findings or really discrepancies between the two studies. That's the really important initial fact. There were some notable differences between the two studies. And I know it's not great to compare two studies. But, for instance, the phase 1B two study was not blinded or did not have a placebo. It had progression free survival as a primary endpoint. There were no subtype specific analyses. And it was a relatively small study, just about 10 sites in the United States. Patients tended to be pretty healthy. But because it was just a signal finding study, many patients were coming on at later lines in therapy. There was no loading dose in the phase 1B two study. And cardio protectants, because we tended to push higher doses of doxorubicin, were used generally after patients received about 300 milligrams per meter squared. This is very different when we think about the phase three study, which again was double blinded, placebo controlled with an overall survival primary endpoint. And what's important is that this primary endpoint was a dual primary endpoint that looked at overall survival in the total soft tissue sarcoma population, but also within the leiomyosarcoma population. So we were actually looking within these two populations. And the study could have been positive if we met either of those primary endpoints. This was a large study, over 110 international sites. And it was rapidly accruing study. So there are some of these differences that are very notable. When we start to think of the differences of why we could have seen the outcomes, the first plausible explanation is that it is possible that olaratumab does not have activity in soft tissue sarcomas. But we would then have to question, why did we see such striking results within the phase 1B two trial. And it's hard to say exactly what that would have been, but it may have been to the small sample size. As you know, sarcoma really represents 50 to 80 different subtypes. And in the sarcoma community, we now look at these as potentially very different diseases with different biology. So you begin to bring in many different histologies or many different diseases into a clinical trial, and that could also explain some of the results that we saw, as these diseases often have really disparate clinical behavior. The other thing is that with an overall survival endpoint, which is a composite primary endpoint, it is possible that subsequent therapies on the phase two study may have really also affected outcomes when we looked at overall survival. We know there have been a lot of advances in many of the very specific sarcoma subtypes. And this potentially could have affected outcomes or even there could have been some chance in a smaller phase two study. The other thing that's very possible is that olaratumab has some activity in soft tissue sarcomas in general, but the outcomes were really missed in the phase three study. And this could possibly be again due to the heterogeneity of the study population, not only with the different sarcoma subtypes, as mentioned, but also within sarcoma subtypes. A disease like leiomyosarcoma can actually be a very heterogeneous disease. The other thing, as mentioned before, there could have been some differences in trial design that contributed or how the ANNOUNCE control arm did in this study. So this was not an upfront study, but still for single agent doxorubicin had one of the highest overall survival benefits for doxorubicin alone noted in any phase three clinical trial. Just to name a few final things, there were a lot of subset analyses that are being done and were done on the phase three study. It did, interestingly, point out two things. One is that patients who had a lower albumin tended to do better with the combination of olaratumab, which suggested the possibility that maybe olaratumab with doxorubicin could work better in sicker patients. And understanding this population in the phase three study seemed to be a healthier patient population in the phase two. That could have affected it. And there were some very interesting trends when we looked at PDGFR alpha signaling. And this is something that we're very interested in. And although exploratory, we're still looking very closely. But overall, PDGFR alpha positive tumors tended to do worse than PDGFR negative tumors. And there was a very interesting trend noted between PDGFR alpha positive and negative tumors that received olaratumab. There was a six month difference in overall survival noted between these populations favoring PDGFR negative tumors. So these analyses are still exploratory. And it is uncertain to the prognostic versus predictive significance of these tumors. But it's just a very interesting trend where when we're using a very selective PDGFR alpha inhibitor. Let me just follow up on that last point, Bill, which seems like a particularly important one. And it's not necessarily intuitive that the biomarker negative population seems to do better. Is it possible that PDGFR alpha is not the actual target for this drug and maybe there's a different target? We're pretty certain of the specificity of this inhibitor towards PDGFR alpha signaling, because it's a very pure monoclonal antibody. I would wonder more if there is something within mesenchymal biology regarding PDGFR signaling that we may not understand. For example, could targeting PDGFR alpha in tumors that express PDGFR alpha allow for potential up regulation of other aspects of PDGFR signaling or potentially even other signaling pathways? So one of the difficulties with soft tissue sarcoma is because it's such a heterogeneous disease, again, we may be seeing disparate biology. And because these tumors really fall into mesenchymal malignancies, we still have so much to learn about oncogenesis along mesenchymal cell lineages, and then the interplay with the tumor microenvironment and even the development of metastasis where often PDGFR or other mesenchymal signals really play a role. So where do we go from here? This drug was approved under the FDA accelerated approval pathway, as you said. That requires that post market confirmatory studies be done. The phase three trial didn't confirm the clinical benefit. And now, the sponsor has announced plans to remove the drug from the market. So first of all, what about patients who have been receiving the drug and are benefiting from it? Will they still be able to receive the drug? So fortunately, they will. As you mentioned, withdrawal is in progress. And that's important for patients and providers to know. And to me, this is the practice changing aspect of this abstract, because olaratumab did gain widespread use in almost over 40 countries. Because of these data and because we have not yet found any specific reason to explain the data, we are not recommending the initiation of olaratumab with doxorubicin in new patients with soft tissue sarcoma. But as you can imagine, many patients have been on this drug for a long period of time. And many patients and clinicians do believe that the patient is benefiting from the drugs. So this really does require informed conversations with the patient specifically regarding the data of now, and then making the decision if the patient should continue or would like to continue on that drug. And if that's the case, there is a patient access program for continuing patients. There's actually a toll free number, which is 1-833-245-8167, to gain more information about the continued use of the drug as the drug is actually withdrawn from the market. Great. That's really good to know. I'm curious to know what you think this whole experience says about the FDA accelerated approval pathway. Do you think that perhaps this drug was approved too soon? Well, I think it's a tough question for me to answer, because I'm somewhat biased, very much so regarding the unmet medical need in soft tissue sarcoma. This was the first drug that was technically approved in the upfront setting in soft tissue sarcoma for over 40 years. Normally in sarcoma, we tend to determine efficacy based on few month benefit in progression free survival. So actually having a phase two trial where we saw such tremendous improvements in overall survival for this patient population, in my mind, I think it was very important to give patients access to this drug. The other caveat to this is when we looked at the safety data between doxorubicin and placebo versus doxorubicin and olaratumab, there was very little, if any, difference regarding that safety profile. So olaratumab added very little downside to doxorubicin. So these data and the accelerated approval was really highly debated within the community. But the drug did gain widespread usage and acceptance. It wasn't unconditional. But many people really started to use the drug. I think the debate was really fueled by a smaller phase two signal, a lack of understanding potentially of the mechanisms of action, which could explain the results that we saw and also the cost, understanding that there was a significant cost with giving this drug to patients. However, being that we did not have any added toxicity, had the phase three study been positive, I would definitely have liked to allow patients in the two to three year period while we were waiting for the data of the ANNOUNCE study to have access to a potentially life improving drug as opposed to saying, we may have missed a window of a few years to get patients access to this drug. So I think the process, understanding the caveat of the data of the phase two study that I mentioned, could have really worked. The appropriate phase three study had been designed and was actually completed before FDA approval or accelerated approval was granted. So it was just a matter of waiting for that data. But I do think this is a really important topic to talk about within our community. And I also do think we should consider potentially some ways to mitigate cost for the community while we're waiting for the confirmatory results of the study to mature. So what else do you see on the horizon for treatment of patients with soft tissue sarcoma? It's clear that there's a high unmet medical need. It's a rare group of patients. As you mentioned, it's a very heterogeneous group of diagnoses and may be difficult to determine the best treatment for this heterogeneous group. Maybe patients need to be sorted. But of course, that's going to make it more challenging to recruit even smaller populations into clinical trials. But as someone who's an expert in the field, where is the field going at this point? There is a lot of hope. And I think it is still an amazing fertile ground for advancements not only in science, but also in drug development. Sarcomas really represent a major route of oncogenesis in cancer that we know very little about. We know so much more about the hematopoietic malignancies and also about the epithelioid malignancies, but very little about mesenchymal malignancies. And I think what we're seeing is a tremendous growth in our understanding of these tumors, how mesenchymal malignancies interact with tumor microenvironment and metastases. And as you mentioned, we are really beginning to also to genetically dissect out the different sarcoma subtypes. And this is yielding to some very nice advances in very specific sarcoma subtypes. So I do think as we move forward, we'll continue to see some amazing advances in single sarcoma subtypes. Examples could be diseases like tenosynovial giant cell tumors, PEComas, what we've seen in gastrointestinal stromal tumors, so a lot of hope. I do think the community is really beginning to look at these data from this and other clinical trials to say, how can we better run larger clinical trials maybe in soft tissue sarcoma in general? And is that really the right way? So there is still a tremendous amount of hope to develop drugs for patients. And really finding that right application in the right patient population is going to be critical moving forward. Bill, thanks so much. Again, today, my guest has been Dr. William Tap of Memorial Sloan Kettering Cancer Center. Thank you for being on our podcast today. Thank you so much. To our listeners, thank you for tuning in to the ASCO Daily News podcast. If you're enjoying the content, we encourage you to rate us and review us on Apple Podcasts. Thank you.

Key Takeaways from the ASCO-SITC Clinical Immuno-Oncology with Dr. Steven Eric Finkelstein. Welcome to the "ASCO Daily News podcast." I'm Lauren Davis and joining me today is the "Immuno-oncology Daily News" Associate Editor, Dr. Steven Eric Finkelstein with Florida Cancer Affiliates the US Oncology Network. Dr. Finkelstein, welcome to the podcast. Thank you so much for having me. The Immuno-oncology Symposium just concluded on Sunday. How was this event compared to last year's? Well, this year's event was, again, extremely exciting. This year's event featured research and discussion surrounding themes of patient-centered rational steps to move the field of immuno-oncology towards the future. Now, as many of us know, immuno-oncology has dramatically altered the treatment landscape for many malignancies, and this progress has been extremely rapid over the last decade. As the field has progressed, researchers and clinicians are pushing it towards a better understanding of how immunotherapy can affect patients and the best and most rational combination approaches can improve responses and long-term outcomes. What presentations stood out to you? Another exciting area of research was that the combination of lenvatinib and pembro yielded promising antitumor activity and progression-free survival in patients with metastatic urothelial carcinoma. In abstract 11, a Phase Ib/II study was reported. And as we know, urothelial cancer can account for 90% of all bladder cancers. Pembro monotherapy is currently approved as a first-line therapy in patients who are ineligible to receive cisplatin or platinum-based chemotherapy. It's also approved as a second-line treatment for patients with advanced or metastatic urothelial cancer. Lenvatinib, a multikinase inhibitor, a VEGFR-1 through 3, FGFR-1 through 4, PDGFR-alpha, RET, and KIT is used as a single agent in several malignancies, including thyroid cancer and hepatocellular cancer. Dr. Vogelzang, who presented the results of the study, discussed the Phase II portion of the study, which included 20 patients with histologically confirmed metastatic urothelial carcinoma. The primary outcome in the trial was immune-related resist objective response at 24 weeks. Five patients achieved such a response for an overall response rate at 24 weeks of 25%. Dr. Vogelzang's conclusion was that lenvatinib plus pembro demonstrated promising antitumor activity with manageable adverse events. The response rate warranted further investigation and lenvatinib plus pembro combination will be studied in a Phase III trial in urothelial carcinoma. What other research were you interested in? A Phase Ia/Ib trial was launched in order to evaluate the safety of LY3321367, an anti-T cell immunoglobulin-domain and mucin-domain containing molecule 3, or TIM-3 antibody. Administered alone or in combination to LY3300054, which is an antiprogrammed death ligand, or PD-L1 antibody in patients with advanced, relapsed, or refractory solid tumors. An analysis of the trial that was presented by Harding at the meeting in Abstract 12. This focused on the safety, efficacy, pharmacokinetics, and pharmodynamic results seen with these treatment regimens. The key points are as follows-- treatment-related adverse reactions were mild, i.e. Grade two or less, in both treatment groups except for one patient with a Grade three anemia in Arm B. No dose-limiting toxicities, dose-limiting equivalent toxicities, treatment-related serious adverse events, or death was observed in either treatment arm. Approximately 68% in Arm A and 88% in Arm B of patients were positive for treatment emergent antidrug antibodies related to the LY3321367. Despite antidrug antibodies, there was no effect on pharmacokinetics noted That's great. Were there any education sessions that caught your attention? I think at the 2019 ASCO SITC Clinical Immuno-Oncology Symposium, what really struck me were the keynote addresses. On March 2, the keynote lecture from Dr. Rafi Ahmed of Emory University examined the basic scientific underpinnings of the field and focused deeply on T cell exhaustion and differentiation. In a second keynote address, Dr. Jedd Wolchok, of Memorial Sloan Kettering, took a broader look of the future of immunotherapy. And his main thesis was there was a need for a more rational approach to combination therapies. Indeed, it is apparent that the combination of therapies will be an important role for our future. That's wonderful. Were there any other takeaways that were important during the symposium? ASCO and the Society of Immunotherapy of Cancer, SITC, have really focused on developing recommendations for clinical trial reporting. Indeed, we need trial reporting that addresses the unique efficacy, toxicity, combination, and sequencing aspects of immuno-oncology treatments. As many know, ASCO and SITC had convened a working group that consisted of medical oncologists, immunologists, clinical research, biostatisticians, and representatives from industry and government to develop important recommendations, also known as Trial Reporting in Immuno-oncology, or TRIO recommendations. The recommendations based on expert consensus are important given that existing data to support evidence-based recommendations are limited. The recommendations given by TRIO are intended to improve the reporting of IO clinical trials and thus, provide more complete evidence on the relative benefits and risks of immuno-oncology. Given the rapid expansion of the number of IO clinical trials and ongoing improvements to evidence base using IO treatments and clinical care, it is apparent that these recommendations will likely need regular revision. And the annual meeting of ASCO and SITC will be an important place for TRIO recommendations to continually be updated. Thank you. Again, today, my guest has been Dr. Steven Eric Finkelstein. Thank you so much for being on our podcast today. It's been an absolute pleasure. Thank you so much. And to our listeners, thank you for tuning into the "ASCO Daily News" podcast. If you're enjoying the content, we encourage you to rate us and review us on Apple Podcast.

Reprogramming of somatic cells into neurons provides a new approach toward cell-based therapy of neurodegenerative diseases. Conversion of postnatal astroglia from the cerebral cortex of mice into functional neurons in vitro can be achieved by forced expression of a single transcription factor. Also skin fibroblasts have been successfully reprogrammed into functional neurons yet through the synergistic action of several transcription factors. A major challenge for the translation of neuronal reprogramming into therapy concerns the feasibility of this approach in adult human tissues. This work demonstrates the potential of perivascular cells isolated from the adult human brain to serve as a substrate prompted to neuronal reprogramming by forced co-expression of neurogenic transcription factors, namely the SRY-related HMG box protein Sox2 and the basic helix loop helix (bHLH) mammalian homologue of achaete-schute-1 Mash1 (also known as Ascl1). The cells used in this study display characteristics of pericytes assessed by immunocytochemistry, fluorescence-activated cell sorting (FACS) and real time RT-PCR. The presence of neural progenitor cells was excluded by real time RT-PCR analysis of mRNAs typically expressed by these cell lineages. Upon expression of Sox2 and Mash1, these cells adopt a neuronal phenotype characterized by the expression of neuronal markers such us ßIII-Tubulin, MAP2, NeuN, GABA and calretinin. Electrophysiological recordings reveal the ability of these cells to fire repetitive action potentials and to integrate into neuronal networks when co-cultured with mouse embryonic neurons. The pericytic nature of the reprogrammed cells was further demonstrated by isolation of PDGFRß-positive cells from adult human brain cultures by FACS and monitoring the Mash1/Sox2-induced neuronal conversion by time-lapse video microscopy. Genetic fate-mapping in mice expressing an inducible Cre recombinase under the tissue non-specific alkaline phosphatase promoter corroborated that pericytes from the adult cerebral cortex can be expanded and reprogrammed in vitro into neurons by co-expression of Sox2 and Mash1. These results demonstrate the feasibility of an in vitro neuronal reprogramming approach on somatic cells isolated from the adult human cerebral cortex which could have important implications in the development of in vivo direct repair strategies in neurodegenerative diseases and brain injury.

In this thesis a novel method to isolate and cultivate pericytes from hamster skeletal muscle is presented. By choosing a two-step approach with magnetic-bead cell sorting for the 3G5 antigen and culture in a selective growth medium a high percentage of pericytes could be reached and their nature could be verified in subsequent characterization steps. Morphologically the cells had a typical phenotype with flat and large cell bodies and long protruding processes. Immunocytochemistry and western blotting could confirm the expression of the previously reported pericyte markers NG2, PDGFR-β, and αSMA. However, in accordance with previous reports, even the cells isolated from the same muscle and tissue, were not a uniform population. A certain heterogeneity was also present in the functional studies investigating pericyte membrane channels by electrophysiology. In these experiments in a subset of the pericyte population the presence of the voltage sensitive potassium channel KV1.5 could be demonstrated. Upon pharmacological stimulation of these channels by FFA they were able to elicit a membrane hyperpolarization and conduct it to neighboring endothelial cells via gap junctions formed by connexin 43. The expression of the KV1.5 channel could also be demonstrated by immunohistochemistry in paraffin sections from hamster skeletal muscle. These findings are consistent with the hypothesis that pericytes could act as signal generators for hyperpolarization and vasodilatation in the vessel wall. The coupling with endothelial cells might relay an electric signal further along the vessel wall and lead to “EDHF mediated” dilations [48]. Interestingly in tissue sections KV1.5 positive pericytes were located predominantly at vascular branchings. We additionally studied whether gap junctions may also form a pathway for the exchange of miRNA between cells in a model co-culture system using HeLa. For the detection of the miRNA a detector system consisting of a luciferase reporter protein under control of a miR124 sensitive 3’ UTR was established. Our experiments could not conclusively confirm transfer of miRNA in this system. Similar results were obtained with human miR15b. Taken together these findings open up new possibilities for studying skeletal muscle pericyte physiology and to test novel concepts integrating the pericyte into the vascular signaling network under conditions of health and disease.

Flt3 is the most recently discovered member of the platelet-derived growth factor receptor (PDGFR) subfamily of receptor tyrosine kinases (RTKs). It is expressed on early hematopoietic progenitor cells and is involved in their growth. Activating mutations of Flt3, such as internal tandem duplications (ITD) in the juxtamembrane (JM) region of Flt3, are among the most common genetic alterations found in patients with acute myeloid leukemia (AML). For this reason Flt3 is an attractive target for specific tyrosine kinase inhibitors, and a number of such compounds are currently being tested in clinical trials. However, the mechanisms of Flt3-mediated signal transduction are poorly understood. Src family tyrosine kinases (SFKs) are involved in the signaling processes of various RTKs, including those of the PDGFR subfamily . Most SFKs are expressed predominantly or exclusively in hematopoietic cells, and at least Hck and Lyn were found to be activated in AML patients. These observations indicate that SFKs could also be involved in Flt3 signaling. In this work the role of SFKs in signal transduction of the Flt3 receptor was investigated. A panel of Hck and Flt3 mutants was used in biochemical and biological assays to deduce the contribution of kinase activity, SH2 and SH3 binding domains and tyrosine phosphorylation status to Flt3-SFK interaction. The work presented shows that SFKs interfere with the maturation of wild type and Flt3 ITD receptors in human embryonic kidney 293 (HEK- 293) cells in a kinase-dependent manner. The SFK-mediated effect on receptor maturation is reflected by accumulation of the immature, intracellular form of Flt3 at the expense of the mature, plasma membrane-inserted form of the receptor. This effect of SFK kinase activity on receptor maturation is not limited to Flt3, because analogous results were also obtained for the Kit receptor, another member of the PDGFR subfamily. The demonstration of the role of SFKs in regulation of receptor maturation is novel and the exact mechanism underlying this effect requires further investigation. Using the HEK-293 cells it was also shown that Hck is able to phosphorylate Flt3 on tyrosine residues and to associate with autophosphorylated Flt3 in an SH2 domain-dependent manner. Hck-mediated tyrosine phosphorylation occurs in the JM region of Flt3. Tyrosine residues 589 and 591 in the JM region, when phosphorylated, were also identified as the docking sites for Hck. Although Hck phosphorylation and binding sites on Flt3 overlap, Hck-mediated phosphorylation of Flt3 is not sufficient for Flt3-Hck association. In contrast to the situation in HEK-293 cells, Hck neither interferes with Flt3 maturation nor phosphorylates Flt3 on tyrosine residues, and does not detectably associate with the Flt3 receptor in the hematopoietic murine cell line 32D clone 3 (32D cl.3). However, the level of the ectopic expression of Hck in 32D cl.3 cells was lower than in HEK-293 cells. This difference in Hck expression level probably accounts for both the lack of the Hck-mediated phosphorylation of Flt3 and the interference with its maturation in 32D cl.3 cells. The lower Hck expression level, however, does not account for the lack of detectable association of Hck with Flt3 in 32D cl.3 cells. Using biological assays in which activation of Flt3 can partially overcome the requirement for cytokine stimulation in 32D cl.3 survival and proliferation, it was shown that Hck is not involved in Flt3 signal transduction leading to Flt3-mediated cell survival and Flt3 ITD-dependent cell growth. Therefore, biological relevance of SFKs in Flt3 signaling remains unclear. In summary, although the binding and phosphorylation of Flt3 by Hck can be shown, the biological relevance of Hck in Flt3 signaling remains to be formally demonstrated. This research led to the novel finding that, at least when over-expressed or hyperactivated, SFKs interfere with the maturation process of RTKs. Various studies have shown that the ligandindependent activation of RTKs as well as their premature phosphorylation can interfere with maturation of RTKs. This study reveals that, by virtue of their phosphorylating of Flt3, Kit and possibly other RTKs, SFKs can regulate maturation of these RTKs and consequently alter their transport to the plasma membrane. Further studies are required to investigate the biological relevance of this function of SFKs.