title: Importance of PKCδ signaling in fractionated-radiation-induced expansion of glioma-initiating cells and resistance to cancer treatment.
abstract: Brain tumors frequently recur or progress as focal masses after treatment with ionizing radiation. However, the mechanisms underlying the repopulation of tumor cells after radiation have remained unclear. In this study, we show that cellular signaling from Abelson murine leukemia viral oncogene homolog (Abl) to protein kinase Cδ (PKCδ) is crucial for fractionated-radiation-induced expansion of glioma-initiating cell populations and acquisition of resistance to anticancer treatments. Treatment of human glioma cells with fractionated radiation increased Abl and PKCδ activity, expanded the CD133-positive (CD133(+)) cell population that possesses tumor-initiating potential and induced expression of glioma stem cell markers and self-renewal-related proteins. Moreover, cells treated with fractionated radiation were resistant to anticancer treatments. Small interfering RNA (siRNA)-mediated knockdown of PKCδ expression blocked fractionated-radiation-induced CD133(+) cell expansion and suppressed expression of glioma stem cell markers and self-renewal-related proteins. It also suppressed resistance of glioma cells to anticancer treatments. Similarly, knockdown of Abl led to a decrease in CD133(+) cell populations and restored chemotherapeutic sensitivity. It also attenuated fractionated-radiation-induced PKCδ activation, suggesting that Abl acts upstream of PKCδ. Collectively, these data indicate that fractionated radiation induces an increase in the glioma-initiating cell population, decreases cellular sensitivity to cancer treatment and implicates activation of Abl-PKCδ signaling in both events. These findings provide insights that might prove pivotal in the context of ionising-radiation-based therapeutic interventions for brain tumors.
authors: Department of Chemistry, Research Institute for Natural Sciences, Hanyang University, Seoul, Korea.
authors: Min-Jung
authors: MJ
authors: Kim
authors: Rae-Kwon
authors: RK
authors: Kim
authors: Chang-Hwan
authors: CH
authors: Yoon
authors: Sungkwan
authors: S
authors: An
authors: Sang-Gu
authors: SG
authors: Hwang
authors: Yongjoon
authors: Y
authors: Suh
authors: Myung-Jin
authors: MJ
authors: Park
authors: Hee Young
authors: HY
authors: Chung
authors: In Gyu
authors: IG
authors: Kim
authors: Su-Jae
authors: SJ
authors: Lee
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D001932:Brain Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy*; D048708:Cell Growth Processes / Q000235:genetics / Q000528:radiation effects; D045744:Cell Line, Tumor; D019583:Dose Fractionation, Radiation; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005910:Glioma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy*; D006023:Glycoproteins / Q000096:biosynthesis; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000528:radiation effects; D016374:Oncogene Proteins v-abl / Q000235:genetics / Q000378:metabolism; D010455:Peptides; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D047368:Tumor Burden / Q000235:genetics
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D006023:Glycoproteins; D016374:Oncogene Proteins v-abl; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse; D034741:RNA, Small Interfering; D051745:Protein Kinase C-delta