title: Increased PKCα activity by Rack1 overexpression is responsible for chemotherapy resistance in T-cell acute lymphoblastic leukemia-derived cell line.
abstract: Chemoresistant mechanisms in T-cell acute lymphoblastic leukemia (T-ALL) patients are not clarified. The apoptotic signaling mediated by receptor of activated C kinase 1 (Rack1), protein kinase C (PKC) and FEM1 homolog b (FEM1b) was investigated in two T-ALL-derived cell lines (Jurkat and CCRF-CEM) following treatment with chemotherapy drugs vincristine and prednisone. Serum starvation or chemotherapeutic drugs significantly reduced Rack1 level and PKC activation, while promoted cellular apoptosis in both cell lines. Rack1 overexpression protected T-ALL cell against starvation or chemotherapeutic drug-induced apoptosis. Moreover, Rack1 overexpression reduced the level of cytochrome c and active caspase 3 as well as FEM1b and apoptotic protease activating factor-1 (Apaf-1), and inhibited induction of cellular apoptosis in chemotherapeutic drug-treated Jurkat cell. Interaction of Rack1 and PKCα, not PKCβ, was detected in both cell lines. Of note, Rack1 overexpression abrogated reduction of PKC kinase activity in chemotherapeutic drug-treated T-ALL cell. PKC kinase inhibitor Go6976 or siPKCα inhibited downregulation of FEM1b and/or Apaf-1, and thus increased cellular apoptosis in Rack1-overexpressed T-ALL cell receiving chemotherapeutic drugs. Accordingly, our data provided evidence that increased Rack1-mediated upregulation of PKC kinase activity may be responsible for the development of chemoresistance in T-ALL-derived cell line potentially by reducing FEM1b and Apaf-1 level.
authors.affiliation: Department of Pediatrics, First Hospital of Jilin University, Changchun, Jilin, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Lei
authors.affiliation: Department of Pediatrics, First Hospital of Jilin University, Changchun, Jilin, PR China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Pediatrics, People's Hospital of Shaanxi Province, Shaanxi, XiAn, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Pediatrics, First Hospital of Jilin University, Changchun, Jilin, PR China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Department of Pediatrics, First Hospital of Jilin University, Changchun, Jilin, PR China.
authors.forename: Yanbo
authors.initials: Y
authors.lastname: Liu
mesh_terms: D053477:Apoptotic Protease-Activating Factor 1 / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D015971:Gene Expression Regulation, Enzymologic; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D019169:Jurkat Cells; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D011239:Prednisolone / Q000494:pharmacology; D051571:Protein Kinase C-alpha / Q000096:biosynthesis* / Q000235:genetics; D000075370:Receptors for Activated C Kinase / Q000096:biosynthesis* / Q000235:genetics; D014750:Vincristine / Q000494:pharmacology
chemical_list: C506592:APAF1 protein, human; D053477:Apoptotic Protease-Activating Factor 1; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C403492:FEM1B protein, human; D009363:Neoplasm Proteins; C419368:RACK1 protein, human; D000075370:Receptors for Activated C Kinase; D014750:Vincristine; D011239:Prednisolone; C496628:PRKCA protein, human; D051571:Protein Kinase C-alpha