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Increased PKC? 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 PKC?, not PKC?, 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 siPKC? 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.

SUBMITTER: Lei J

PROVIDER: S-EPMC5028770 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Increased PKCα activity by Rack1 overexpression is responsible for chemotherapy resistance in T-cell acute lymphoblastic leukemia-derived cell line.

Lei Jie J Li Qi Q Gao Ying Y Zhao Lei L Liu Yanbo Y

Scientific reports 20160920

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 apoptos ...[more]

PMID: 27644318

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Project description:BackgroundA20 is a dual inhibitor of NF-κB activation and apoptosis in the tumor necrosis factor receptor 1 signaling pathway, and both are related to tumorigenesis. A20 is frequently inactivated by deletions and/or mutations in several B and T cell lymphoma subtypes; however, knowledge of the role of A20 in B-cell acute lymphoblastic leukemia (B-ALL) remains limited. In this study, we characterized the A20 gene expression pattern, the expression level of its upstream regulating factor MALT1, and its downstream target NF-κB in adult B-ALL.MethodsThe expression level of MALT1, A20 and NF-κB1 was detected in peripheral blood mononuclear cells (PBMCs) from 20 patients with adult B-ALL (including 12 de novo B-ALL and 8 refractory/relapse B-ALL cases), and nine patients with B-ALL in complete remission (CR) using real-time PCR. Sixteen healthy individuals served as controls.ResultsSignificant A20 overexpression was found in the B-ALL (median: 13.489) compared with B-ALL CR (median: 3.755) (P = 0.003) patients and healthy individuals (median: 8.748) (P = 0.002), while there was no significant difference in A20 expression between B-ALL CR patients and healthy individuals (P = 0.107). Interestingly, the A20 expression level in the B-ALL samples was relatively different with approximately 50% of the B-ALL cases showing a relatively high A20 expression level, while the remaining 50% cases demonstrated slight upregulation or a similar expression level as the healthy controls. However, there was no significant difference in the A20 expression level between de novo B-ALL (median 12.252) and refractory/relapse B-ALL patients (median 21.342) (P = 0.616). Similarly, a significantly higher expression level of NF-κB1 was found in the B-ALL (median 1.062) patients compared with healthy individuals (median 0.335) (P < 0.0001), while the NF-κB1 expression level was downregulated in the B-ALL CR group (median 0.339), which was significantly lower than that in those with B-ALL (P = 0.001). Moreover, the MALT1 expression level in B-ALL was upregulated (median 1.938) and significantly higher than that in healthy individuals (median 0.677) (P = 0.002) and B-ALL CR patients (median 0.153) (P = 0.008). The correlation of the expression levels of all three genes was lost in B-ALL.ConclusionsWe found that MALT1-A20-NF-κB is overexpressed in adult B-ALL, which may be related to the pathogenesis of B-ALL, and this pathway may be considered a potentially attractive target for the development of B-ALL therapeutics.

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Increased PKC? activity by Rack1 overexpression is responsible for chemotherapy resistance in T-cell acute lymphoblastic leukemia-derived cell line.

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Increased PKCα activity by Rack1 overexpression is responsible for chemotherapy resistance in T-cell acute lymphoblastic leukemia-derived cell line.

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