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Mcl1 downregulation sensitizes neuroblastoma to cytotoxic chemotherapy and small molecule Bcl2-family antagonists.

ABSTRACT: Neuroblastoma (NB) is a common, highly lethal pediatric cancer, with treatment failures largely attributable to the emergence of chemoresistance. The pro-survival Bcl2 homology (BH) proteins critically regulate apoptosis, and may represent important therapeutic targets for restoring drug sensitivity in NB. We used a human NB tumor tissue microarray to survey the expression of pro-survival BH proteins Mcl1 and Bcl2, and correlated expression to clinical prognostic factors and survival. Primary NB tumors heterogeneously expressed Mcl1 or Bcl2, with high expression correlating to high-risk phenotype. Co-expression is infrequent (11%), but correlates to reduced survival. Using RNA interference, we investigated the functional relevance of Mcl1 and Bcl2 in high-risk NB cell lines (SK-N-AS, IMR-5, NLF). Mcl1 knockdown induced apoptosis in all NB cell lines, while Bcl2 knockdown inhibited only NLF, suggesting functional heterogeneity. Finally, we determined the relevance of Mcl1 in resistance to conventional chemotherapy (etoposide, doxorubicin) and small molecule Bcl2-family antagonists (ABT-737 and AT-101). Mcl1 silencing augmented sensitivity to chemotherapeutics 2- to 300-fold, while Bcl2 silencing did not, even in Bcl2-sensitive NLF cells. Resistance to ABT-737, which targets Bcl2/-w/-x, was overcome by Mcl1 knockdown. AT-101, which also neutralizes Mcl1, had single-agent cytotoxicity, further augmented by Mcl1 knockdown. In conclusion, Mcl1 appears a predominant pro-survival protein contributing to chemoresistance in NB, and Mcl1 inactivation may represent a novel therapeutic strategy. Optimization of compounds with higher Mcl1 affinity, or combination with additional Mcl1 antagonists, may enhance the clinical utility of this approach.

SUBMITTER: Lestini BJ

PROVIDER: S-EPMC3770183 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Mcl1 downregulation sensitizes neuroblastoma to cytotoxic chemotherapy and small molecule Bcl2-family antagonists.

Lestini Brian J BJ Goldsmith Kelly C KC Fluchel Mark N MN Liu Xueyuan X Chen Niel L NL Goyal Bella B Pawel Bruce R BR Hogarty Michael D MD

Cancer biology & therapy 20090808 16

Neuroblastoma (NB) is a common, highly lethal pediatric cancer, with treatment failures largely attributable to the emergence of chemoresistance. The pro-survival Bcl2 homology (BH) proteins critically regulate apoptosis, and may represent important therapeutic targets for restoring drug sensitivity in NB. We used a human NB tumor tissue microarray to survey the expression of pro-survival BH proteins Mcl1 and Bcl2, and correlated expression to clinical prognostic factors and survival. Primary NB ...[more]

PMID: 19556859

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Project description:ObjectiveRho-associated coiled-coil kinase 2 (ROCK2) is an attractive therapeutic target because it is overexpressed in many malignancies, including glioma. Therefore, we designed the current study to determine whether the downregulation of ROCK2 would sensitize the cytotoxic effect of temozolomide (TMZ) in U251 cells.MethodsGlycol-polyethyleneimine (PEG-PEI) was used to deliver siROCK2 to U251 cells, and the physical characteristics of the PEG-PEI/siROCK2 complex (referred to as the siROCK2 complex) were investigated. The transfection efficiency and cell uptake were determined by flow cytometry (FCM) and confocal laser microscopy (CLSM), respectively. U251 cells were then treated with 100 μM TMZ, siROCK2 complexes or their combination. The apoptosis rate and cell migration were measured by FCM and wound-healing assay, respectively. The levels of Bax, Bcl-2, cleaved caspase-3, MMP-2, and MMP-9 were detected to analyze the degrees of apoptosis and migration.ResultsOur results revealed that the characteristics of the siROCK2 complexes depended closely on the N/P ratios. PEG-PEI served as a good vector for siROCK2 and exhibited low cytotoxicity toward U251 cells. The CLSM assay showed that the siROCK2 complexes were successfully uptaken and that both the protein and mRNA levels of ROCK2 were significantly suppressed. Furthermore, the combination treatment induced a higher apoptosis rate and markedly increased the gap distance of U251 cells in the wound-healing assay. Levels of the proapoptotic proteins Bax and cleaved caspase-3 were significantly increased, whereas levels of the antiapoptotic protein Bcl-2 and the migration-related proteins MMP-2 and MMP-9 were significantly reduced by the combination treatment compared with either treatment alone.ConclusionsIn conclusion, our results demonstrate that the combination of TMZ and siROCK2 effectively induces apoptosis and inhibits the migration of U251 cells. Therefore, the combination of TMZ and siROCK2 complex is a potential therapeutic approach for human glioma.

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Mcl1 downregulation sensitizes neuroblastoma to cytotoxic chemotherapy and small molecule Bcl2-family antagonists.

Publications

Mcl1 downregulation sensitizes neuroblastoma to cytotoxic chemotherapy and small molecule Bcl2-family antagonists.

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