RESUMO
The purpose of this present study was to investigate the role of inhibitor of apoptosis proteins (IAPs), their inhibitor, Smac, and the focal adhesion kinase (FAK) in the laminin enhancement of cisplatin-induced apoptosis in a testicular tumor germ cell line, NCCIT. We demonstrated that specifically in laminin-adherent NCCIT cells, cisplatin-induced apoptosis followed a significant decrease of c-IAP-2 protein expression and of both XIAP mRNA and protein expression. Smac expression was not modified in any tested conditions. We also found that FAK, which mediates the ECM-integrin antiapoptotic signal was down-regulated early in cells cultured on laminin. Our results provide a possible mechanistic explanation to cisplatin-induced apoptosis in NCCIT cells adhered on laminin. Cisplatin down-regulated FAK protein expression early, which therefore failed to activate c-IAP-2 and XIAP expression, resulting in a defect in the abrogation of the activation of caspases. Thus, the laminin signaling enhances the cisplatin-induced apoptosis, at least partly, through a down-regulation of survival signal molecules. Our data raise an interesting possibility that a therapeutic strategy targeting these survival molecules would be efficient to overcome chemo-resistance in testicular germ cell tumor.
Assuntos
Antineoplásicos/farmacologia , Apoptose , Cisplatino/farmacologia , Quinase 1 de Adesão Focal/metabolismo , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Proteínas Inibidoras de Apoptose/metabolismo , Laminina/farmacologia , Adesão Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Regulação para Baixo , Quinase 1 de Adesão Focal/genética , Humanos , Proteínas Inibidoras de Apoptose/genética , Masculino , Neoplasias Embrionárias de Células Germinativas , RNA Mensageiro/metabolismo , Neoplasias Testiculares , Fatores de Tempo , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/genética , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/metabolismoRESUMO
Our study demonstrates that laminin potentiates cisplatin-induced apoptosis in NCCIT, a testicular tumor germ cell line. When cultured on laminin, NCCIT cells displayed a significantly higher susceptibility to cisplatin-induced apoptosis than on plastic or on other ECM components including fibronectin, Type IV collagen and vitronectin. This high cisplatin sensitivity observed on NCCIT cell cultured on laminin was mediated by the alpha6-integrin signaling. The knockdown of the alpha6-integrin subunit by small interfering RNAs suppressed the higher cisplatin-sensitivity supporting the existence of a crosstalk between laminin-alpha6-integrin signaling and cisplatin-induced apoptosis. Our findings indicate that in cisplatin-treated NCCIT cells, the laminin-alpha6-integrin signaling induces the activation of executioner procaspase-3 and -6 as well as apoptosis-inducing factor (AIF) transcription and expression. The ability of integrin-mediated specific stroma-tumor cell interactions to modulate the chemosensitive phenotype of a tumor cell might provide new insights to overcome cisplatin resistance of tumor cells.
