Inhibition of c-Jun N-Terminal Kinase 2 Expression Suppresses Growth and Induces Apoptosis of Human Tumor Cells in a p53-Dependent Manner

Abstract

C-Jun N-terminal kinase (JNK) plays a critical role in coordinating the cellular response to stress and has been implicated in regulating cell growth and transformation. To investigate the growth-regulatory functions of JNK1 and JNK2, we used specific antisense oligonucleotides (AS) to inhibit their expression. A survey of several human tumor cell lines revealed that JNKAS treatment markedly inhibited the growth of cells with mutant p53 status but not that of cells with normal p53 function. To further examine the influence of p53 on cell sensitivity to JNKAS treatment, we compared the responsiveness of RKO, MCF-7, and HCT116 cells with normal p53 function to that of RKO E6, MCF-7 E6, and HCT116 p53^−/−, which were rendered p53 deficient by different methods. Inhibition of JNK2 (and to a lesser extent JNK1) expression dramatically reduced the growth of p53-deficient cells but not that of their normal counterparts. JNK2AS-induced growth inhibition was correlated with significant apoptosis. JNK2AS treatment induced the expression of the cyclin-dependent kinase inhibitor p21^Cip1/Waf1 in parental MCF-7, RKO, and HCT116 cells but not in the p53-deficient derivatives. That p21^Cip1/Waf1 expression contributes to the survival of JNK2AS-treated cells was supported by additional experiments demonstrating that p21^Cip1/Waf1deficiency in HCT116 cells also results in heightened sensitivity to JNKAS treatment. Our results indicate that perturbation of JNK2 expression adversely affects the growth of otherwise nonstressed cells. p53 and its downstream effector p21^Cip1/Waf1are important in counteracting these detrimental effects and promoting cell survival.