Abstract 341: Imatinib induces expression of Bim and apoptosis in chronic myelogenous leukemia cells via p38/H2AX pathway

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA H2AX is a novel human tumor suppressor protein and plays an important role in apoptosis of cancer cells. Increasing published data indicate that H2AX phosphorylation (Ser139) contributes to its regulation of cancer cell apoptosis. Thus, charactering the mechanisms and signaling pathways involved in H2AX phosphorylation (Ser139) will certainly provide better understanding on H2AX function in cancer cells. Our previous report showed that caspase-3/Mst1 pathway regulates phosphorylation of H2AX at Ser139 in chronic myelogenous leukemia (CML) cells. Recently we found another pathway which regulates H2AX phosphorylation (Ser139) in CML cells. When the CML cells were subjected to imatinib treatment, MAPK family member ERK1/2 activity was inhibited, but p38 activity was increased, another member JNK1/2 had no response. Then we used p38 inhibitor SB202190 and siRNA against p38 to block p38 activation and observed that H2AX phosphorylation and apoptosis of CML cells was concurrently inhibited. Our results also showed that inhibition of MSK1/MSK2 did not affect H2AX phosphorylation (Ser139), although the p38 and ERK1/2 downstream MSK1/MSK2 could be activated by imatinib in CML cells. Overall, these data confirmed that p38 signaling pathway is also required for H2AX phosphorylation (Ser139) in CML cells. Our further evidences indicated that inhibition of H2AX phosphorylation (Ser139) regulated by p38 during apoptotic induction with imatinib suppressed the expression of apoptosis-related gene Bim. Taken together, these data demonstrated that p38/H2AX pathway regulates Bim expression and subsequent apoptosis in CML cells. Citation Format: Min Xiong, Tianhui Niu, Yaqiong Dong, Chengrong Lu. Imatinib induces expression of Bim and apoptosis in chronic myelogenous leukemia cells via p38/H2AX pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 341. doi:10.1158/1538-7445.AM2014-341