H2AX phosphorylation regulated by p38 is involved in Bim expression and apoptosis in chronic myelogenous leukemia cells induced by imatinib

Abstract

Increasing evidence suggests that histone H2AX plays a critical role in regulation of tumor cell apoptosis and acts as a novel human tumor suppressor protein. However, the action of H2AX in chronic myelogenous leukemia (CML) cells is unknown. The detailed mechanism and epigenetic regulation by H2AX remain elusive in cancer cells. Here, we report that H2AX was involved in apoptosis of CML cells. Overexpression of H2AX increased apoptotic sensitivity of CML cells (K562) induced by imatinib. However, overexpression of Ser139-mutated H2AX (blocking phosphorylation) decreased sensitivity of K562 cells to apoptosis. Similarly, knockdown of H2AX made K562 cells resistant to apoptotic induction. These results revealed that the function of H2AX involved in apoptosis is strictly related to its phosphorylation (Ser139). Our data further indicated that imatinib may stimulate mitogen-activated protein kinase (MAPK) family member p38, and H2AX phosphorylation followed a similar time course, suggesting a parallel response. H2AX phosphorylation can be blocked by p38 siRNA or its inhibitor. These data demonstrated that H2AX phosphorylation was regulated by p38 MAPK pathway in K562 cells. However, the p38 MAPK downstream, mitogen- and stress-activated protein kinase-1 and -2, which phosphorylated histone H3, were not required for H2AX phosphorylation during apoptosis. Finally, we provided epigenetic evidence that H2AX phosphorylation regulated apoptosis-related gene Bim expression. Blocking of H2AX phosphorylation inhibited Bim gene expression. Taken together, these data demonstrated that H2AX phosphorylation regulated by p38 is involved in Bim expression and apoptosis in CML cells induced by imatinib.

Resveratrol induces apoptosis of human chronic myelogenous leukemia cells in vitro through p38 and JNK-regulated H2AX phosphorylation

“…Resveratrol induced p38 and JNK phosphorylation in a time-dependent manner (Figure 2), following a response similar to that for H2AX phosphorylation ( Figure 1A). Unexpectedly, resveratrol strongly inhibited ERK phosphorylation (Figure 2), which is activated by BCR-ABL with constitutively active tyrosine kinase activity in CML cells [25] . This finding is not consistent with the results reported by Mustafi et al, indicating that resveratrol stimulates ERK activity in K562 cells [29] .…”

“…Therefore, the MAPK pathways have become a focus of intense investigation for developing small-molecule inhibitors as targeted therapeutics [28] . Our previous data demonstrated that p38 MAPK is involved in imatinib-induced apoptosis in CML cells [25] . In the current study, we investigated the role of MAPK pathways (ERK, p38, and JNK) in apoptosis and in H2AX phosphorylation in CML cells induced by resveratrol.…”

“…In particular, H2AX phosphorylation at Ser139 has an important role in the apoptosis of tumor cells [24,25,27] . Hence, we investigated whether resveratrol could induce H2AX phosphorylation in CML cells.…”

“…Apoptosis is almost completely blocked in H2AX -/-mouse embryo fibroblasts (MEFs). The transfection of H2AX-wt, but not H2AX-139m (Ser139 was mutated to block H2AX phosphorylation), into H2AX -/-MEFs restored the ability to Increasing evidence has also demonstrated that H2AX phosphorylation is involved in the apoptosis of tumor cells [23,25,27] . To investigate the important role of γH2AX in the resveratrol-induced apoptosis of CML cells, we assessed the effects of H2AX overexpression and knockdown on the apoptosis of CML cells.…”

“…H2AX is known as a novel tumor suppressor protein owing to its role in the regulation of cancer cell apoptosis [23] . Our previous studies have demonstrated that H2AX phosphorylation at Ser139 is related to apoptosis in CML cells (K562 cells) [24,25] . In the current study, we used resveratrol to induce the apoptosis of K562 cells and to investigate the signaling pathways involved in the regulation of H2AX phosphorylation.…”