Mus81 knockdown improves chemosensitivity of hepatocellular carcinoma cells by inducing S‐phase arrest and promoting apoptosis through CHK1 pathway

Abstract

As a critical endonuclease in DNA repair, Mus81 is traditionally regarded as a tumor suppressor, but recently correlated with the sensitivity of mitomycin C and 5‐fluorouracil in colon cancer and breast cancer cells. However, its role in chemosensitivity of other human malignancies still remains unknown. This study therefore aims to investigate the effects of Mus81 knockdown on the chemosensitivity of hepatocellular carcinoma (HCC), a usually chemorefractory tumor, and explore the underlying mechanisms. Mus81 expression in HepG2 and Bel‐7402 HCC cell lines was depleted by lentivirus‐mediated short hairpin RNA and the elevated sensitivity of these Mus81‐inhibited HCC cells to therapeutic agents, especially to epirubicin (EPI), was evidenced by MTT assay and an HCC chemotherapy mouse model. Flow cytometric analysis also showed that Mus81 knockdown lead to an obvious S‐phase arrest and an elevated apoptosis in EPI‐treated HepG2 and Bel‐7402 cells, which could be rescued by CHK1 inhibition. The activation of CHK1/CDC25A/CDK2 pathway was also demonstrated in Mus81‐inhibited HepG2 cells and xenograft mouse tumors under EPI treatment. Meanwhile, the apoptosis of HepG2 cells in response to EPI was remarkably promoted by Mus81 knockdown through activating p53/Bax/Caspase‐3 pathway under the controlling of CHK1. In addition, CHK2 inhibition slightly raised CHK1 activity, thereby enhancing the S‐phase arrest and apoptosis induced by EPI in Mus81‐suppressed HCC cells. In conclusion, Mus81 knockdown improves the chemosensitivity of HCC cells by inducing S‐phase arrest and promoting apoptosis through CHK1 pathway, suggesting Mus81 as a novel therapeutic target for HCC.

MUS81 is associated with cell proliferation and cisplatin sensitivity in serous ovarian cancer

“…These data suggest that down-regulation of MUS81 could enhance the sensitivity of cisplatin in ovarian cancer cells. Recently, Mus81 was reported to be associated with chemosensitivity in human malignancies such as colon cancer [22], breast cancer [26] and hepatocellular carcinoma [27]. All the data suggest that MUS81 would contribute to chemosensitization.…”

Feedback regulation of methyl methanesulfonate and ultraviolet-sensitive gene clone 81 via ATM/Chk2 pathway contributes to the resistance of MCF-7 breast cancer cells to cisplatin

“…The results were consistent with the recent study in HCC cells. 16 These findings suggest that knockdown of Mus81 activates the p53/Bcl-2 pathway to induce cell apoptosis of MCF-7 cells under the treatment of cisplatin. But how the p53/Bcl-2 pathway is activated by knockdown of Mus81, and whether p53/Bcl-2 is downstream of ATM/Chk2 pathway when the MCF-7 cells are treated with cisplatin should be explored by further research.…”

“…22 Other studies also indicated that Mus81 was associated with the chemosensitivity in human malignancies such as colon cancer and HCC. 16,34 However, the molecular mechanism is largely unclear. In this study, our results demonstrated that Mus81 knockdown by lentivirus-mediated shRNA could remarkably improve the sensitivity to cisplatin in MCF-7 cells.…”

“…Previous studies also demonstrated that downregulation of Mus81 in hepatocellular carcinoma (HCC), colorectal cancer, astrocytoma, and gastric cancer was closely correlated with the bad progression and prognosis of these malignancies. [16][17][18][19][20] Mus81-deficient mice and cells were hypersensitive to the DNA crosslinking agent mitomycin C (MMC). 15 Deleting Mus81 gene could increase the sensitivity of MMC and cisplatin in the human colon cancer cell line HCT116 and HCC.…”

“…15 Deleting Mus81 gene could increase the sensitivity of MMC and cisplatin in the human colon cancer cell line HCT116 and HCC. 16,21 Our previous studies showed that knockdown of Mus81 by small interfering RNA (siRNA) enhanced the sensitivity to 5-fluorouracil (5-FU) in breast cancer cell lines MCF-7 and T47D. 22 These findings suggest that Mus81 may be the potential marker and target to improve chemosensitivity in human tumors.…”