Wu Fan, Chen Wei-Jia, Yan Lun, Tan Guo-Qian, Li Wei-Tao, Zhu Xuan-Jin, Ge Xiao-Chuan, Liu Jian-Wei, Wang Bai-Lin
Department of Hepatobiliary Surgery, Guangzhou Red Cross Hospital /Fourth Affiliated Hospital of Jinan University, Tongfu Roud 396, Guangzhou, 510220, China.
Cancer Med. 2016 Feb;5(2):370-85. doi: 10.1002/cam4.588. Epub 2015 Dec 29.
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.
作为DNA修复中的关键核酸内切酶，Mus81传统上被视为一种肿瘤抑制因子，但最近发现它与结肠癌细胞和乳腺癌细胞对丝裂霉素C和5-氟尿嘧啶的敏感性相关。然而，其在其他人类恶性肿瘤化疗敏感性中的作用仍不清楚。因此，本研究旨在探讨敲低Mus81对肝癌（一种通常对化疗耐药的肿瘤）化疗敏感性的影响，并探索其潜在机制。通过慢病毒介导的短发夹RNA降低了HepG2和Bel-7402肝癌细胞系中Mus81的表达，MTT法和肝癌化疗小鼠模型证明，这些Mus81抑制的肝癌细胞对治疗药物，尤其是表柔比星（EPI）的敏感性增加。流式细胞术分析还显示，敲低Mus81导致EPI处理的HepG2和Bel-7402细胞明显停滞于S期并增加凋亡，这可通过抑制CHK1来挽救。在EPI处理下，Mus81抑制的HepG2细胞和异种移植小鼠肿瘤中也证实了CHK1/CDC25A/CDK2途径的激活。同时，在CHK1的控制下，通过激活p53/Bax/Caspase-3途径，敲低Mus81可显著促进HepG2细胞对EPI的凋亡。此外，抑制CHK2可轻微提高CHK1活性，从而增强EPI在Mus81抑制的肝癌细胞中诱导的S期停滞和凋亡。总之，敲低Mus81通过诱导S期停滞并通过CHK1途径促进凋亡来提高肝癌细胞的化疗敏感性，提示Mus81是肝癌的一个新的治疗靶点。
