Okumura Toshiyuki, Ikeda Kazuhiro, Ujihira Takafumi, Okamoto Koji, Horie-Inoue Kuniko, Takeda Satoru, Inoue Satoshi
Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, 1397-1 Yamane, Hidaka-shi, Saitama 350-1241, Japan.
Department of Obstetrics and Gynecology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8431, Japan.
J Biochem. 2018 Jan 1;163(1):19-29. doi: 10.1093/jb/mvx053.
Endocrine therapy using antiestrogens and aromatase inhibitors is usually efficient to treat patients with hormone-sensitive breast cancer. Many patients with endocrine therapy, however, often acquire resistance. In the present study, we performed functional screening using short hairpin RNA library to dissect genes involved in antiestrogen tamoxifen resistance in MCF-7 breast cancer cells. We identified seven candidate genes that are associated with poor prognosis of breast cancer patients based on clinical dataset. The expression levels of six out of seven genes were higher in 4-hydroxytamoxifen (OHT) resistant MCF-7 (OHTR) cells compared with parental MCF-7 cells. Among the six selected genes, siRNA-mediated knockdown of PSMD1 and TSPAN12 markedly reduced the proliferation of OHTR cells. Notably, the knockdown of proteasome 26S subunit PSMD1 exhibited cell cycle arrest and the accumulation of p53 protein through inhibiting p53 protein degradation. In accordance with p53 accumulation, its target genes p21 and SFN were also upregulated by PSMD1 silencing. Taken together, PSMD1 was identified as a potential gene that plays a role in the development of tamoxifen resistance in breast cancer cells. These findings will provide a new insight for the mechanism underlying endocrine therapy resistance and a prognostic and therapeutic molecular target for advanced breast cancer.
使用抗雌激素药物和芳香化酶抑制剂的内分泌治疗通常对激素敏感性乳腺癌患者有效。然而，许多接受内分泌治疗的患者常产生耐药性。在本研究中，我们利用短发夹RNA文库进行功能筛选，以剖析MCF-7乳腺癌细胞中与抗雌激素他莫昔芬耐药相关的基因。基于临床数据集，我们鉴定出七个与乳腺癌患者预后不良相关的候选基因。与亲本MCF-7细胞相比，七个基因中的六个在4-羟基他莫昔芬（OHT）耐药的MCF-7（OHTR）细胞中的表达水平更高。在这六个选定的基因中，siRNA介导的PSMD1和TSPAN12敲低显著降低了OHTR细胞的增殖。值得注意的是，蛋白酶体26S亚基PSMD1的敲低通过抑制p53蛋白降解导致细胞周期停滞和p53蛋白积累。与p53积累一致，其靶基因p21和SFN也因PSMD1沉默而上调。综上所述，PSMD1被鉴定为在乳腺癌细胞他莫昔芬耐药发展中起作用的潜在基因。这些发现将为内分泌治疗耐药的潜在机制提供新的见解，并为晚期乳腺癌提供一个预后和治疗的分子靶点。
