Prostate cancer (PCa), an extremely common malignancy in males, is the most prevalent disease in several countries. Norcantharidin (NCTD) has antiproliferation, antimetastasis, apoptosis, and autophagy effects in various tumor cells. Nevertheless, the antitumor effect of NCTD combined with paclitaxel (PTX), a chemotherapeutic drug, in PCa remains unknown. The cell growth, proliferative rate, cell cycle distribution, and cell death were determined by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide, colony formation assay, PI staining, and Annexin V/PI staining by flow cytomertry, whereas the mitochondrial membrane potential (MMP) and endoplasmic reticulum (ER) stress was evaluated using the MitoPotential assay and ER-ID red assay. We also evaluated the protein and mRNA expression of SIRTs by Western blotting and qRTPCR assay. Overexpression effectivity was measured by DNA transfection assay. Our study showed that cell viability and proliferative PC3 and DU145 rates were effectively inhibited after NCTD-PTX combination. We also found that NCTD-PTX combination treatment significantly enhance G2/M phase arrest, induction of cell death and ER stress, loss of MMP, and ER- or apoptotic-related protein expression. Furthermore, NCTD-PTX combination treatment was significantly decreasing the protein and mRNA expression of SIRT7 in PCa cells. Combination therapy effectively reduced cell viability, ER stress-mediated apoptosis and p-eIF2α/ATF4/CHOP/cleaved-PARP expression inhibition in SIRT7 overexpression of PCa cells. These results indicate that NCTD combined with PTX induces ER stress-mediated apoptosis of PCa cells by regulating the SIRT7 expression axis. Moreover, combination therapy may become a potential therapeutic strategy against human PCa.

中文翻译：

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去甲斑蝥素联合紫杉醇通过靶向SIRT7表达诱导前列腺癌细胞内质网应激介导的凋亡作用

前列腺癌 (PCa) 是一种极为常见的男性恶性肿瘤，在多个国家是最普遍的疾病。去甲斑蝥素（NCTD）在多种肿瘤细胞中具有抗增殖、抗转移、凋亡和自噬作用。然而，NCTD 联合紫杉醇 (PTX)（一种化疗药物）在 PCa 中的抗肿瘤作用仍然未知。细胞生长、增殖率、细胞周期分布和细胞死亡通过3-[4,5-二甲基噻唑-2-基]-2,5溴化二苯基四唑、集落形成试验、PI染色和Annexin V/PI染色测定通过流式细胞仪检测，而线粒体膜电位 (MMP) 和内质网 (ER) 应激使用 MitoPotential 测定和 ER-ID 红色测定进行评估。我们还通过蛋白质印迹和 qRTPCR 测定评估了 SIRT 的蛋白质和 mRNA 表达。通过DNA转染测定法测量过表达有效性。我们的研究表明，NCTD-PTX 组合后细胞活力和增殖 PC3 和 DU145 率得到有效抑制。我们还发现 NCTD-PTX 联合治疗显着增强了 G2/M 期阻滞、细胞死亡和 ER 应激的诱导、MMP 的丧失以及 ER 或凋亡相关蛋白的表达。此外，NCTD-PTX 联合治疗显着降低了 PCa 细胞中 SIRT7 的蛋白质和 mRNA 表达。联合治疗有效降低了细胞活力、ER 应激介导的细胞凋亡和 p-eIF2α/ATF4/CHOP/cleaved-PARP 在 PCa 细胞 SIRT7 过表达中的表达抑制。这些结果表明NCTD联合PTX通过调节SIRT7表达轴诱导ER应激介导的PCa细胞凋亡。而且，