BACKGROUND Tamoxifen resistance presents a huge clinical challenge for breast cancer patients. An understanding of the mechanisms of tamoxifen resistance can guide development of efficient therapies to prevent drug resistance. METHODS We first tested whether peptidylarginine deiminase 2 (PAD2) may be involved in tamoxifen-resistance in breast cancer cells. The effect of depleting or inhibiting PAD2 in tamoxifen-resistant MCF-7 (MCF7/TamR) cells was evaluated both in vitro and in vivo. We then investigated the potential of Cl-amidine, a PAD inhibitor, to be used in combination with tamoxifen or docetaxel, and further explored the mechanism of the synergistic and effective drug regimen of PADs inhibitor and docetaxel on tamoxifen-resistant breast cancer cells. RESULTS We report that PAD2 is dramatically upregulated in tamoxifen-resistant breast cancer. Depletion of PAD2 in MCF7/TamR cells facilitated the sensitivity of MCF7/TamR cells to tamoxifen. Moreover, miRNA-125b-5p negatively regulated PAD2 expression in MCF7/TamR cells, therefore overexpression of miR-125b-5p also increased the cell sensitivity to tamoxifen. Furthermore, inhibiting PAD2 with Cl-amidine not only partially restored the sensitivity of MCF7/TamR cells to tamoxifen, but also more efficiently enhanced the efficacy of docetaxel on MCF7/TamR cells with lower doses of Cl-amidine and docetaxel both in vivo and in vivo. We then showed that combination treatment with Cl-amidine and docetaxel enhanced p53 nuclear accumulation, which synergistically induced cell cycle arrest and apoptosis. Meanwhile, p53 activation in the combination treatment also accelerated autophagy processes by synergistically decreasing the activation of Akt/mTOR signaling, thus enhancing the inhibition of proliferation. CONCLUSION Our results suggest that PAD2 functions as an important new biomarker for tamoxifen-resistant breast cancers and that inhibiting PAD2 combined with docetaxel may offer a new approach to treatment of tamoxifen-resistant breast cancers.

中文翻译：

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抑制PAD2可增强多西他赛在他莫昔芬耐药性乳腺癌细胞中的抗肿瘤作用。

背景技术对于乳腺癌患者，他莫昔芬的耐药性提出了巨大的临床挑战。对他莫昔芬耐药机制的理解可以指导开发有效的预防药物耐药性的疗法。方法我们首先测试了肽基丝氨酸精氨酸脱亚氨酶2（PAD2）是否可能与乳腺癌细胞中的他莫昔芬耐药有关。在体内和体外均评估了在他莫昔芬耐药的MCF-7（MCF7 / TamR）细胞中消耗或抑制PAD2的作用。然后，我们研究了PAD抑制剂Cl-am与他莫昔芬或多西他赛联合使用的潜力，并进一步探索了PADs抑制剂和多西他赛对他莫昔芬耐药的乳腺癌细胞协同有效的药物治疗机制。结果我们报告PAD2在他莫昔芬耐药的乳腺癌中显着上调。MCF7 / TamR细胞中PAD2的耗尽促进了MCF7 / TamR细胞对他莫昔芬的敏感性。此外，miRNA-125b-5p负调节MCF7 / TamR细胞中PAD2的表达，因此miR-125b-5p的过表达也增加了细胞对他莫昔芬的敏感性。此外，用Cl-am抑制PAD2不仅可以部分恢复MCF7 / TamR细胞对他莫昔芬的敏感性，而且可以更有效地增强多西他赛对MCF7 / TamR细胞的体内和体外剂量较低的Cl-am和多西他赛的疗效。体内。然后，我们表明用Cl-am和多西他赛联合治疗可增强p53核积累，从而协同诱导细胞周期停滞和凋亡。同时，联合治疗中的p53激活还通过协同降低Akt / mTOR信号的激活来加速自噬过程，从而增强了对增殖的抑制作用。结论我们的结果表明，PAD2可以作为抗他莫昔芬的乳腺癌的重要新生物标志物，而抑制PAD2与多西他赛的结合可能为治疗抗他莫昔芬的乳腺癌提供一种新的方法。