Department of Urology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China.
Key Laboratory of Diagnostics Medicine Designated by The Ministry of Education, Chongqing Medical University, Chongqing 400016, P.R. China.
Oncol Rep. 2020 May;43(5):1397-1412. doi: 10.3892/or.2020.7520. Epub 2020 Feb 26.
Radiotherapy (RT) has been used as a therapeutic option for treatment of prostate cancer (PCa) for a number of years; however, patients frequently develop RT resistance, particularly in castration‑resistant PCa (CRPC), although the underlying mechanisms remain unknown. Understanding the underlying mechanism of RT resistance in CRPC may potentially highlight novel targets to improve therapeutic options for patients with PCa. In the present study, the expression levels of phospholipase Cε (PLCε), androgen receptor (AR) and DNA‑dependent protein kinase catalytic subunit (PKcs) were examined in PCa tissue samples and PCa cells, and the effects of PLCε knockdown on AR and DNA damage repair (DDR)‑related molecules were determined. The association between PLCε, AR and Poly (ADP‑ribose) polymerase 1 (PARP1), as well as their respective roles in radiation resistance, were assessed using gene knockdown and pharmaceutical inhibitors or activators. A chromatin immunoprecipitation assay was used to determine the epigenetic regulatory effects of PLCε on PARP1. Animal experiments were performed to assess whether the mechanisms observed in vitro could be replicated in vivo. The expression levels of PLCε, AR and DNA‑PKcs were significantly upregulated in PCa, particularly in CRPC. PLCε knockdown reduced the viability and increased apoptosis of cells subjected to radiation. Additionally, PLCε deficiency suppressed DDR progression by downregulating an AR and PARP1 positive feedback loop and the associated downstream molecules following radiation. PLCε depletion also increased the presence of histone H3 lysine 27 trimethylation in the PARP1 promoter region, suggesting increased methylation of the PARP1 gene and thus resulting in reduced expression of PARP1. In vivo, PLCε knockdown significantly potentiated the effects of radiation on tumor growth. Taken together, the results of the present study demonstrated that PLCε knockdown enhanced the radiosensitivity of CRPC by downregulating the AR/PARP1/DNA‑PKcs axis.
放射治疗（RT）作为治疗前列腺癌（PCa）的一种治疗选择已经使用了多年；然而，患者经常发生 RT 抵抗，特别是在去势抵抗性前列腺癌（CRPC）中，尽管其潜在机制尚不清楚。了解 CRPC 中 RT 抵抗的潜在机制可能会突出改善 PCa 患者治疗选择的新靶点。在本研究中，检查了前列腺癌组织样本和前列腺癌细胞中磷酸脂酶 Cε（PLCε）、雄激素受体（AR）和 DNA 依赖性蛋白激酶催化亚基（PKcs）的表达水平，并确定了 PLCε 敲低对 AR 和 DNA 损伤修复（DDR）相关分子的影响。使用基因敲低和药物抑制剂或激活剂评估了 PLCε 与多聚（ADP-核糖）聚合酶 1（PARP1）之间的关联及其各自在辐射抵抗中的作用。使用染色质免疫沉淀测定法来确定 PLCε 对 PARP1 的表观遗传调控作用。进行动物实验以评估在体外观察到的机制是否可以在体内复制。PLCε、AR 和 DNA-PKcs 的表达水平在前列腺癌中显著上调，特别是在 CRPC 中。PLCε 敲低降低了细胞的活力并增加了辐射后的细胞凋亡。此外，PLCε 缺陷通过下调 AR 和 PARP1 阳性反馈环以及辐射后相关下游分子来抑制 DDR 进展。PLCε 耗竭还增加了 PARP1 启动子区域组蛋白 H3 赖氨酸 27 三甲基化的存在，表明 PARP1 基因的甲基化增加，从而导致 PARP1 表达减少。在体内，PLCε 敲低显著增强了辐射对肿瘤生长的影响。综上所述，本研究结果表明，通过下调 AR/PARP1/DNA-PKcs 轴，PLCε 敲低增强了 CRPC 的放射敏感性。
