Microwave hyperthermia enhances radiosensitization by decreasing DNA repair efficiency and inducing oxidative stress in PC3 prostatic adenocarcinoma cells

Radiotherapy (RT) is the primary treatment for prostate cancer (PCa); however, the emergence of castration-resistant prostate cancer (CRPC) often leads to treatment failure and cancer-related deaths. In this study, we aimed to explore the use of microwave hyperthermia (MW-HT) to sensitize PCa to RT and investigate the underlying molecular mechanisms. We developed a dedicated MW-HT heating setup, created an <i>in vitro</i> and <i>in vivo</i> MW-HT + RT treatment model for CRPC. We evaluated PC3 cell proliferation using CCK-8, colony experiments, DAPI staining, comet assay and ROS detection method. We also monitored nude mouse models of PCa during treatment, measured tumor weight, and calculated the tumor inhibition rate. Western blotting was used to detect DNA damage repair protein expression in PC3 cells and transplanted tumors. Compared to control, PC3 cell survival and clone formation rates decreased in RT + MW-HT group, demonstrating significant increase in apoptosis, ROS levels, and DNA damage. Lower tumor volumes and weights were observed in treatment groups. Ki-67 expression level was reduced in all treatment groups, with significant decrease in RT + MW-HT groups. The most significant apoptosis induction was confirmed in RT + MW-HT group by TUNEL staining. Protein expression levels of DNA-PKcs, ATM, ATR, and P53/P21 signaling pathways significantly decreased in RT + MW-HT groups. MW-HT + RT treatment significantly inhibited DNA damage repair by downregulating DNA-PKcs, ATM, ATR, and P53/P21 signaling pathways, leading to increased ROS levels, aggravate DNA damage, apoptosis, and necrosis in PC3 cells, a well-established model of CRPC.

放射治疗（Radiotherapy, RT）是前列腺癌（prostate cancer, PCa）的首选治疗方案，但去势抵抗性前列腺癌（castration-resistant prostate cancer, CRPC）的发生常引发治疗失败与肿瘤相关性死亡。本研究旨在探讨微波热疗（microwave hyperthermia, MW-HT）对PCa的放射治疗增敏效应，并解析其潜在分子机制。我们搭建了专用的MW-HT加热装置，构建了针对CRPC的体外（in vitro）与体内（in vivo）MW-HT联合RT治疗模型。采用CCK-8法、集落形成实验、DAPI染色、彗星实验及活性氧（reactive oxygen species, ROS）检测法评估PC3细胞的增殖情况；同时监测PCa裸鼠模型的治疗进程，称量瘤重并计算肿瘤抑制率。通过蛋白质免疫印迹（Western blotting）检测PC3细胞及移植瘤中的DNA损伤修复蛋白表达水平。
与对照组相比，RT联合MW-HT组的PC3细胞存活率与集落形成率均下降，细胞凋亡率、ROS水平及DNA损伤程度均显著升高。各治疗组的肿瘤体积与瘤重均更低。所有治疗组的Ki-67抗原表达水平均下调，其中RT联合MW-HT组的下调幅度最为显著。原位末端转移酶标记（TUNEL）染色证实，RT联合MW-HT组的细胞凋亡诱导效应最为显著。RT联合MW-HT组的DNA依赖蛋白激酶催化亚基（DNA-PKcs）、毛细血管扩张性共济失调突变激酶（ATM）、共济失调毛细血管扩张症和Rad3相关激酶（ATR）及P53/P21信号通路的蛋白表达水平均显著下调。
MW-HT联合RT治疗可通过下调DNA-PKcs、ATM、ATR及P53/P21信号通路，显著抑制DNA损伤修复过程，进而升高ROS水平，在作为经典CRPC细胞模型的PC3细胞中加重DNA损伤、凋亡及坏死。