Division of Endocrinology and Metabolism, Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
Department of Oncology, McMaster University, Hamilton, Ontario, Canada.
Prostate. 2019 Apr;79(5):489-497. doi: 10.1002/pros.23755. Epub 2019 Jan 4.
Radiotherapy (RT) is a key therapeutic modality for prostate cancer (PrCa), but RT resistance necessitates dose-escalation, often causing bladder and rectal toxicity. Aspirin, a prodrug of salicylate (SAL), has been associated with improved RT response in clinical PrCa cases, but the potential mechanism mediating this effect is unknown. SAL activates the metabolic stress sensor AMP-activated protein kinase (AMPK), which inhibits de novo lipogenesis, and protein synthesis via inhibition of Acetyl-CoA Carboxylase (ACC), and the mammalian Target of Rapamycin (mTOR), respectively. RT also activates AMPK through a mechanism distinctly different from SAL. Therefore, combining these two therapies may have synergistic effects on suppressing PrCa. Here, we examined the potential of SAL to enhance the response of human PrCa cells and tumors to RT.
Androgen-insensitive (PC3) and -sensitive (LNCaP) PrCa cells were subjected to proliferation and clonogenic survival assays after treatment with clinically relevant doses of SAL and RT. Balb/c nude mice with PC3 xenografts were fed standard chow diet or chow diet supplemented with 2.5 g/kg salsalate (SAL pro-drug dimer) one week prior to a single dose of 0 or 10 Gy RT. Immunoblotting analysis of signaling events in the DNA repair and AMPK-mTOR pathways and lipogenesis were assessed in cells treated with SAL and RT.
SAL inhibited proliferation and clonogenic survival in PrCa cells and enhanced the inhibition mediated by RT. Salsalate, added to diet, enhanced the anti-tumor effects of RT in PC3 tumor xenografts. RT activated genotoxic stress markers and the activity of mTOR pathway and AMPK and mediated inhibitory phosphorylation of ACC. Interestingly, SAL enhanced the effects of RT on AMPK and ACC but blocked markers of mTOR activation.
Our results show that SAL can enhance RT responses in PrCa. Salsalate is a promising agent to investigate this concept in prospective clinical trials of PrCa in combination with RT.
放射治疗（RT）是前列腺癌（PrCa）的一种重要治疗方式，但 RT 耐药性需要提高剂量，这往往会导致膀胱和直肠毒性。阿司匹林是水杨酸（SAL）的前体药物，已与临床 PrCa 病例中改善 RT 反应相关，但介导这种作用的潜在机制尚不清楚。SAL 激活代谢应激传感器 AMP 激活的蛋白激酶（AMPK），通过抑制乙酰辅酶 A 羧化酶（ACC）和哺乳动物雷帕霉素靶蛋白（mTOR）分别抑制从头脂肪生成和蛋白质合成。RT 通过一种与 SAL 明显不同的机制激活 AMPK。因此，联合这两种治疗方法可能对抑制 PrCa 有协同作用。在这里，我们研究了 SAL 增强人 PrCa 细胞和肿瘤对 RT 反应的潜力。
用临床相关剂量的 SAL 和 RT 处理雄激素不敏感（PC3）和敏感（LNCaP）PrCa 细胞后，进行增殖和克隆存活实验。在给予 0 或 10Gy RT 单次剂量前一周，将携带 PC3 异种移植瘤的 Balb/c 裸鼠用标准饲料或添加 2.5g/kg 水杨酸钠（SAL 前体药物二聚体）的饲料喂养。用 SAL 和 RT 处理细胞后，用免疫印迹分析 DNA 修复和 AMPK-mTOR 通路及脂肪生成的信号事件。
SAL 抑制 PrCa 细胞的增殖和克隆存活，并增强 RT 介导的抑制作用。在 PC3 肿瘤异种移植瘤中，添加到饮食中的水杨酸钠增强了 RT 的抗肿瘤作用。RT 激活了遗传毒性应激标志物和 mTOR 通路的活性以及 AMPK 和 ACC 的抑制性磷酸化。有趣的是，SAL 增强了 RT 对 AMPK 和 ACC 的作用，但阻断了 mTOR 激活的标志物。
我们的结果表明，SAL 可以增强 PrCa 对 RT 的反应。水杨酸钠是一种很有前途的药物，可在 RT 联合治疗前列腺癌的前瞻性临床试验中对此进行研究。
