Purpose

Oxaliplatin is one of the most commonly used chemotherapeutic agents in the treatment of various cancers, including gastric cancer. It has, however, a narrow therapeutic index due to its toxicity and the occurrence of drug resistance. Therefore, there is a pressing need to develop novel therapies to potentiate the efficacy and reduce the toxicity of oxaliplatin. Piperlongumine (PL), an alkaloid isolated from Piper longum L., has recently been identified as a potent agent against cancer cells in vitro and in vivo. In the present study, we investigated whether PL can potentiate the antitumor effect of oxaliplatin in gastric cancer cells.

Methods

Cellular apoptosis and ROS levels were analyzed by flow cytometry. Thioredoxin reductase 1 (TrxR1) activity in gastric cancer cells or tumor tissues was determined using an endpoint insulin reduction assay. Western blotting was used to analyze the expression levels of the indicated proteins. Nude mice xenograft models were used to test the effects of PL and oxaliplatin combinations on gastric cancer cell growth in vivo.

Results

We found that PL significantly enhanced oxaliplatin-induced growth inhibition in both gastric and colon cancer cells. Moreover, we found that PL potentiated the antitumor effect of oxaliplatin by inhibiting TrxR1 activity. PL combined with oxaliplatin markedly suppressed the activity of TrxR1, resulting in the accumulation of ROS and, thereby, DNA damage induction and p38 and JNK signaling pathway activation. Pretreatment with antioxidant N-acetyl-L-cysteine (NAC) significantly abrogated the combined treatment-induced ROS generation, DNA damage and apoptosis. Importantly, we found that activation of the p38 and JNK signaling pathways prompted by PL and oxaliplatin was also reversed by NAC pretreatment. In vivo, we found that PL combined with oxaliplatin significantly suppressed tumor growth in a gastric cancer xenograft model, and effectively reduced the activity of TrxR1 in tumor tissues. Remarkably, we found that PL attenuated body weight loss evoked by oxaliplatin treatment.

Conclusions

Our data support a synergistic effect of PL and oxaliplatin and suggest that application of its combination may be more effective for the treatment of gastric cancer than oxaliplatin alone.

中文翻译：

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Piperlongumine 通过诱导胃癌细胞中的 ROS 增强奥沙利铂的抗肿瘤功效。

 目的

奥沙利铂是治疗各种癌症（包括胃癌）最常用的化疗药物之一。然而，由于其毒性和耐药性的发生，其治疗指数较窄。因此，迫切需要开发新的疗法来增强奥沙利铂的疗效并降低其毒性。 Piperlongumine (PL) 是一种从Piper longum L.中分离出来的生物碱，最近被鉴定为体外和体内抗癌细胞的有效药物。在本研究中，我们研究了 PL 是否可以增强奥沙利铂对胃癌细胞的抗肿瘤作用。

 方法

通过流式细胞术分析细胞凋亡和ROS水平。使用终点胰岛素减少测定法测定胃癌细胞或肿瘤组织中的硫氧还蛋白还原酶 1 (TrxR1) 活性。使用蛋白质印迹分析所示蛋白质的表达水平。使用裸鼠异种移植模型来测试PL和奥沙利铂组合对体内胃癌细胞生长的影响。

 结果

我们发现 PL 显着增强奥沙利铂诱导的胃癌和结肠癌细胞的生长抑制。此外，我们发现PL通过抑制TrxR1活性来增强奥沙利铂的抗肿瘤作用。 PL与奥沙利铂联合显着抑制TrxR1的活性，导致ROS的积累，从而诱导DNA损伤以及p38和JNK信号通路的激活。用抗氧化剂 N-乙酰基-L-半胱氨酸 (NAC) 进行预处理可显着消除联合治疗诱导的 ROS 生成、DNA 损伤和细胞凋亡。重要的是，我们发现 PL 和奥沙利铂促进的 p38 和 JNK 信号通路的激活也被 NAC 预处理逆转。在体内，我们发现PL联合奥沙利铂显着抑制胃癌异种移植模型中的肿瘤生长，并有效降低肿瘤组织中TrxR1的活性。值得注意的是，我们发现 PL 减弱了奥沙利铂治疗引起的体重减轻。

 结论

我们的数据支持 PL 和奥沙利铂的协同作用，并表明其组合应用可能比单独使用奥沙利铂更有效地治疗胃癌。