Interventional Cancer Institute of Integrative Medicine, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.
Carcinogenesis. 2011 May;32(5):667-75. doi: 10.1093/carcin/bgr016. Epub 2011 Feb 3.
Cross-drug resistance in multidrug-resistant (MDR) cells, which overexpress P-glycoprotein (P-gp) encoded by the MDR1 gene, is a major impediment to successful chemotherapy for colorectal cancer. In the present study, drug-sensitive HCT8 and multidrug-resistant (vincristine, VCR) HCT8/V colorectal cancer cell lines were used to examine the role of c-Jun NH2-Terminal Kinase- (JNK) signaling pathway in P-gp-mediated MDR associated with Cyclo-oxygenase-2 (COX-2). The results showed that SP600125, a JNK inhibitor, and NS-398, a COX-2 inhibitor, significantly reduced the degree of MDR in HCT8/V cells. This was accompanied by a significant decrease in gene level of MDR1 and protein level of P-gp in HCT8/V cells. Notably, addition of a JNK inhibitor had no significant effect on the expression of COX-2 in both HCT8 and HCT8/V cells. Interestingly, inhibition of COX-2 activity by a chemical inhibitor or its silence by small interfering RNA significantly decreased the level of phosphorylated c-Jun at Ser63/73 in HCT8/V cells. In contrast, upregulation of COX-2 significantly increased the levels of P-gp and p-c-Jun at Ser63/73 in HCT8 cells, but not in HCT8/V cells. Moreover, the intracellular vincristine accumulation in HCT8/V cells significantly increased after inhibiting COX-2 and JNK activity. Taken together, our study has provided the first direct evidence that COX-2 contributes to P-gp-mediated multidrug resistance via phosphorylation of c-Jun at Ser63/73 in colorectal cancer cells.
多药耐药（MDR）细胞中的交叉耐药性是结直肠癌化疗成功的主要障碍，这些细胞过度表达由 MDR1 基因编码的 P-糖蛋白（P-gp）。在本研究中，使用药物敏感的 HCT8 和多药耐药（长春新碱，VCR）HCT8/V 结直肠癌细胞系来研究 c-Jun NH2-末端激酶-（JNK）信号通路在与环氧化酶-2（COX-2）相关的 P-gp 介导的多药耐药中的作用。结果表明，JNK 抑制剂 SP600125 和 COX-2 抑制剂 NS-398 显著降低了 HCT8/V 细胞的多药耐药程度。这伴随着 HCT8/V 细胞中 MDR1 基因水平和 P-gp 蛋白水平的显著降低。值得注意的是，JNK 抑制剂的添加对 HCT8 和 HCT8/V 细胞中 COX-2 的表达没有显著影响。有趣的是，化学抑制剂抑制 COX-2 活性或小干扰 RNA 沉默 COX-2 显著降低了 HCT8/V 细胞中磷酸化 c-Jun 在 Ser63/73 的水平。相比之下，COX-2 的上调显著增加了 HCT8 细胞中 P-gp 和 p-c-Jun 在 Ser63/73 的水平，但在 HCT8/V 细胞中没有。此外，抑制 COX-2 和 JNK 活性后，HCT8/V 细胞内长春新碱的积累明显增加。总之，我们的研究首次直接证明 COX-2 通过在结直肠癌细胞中磷酸化 c-Jun 在 Ser63/73 来促进 P-gp 介导的多药耐药。
