辣椒碱通过下调SCD-1阻断细胞自噬在其增敏顺铂杀伤食管癌细胞中的作用和机制研究

Chemotherapy in esophageal cancer therapy has an important position. Due to the continuously usage of chemotherapeutics, a large number of esophageal cancer cells developed drug-resistance, which was an important cause of chemotherapy failure. Our team have demonstrated that capsaicin could sensitize esophageal cancer cells to cisplatin by blocking autophagy in preliminary study. The transcriptome sequencing result showed that capsaicin downregulated the transcriptional level of stearoyl-coenzyme A desaturase 1(SCD-1) significantly. Our western data demonstrated capsaicin decreased the transported frequency of SERBP to the nucleus, an important transcription factor for fatty acid biosynthesis metabolism. These information indicated that capsaicin may inhibited the transcriptional level of SCD-1 through SREBP, while the underlying mechanism was unclear. To proceed the further investigation, we construct the SCD-1 report-gene recombinant plasmid and genetic recombination cells with stably over-expressed SCD-1 or SREBP to explore whether SREBP played a crucial role in transcriptional inhibition of SCD-1 by capsaicin. This study was profound for us to explore the molecular mechanism of capsaicin sensitized drug-resistant cells to cisplatin and provides important theoretical fundation for designing new sensitizer for chemotherapeutics.

化疗在食管癌治疗中具有重要地位，但由于药物连续、大量的使用导致食管癌细胞产生耐药性，是化疗失败的一个重要原因。课题组前期研究发现辣椒碱能通过阻断自噬显著增强顺铂对食管癌耐药细胞的杀伤作用，转录组测序结果显示，辣椒碱处理后细胞硬脂酰辅酶A去饱和酶（SCD-1）的转录水平明显下调，western结果暗示辣椒碱可能是通过SREBP下调SCD-1，但具体分子机制目前仍不清楚。鉴于此，拟在前期研究基础上，构建SCD-1报告基因重组质粒、过表达SCD-1及SREBP稳转细胞，体内体外探讨辣椒碱是否通过SREBP下调SCD-1 mRNA水平从而阻断自噬增敏顺铂。这不但有助于我们理解辣椒碱增敏顺铂杀伤食管癌耐药细胞的分子机制，而且可为设计新的化疗药物增敏剂提供重要的理论依据。

食管癌一种恶性程度高，预后极差的恶性肿瘤，我国食管癌死亡人数居世界之最。食管癌仍是严重威胁我国居民健康的恶性肿瘤之一，术后化疗在食管癌的综合治疗中占据着举足轻重的地位，但食管癌耐药问题严重限制了化疗在食管癌临床治疗中的应用。在本研究中，我们发现辣椒碱这一种天然的化合物，可以通过阻断细胞自噬有效增敏顺铂对耐药食管癌细胞的杀伤作用，在体内和体外均能抑制食管癌细胞的增殖，并诱导细胞产生凋亡。进一步研究分子机制，我们发现辣椒碱（CAP）处理后，食管癌细胞的硬脂硬脂酰辅酶a去饱和酶1（SCD-1）的转录水平被明显抑制，从而打破细胞内脂代谢平衡，使细胞内磷脂酰胆碱含量下降，磷脂酰乙醇胺和磷脂酰丝氨酸的含量明显上升。导致自噬小体与溶酶体无法融合，阻断细胞自噬。SCD-1转录水平被抑制是由于其转录因子固醇调节元件结合蛋白（SREBP）入核减少，该过程由固醇调节元件结合蛋白裂解激活蛋白（SCAP）介导。我们发现CAP处理后SCAP蛋白量明显减少，这可能是CAP阻断细胞自噬增敏顺铂的关键，但这一机制仍需进一步探索。