SMYD2表观遗传调控鞘脂代谢重编程介导胰腺癌细胞焦亡及耐药的机制研究

Pyroptosis has been shown to play an important role in determining cancer chemoresistance. However, the underlying mechanism behind this still remains unclear. Herein, we showed that expression of methyltransferase SMYD2 and sphingolipid metabolic enzyme ASAH2 was up-regulated in chemoresistant pancreatic cancer cell lines as compared to sensitive cells, while their expression was positively correlated with poor prognosis in pancreatic cancer patients. Mechanistically, we showed that SMYD2 expression modulated the level of histone H3K4me2 modification in order to regulate ASAH2 expression. Importantly, depleting SMYD2or ASAH2 expression significantly promoted the pyroptosis of chemoresistant cancer cells and rescued their sensitivity to gemcitabine, indicating that SMYD2 may regulate sphingolipid metabolic reprogramming to affect cancer cell pyroptosis. Indeed, our preliminary experiments showed that overexpression of ASAH2 in cancer cells up-regulatedthe level of its metabolite sphingosine-1-phosphate, which may then affect the pyroptosis-related NLRP3 inflammatory pathway. We therefore propose that this is a new regulatory mechanism of pyroptosis has yet to be discovered. In this study, we will employa range of molecular biology experiments, including metabolomics technique, patient-derived organoids, and orthotopic animal models, in order to revealthe molecular mechanism of SMYD2-ASAH2 mediated sphingolipid metabolic reprogramming, and to explore its function in regulating cancer cell pyroptosis. Overall, this study will provide new molecular targets for an improved pancreatic cancer treatment.

新近研究指出肿瘤细胞焦亡与化疗效果相关，但其机制未明。我们发现甲基转移酶SMYD2及鞘脂代谢酶ASAH2的表达在胰腺癌化疗耐药株上调，并且其高表达与患者的不良预后正相关。进一步实验证实SMYD2调控组蛋白H3K4me2修饰水平来调节ASAH2表达。敲除SMYD2或ASAH2的表达，促进了耐药细胞焦亡，并逆转癌细胞耐药。我们提出SMYD2介导鞘脂代谢重编程调控癌细胞焦亡的新机制，预实验也显示过表达ASAH2细胞上调其代谢产物并影响焦亡相关NLRP3通路。我们推测其为细胞焦亡有待发现新调控机制。本课题拟釆用代谢组学、类器官和我们建立的胰腺癌原位模型等揭示SMYD2表观遗传调控ASAH2介导鞘脂代谢的分子机理，阐述其调控癌细胞焦亡的功能，为耐药性治疗提供新的分子靶点。

癌细胞经常对化疗诱导的p53-caspase-3依赖性细胞凋亡（apoptosis）产生抗性，这表明了靶向其他非凋亡相关细胞死亡，例如细胞焦亡（pyroptosis）的重要性。在此，我们确定ASAH2驱动的鞘脂代谢重编程可介导了胰腺癌的细胞焦亡。临床上，ASAH2高表达与患者的不良预后及对化疗的不良反应正相关。耐药细胞对化疗药物诱导的细胞焦亡无反应，主要原因是耐药细胞高表达ASAH2。从机制上讲，β5-整合素通过Src-STAT3信号上调了中性神经酰胺酶ASAH2的表达，从而阻止了化学疗药物诱导的细胞焦亡。最后，神经酰胺抑制剂的应用挽救了化疗耐药的原位胰腺肿瘤对吉西他滨的反应，同时通过重新激活焦亡延长了小鼠的生存，这表明靶向焦亡可能是化疗耐药患者的有效治疗策略。我们的研究表明，靶向β5-整合素-Src-STAT3-ASAH2驱动的鞘脂代谢重编程可通过激活细胞焦亡克服癌症的化学耐药性。我们的数据表明，联用化疗药物和神经酰胺酶抑制剂，可以通过增加细胞焦亡来克服胰腺癌的化学耐药性。

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