胰腺癌恶性程度高，对化疗药物耐药是预后差的重要原因。胰腺癌的Fas相关死亡域蛋白样白介素-1β转换酶抑制蛋白c-FLIP过表达抑制死亡受体通路关键环节Caspase-8激活，导致对TRAIL耐药。我们前期研究发现，Triptolide对c-FLIP的剪切调控诱导Caspase-8活化，致敏TRAIL耐药胰腺癌细胞凋亡，但机制仍不清楚。酪氨酸激酶Fyn通过调控hnRNP A2/B1，参与下游基因剪切调控。本研究基于前期工作发现，提出Triptolide通过抑制Fyn活性，下调hnRNP A2/B1，参与c-FLIP选择性剪切，激活Caspase-8，最终诱导胰腺癌细胞凋亡的假说。本研究拟从组织细胞学水平，探索Triptolide诱导c-FLIP选择性剪切的信号通路，并通过动物实验在体证实。本研究有望阐明Triptolide突破胰腺癌细胞TRAIL耐受屏障的机制，为胰腺癌的治疗提供新思路。

Pancreatic cancer is the fourth leading cause of cancer-related deaths in the United States with a five year survival of less than 5%. The poor outcome of this disease is due to lack of effective chemotherapeutic options. TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, selectively kills a wide range of cancer cells, while leaving the normal cells unaffected. However, many cancers, including pancreatic cancer, are resistant to TRAIL therapy. TRAIL initiates the extrinsic apoptotic pathway by activation of pro-caspase-8. An important modulator of caspase-8, c-FLIP, plays a key role in resistance to death receptor-mediated apoptosis in many cancer cells. Triptolide, a diterpene triepoxide extracted from the Chinese herb Tripterygium wilfordii decreases viability of pancreatic cancer cells in vitro and reduce growth and metastases of tumors in vivo. Previous data from our group has shown that a combination of low doses of TRAIL and triptolide induces significant pancreatic cancer cell death compared with either treatment alone. We therefore evaluated the effect of triptolide on c-FLIP and found that triptolide regulates c-FLIP splicing in pancreatic cancer cells. This down-regulation of c-FLIP alone allowed TRAIL to induce caspase-8 activation. However, the underlying mechanism of c-FLIP splicing by triptolide is still unclear. Our previous NSFC grant revealed that non-receptor tyrosine kinase Fyn regulates RNA-binding protein hnRNP A2/B1 expression, which further participates in Bcl-X alternative splicing. Others have shown that hnRNP A2/B1 also regulates c-FLIP splicing and triptolide down-regulates tyrosine kinase JAK and Bcr/Abl activity. Since tyrosine kinases have similar structural domains, we speculate that triptolide also regulates Fyn activity and in turn, regulates c-FLIP splicing. On the basis of our previous work, we hypothesized that triptolide modulates c-FLIP alternative splicing by down-regulation of non-receptor tyrosine kinase Fyn and RNA binding protein hnRNP A2/B1. The down-regulation of c-FLIP splicing sensitizes TRAIL resistance pancreatic cancer cells apoptosis by activating caspase-8. Since TRAIL is already in use against several cancers, understanding the mechanism by which triptolide sensitizes pancreatic cancer cells to TRAIL may result in a novel therapeutic strategy against pancreatic cancer.