酪氨酸代谢调控胃肠间质瘤伊马替尼耐药的机制研究

Treatment with the KIT and PDGFR inhibitor imatinib can control advanced disease in the most of GIST patients and has gained wide recognition as the first-line therapy. But, the beneficial effect is not durable.Imatinib acquired resistance is a major problem for advanced GIST patients in general. In our preliminary studies, the imatinib-resistant GIST models were established. We performed a genome-wide transcriptome analysis and observed that tyrosine metabolism was specifically initiated in imatinib-resistant GIST cells. Acetyl-CoA which was produced by tyrosine metabolism can acetylate RACK1. And acetylation of RACK1 can roll and phosphorylate NRF2. The NRF2 can upregulation the expression of YAP1 in the nucleus. Importantly, overexpression of YAP1 can lead to the activation of downstream pathway of c-kit. Accordingly, we hypothesized a new mechanism for imatinib resistance: Imatinib secondary resistance by tyrosine metabolism in the gastrointestinal stromal tumors is mediated by RACK1-Nrf2-YAP1 pathway..We attempt to reveal the critical role of tyrosine metabolism in acquisition of imatinib resistance in GIST both in vitro and in vivo. Utilizing promoter reporter system, small RNA interference and ChIP-PCR, we aim to clarify the epigenetic mechanism involved in tyrosine metabolism-mediated acquired imatinib resistance via the RACK1-Nrf2-YAP1 axis. Therefore, further support of this program would provide a new insight into the process of acquired imatinib resisrance and experimental evidence for improvement of GIST prognosis.

伊马替尼是晚期胃肠间质瘤（gastrointestinal stromal tumors，GIST）治疗的首选，然而继发性耐药成为临床治疗的一大难点。我们的前期研究证实伊马替尼继发耐药的GIST细胞发生了代谢重编程，即特异性的开启了酪氨酸代谢途径；酪氨酸代谢产生的乙酰辅酶A能乙酰化修饰RACK1，从而召集并磷酸化NRF2，促其入核上调YAP1的基因表达。重要的是，YAP1基因的上调能导致c-kit下游通路的再激活。据此，我们提出伊马替尼耐药的新机制：酪氨酸代谢通过调控RACK1-Nrf2-YAP1通路介导GIST伊马替尼继发耐药。为验证该机制，本项目拟利用伊马替尼耐药GIST体内外模型以及临床标本等，采用启动子报告基因、RNAi干扰、染色质免疫共沉淀等方法，从体内外两方面证实酪氨酸代谢途径参与了GIST获得伊马替尼耐药的过程，为有效改善伊马替尼耐药GIST的临床预后提供新策略和新方法。

SDH缺失突变与原发耐药的野生型胃肠间质瘤的发生密切相关，但确切的机制仍不清楚。我们发现在GIST细胞系中SDHB的缺失能增加ZNF148的表达并导致琥珀酸的聚集。同时，ZNF148的Ser306位点能被ERK磷酸化并导致ZNF148与FOXM1的结合。通过这个促进子复合物的形成，ZNF148通过组蛋白H3乙酰化和FOXM1介导的Snail转录，最终促进细胞的侵袭和肿瘤的生长。临床分析显示SDHB的缺失与ZNF148表达水平的提升密切相关，ZNF148-S306磷酸化水平与GIST患者预后差密切相关。这些发现揭示了SDH缺失突变GIST患者侵袭性增加的原因可能通过FOXM1调节相关基因的转录。