BET蛋白家族溴结构域抑制剂治疗恶性胰腺导管内乳头状黏液瘤及相关耐药机制的研究

IPMNs are a heterogeneous disease with activating mutations in GNAS or KRAS occurring in >90% of tumors. Tumors with mutations in GNAS, KRAS, and both GNAS and KRAS are found in approximately equal frequency, however, the mechanisms by which these distinct genetic backgrounds drives the disease are not understood. The BET family of chromatin adaptors has recently been implicated in pancreatic cancers. BET proteins (BRD2, BRD3, and BRD4) have two bromodomains (BD1 and BD2) that mediate interaction with acetylated lysines on target proteins to regulate gene expression. The aim of this study was to define the contribution of BET proteins to IPMNs. .Growth of the low passage patient derived IPMN cell line IP25 (KRASG12D;GNASWT) was highly sensitive to the pan-BET bromodomain inhibitor CPI203, with a GI50 < 0.2 M. In contrast, low passage 950 cell(KRASG12D;GNASR201H) were largely refractory to CPI203, exhibiting growth reduction of less than 40% at concentrations as high as 12.8 M.Evaluation of key BET-dependent pathways demonstrated reduced expression of MYC (50%), IL6 (95%), and SHH (95%) in IP25 cells treated with CPI203. These results define a prominent role for BET in growth of GNASWT IPMNs, and suggest unique GNAS effector pathways with key roles in IPMN.

胰腺导管内乳头状粘液性肿瘤（IPMNs）是临床较少见的胰腺外分泌肿瘤，为胰腺癌癌前病变之一。主要基因突变背景为GNAS和或KRAS激活性突变，存在于> 90％的IPMNs中。但GNAS或KRAS突变调控IPMNs疾病发生发展的机制不明。组蛋白赖氨酸乙酰化的识别是组蛋白乙酰化参与表观遗传调控的关键步骤，Bromodomain and extra-terminal (BET)蛋白家族通过识别结合组蛋白乙酰化赖氨酸残基调控基因表达。表观基因组靶向药物BET蛋白抑制剂显著抑制患者来源低传代数的KRASG12D;GNASWT型IPMN细胞IP25细胞活性（GI 50 <0.2μM），相关机制与BET调控SHH、GLI、MYC等关键因子有关。而BET抑制剂对KRASMT GNASMT型950细胞生长抑制率仅40％，提示GNAS突变诱导IPMN细胞的BET抑制剂耐药性，本研究将进一步探讨相关机制。

胰腺导管内乳头状粘液性肿瘤（IPMNs）是临床较少见的胰腺外分泌肿瘤，为胰腺癌癌前病变之一。主要基因突变背景为GNAS和或KRAS激活性突变，存在于多余90％的IPMNs中。组蛋白赖氨酸乙酰化的识别是组蛋白乙酰化参与表观遗传调控的关键步骤，Bromodomain and extra-terminal(BET)蛋白家族通过高度相似的串联溴结构域（Bromodomai,BD)1,2(BD1,BD2)识别结合组蛋白乙酰化赖氨酸残基调控基因表达。人胰腺组织中表达BET蛋白家族成员中的BRD2,BRD3及BRD4。本研究发现BET蛋白家族成员BRD2、BRD3及BRD4在不同基因背景的IPMN中表达，而BET蛋白溴结构域活性抑制剂可显著抑制患者来源低传代数的KRAS突变GNAS野生型 IPMN细胞IP25细胞活性（GI50<0.2μM）且主要通过抑制BD1活性。慢病毒分别稳定干扰BET蛋白家族成员提示IP25细胞活性受BRD2调控更为显著。其相关机制与BET调控SHH、GLI、MYC及抑制细胞S周期相关。提示BET 蛋白活性抑制剂可作为KRAS突变GNAS野生型IPMNs潜在治疗靶点。以上研究结果已整理成论文一篇即将投稿。另在2019美国胰腺病年会中发表壁报一篇，以通讯作者发表中文核心期刊一篇，参与作者发表SCI论著一篇，同时协助培养4名研究生。

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