MUC1入核下调DNAJB6激活AKT信号通路在食管鳞癌恶性生物学行为中的作用及机制研究

The esophageal squamous cell carcinoma(ESCC) is one of the most common digestive tumor in China. As a highly aggressive malignant tumor, the prognosis is not satisfying. Previous studies by applicant found that up-regulation of MUC1 was related to lymph node metastasis and recurrence in patients with esophageal squamous cell carcinoma, and blocking the nucleus accumluation of MUC1 could suppress the malignant biological behavior and the activation of AKT pathway of ESCC cell lines. Subsequently, we confirmed the close relationship between the nucleus accumluation of MUC1 and the down-regulation of DNAJB6 and AKT signaling pathway. At the same time, we found that transcription factor HSF-1 plays an important role in the down-regulation of DNA JB6 induced by MUC1. Considering DNAJB6 as one of the candidate tumor suppressor genes in recent years, the applicant assumed that MUC1 could down-regulate the expression of DNA JB6 through HSF-1 in ESCC, thereby activating Akt signaling pathway to promote malignant biological behavior of ESCC cells. This study intends to use downstream key heat shock protein DNAJB6 as a breakthrough point to verify the role of DNAJB6 in MUC1-induced invasive malignant biological behavior and its impact on WNT signaling pathway in ESCC, and unveill the MUC1 nuclear regulatory DNAJB6 molecules Mechanism to further elucidate the specific molecular mechanism of MUC1 promoting lymph node metastasis of esophageal squamous cell carcinoma. This study intends to verify the role of DNAJB6 in MUC1-induced malignant biological behavior and its impact on AKT signaling pathway by various methods, and to explore the molecular mechanism of down-regulation of DNAJB6 by MUC1-HSF-1. Which could elucidate the mechanism of activation of AKT pathway to promote malignant biological behavior of esophageal squamous cell carcinoma by MUC1 nucleus accumulation and provide a theoretical basis for the treatment of esophageal squamous cell carcinoma targeting MUC1.

食管鳞癌作为一种高度恶性肿瘤，多数患者预后不佳。申请者前期研究发现食管鳞癌中MUC1的高表达与淋巴结转移密切相关，并证实阻断MUC1入核能够抑制食管鳞癌细胞的恶性生物学行为及AKT信号通路的激活；随后在食管鳞癌细胞中证实了MUC1入核与抑癌基因DNAJB6下调及AKT信号通路的密切关系，并发现转录因子HSF-1在MUC1诱导的DNAJB6下调中的重要作用，因此申请者推测在食管鳞癌中MUC1入核能够通过HSF-1下调DNAJB6的表达, 进而激活Akt信号通路来促进食管鳞癌的恶性生物学行为。本研究拟通过多种方法验证DNAJB6在MUC1所诱导的食管鳞癌恶性生物学行为及对Akt信号通路的影响，并重点探索MUC1入核通过HSF-1调控DNAJB6的分子机制，以期帮助我们进一步完善MUC1入核在驱动食管鳞癌侵袭转移过程中的基因调控网络，为食管鳞癌以阻断MUC1入核为方向的靶向治疗提供理论基础。

食管鳞癌作为一种高侵袭性恶性肿瘤，多数患者预后不佳。因此探索促进食管鳞癌恶性生物学行为的驱动基因有着十分重要的意义。研究者先前的工作证实MUC1在食管鳞癌的恶性生物学行为尤其是淋巴结转移过程中起着重要作用，但其具体分子机制仍然需要进一步探索。在本项目中，研究者通过对食管鳞癌组织标本的检测证实了食管鳞癌中存在MUC1与DNAJB6的负相关表达，且二者的表达均与食管鳞癌患者的淋巴结转移及复发密切相关。随后通过构建过表达MUC1食管鳞癌细胞株发现上调MUC1的表达能够促进食管鳞癌细胞的恶性生物学行为、激活AKT信号通路并能下调DNAJB6的表达水平；而应用Go-203特异性阻断MUC1则能够抑制食管鳞癌细胞的恶性生物学行为、抑制AKT信号通路的激活并能恢复DNAJB6的表达水平；另外通过在MUC1过表达食管鳞癌细胞株的基础上再次上调DNAJB6的表达则同样能够抑制食管鳞癌细胞的恶性生物学行为并抑制AKT信号通路的激活，以上结果证实在食管鳞癌中MUC1可以通过抑制DNAJB6的表达激活AKT信号通路并促进其恶性生物学行为。在此研究结果基础上，研究者对MUC1调控DNAJB6表达的分子机制进行了进一步探索，首先发现过表达MUC1能够促进转录因子HSF-1的磷酸化，而应用Go-203特异性阻断MUC1则能够抑制上述过程，而进一应用AKT信号通路抑制剂MK2206或HSF-1抑制剂KRIBB11均能够抑制HSF1的磷酸化并能够上调DNAJB6的转录表达；并且进一步通过ChIP实验证实过表达MUC1能够促进HSF1与DNAJB6启动子的结合，而应用MUC1特异性阻断剂Go-203、AKT信号通路抑制剂MK2206或HSF1抑制剂KRIBB11均能够抑制上述过程，以上结果证实了AKT-HSF1信号通路在MUC1下调DNAJB6转录表达过程中的作用。本课题研究证实DNAJB6作为MUC1调控的下游关键基因在MUC1在食管鳞癌中通过激活AKT信号通路促进其恶性生物学行为中的重要作用，阐明了MUC1通过AKT-HSF1信号通路下调DNAJB6转录表达的分子机制，进一步揭示了MUC1在促进食管鳞癌发生发展过程中的网络调控机制，为食管鳞癌的靶向治疗提供了理论基础。