Zhang Xiao-Dan, Xie Jian-Jun, Liao Lian-Di, Long Lin, Xie Yang-Min, Li En-Min, Xu Li-Yan
The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Medical College of Shantou University, Shantou 514041, Guangdong, P.R. China; Institute of Oncologic Pathology, Medical College of Shantou University, Shantou 514041, Guangdong, P.R. China.
The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Medical College of Shantou University, Shantou 514041, Guangdong, P.R. China; Department of Biochemistry and Molecular Biology, Medical College of Shantou University, Shantou 514041, Guangdong, P.R. China.
PLoS One. 2015 Apr 27;10(4):e0124680. doi: 10.1371/journal.pone.0124680. eCollection 2015.
The membrane-cytoskeleton link organizer ezrin may be the most "dramatic" tumor marker, being strongly over-expressed in nearly one-third of human malignancies. However, the molecular mechanisms of aberrant ezrin expression still need to be clarified. Ezrin, encoded by the VIL2 gene, has two transcript variants that differ in the transcriptional start site (TSS): V1 and V2. Both V1 and V2 encode the same protein. Here, we found that 12-O-tetradecanoylphorbol-13-acetate (TPA) induced over-expression of human VIL2 in esophageal squamous cell carcinoma (ESCC) cells. Furthermore, VIL2 V1 but not V2 was up-regulated after TPA stimulation in a time-dependent manner. AP-1 and Sp1 binding sites within the promoter region of VIL2 V1 acted not only as basal transcriptional elements but also as a composite TPA-responsive element (TRE) for the transcription of VIL2 V1. TPA stimulation enhanced c-Jun and Sp1 binding to the TRE via activation of the ERK1/2 pathway and increased protein levels of c-Jun, c-Fos, and Sp1, resulting in over-expression of VIL2 V1, whereas the MEK1/2 inhibitor U0126 blocked these events. Finally, we showed that TPA promoted the migration of ESCC cells whereas MEK1/2 inhibitor or ezrin silencing could partially inverse this alteration. Taken together, these results suggest that TPA is able to induce VIL2 V1 over-expression in ESCC cells by activating MEK/ERK1/2 signaling and increasing binding of Sp1 and c-Jun to the TRE of the VIL2 V1 promoter, and that VIL2 is an important TPA-induced effector.
膜细胞骨架连接组织者埃兹蛋白可能是最“显著”的肿瘤标志物，在近三分之一的人类恶性肿瘤中强烈过表达。然而，埃兹蛋白异常表达的分子机制仍有待阐明。埃兹蛋白由VIL2基因编码，有两种转录变体，其转录起始位点（TSS）不同：V1和V2。V1和V2编码相同的蛋白质。在此，我们发现12 - O - 十四酰佛波醇 - 13 - 乙酸酯（TPA）诱导人VIL2在食管鳞状细胞癌（ESCC）细胞中过表达。此外，TPA刺激后，VIL2 V1而非V2以时间依赖性方式上调。VIL2 V1启动子区域内的AP - 1和Sp1结合位点不仅作为基础转录元件，还作为VIL2 V1转录的复合TPA反应元件（TRE）。TPA刺激通过激活ERK1/2途径增强c - Jun和Sp1与TRE的结合，并增加c - Jun、c - Fos和Sp1的蛋白质水平，导致VIL2 V1过表达，而MEK1/2抑制剂U0126可阻断这些事件。最后，我们表明TPA促进ESCC细胞迁移，而MEK1/2抑制剂或埃兹蛋白沉默可部分逆转这种改变。综上所述，这些结果表明TPA能够通过激活MEK/ERK1/2信号并增加Sp1和c - Jun与VIL2 V1启动子TRE的结合来诱导ESCC细胞中VIL2 V1过表达，并且VIL2是TPA诱导的重要效应分子。
