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骨桥蛋白(osteopontin,OPN)是人体内一种重要的分泌蛋白,在细胞黏附、迁移、机体免疫等作用中发挥重要的生理功能。近年来的研究发现,OPN在恶性肿瘤组织中参与诱导细胞外基质的降解及重构,对肿瘤细胞的侵袭能力有重要调控作用。此外,OPN在肝癌及其他多种肿瘤类型中表达均显著上调,但调控机制尚未完全阐明。该研究从肝癌细胞株中克隆了OPN基因SPP1的启动子序列p SPP1,尝试鉴定肝癌中SPP1的主要调控机制。截断突变体及点突变体分析发现,完整的区域(–24~–17)是p SPP1转录活性所必需的,外源表达AP-1转录因子的c-jun亚基,能够显著提高这一区域的转录活性,然而,c-fos没有这种作用效果。凝胶迁移实验进一步证明AP-1转录因子与p SPP1的直接相互作用。利用实时定量PCR和Western blot还发现,外源表达c-jun能够显著提高内源性OPN的表达水平。以上实验结果揭示,AP-1转录因子介导的转录调控很可能是肝癌细胞OPN表达调控的关键机制,这一研究发现有望为肝癌诊断及治疗提供新的思路。
Osteopontin (OPN) is an important secretory protein in human body and plays an important physiological function in cell adhesion, migration and immune function. In recent years, the study found that OPN in malignant tumor tissue involved in the induction of extracellular matrix degradation and remodeling, invasion of tumor cells have an important regulatory role. In addition, OPN expression in liver cancer and many other types of tumors were significantly increased, but the regulatory mechanism has not been fully elucidated. This study cloned the promoter sequence of OPN gene SPP1, p SPP1, from hepatoma cell lines and tried to identify the main regulatory mechanism of SPP1 in hepatocellular carcinoma. Analysis of truncated mutants and point mutants revealed that the complete region (-24 ~ -17) was required for the transcriptional activity of p SPP1 and exogenous expression of the c-jun subunit of AP-1 transcription factor could significantly increase this region Of transcriptional activity, however, c-fos does not have this effect. Gel-migration experiments further demonstrated the direct interaction of AP-1 transcription factor with pSPP1. Using real-time PCR and Western blot, it was also found that the exogenous expression of c-jun can significantly increase the expression of endogenous OPN. The above experimental results revealed that AP-1 transcription factor-mediated transcriptional regulation is likely to be a key mechanism regulating the expression of OPN in hepatocellular carcinoma cells. This study is expected to provide a new idea for the diagnosis and treatment of liver cancer.