潜在抑癌基因CMTM7在食管癌中的分子机制和临床应用研究

CKLF-like MARVEL transmembrane domain-containing family (CMTM) is a novel gene family which was firstly reported by Peking University. Previous studies indicated that CMTM7 is a novel candidate tumor suppressor gene. CMTM7 is broadly expressed in human normal tissues and esophageal epithelial cell lines, however it is silenced or downregulated in esophageal carcinoma cell lines and primary tumors due to its methylation and high frequent loss of heterozygosity; the expression of CMTM7 is closely correlated with TNM of esophageal carcinoma; ectopic CMTM7 expression in esophageal carcinoma cell lines leads to the inhibition of proliferation and motility both in vitro and in vivo; mouse Cmtm7 interacted with tumor suppressor gene Blnk. Based on the result of previous studies, this project will study the interacted proteins and signaling pathway of CMTM7, and identify molecular mechanism of CMTM7 in esophageal carcinoma. Meanwhile, we will analyse the genetic and epigenetic characteristics of serum CMTM7, and evaluate the potential value of serum CMTM7 detection in early diagnosis and prognosis of esophageal carcinoma.

CMTM(CKLF-like MARVEL transmembrane domain containing family)是北京大学在国际上首次报道的一个新基因家族。前期研究提示CMTM7是食管癌的潜在抑癌基因。CMTM7在人正常组织及食管上皮细胞系中广泛表达，但在食管癌来源的细胞系和原发组织中表达下调或缺失，与其较高频率的甲基化修饰和杂合性缺失密切相关；CMTM7在食管癌组织中表达下调与TNM分期相关；体内和体外功能试验提示CMTM7可抑制食管癌细胞的增殖和迁移；小鼠Cmtm7与抑癌基因Blnk存在相互作用。因此，本项目将在前期研究的基础上，鉴定CMTM7的相互作用蛋白，分析CMTM7作用的信号转导通路，明确抑癌的分子机制。同时，分析食管癌患者血清DNA中CMTM7的遗传学和表观遗传学特点，并探讨血清CMTM7在食管癌早期诊断和判断预后中的价值。

CMTM(CKLF-like MARVEL transmembrane domain containing family)是北京大学在国际上首次报道的一个新基因家族。前期研究提示CMTM7 是食管癌的潜在抑癌基因，但目前对CMTM7 的抑癌机制尚不明确，其临床应用也有待研究。本项目研究发现BLNK与内源性CMTM7有部分共定位，免疫共沉淀结果显示CMTM7与BLNK可以共沉淀，但共沉淀的BLNK分子量比实际分子量偏大，推测CMTM7可能与多个分子同时发生相互作用。BLNK的表达在食管癌组织中明显下调，食管癌患者血清中BLNK的微卫星不稳定或杂合性缺失与食管癌发生相关，可能也会影响其与CMTM7的相互作用，有必要对BLNK在食管癌中的作用进行更深入的研究。抑癌分子机制研究表明抑制CMTM7内源性表达可以抑制细胞的增殖和迁移。敲减CMTM7可以抑制EGFR内吞，促进EGFR-AKT信号通路的活化，并且CMTM7的抑癌功能依赖于AKT信号通路。CMTM7与早期内体膜上Rab5和EEA1微区共定位，可通过抑制Rab5的活化延迟早期内体的融合。临床应用研究显示CMTM7在食管癌患者血清游离DNA检测中发生遗传学改变（微卫星不稳定和/或杂合性缺失）的比例高于正常人血清游离DNA（43.3% vs 23%）。本项目的研究结果将推动四次跨膜蛋白及食管癌发病机理和临床应用的研究，具有重要的理论意义和潜在的应用价值。