EVALUATION OF GRADE OF MALIGNANCY AND ITS CLINICAL USE ON THE BASIS OF SFRP METHYLATION IN ORAL SQUAMOUS CELL CARCINOMA

虽然APC、CTNNB1(β-catenin)和AXIN1基因突变在口腔鳞状细胞癌中很少见，但Wnt信号通路的激活被认为在口腔癌的发生中起着重要作用。在本研究中，我们研究了Wnt信号与口腔鳞状细胞癌分泌型卷曲相关蛋白(SFRP)基因表观遗传学改变的关系。我们经常在口腔鳞癌细胞系中检测到β-连环素的膜定位丢失及其胞浆或胞核聚集，尽管这些细胞系没有发现β或CTNNB1(钙粘附素)突变，也没有CDH1(E-钙粘附素)甲基化。相反，我们在一组口腔鳞癌细胞系以及44例口腔鳞癌患者的原发肿瘤标本中经常检测到SFRP1(7/17，41%)、SFRP2(16/17，94%)和SFRP5(14/17，82%)的甲基化(SFRP1，10/42，24%；SFRP2，16/44，36%；SFRP5，7/43，16%)。我们还观察到口腔鳞状细胞癌细胞株表达各种Wnt配体，并且异位表达SFRPs抑制了癌细胞的增殖。我们的结果证实了口腔鳞状细胞癌中SFRP基因频繁的甲基化和沉默，并提示它们的功能丧失导致了Wnt信号的激活，从而导致了口腔鳞癌的细胞增殖。

Although mutations of APC, CTNNB1 (β-catenin) and AXIN1 are rare in oral squamous cell carcinoma (OSCC), activation of the Wnt signaling pathway is thought to play an important role in oral carcinogenesis. In the present study, we examined the relationship between Wnt signaling and epigenetic alteration of the secreted frizzled-related protein (SFRP) genes in OSCC. We frequently detected loss of menbrane localization of β-catenin and its cytoplasmic or nuclear accumulation in OSCC cell lines, although these cell lines showed no APC or CTNNB1 (β-catenin) mutations and no methylation of CDH1 (E-cadherin). By contrast, we frequently detected methylation of SFRP1 (7/17, 41%), SFRP2 (16/17, 94%) and SFRP5 (14/17, 82%) in a panel of OSCC cell lines, as well as in specimens of primary tumors collected from 44 OSCC patients (SFRP1, 10/42, 24%; SFRP2, 16/44, 36%; SFRP5, 7/43, 16%). We also observed that OSCC cell lines express various Wnt ligands, and that ectopic expression of SFRPs inhibited cancer cell proliferation. Our results confirm the frequent methylation and silencing of SFRP genes in OSCC, and suggest, that their loss of function contributes to activation of Wnt signaling that leads to cell proliferation during oral carcinogenesis.