Kuzmin Igor, Liu Limin, Dammann Reinhard, Geil Laura, Stanbridge Eric J, Wilczynski Sharon P, Lerman Michael I, Pfeifer Gerd P
Basic Research Program, Science Applications International Corporation-Frederick, Inc., NCI Frederick, Frederick, Maryland, 21702, USA.
Cancer Res. 2003 Apr 15;63(8):1888-93.
Recently, we have identified a new putative tumor suppressor gene, RASSF1A (Ras association domain family 1A gene), located at human chromosome 3p21.3, the segment that is often lost in many types of human cancers. The RASSF1A promoter was shown to be frequently hypermethylated in various epithelial tumors, including small cell lung, breast, bladder, prostate, gastric, and renal cell carcinomas. In this study, we have analyzed the methylation status of the RASSF1A gene in primary human cervical cancers and in eight cervical cancer cell lines. The RASSF1A promoter is hypermethylated in 4 of 42 (= 10%) of squamous cell carcinomas, in 4 of 19 (= 21%) of adenosquamous carcinomas, and in 8 of 34 (= 24%) of cervical adenocarcinomas. Although in adenocarcinomas, methylation of RASSF1A and presence of human papillomavirus (HPV) type 16 or 18 sometimes coexisted, not a single case of HPV-16/18-positive squamous cell carcinomas had RASSF1A methylation. Similarly, in all eight analyzed cervical cell lines, RASSF1A inactivation and HPV infection were mutually exclusive (Fisher's exact test; P = 0.0357): two HPV-negative cervical cancer cell lines had a methylated and silenced RASSF1A promoter (C-33A and HT-3), whereas the other six HPV-positive lines expressed RASSF1A mRNA (ME 180, MS751, SiHa, C-4I, HeLa, and CaSki). For cervical tumors and cell lines combined, the Pearson's chi(2) test (chi(2) = 3.99; P <or= 0.05) indicates a borderline-significant reverse correlation between inactivation of RASSF1A and the presence of high-risk HPVs. Our data imply that the presence of HPVs in cervical carcinomas alleviates the requirement for RASSF1A inactivation and suggests that these two events may engage the same tumorigenic pathway.
最近，我们鉴定出一个新的假定肿瘤抑制基因RASSF1A（Ras关联结构域家族1A基因），它位于人类3号染色体p21.3区域，该区域在多种人类癌症中常发生缺失。研究表明，RASSF1A启动子在包括小细胞肺癌、乳腺癌、膀胱癌、前列腺癌、胃癌和肾细胞癌在内的多种上皮性肿瘤中经常发生高甲基化。在本研究中，我们分析了原发性人类宫颈癌及8种宫颈癌细胞系中RASSF1A基因的甲基化状态。在42例鳞状细胞癌中有4例（=10%）、19例腺鳞癌中有4例（=21%）以及34例宫颈腺癌中有8例（=24%）的RASSF1A启动子发生了高甲基化。虽然在腺癌中，RASSF1A甲基化与人乳头瘤病毒（HPV）16型或18型感染有时并存，但HPV - 16/18阳性的鳞状细胞癌中没有一例发生RASSF1A甲基化。同样，在所有8种分析的宫颈癌细胞系中，RASSF1A失活与HPV感染相互排斥（Fisher精确检验；P = 0.0357）：两种HPV阴性的宫颈癌细胞系（C - 33A和HT - 3）的RASSF1A启动子发生甲基化并沉默，而其他6种HPV阳性细胞系表达RASSF1A mRNA（ME 180、MS751、SiHa、C - 4I、HeLa和CaSki）。对于宫颈肿瘤和细胞系合并分析，Pearson卡方检验（χ2 = 3.99；P≤0.05）表明RASSF1A失活与高危HPV的存在之间存在临界显著的负相关。我们的数据表明，宫颈癌中HPV的存在减轻了RASSF1A失活的需求，并提示这两个事件可能参与了相同的致瘤途径。
