Kang J H, Kim S J, Noh D Y, Park I A, Choe K J, Yoo O J, Kang H S
Department of Biological Science, Biomedical Research Center, Korean Advanced Institute of Science and Technology, Taejon.
Lab Invest. 2001 Apr;81(4):573-9. doi: 10.1038/labinvest.3780266.
Aberrant methylation in the CpG sites located in the promoter region of several tumor suppressor genes has been reported in various types of cancers. However, the methylation status of the p53 promoter has not been clearly determined and no information is available on its role in breast cancer. The aim of the study was to determine the presence and timing of the methylation of CpG sites in the p53 promoter, in the progression from ductal carcinoma in situ to invasive cancer. We also explored the correlation between the CpG methylation of the p53 promoter and p53 mutation during the progression of breast cancer. The corresponding lesions of both the invasive and noninvasive types were microdissected in paraffin-embedded tissue of 26 breast carcinomas. Bisulfite-modified DNA sequencing for methylation status in the p53 promoter was carried out, and double-strand DNA sequencing was performed in the promoter region and exons 4 to 9 of the p53 gene. CpG site methylation in the p53 promoter was detected in three cases (11.5%). Two noninvasive and three invasive lesions harbored CpG methylation in the p53 promoter. Methylations in more than one site were observed in three lesions, all of which contained methylation in two sites. The methylated CpG sites were located near the AP1 and YY-1 binding sites and at the YY-1 binding site. The p53 mutation was not found in the lesions where methylation in p53 promoter region was evident. In 16 cases (61.5%), neither methylation nor p53 mutation was detected. We conclude that the methylation in the p53 promoter region is found in the breast cancer irrespective of the status of invasion, and that the hypermethylation in the p53 promoter region is an alternative pathway to tumorigenesis where there is no p53 gene mutation.
据报道，在各类癌症中，几种抑癌基因启动子区域的CpG位点存在异常甲基化。然而，p53启动子的甲基化状态尚未明确确定，且尚无关于其在乳腺癌中作用的信息。本研究的目的是确定在导管原位癌进展为浸润性癌的过程中，p53启动子中CpG位点甲基化的存在情况及时间。我们还探讨了乳腺癌进展过程中p53启动子的CpG甲基化与p53突变之间的相关性。对26例乳腺癌石蜡包埋组织中的浸润性和非浸润性相应病变进行显微切割。对p53启动子的甲基化状态进行亚硫酸氢盐修饰的DNA测序，并对p53基因的启动子区域和外显子4至9进行双链DNA测序。在3例病例（11.5%）中检测到p53启动子中的CpG位点甲基化。2例非浸润性病变和3例浸润性病变的p53启动子存在CpG甲基化。在3个病变中观察到不止一个位点的甲基化，所有这些病变均有两个位点的甲基化。甲基化的CpG位点位于AP1和YY-1结合位点附近以及YY-1结合位点处。在p53启动子区域甲基化明显的病变中未发现p53突变。在16例病例（61.5%）中，未检测到甲基化和p53突变。我们得出结论，无论浸润状态如何，乳腺癌中均存在p53启动子区域的甲基化，且p53启动子区域的高甲基化是在无p53基因突变情况下的另一种肿瘤发生途径。
