Vertino P M, Spillare E A, Harris C C, Baylin S B
Oncology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231.
Cancer Res. 1993 Apr 1;53(7):1684-9.
Abnormal methylation of CpG island sequences on chromosomes 11p and 17p, and tumor phenotype-associated differential methylation of chromosome 3p loci have been described in human lung tumors (S.B. Baylin, J.W.M. Hoppener, A. de Bustros, P.H. Steenbergh, C.J.M. Lips, and B. D. Nelkin, Cancer Res., 46: 2917-2922, 1986; M. Makos, B.D. Nelkin, M. I. Lerman, F. Latif, B. Zbar, and S.B. Baylin, Proc. Natl. Acad. Sci. USA, 89: 1929-1933, 1992; A. de Bustros, B. D. Nelkin, A. Silverman, G. Ehrlich, B. Poiesz, and S. B. Baylin, Proc. Natl. Acad. Sci. USA, 85: 5693-5697, 1988). Using an in vitro model of lung tumor progression, we now show that these aberrant methylation patterns occur at different stages during cellular immortalization and oncogene-induced neoplastic transformation of normal human bronchial epithelial cells (NHBE). The CALC1 CpG island locus on chromosome 11p15.4 was essentially unmethylated in NHBE and simian virus 40 T-antigen immortalized NHBE (BEAS-2B cells) but became de novo methylated in 5 of 6 BEAS-2B derived cell lines that were transfected or infected with various oncogenes and in a spontaneously neoplastically transformed subline of BEAS-2B cells. By contrast, an additional CpG island locus, pYNZ22, at 17p13.3 became fully methylated following the immortalization of NHBE and was not further changed by oncogene-induced transformation. Finally, at a non-CpG island locus pYNZ86.1 on chromosome 3p14, different tumor phenotype-associated methylation patterns became apparent only after passage of the turmorigenic oncogene-transformed bronchial epithelial cell lines in athymic nude mice. Whereas cell lines derived from tumors with a non-small cell lung carcinoma-like phenotype were significantly hypomethylated relative to their parental cell lines, a cell line derived from a tumor with a more small cell lung carcinoma-like phenotype retained the methylation status of its parental cell line. The data indicate that altered DNA methylation patterns, including the de novo methylation of normally unmethylated CpG island sequences and demethylation of nonisland sequences, arise at different stages during immortalization and oncogene-induced neoplastic transformation of bronchial epithelial cells. These findings suggest that DNA methylation abnormalities accompany, or may play a role in, the genetic changes that occur during lung tumor progression.
在人类肺癌中已发现11号染色体短臂（11p）和17号染色体短臂（17p）上CpG岛序列的异常甲基化，以及3号染色体短臂（3p）位点与肿瘤表型相关的差异甲基化（S.B. 贝林、J.W.M. 霍彭纳、A. 德布斯特罗斯、P.H. 斯滕伯格、C.J.M. 利普斯和B.D. 内尔金，《癌症研究》，46: 2917 - 2922, 1986；M. 马科斯、B.D. 内尔金、M.I. 勒曼、F. 拉蒂夫、B. 兹巴尔和S.B. 贝林，《美国国家科学院院刊》，89: 1929 - 1933, 1992；A. 德布斯特罗斯、B.D. 内尔金、A. 西尔弗曼、G. 埃利希、B. 波伊斯和S.B. 贝林，《美国国家科学院院刊》，85: 5693 - 5697, 1988）。利用肺癌进展的体外模型，我们现在表明这些异常甲基化模式出现在正常人支气管上皮细胞（NHBE）细胞永生化和癌基因诱导的肿瘤转化的不同阶段。11号染色体短臂15.4区域（11p15.4）的CALC1 CpG岛位点在NHBE细胞和猿猴病毒40大T抗原永生化的NHBE细胞（BEAS - 2B细胞）中基本未甲基化，但在6个BEAS - 2B衍生细胞系中的5个中发生了从头甲基化，这些细胞系转染或感染了各种癌基因，以及在BEAS - 2B细胞的一个自发肿瘤转化亚系中。相比之下，另一个位于17号染色体短臂13.3区域（17p13.3）的CpG岛位点pYNZ22在NHBE细胞永生化后完全甲基化，并且未因癌基因诱导的转化而进一步改变。最后，在3号染色体短臂14区域（3p14）的一个非CpG岛位点pYNZ86.1，只有在致瘤性癌基因转化的支气管上皮细胞系在无胸腺裸鼠中传代后，不同的与肿瘤表型相关的甲基化模式才变得明显。与非小细胞肺癌样表型肿瘤来源的细胞系相比，其亲本细胞系显著低甲基化，而一个来源于更具小细胞肺癌样表型肿瘤的细胞系保留了其亲本细胞系的甲基化状态。数据表明，DNA甲基化模式的改变，包括正常未甲基化的CpG岛序列的从头甲基化和非岛序列的去甲基化，出现在支气管上皮细胞永生化和癌基因诱导的肿瘤转化的不同阶段。这些发现表明DNA甲基化异常伴随着肺癌进展过程中发生的基因变化，或者可能在其中起作用。
