Forgacs E, Biesterveld E J, Sekido Y, Fong K, Muneer S, Wistuba I I, Milchgrub S, Brezinschek R, Virmani A, Gazdar A F, Minna J D
Hamon Center for Therapeutic Oncology Research, University of Texas, Southwestern Medical Center, Dallas 75235, USA.
Oncogene. 1998 Sep 24;17(12):1557-65. doi: 10.1038/sj.onc.1202070.
We studied PTEN/MMAC1, a newly discovered candidate tumor suppressor gene at 10q23.3, for mutations in lung cancer. One hundred and thirty-six lung cancer cell line DNAs (66 small cell lung cancers, SCLC, 61 non-small cell lung cancers, NSCLC, four mesotheliomas, five extrapulmonary small cell cancers) were analysed for PTEN/MMAC1 homozygous deletions and five (8%) SCLC lines showed homozygous deletions interrupting the PTEN/MMAC1 gene. Using single stranded conformation polymorphism (SSCP) analysis, we screened the PTEN/MMAC1 open reading frame of 53 lung cancer cell line cDNAs for point mutations and found that 3/35 SCLCs and 3/18 NSCLCs contained homozygous amino acid sequence altering mutations. Northern blot analysis revealed that expression of the PTEN/MMAC1 gene was considerably lower in all the tumor cell lines with point mutations while no expression was detected for cell lines with PTEN/MMAC1 homozygous deletions. Mutation analysis of 22 uncultured, microdissected, primary SCLC tumors and metastases showed two silent mutations, and two apparent homozygous deletions. We also discovered a processed pseudogene (PTEN2) which has 98.5% nt identity to PTEN/MMAC1, that needs to be accounted for in cDNA mutation analysis. Our findings suggest that genetic abnormalities of the PTEN/MMAC1 gene are only involved in a relatively small subset of lung cancers.
我们研究了位于10q23.3的新发现的候选肿瘤抑制基因PTEN/MMAC1在肺癌中的突变情况。对136个肺癌细胞系DNA（66个小细胞肺癌、61个非小细胞肺癌、4个间皮瘤、5个肺外小细胞癌）进行了PTEN/MMAC1纯合缺失分析，5个（8%）小细胞肺癌细胞系显示有中断PTEN/MMAC1基因的纯合缺失。利用单链构象多态性（SSCP）分析，我们筛查了53个肺癌细胞系cDNA的PTEN/MMAC1开放阅读框中的点突变，发现35个小细胞肺癌中有3个、18个非小细胞肺癌中有3个含有改变氨基酸序列的纯合突变。Northern印迹分析显示，在所有具有点突变的肿瘤细胞系中，PTEN/MMAC1基因的表达明显较低，而对于具有PTEN/MMAC1纯合缺失的细胞系未检测到表达。对22个未经培养、显微切割的原发性小细胞肺癌肿瘤及转移灶进行突变分析，发现了2个沉默突变和2个明显的纯合缺失。我们还发现了一个加工假基因（PTEN2），其与PTEN/MMAC1有98.5%的核苷酸同一性，在cDNA突变分析中需要考虑到这一点。我们的研究结果表明，PTEN/MMAC1基因的遗传异常仅涉及相对较小一部分肺癌。
