No evidence of microsatellite instability but frequent loss of heterozygosity in primary resected lung cancer.

We examined microsatellite instability and loss of heterozygosity (LOH) in primary lung tumors from 93 cancer patients, using 16 microsatellite markers. The cases studied included 87 non-small-cell lung cancers (NSCLC) and six small-cell lung cancers (SCLC). All the patients except two were current or former smokers. The microsatellite markers were all dinucleotide repeat sequences from chromosomal locations 1p, 3p, 5q, 8p, 9p, 10p, 11p, 13q, and 17q. None of the tumors showed microsatellite instability (0/93). In NSCLC, 28% (24/87) of the cases showed LOH in at least one locus, whereas, in SCLC, 67% (4/6) had allelic losses. The frequency of LOH differed between the various cell types of NSCLC. The highest frequency was seen in large cell carcinoma (3/6, 50%) followed by squamous cell carcinoma (16/43, 37%) and adenocarcinoma (5/35, 14%). The most common site of LOH was 3p, where markers D3S1284, D3S659, D3S1289, D3S966, D3S647, and D3S1038 were studied. LOH, studied with 9p markers (D9S126, D9S171, D9S162), was less common. The present results, together with earlier reports, suggest that smoking-related primary lung cancers seldom show microsatellite instability but are characterized by frequent LOH.