RESUMO
BACKGROUND: Non-small lung cancer(NSCLC) develops as a result of the accumulation of multiple genetic abnormalities. Loss of heterozygosity(LOH) is one of the most frequent genetic alterations that is found in NSCLC, and the chromosomal regions that display a high rate of LOH are though to harbor tumor suppressor genes(TSGs). This study was done to determine the frequency of LOH in 21q with the aim of identifying potential TSG loci. METHOD: Thirty-nine surgically resected NSCLCs were analysed. Patietns peripheral lymphocytes were used as the source of the normal DNA. Five microsatellite markers of 21q were used to study LOH : 21q21.1(D21S1432, and D21S1994) ; 21q21.2-21.3(D21S1442) ; 21q22.1(21S1445) ; and 21q22.2-22.3(D21S266). The fractional allelic loss(FAL) in a tumor was calculated as the ratio of the number of markers showing LOH to the number of informative markers. RESULT: LOH for at least one locus was detected in 21 of 39 tumors(53.8%). Among the 21 tumors with LOH, 5(21.8%) showed LOH at almost all informative loci. Although statistically not significant, LOH was found more frequently in squamous cell carcinomas(15 of 23, 65.2%) than in adenocarcinomas(6 of 16, 37.5%). In the squamous cell carcinomas the frequency of LOH was higher in stage II-III (80.0%) than in stage I (53.8%). The FAL value in squamous cell carcinomas(0.431±0.375) was significantly higher than that found in adenocarcinomas(0.192±0.276). CONCLUSION: These results suggest that LOH on 21q may be involved in the development of NSCLC, and that TSG(s) that contribute to the pathogenesis of NSCLC may exist on 21q.