[Detection of loss of heterozygosity by microsatellite probe and DNA content analysis]

We examined replication error (RER) and loss of heterozygosity (LOH) in the region of microsatellites in 60 cases of resected lung cancer. We used microsatellite probes for the short arm of the 2nd chromosome (D2S123, D2S136), the short arm of the 3rd chromosome (D3S1067), and the short arm of the 17th chromosome (TP53). According to stage, the frequency of LOH was 25% in stage I, 33% in stage II, 44% in stage IIIA, 11% in stage III B, and 63% in stage IV. According to histological classification, the frequency of LOH was 41% for squamous cell carcinoma, 24% for adenocarcinoma, and 100% for small cell carcinoma. According to microsatellite probe results, the frequency of LOH was 6.7% for D2S123, 5.0% for D2S136, 16.7% for D3S1067, and 18.3% for TP53. Two of the 60 cases showed RER. One case was stage I squamous cell carcinoma, and the other was stage IV adenocarcinoma. Except for stage III B,LOH in the microsatellite region increases with the stage. LOH is often detected in the order of small cell carcinoma, squamous cell carcinoma, and adenocarcinoma. According to the chromosome number, LOH is detected more often in the 3rd and 17th chromosomes than in the 2nd chromosome. In 20 cases with LOH, only two showed DNA diploidy. Compared to LOH of the microsatellite region, DNA content analysis by flow cytometry has accuracy problems.