Amplotyping of microdissected, methanol-fixed lung carcinoma by arbitrarily primed polymerase chain reaction

The arbitrarily primed polymerase chain reaction (AP-PCR) was used to detect somatic genetic alterations in lung carcinomas. DNA fingerprints generated by a single arbitrary primer were compared between normal and tumor tissues of the same individuals. We adapted the technique to the use of tissue fixed with methanol, which allowed the analysis of small areas of tissue by microdissection. This improvement of the fingerprinting technique permitted the study of tumors at early stages of progression. Loss of sequences from chromosome 7 was detected in 41.7% of adenocarcinomas and from chromosome 22 in 84.6% of small-cell carcinomas. Gains of sequences from chromosomes 1, 8 and 13 were detected in more than 40% of adenocarcinomas and in chromosome 2 in 63.3% of squamous-cell carcinomas. Our results indicate that allelic imbalances at these chromosomal regions are common genetic abnormalities in lung carcinomas. Loss of sequences from chromosome 22q13.3, found in 11 of 13 small-cell carcinomas, were confirmed by microsatellite PCR analysis. We show that the use of our improved AP-PCR fingerprinting permits the detection of both losses and gains of novel chromosomal regions early during lung cancer development. Our results indicate that early-stage tumors tend to have more allelic imbalances than relatively advanced tumors, suggesting a high tumor genetic heterogeneity in the early stages of lung tumor progression.