Detection of tumor-specific homozygous deletions in human biopsies by polymerase chain reaction.

Cancer is associated with homozygous deletions of specific DNA sequences that are in some instances too small to be detectable by cytogenetic methods or Southern blot analysis. Such small tumor-specific deletions can be detected, however, by the polymerase chain reaction (PCR) provided that tumor cells are meticulously and verifiably isolated from contaminating nontumor cells. Nontumor cells can give positive PCR results and thus obscure the detection of deletions. Using a method that allows accurate and verifiable excision of tumor cells for subsequent PCR analysis, homozygous deletions, one in a putative tumor suppressor gene on chromosome 8 and one in the p53 gene, were detected in two out of 20 human lung carcinomas investigated.