DETECTION OF LOSS OF HETEROZYGOSITY IN THE P53 TUMOR-SUPPRESSOR GENE USING A PCR-BASED ASSAY

Inactivation of the p53 tumor suppressor gene has been reported to be a prognostic factor in several human cancer types. Normal function of the gene is affected by deletion in one allele; dysfunction of the oth er allele is often caused by a mutation. In tumors of heterozygous ind ividuals, deletion of one allele can be detected as loss of heterozygo sity (LOH). A recently found variable number of tandem repeats (VNTR) segment in intron 1 of the p53 gene seems to be highly polymorphic and , therefore, a very useful marker in detecting LOH in various types of tumor samples. We in vitro amplified the VNTR segment from genomic DN A samples of 101 lung cancer patients and run conventional agarose gel electrophoreses in order to detect the alleles of various length, dif fering by the number of repeats. The usefulness of the method was stud ied using DNA from white blood cell samples and from fresh and formali n-fixed, paraffin-embedded tumor samples. Of the patients, 56% were fo und to have two different alleles, i.e. were informative in this assay . In 18% of the lung tumors from the informative cases, LOH in the p53 suppressor gene was detected.