DETECTION OF LOSS OF HETEROZYGOSITY OF P53 GENE IN PARAFFIN-EMBEDDED BREAST CANCERS BY NONISOTOPIC PCR-SSCP

A rapid non-isotopic PCR-SSCP (polymerase chain reaction-single-strand ed conformation polymorphism) method was developed in this study to de tect polymorphism and loss of heterozygosity (LOH) of p53 in formalin- fixed and paraffin-embedded samples of normal breast tissue and of bre ast cancer. p53 expression was also examined by immunohistochemistry. In 35 paired samples, heterozygosity in exon 3 of p53 was detected in 17 cases (49 per cent) and LOH of the p53 gene in breast cancer tissue s was observed in 7 out of 15 informative cases (47 per cent). The cor relation of LOH of p53 with positive p53 immunostaining did not reach statistical significance, but all immunostaining-positive rumours amon g informative cases had LOH of p53. The results support the hypothesis that in most cases the allelic deletion of p53 may uncover the 'reces sive mutation' in the remaining allele. However, LOH of p53 was more f requent than positive immunostaining and was significantly associated with poor differentiation of breast cancer (P<0.05). The results sugge st that the allelic deletion of p53 may also contribute to the develop ment and progression of breast cancer by reducing the amount of normal p53 protein. These results show that non-isotopic PCR-SSCP is a simpl e, fast, and effective method for detecting polymorphism and LOH of th e p53 gene, which is especially useful for retrospective studies.