OVEREXPRESSION OR MUTATION OF THE P53 TUMOR-SUPPRESSOR GENE DOES NOT OCCUR IN MALIGNANT OVARIAN GERM-CELL TUMORS

Background. The p53 tumor suppressor gene has been well studied in epi thelial ovarian cancers. However, little is known of the expression of this gene in ovarian germ cell tumors. The authors attempted to inves tigate whether p53 alterations occurred in this group of tumors. Metho ds. Twenty-two patients with malignant ovarian germ cell tumors were i ncluded in this study. Immunohistochemical staining for p53 was perfor med on paraffin embedded tissue of each case. Single-strand conformati on polymorphism analysis of exons 4-9 of the p53 gene was performed on 9 of the 22 tumors where genomic DNAs were obtained from the frozen t issue samples. Three tumors that revealed focal p53 positivity by immu nostaining were studied further with direct DNA sequencing. Results. O verexpression of p53 was not observed in all of the 22 ovarian germ ce ll tumors; only 3 were found to have nuclear staining in a small fract ion of the malignant cells (<5% in 1 immature teratoma, 5-10% in 2 yol k-sac tumors). Among the nine frozen tumors subjected to single-strand conformation polymorphism analysis, none revealed p53 mutation in exo ns 4-9. There was no p53 mutation detected by DNA sequencing of the th ree tumors with focal immunoreactivity. Conclusions. Alterations of th e p53 tumor suppressor gene may not be associated with the pathogenesi s of ovarian germ cell tumors. Instead, genetic changes such as inacti vation of other tumor suppressor genes and/or activation of some proto oncogenes need to be studied to determine the genetic mechanisms of th e tumor development.