Co-expression of p53 by epithelial and stromal elements in carcinosarcoma of the female genital tract: an immunohistochemical study of 19 cases.

Carcinosarcoma is an aggressive neoplasm of the female genital tract, which comprises 1-2% of malignancies of the uterine corpus. Because of the broad range of differentiation exhibited by these tumors, the precise nature of the relationship between epithelial and stromal components in this unique tumor remain unclear. Previous studies have demonstrated that mutation and consequent overexpression of the tumor suppressor gene p53 occurs frequently in carcinosarcoma and is conserved from primary to metastastic sites. We examined p53 accumulation in formalin-fixed, paraffin-embedded archival sections in 19 cases previously shown to have mutations in the p53 gene and performed semi-quantitative analysis of the intensity of staining and relative density of positive cells and stromal and glandular elements. There was a high level of concordance of immunohistochemical staining for the p53 oncoprotein between glandular and stromal elements. These results further suggest a clonal origin for the diverse elements of carcinosarcoma.

Relationship between p21 expression and mutation of the p53 tumor suppressor gene in normal and malignant ovarian epithelial cells.

In many cell types, p53-mediated growth inhibition is dependent on induction of p21, which is an inhibitor of cyclin-dependent kinases that are required for cell cycle progression. Failure of mutant p53 proteins to transactivate p21 may lead to uncontrolled proliferation. Because many ovarian cancers have mutations in the p53 gene, we examined p21 levels in normal and malignant ovarian epithelial cells to determine whether p21 expression is dependent on wild-type p53. Normal ovarian epithelial cells and two ovarian cancer cell lines with wild-type p53 expressed readily detectable levels of p21, whereas in p53 null and mutant cell lines, expression of p21 was diminished strikingly. A correlation between the status of the p53 gene and p21 expression also was noted in 23 primary epithelial ovarian cancers. Normal levels of p21 RNA were seen in 4/7 (57%) cancers with wild-type p53, whereas 14/16 (88%) cancers with mutant p53 had reduced p21 expression (P < 0.05). In addition, we found that lambda-irradiation of normal and malignant ovarian epithelial cells with wild-type, but not mutant, p53 resulted in induction of p21. These data are suggestive that induction of p21 is a feature of p53-mediated growth inhibition in normal ovarian epithelial cells. Conversely, mutation of the p53 gene in ovarian cancers usually is associated with decreased p21 expression. The lack of an absolute correlation between p21 expression and the status of the p53 gene in ovarian cancers is consistent with other studies that have suggested that p21 may also be regulated by p53-independent pathways.