p21 and p53 in ovarian carcinoma: their combined staining is more valuable than either alone

Background: Mutations in p53 are the most common genetic alterations in human malignancies. Expression of its protein product has been linked to decreased survival rate in ovarian carcinoma. Less is known about the importance of p21 expression. The purpose of this study was to determine the value of the combination of p21 and p53 expression in patients with epithelial ovarian malignancies.

Methods: One hundred three consecutive patients with epithelial ovarian carcinoma were studied using snap-frozen tissue specimens. Immunohistochemical staining utilizing the pAb1801 monoclonal antibody to p53 and NCL-WAF-1 monoclonal antibody to p21 was performed. Image analysis was used to determine whether nuclear staining for either antibody was present. In addition to p21 and p53, International Federation of Gynecology and Obstetrics stage, grade, histology, level of cytoreduction, and DNA index were analyzed as prognostic factors. Univariate and multivariate analyses was performed.

Results: One hundred three patients were observed for more than 5 years. Immunohistochemical staining for p21 and p53 were significantly inversely related (P = 0.041). Among the patients whose tumors showed p21 staining but no p53 staining, there were no recurrences and all patients were alive at 5-year follow-up. The 5-year survival rate for these patients was significantly better than for the patients with other combinations of p21/p53 staining (P < 0.0001). The DNA index between these 2 groups was not significantly different (P = 0.057). Multivariate analysis shows the combination of p21 and p53 (P = 0.013) staining to be more valuable as a prognostic indicator than either p53 (P = 0.015) or p21 (P = 0.5) alone.

Conclusions: This study confirms the importance of the combination of p21 and p53 nuclear staining in patients with ovarian carcinoma. Cox regression analysis revealed combination of p21 positive and p53 negative to be a better independent indicator of prognosis and survival in patients with ovarian carcinoma than either p21 or p53 alone.