Poly(adenosine diphosphate-ribose) polymerase expression in serous ovarian carcinoma: correlation with p53, MIB-1, and outcome.

This study investigated the expression of poly(adenosine diphosphate-ribose) polymerase (PARP) in a cohort of ovarian serous carcinomas by immunohistochemistry with regard to outcome, clinicopathologic parameters, proliferation as assessed by MIB-1 labeling indices (LIs), and p53 immunoexpression. Formalin-fixed, paraffin-embedded archival tissues of 50 ovarian serous carcinomas were immunostained with antibodies to PARP, MIB-1, and p53. In addition, 10 benign serous cystadenomas and 10 typical serous borderline ovarian tumors were included in the PARP immunostudy. Immunostaining for PARP was scored with regard to quantity and intensity of positively stained nuclei as negative, low, or strong. The MIB-1 LIs were quantitated as the percentage of positively stained nuclei in 1000 nuclei. For p53, at least 10% of tumor cells had to display nuclear staining. The expression of PARP was scored negative in all serous cystadenomas and low in serous borderline ovarian tumors. Strong PARP expression was determined in 38 cases (76%), and low expression in 12 cases (12%) of ovarian serous carcinomas; MIB-1 staining was noted in all cases (mean, 44.2; range, 10.8-66.5), positivity for p53 in 39 cases (78%). The PARP immunoreactivity increased with the International Federation of Gynecology and Obstetrics stage (P = 0.0075), as well as p53 positivity (P = 0.0141) and MIB-1 LIs (P = 0.0102), with grade determined after Malpica et al. (P = 0.0445) but not with grade assessed after Shimizu et al. (P = 0.1495). A trend for poor outcome was observed in patients whose tumors displayed high levels of PARP immunoexpression (P = 0.0196, log-rank test). This study indicates that PARP expression is frequently upregulated in ovarian serous carcinomas, related with MIB-1 LIs and p53 expression, and may serve as a marker of aggressive behavior with prognostic value.