Expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) in primary human ovarian carcinoma

Abstract

The mitogen-activated protein kinase phosphatase-1, MKP-1 (CL100) is involved in inactivation of MAP-kinase pathways, regulation of stress-responses and suppression of apoptosis. We investigated expression of MKP-1 in 90 cases of primary ovarian tumors, 11 normal ovaries as well as 4 ovarian carcinoma cell lines. Immunohistochemical expression of MKP-1 protein was reduced in tissue from LMP tumors and invasive ovarian carcinomas compared to normal ovaries and cystadenomas. A moderate to strong expression of MKP-1 was detected in 57.6% of invasive ovarian carcinomas. In a descriptive univariate survival analysis, MKP-1 expression was a prognostic marker for shorter progression-free survival of patients with invasive ovarian carcinomas. Patients with carcinomas positive for MKP-1 had a median progression-free survival of only 18.3 months compared to 40.6 months for patients with carcinomas negative for MKP-1 (log-rank test, p = 0.019). Other prognostic parameters for progression-free survival were FIGO stage, grade and pT stage. In an exploratory multivariate analysis, we found that MKP-1 expression as well as FIGO stage and grade were independent prognostic factors for progression-free survival. In contrast to progression-free survival, we did not find any influence of MKP-1 expression on patient overall survival. We investigated expression and regulation of MKP-1 mRNA by Northern Blot in vitro using 4 ovarian carcinoma cell lines (SKOV-3, OVCAR-3, CAOV-3, OAW-42). MKP-1 mRNA was inducible by interleukin-1beta and tumor necrosis factor-alpha in SKOV-3 and OVCAR-3 cells, whereas CAOV-3 and OAW-42 expressed MKP-1 mRNA constitutively. In OVCAR-3 cells MKP-1 mRNA levels were strongly inducible upon treatment of cells with cisplatin. Our data indicate that MKP-1 is expressed in a subset of ovarian carcinomas and regulated by inflammatory mediators. Expression of MKP-1 may be associated with shorter progression-free survival times. Further studies are needed to determine whether MKP-1 expression is a clinically useful marker to estimate patient prognosis as well as the response to chemotherapy.