Significance of cyclin e and p27 expression in malignant ovarian germ cell tumors: Correlation with the cell proliferation activity and clinicopathologic features

Abstract

Although elevated cell proliferation activity is one of the most remarkable features known to characterize malignant ovarian germ cell tumors (MOGCTs), abnormalities in cell cycle regulation have yet to be thoroughly investigated in MOGCTs. Forty-two MOGCTs were immunohistochemically examined to determine their cyclin E and p27Kip1 (p27) expression in correlation with their cell proliferation activity and clinicopathological features. Cytosine methylation of p27 gene promoter CpG islands was estimated by methylation-specific PCR. The labeling index (LI) was calculated as a percentage of the positively stained tumor cells per total tumor cells counted. p27 LIs showed a significant inverse correlation with Ki-67 LIs in MOGCTs examined (p<0.05). The cyclin E LIs of yolk sac tumors were significantly higher than those of dysgerminomas (p<0.01). Two MOGCTs were methylation-positive (5%). Both p27 and cyclin E are thought to be involved in the cell cycle regulation of MOGCTs. p27 gene promoter methylation is rare in MOGCTs. An immunohistochemical evaluation of cyclin E may be a useful diagnostic modality for differentiating MOGCTs.