Minichromosome maintenance protein 7 as a potential prognostic factor for progression-free survival in high-grade serous carcinomas of the ovary

Minichromosome maintenance protein 7 (MCM7) is involved in replicative licensing and synthesis of DNA. It was previously identified as an overexpressed gene in high-grade serous carcinomas compared with serous borderline tumors of the ovary in cDNA microarray studies. In this study, we sought to validate MCM7 expression in 342 ovarian tumors on tissue microarrays. MCM7 expression was quantified as the MCM7 labeling index, and it was independently generated by two methods: a score provided by manual review of each sample by a pathologist observer and by an automated cellular imaging system. Analyses of MCM7 scores indicated a high degree of concordance and distribution between the observer- and machine-generated MCM7 labeling indexes. MCM7 expression was significantly higher in high-grade serous carcinomas than in serous borderline tumors or other histological subtypes of ovarian cancer. For both observer- and machine-derived scores, univariate analyses indicated the significant association of a high MCM7 labeling index with better progression-free survival in high-grade serous carcinomas. These results suggest the clinical importance of MCM7 expression in high-grade serous carcinomas of the ovary and the need for further evaluation of MCM7 as a potential prognostic factor in ovarian cancer.