Minichromosome maintenance protein 2 expression in prostate: Characterization and association with outcome after therapy for cancer

The minichromosome maintenance (MCM) proteins are highly conserved proteins essential for initiating and regulating eukaryotic DNA replication. Recent studies have demonstrated the potential use of MCM proteins as markers of proliferation. We characterized the pattern of Mcm 2 staining in benign and malignant prostate tissues and examined the role of Mcm 2 expression in di sease-free survival after surgery in men with localized prostate cancer. Tumors from 92 patients who underwent radical prostatectomy for prostate ca ncer (median follow-up of 54 months) were examined for Mcm 2 expression by immunohistochemistry using a monoclonal antibody. Prostate tissue from five men without histopathological evidence of prostate cancer was also stained for Mcm 2. Mcm 2 expression was quantified by calculating a labeling index , and patients were grouped according to degree of staining. An analysis of the association between Mem 2 expression with traditional clinicopathologi cal characteristics of prostate cancer was carried out. A Cox proportional hazards analysis was performed to determine whether Mem 2 staining was a si gnificant independent predictor of disease-free survival. Mcm 2 expression is low (<2%) and limited to the basal cell layer in nonmal ignant prostate glands. Mcm 2 expression is consistently increased in malig nant glands and is significantly associated with disease-free survival in u nivariate (P = 0.002) and multivariate (P = 0.01) analyses. Patients with h igh Mem 2 expression exhibited shorter disease-free survival. Mcm 2 express ion was not associated with any traditional clinical or pathological factor s and therefore is an independent predictor of survival in these patients w ith prostate cancer. These data support evidence that Mcm 2 may serve as a novel proliferation m arker in the prostate. Mcm 2 expression is an independent predictor of dise ase-free survival after definitive local therapy and has potential as a mol ecular marker for clinical outcome in prostate cancer.