Cyclin E and Ki67 (MIB1) as markers of proliferative activity in human prostate cancers: an immunohistochemical study

Recent evidence has implicated cyclins in the evolution and progression of various malignancies. We immunohistochemically evaluated the expression of cyclin E, a G1 cyclin, along with Ki67-assessed proliferative activity in prostatic carcinoma. Formalin-fixed, paraffin embedded tissue sections from eighty-four previously untreated prostate carcinomas were distributed according to tumor grade and examined for the expression of cyclin E. Results were compared with Ki67 expression as well as tumor grade. Cyclin E was detected in 22 of 84 cases (26.2%) and its expression varied substantially (mean index varied from 4,7–9,0). Ki67 staining was present in 35.7% of cases. Although no correlation with tumor grade was found for either cyclin E or Ki67, a statistically significant correlation was present between the expression of the two biomarkers (Fisherʹs test, p<0.0001). We examined the proliferative activity of prostatic carcinomas of different tumor grades with markers for Ki67 and cyclin E. Our findings indicate that reactivities with these markers are strongly correlated with each other but their expression seems independent of tumor grade. Further studies on the clinical implications of the combined variable of cyclin E and Ki67 expression might disclose a useful prognostic indicator of survival or tumor relapse in patients with prostate carcinoma.