Pim-1 Expression in Prostatic Intraepithelial Neoplasia and Human Prostate Cancer

Background: PIM-1, an oncogene product of serine/threonine kinase, has been found to play an important role in induction/suppression of apoptosis, cell cycle progression, and transcriptional regulation by phosphorylating the target proteins involved in these processes. Recently, the expression of PIM-1 has been shown to correlate significantly with measures of prostate cancer clinical outcome.

Methods: Immunohistochemical analysis was used to characterize the patterns of PIM-1 expression in high grade prostatic intraepithelial neoplasia (HGPIN) and cancer in 121 radical prostatectomy specimens.

Results: Moderate to strong cytoplasmic staining was observed in 68% of cancers, 12% presented nuclear positivity as well. Moderate to strong expression was seen in 76% of tumors with Gleason score (GS) 7 or higher compared to 58% in tumors with GS 6 or lower (P = 0.04). The staining intensity was moderate or strong in 97% of HGPIN lesions. PIM-1 was overexpressed in HGPIN compared to cancer in 65% of cases. Expression in benign glands was negative or only weakly positive.

Conclusion: Our data suggest that PIM-1 overexpression in HGPIN may be an early event in the development of prostate malignancy. Additionally, PIM-1 expression provides supplementary information for distinguishing HGPIN from benign epithelium.