Expression of Phospholipase A2 Correlates with the Progression and Metastasis of Prostate Cancer
Frances J Hairston, Raveena Reddy, Zhi He, Jack R Lewin, Xinchun Zhou. University of Mississippi Medical Center, Jackson, MS
Background: Phospholipase A2 (PLA2) is a group of enzymes involved in the metabolism of phospholipids. Previous studies have shown an abnormal expression of these enzymes in several cancers, including prostate cancer. The purpose of this study was to examine the differences in the expression of secreted PLA2 (sPLA2) and cytosolic PLA2 (cPLA2) in benign and malignant prostatic tissue.
Design: Tissue microarrays (TMAs) were constructed from 248 archival specimens of benign and malignant prostate from 1992-2012, including 56 benign prostates, 23 cases of prostatic intraepithelial neoplasia (PIN), 62 low grade prostatic carcinomas (LGPC, Gleason score <7), 77 high grade prostatic carcinomas (HGPC, Gleason score ≥7), and 30 metastatic prostate cancers. Immunohistochemistry (IHC) for sPLA2 and cPLA2 was performed on the TMAs. The total IHC score was calculated by the intensity score (0-3) multiplied by the area score (0-3) with a maximum total score of 9. The nuclear and cytoplasmic expression levels of sPLA2 and cPLA2 were compared by ANOVA analysis and Student t-test to examine the differences among and between the pathologic categories, respectively.
Results: The mean IHC scores for each category are shown in Table 1. The expression of nuclear sPLA2 was highest in metastatic cancer and the difference was significant when compared to the benign, PIN and LGPC groups (p=0.017, p=0.001, and p=0.000023, respectively). Nuclear expression of sPLA2 was also significantly higher in HGPC than in LGPC (p=0.00025). ANOVA analysis showed no significant differences in cytoplasmic sPLA2 expression among the groups. The nuclear cPLA2 IHC scores in the metastatic and HGPC groups were higher than in the LGPC group. However, a significant difference was only seen between HGPC and LGPC groups (p=0.003). Similarly, the cytoplasmic cPLA2 IHC scores were higher in the metastatic and HGPC groups than in the LGPC group (p=0.002, p=0.034, respectively).