Abstract B28: Tumor-associated macrophages and angiogenesis in prostate cancer

Abstract

Abstract Introduction: Role of tumor associated macrophages (TAM) and angiogenesis is being extensively evaluated. Macrophages are subdivided in two phenotypes: M1 (classically activated: promote inflammation, act against cancer growth) and M2 (alternatively activated: promote healing, angiogenesis; could support tumor growth). Our preliminary study was intended to study number of macrophages (CD68 positive), M2 macrophages (CD163 positive) and microvessels (ERG positive) between non-neoplastic and neoplastic prostate tissue. Methods: We evaluated 10 radical prostatectomy specimens (RP) with prostate cancer (PCA) (cases) and 10 cystoprostatectomy specimens (CP) negative for PCA (controls). Representative paraffin blocks were selected for analysis and stained by immunohistochemistry for CD68 PGM1, CD163 and ERG. For RP specimens, two distinct blocks were selected: one with tumor (RP-T) and one away from tumor (RP-NT). Macrophages count was done using two methods. Method 1: average manual count in 12 fields at 400X magnification in areas uninvolved by chronic inflammation (CI), away from hotspots. Method 2: average count in three hotspots (associated with CI) at 400X magnification with manual assistance on Aperio Image Spectrum Software. Vessels count was done using a Chalkley point counting technique at 100X magnification. Statistical analysis was done using t test and Pearson correlation. Results: Different degree of CI was found in most CP and RP samples, ranging from focal mild to multifocal severe (hotspots). Mean age of CP and RP patients was 58 and 60 years, respectively. RP Gleason score ranged from 6 to 9. No significant difference in CD68, CD163 and ERG positive cells existed between the three groups by t-test. The CD68 count in RP-T was 104 by method 1 and 114 by method 2. The CD163 count in RP-T was 51 by method 1 and 54 by method 2. ERG count in RP-T was 6.9. A positive correlation of M2 macrophages (method 2) with microvessels in RP-T (p=0.046) was found. None of the counts correlated with Gleason score. Conclusions: Our preliminary study found no significant difference in TAM between non-neoplastic and neoplastic prostate tissue, independently from the association with CI. The vessel count in prostate tumor positively correlated with M2 macrophages, suggesting a possible crosstalk between M2 macrophages and tumor cells promoting angiogenesis. These findings require further validation in additional studies including a larger sample size. Citation Format: Pallavi Patil, Paula Carver, Karen Streator Smith, Jeffrey Lin, Cristina Magi-Galluzzi. Tumor-associated macrophages and angiogenesis in prostate cancer. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr B28.