Prostate cancer (PCa) kills 2 to 3 times as many Black men as White men each year. Disparities in socioeconomic position and access to high-quality healthcare are contributing factors to this gap. According to studies, PCa may become more aggressive in Black males due to changes in the predominance of innate immune cells and heightened function in the tumor microenvironment.

On formalin-fixed paraffin-embedded tissues from organ donor “normal” prostate (n=9) and radical prostatectomy (n=38) tissues from Black & White men, researchers assessed the spatial localization of and quantified CD66ce+ neutrophils by immunohistochemistry, CD68+ (pan), CD80+ (M1), & CD163+ (M2) macrophages by RNA in situ hybridization. In tissue microarray (TMA) sets made up of 560 White & 371 Black males, neutrophils were measured in PCa & matched benign tissues. Similar to this, the number of macrophages was measured in TMA sets made up of tissues from 60 White and 120 Black males. Each TMA PCa case was examined using immunohistochemistry to determine the expression levels of ETS transcription factor ERG (ERG) and phosphatase and tensin homolog (PTEN). The TMA set of distant metastatic PCa tissues obtained at autopsy (n = 6) and sampled across several locations was used to analyze neutrophils and macrophage subsets.

Normal prostates had very few CD66ce+ neutrophils, but PCa tissues had more of them than benign tissues, lower-grade PCa had more of them than higher-grade PCa, PCa tissues from White men had more of them than Black men, and PCa with PTEN loss or ERG positive had more of them than benign tissues. Both Black and White men’s normal prostate tissues from organ donors had a high percentage of CD163+ macrophages, which were also substantially more prevalent in normal organ donor prostate tissues than in prostatectomy PCa tissues. When compared to benign tissues and in malignancies that had an ERG-positive status, CD68+, CD80+, and CD163+ macrophages were substantially more prevalent in cancerous tissues. Higher-grade tumors had more CD68+ and CD163+ macrophages than low-grade cancers, while benign prostatectomy tissues from Black men had much more CD80 expression than those from White men.

Both Black and White men had greater innate immune cell infiltration in the prostate tumor microenvironment, while there may be racial differences in the makeup of the infiltration.

Reference: onlinelibrary.wiley.com/doi/10.1002/pros.24424