Immune-stimulatory gene expression in stroma cells of African-American prostate cancer tissues.

Abstract

e16544 Background: Prostate cancer (PCa) of African Americans (AA) has a two-fold higher mortality compared to PCa of European Americans (EA). PCa-adjacent stroma cells from these two populations were examined for differences in their cytokine secretion and gene transcription. Methods: Primary PCa-adjacent stroma cells (carcinoma-associated fibroblasts (CAFs)) and PCa-distant normal fibroblasts of the same gland (dNFs) from 15 AA and 27 EA patients were grown to passage 5. A multiplex immunoassay was then used to measure the secretion of 30 cytokines/chemokines in conditioned medium. In addition, RNA-Seq was performed on four AA and four EA CAF lines, and on PCa-adjacent stroma FFPE tissues of seven AA and five EA patients. Self-identified ethnicity was confirmed using the LASER program and SNPs present in the RNA-Seq. Results: Conditioned media from 42 AA and EA CAFs and dNFs were assayed for 30 immuno-regulatory cytokines/chemokines and growth factors, 20 of which (66%) were secreted at lower levels ( p < 0.05) in AA vs. EA CAFs. Remarkably, dNFs did not show this difference. RNA-Seq analysis of AA vs EA CAFs in culture identified 413 upregulated and 893 downregulated genes (FDR < 0.05, ≥ ±1.5 fold). Several interleukins, interferons, and 120 of 154 differentially transcribed interferon-stimulated genes were downregulated in AA vs. EA CAFs. RNA-Seq of PCa-adjacent stroma from FFPE tissues of seven AA and five EA patients revealed significantly reduced transcription of many immunomodulatory genes in AA stroma, including type I IFN-stimulated genes (ISGs). CIBERSORT analysis of the FFPE RNA-Seq data indicated the presence of significantly less numbers of dendritic cells and higher levels of naïve CD4 Th cells in AA vs. EA stroma. Conclusions: We observed reduced transcription of immunomodulators in CAFs of AA vs. EA, accompanied by profound decreases in the levels of many secreted cytokines and chemokines. These differences may indicate reduced innate and adaptive immune responses in AA PCa, compared to EA PCa. The differences observed here in primary cell lines may permit functional studies of the underlying mechanism(s) of the striking dissimilarity in disease outcome of AA PCa compared to EA PCa