Differential expression of efferocytosis and phagocytosis associated genes in tumor associated macrophages exposed to African American patient derived prostate cancer microenvironment

Abstract

Macrophages are the first line of defense in the cellular environment in response to any antigenic or foreign invasion. Since cancer cells express antigenic molecules and create a tumor microenvironment quite different from the normal cellular environment, macrophages will attack this cancer cells as foreign Invaders. However, the cancer cells adept their ability to suppress macrophage activity by secreting compounds/proteins through unknown mechanisms and train these macrophages to aid in tumorigenesis. These macrophages are commonly known as tumor associated macrophages (TAM). In this study, our goal was to find out key regulatory molecules involved in this conversion of cancer-fighting macrophages to cancer friendly macrophages. We used African American(AA) patient derived established human prostate cancer cells along with the human derived macrophages followed by Affymetrix cDNA microarray analysis. Microarray analysis of the PCa cell exposed macrophages revealed appreciable decrease in mRNA expression of several genes associated with phagocytosis process. Aberrant expression of several noncoding RNAs that control the expression of such phagocytosis associated molecules were also evident. Increased expression of oncogenic miR such as, miR-148, 615, 515, 130, 139 and markedly decreased expression of tumor suppressive miR’s MiR-3130, let7c,101,103, 383 were noted. Further, TARGET SCAN analysis demonstrated these differential expression of non-coding RNA’s causing down regulation of phagocytosis promoting genes elf5A, Meg3, Tubb5, Sparcl-1, Uch-1, Bsg(CD147), Ube2v, GULP, Stabilin 1 and Pamr1. There is an increase of RAP1GAP gene that causes concomitant decrease in the expression of tubulin genes that promote cytoskeletal assembly in forming phagosomes. In addition Ingenuity pathway analysis of the gene expression data also showed upregulation of antiphagocytic genes IL-10, CD16, IL-18 and MMP-9. Some core canonical pathways showing physiology of cellular signaling obtained by data analyzed by the Ingenuity software is confirmed a very complex mechanism still to be deciphered involved in the biology of TAM formation by which the rogue cancer cells tame their enemies, the macrophages and actually make them their helper cells to survive and propagate in the tumor microenvironment and thus prepare for epithelial mesenchymal transition for future metastasis and cancer stem cell formation and progression.