Effects of tumor microenvironment on the efferocytic and phagocytic genes of human macrophages

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 suppress the macrophage activity by secreting compounds unknown to the cancer, biologists even today and recruit these macrophages to their benefit as tumor associated macrophages or TAM. In this study, we were interested to find out the genes and proteins that are involved in this conversion of cancer-fighting macrophages to cancer friendly macrophages. We co-cultured the prostate cancer cells along with the human macrophages, then collected these tumor micro environment (TME) exposed human macrophages, and isolated RNA from these cells. We further analyzed these tumor associated macrophages (TAM’s) along with control macrophages RNA by Microarray analysis using Affymetrix platform for gene expression studies. Our Phagocytosis results showed decreased phagocytic index in the tumor medium exposed macrophage cells as evidenced by the much lower relative fluorescence unit (RFU) recorded by the fluorometer in comparison to macrophages grown in absence of tumor medium. Further analysis of the gene expression studies by PARTEK coupled with Ingenuity Pathway Analysis (IPA®) showed down-regulation of several genes helping in the phagocytosis process and differential expression of several noncoding RNAs that control the expression of such phagocytic genes. The following oncomiR’s, miR 148,615,515,130,139 were -upregulated and tumor suppressor miR’s3130, let7c,101,103,383 were downregulated. The TARGET SCAN Software results showed these differential expression of noncoding RNA’s causing down regulation of phagocytosis promoting genes elf5A, Meg3, Tubb5, Sparcl-1, Uch-1, Bsg (CD147), Ube2v, and Pamr1. There is an up-regulation of RAP1GAP gene that causes downregulation of the tubulin genes that promote cytoskeletal assembly in forming phagosomes. Ingenuity Software analysis of the gene expression data also showed upregulation of anti-phagocytic genes IL10, CD16.IL18 and MMP9. IPA core canonical pathways analysis revealed the pathophysiology of complex cellular signaling, 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. Further work is underway in our laboratory to decipher the complete biology of TAM formation. Acknowledgement: Supported by ECSU-NIH-MARC2T34GM100831-06, ECSU-NSF-LSAMP, and 5G12MD007597-25(NIMHD) Citation Format: Hirendra N. Banerjee, Kayla Johnston, Christopher Krauss, Santanu Dasgupta, Somiranjan Ghosh, Santosh Mandal. Effects of tumor microenvironment on the efferocytic and phagocytic genes of human macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2786.