<i>In Vitro</i> Evaluation of Inhibitory Effect of Nuclear Factor-KappaB Activity by Small Interfering RNA on Pro-tumor Characteristics of M2-Like Macrophages

Abstract

Tumor-associated macrophages (TAMs) have an alternatively activated macrophage phenotype (M2) and promote cancer cell proliferation, angiogenesis and metastasis. Nuclear factor-kappaB (NF-κB) is one of the master regulators of macrophage polarization. Here, we investigated the effect of inhibition of NF-κB activity by small interfering RNA (siRNA) on the pro-tumor response of macrophages located in the tumor microenvironment in vitro. We used mouse peritoneal macrophages cultured in conditioned medium from colon-26 cancer cells as an in vitro TAM model (M2-like macrophages). Transfection of NF-κB (p50) siRNA into M2-like macrophages resulted in a significant decrease in the secretion of interleukin (IL)-10 (a T helper 2 (Th2) cytokine) and a significant increase of T helper 1 (Th1) cytokine production (IL-12, tumor necrosis factor-α, and IL-6). Furthermore, vascular endothelial growth factor production and matrix metalloproteinase-9 mRNA expression in M2-like macrophages were suppressed by inhibition of NF-κB expression with NF-κB (p50) siRNA. In addition, there was a reduction of arginase mRNA expression and increase in nitric oxide production. The cytokine secretion profiles of macrophages cultured in conditioned medium from either B16BL6 or PAN-02 cancer cells were also converted from M2 to classically activated (M1) macrophages by transfection of NF-κB (p50) siRNA. These results suggest that inhibition of NF-κB activity in M2-like macrophages alters their phenotype toward M1.

NF-κB p50-deficient immature myeloid cell (p50-IMC) adoptive transfer slows the growth of murine prostate and pancreatic ductal carcinoma

“…[33][34][35][36][37] Deletion of p50 in IMC likely impacts these factors and contributes to activation of resulting macrophages and DCs. [9][10][11][12][13][14][15][16] Consistent with this idea, we find that p50-IMC generate tumor and lymph node macrophages that co-express Ly6C and MHCII, a combination indicative of activated, tumor suppressive macrophages. 28 38-40 We previously found increased Ly6C + MHCII + tumor macrophages in glioblastomas developing in the central nervous system of p50 -/compared with WT hosts, associated with reduced glioblastoma tumor growth.…”

“…Proinflammatory gene induction by p50 (Nfkb1) gene deletion or RNA knockdown leads to activation of macrophages, as well as DCs, favouring T cell activation. [9][10][11][12][13][14] Melanoma, fibrosarcoma, colon cancer, and glioblastoma cells grow slower in syngeneic p50 −/− than wild-type (WT) recipients; TAMs are reprogrammed from M2 to M1; and tumor T cells are more activated. 9 15 16 Prostate cancer (PCa) and pancreatic ductal carcinoma (PDC) also contain evident M2 TAMs, which are correlated with poor prognosis.…”

Colonic macrophage polarization in homeostasis, inflammation, and cancer

“…Pello and colleagues (73) these cells by conditioned media from CT26 mouse colon cancer cells (43). Conditioned media from CT26 cancer cells were also found by Ryan and colleagues (84) to induce an M2-like phenotype in mouse macrophages from the RAW cell line; however, conditioned media from CT26 cancer cells transfected to express a degradation-resistant version of the NF-B inhibitor IB (therefore rendered NF-B-deficient), induced an M1-like phenotype in RAW macrophages, which was characterized by increased IL-12p40 and NO 2 Ϫ secretion.…”

The role of PIM1/PIM2 kinases in tumors of the male reproductive system

“…Activation of the NFκB and STAT3 pathways remove the immune mask set by the CSC64. It has been proposed that the tumorigenic potential of CD14+ cells is due to their expression of several inflammatory mediators, such us IL-6, IL-8, FGF-2, and VEGF-165.…”