Comprehensive Integrative Analysis Reveals the Association of with Macrophage Infiltration and Polarization in Lung Cancer Microenvironment.

Macrophage polarization and infiltration to the tumor microenvironment (TME) is a critical determining factor for tumor progression. Macrophages are polarized into two states-M1 (pro-inflammatory, anti-tumorigenic and stimulated by LPS or ) and M2 (anti-inflammatory pro-tumorigenic and stimulated by ) phenotypes. Specifically, M2 macrophages enhance tumor cell growth and survival. Recent evidences suggest the pivotal role of microRNAs in macrophage polarization during the development of Non-small cell lung cancer (NSCLC), thus proposing a new therapeutic option to target lung cancer. In silico analysis determined cogent upregulation of , downregulation of and miR-34a-5p in NSCLC tissues, consequently worsening the overall survival of NSCLC patients. We observed a significant association of with macrophage infiltration and polarization in NSCLC. We found that is critically implicated in M2 polarization of macrophages, which, in turn, promotes tumorigenesis. expression correlated with miR-34a-5p and in a feed-forward loop (FFL), both of which are implicated in immune regulation. Mechanistic overexpression of miR-34a-5p in macrophages ( stimulated) inhibits , along with downregulation of , (M2 macrophage specific markers), and upregulation of , , (M1 macrophage specific markers), demonstrating macrophage polarization switch from M2 to M1 phenotype. Moreover, co-culture of these macrophages with NSCLC cells reduces their proliferation, wound healing, clonogenic capacity and enhanced NO-mediated apoptosis. Further, transfection of miR-34a-5p in NSCLC cells, also degrades , but enhances the expression of regulated genes-, (pro-inflammatory mediators), which is further enhanced upon co-culture with stimulated macrophages. Additionally, we observed a significant increase in /NO content upon co-culture, suggesting polarization reversion of macrophages from M2 to M1, and eventually leading to anti-tumor effects. Our findings thus show a significant role of in tumorigenesis and TAM polarization of NSCLC. However, miR-34a-5p mediated targeting of these molecular networks will provide a better therapeutic intervention for NSCLC.