Tumor cells modulate macrophage phenotype in a novel in vitro co-culture model of the non-small cell lung cancer tumor microenvironment

Introduction: Macrophage phenotype in the tumor microenvironment correlates with prognosis in non-small cell lung cancer (NSCLC). Immunosuppressive macrophages promote tumor progression, while pro-inflammatory macrophages may drive an anti-tumor immune response. How individual NSCLCs impact macrophage phenotype is a major knowledge gap. Methods: To systematically study the impact of lung cancer cells on macrophage phenotypes, we developed an in vitro co-culture model comprised of molecularly and clinically-annotated patient-derived NSCLC lines, human cancer-associated fibroblasts, and murine macrophages. Induced macrophage phenotype was studied through qRT-PCR and validated in vivo using NSCLC xenografts through quantitative immunohistochemistry and clinically with TCGA “matched” patient tumors. Results: 72 NSCLC cell lines were studied. The most frequent highly induced macrophage-related gene was Arginase-1, reflecting an immunosuppressive M2-like phenotype. This was independent of multiple clinicopathologic factors, which also did not impact M2:M1 ratios in matched TCGA samples. In vivo, tumors established from high Arginase-1-inducing lines (Arghi) had a significantly elevated density of Arg1+ macrophages. Matched TCGA clinical samples to Arghi NSCLC lines had a significantly higher ratio of M2:M1 macrophages. Conclusions: In our preclinical model, a large panel of patient-derived NSCLC lines most frequently induced high expression Arginase-1 in co-cultured mouse macrophages, independent of major clinicopathologic and oncogenotype-related factors. Arghi cluster-matched TCGA tumors contained a higher ratio of M2:M1 macrophages. Thus, this preclinical model reproducibly characterizes how individual NSCLCs modulate macrophage phenotype, correlates with macrophage polarization in clinical samples, and can serve as an accessible platform for further investigation of macrophage-specific therapeutic strategies. Overall design: 15 unique co-cultures were submitted for RNA seq and human transcripts were filtered out.