Macrophage immunometabolism as a targetable driver of early lung cancer progression

Background Lung cancer is a leading cause of cancer-related mortality and early progression is driven by interactions between epithelial cells and the tumor-immune microenvironment. Macrophages shape cancer progression through both inflammatory and immunosuppressive programs. Prior work has shown dysbiosis, cytokine enrichment, and increased stearic acid (SA) levels in tumor affected lobes of early-stage lung cancer patients. To better understand the role of SA within the tumor microenvironment, we consider its effect on macrophage polarization, altered immune signaling, and epithelial response. We modeled the effect of macrophage-derived signals on the early transformation of lung epithelial cells to identify conserved transcriptional programs that may be leveraged to improve prevention and treatment strategies. Methods To characterize the effect of SA on macrophages, U937 pro-monocytic cells were differentiated into macrophage-like cells (M0, M1, M2) with PMA and further stimulated with some combination of LPS, IFN-gamma, IL-4, SA, or BSA (vehicle). Conditioned media from macrophage cell cultures was collected before RNA was extracted using TRIzol and sequenced on an Illumina platform. To characterize the effect of SA on macrophage immune signaling, BEAS2B epithelial cells were treated with macrophage-like conditioned media and malignant potential was assessed with a methylcellulose-based soft agar assay. Total RNA was extracted using NEB Monarch Total RNA Miniprep kit and sequenced on an Illumina platform. Differential gene expression for U937 and BEAS2B treatment groups were analyzed, and pathway enrichment was assessed using GO terms and KEGG analysis. Results SA exposure modified transcription across M0-, M1-, and M2-like macrophage phenotypes and lead to altered expression of 83 common genes. Gene ontology (GO) functional analysis showed evidence of modified cholesterol and alcohol metabolism and steroid biosynthesis in M0- and M2-like macrophages. SA exposure was associated with increased expression of MVK , STARD4 , and INSIG1 related to sterol and lipid metabolism. SA exposure was also associated with decreased expression of KIF4A , TOP2A , and BRCA2 related to cell cycle regulation and genomic stability. Modified expression of these and other genes identified during our analysis may be involved in early tumor processes. Conclusions Stearic acid modulates macrophage transcription across phenotypes, supporting our hypothesis that immunometabolic signaling plays an important role in lung cancer initiation. These findings provide a molecular foundation for future studies characterizing the transcriptional changes identified and their effect on lung cancer initiation. Furthermore, they highlight macrophages as potential targets for preventive or early therapeutic interventions in lung cancer.