Taxifolin Inhibits the Growth of Non-Small-Cell Lung Cancer via Downregulating Genes Displaying Novel and Robust Associations with Immune Evasion Factors

SIMPLE SUMMARY: Lung cancer (LC) is the leading cause of cancer deaths. While the current immunotherapies are beneficial to patients, the effects are minimal and heterogeneous, which calls for improvements in patient selection and treatment effectiveness. We discovered taxifolin to inhibit LC. The inhibition was associated with alterations of gene expressions. Among those genes affected, a panel of 12 genes, which we named TxflSig (taxifolin signature), and its subpanel of 7 genes (TxflSig1) effectively predicted responses of lung cancer patients to immunotherapy; TxflSig and TxflSig1 are valuable biomarkers for patient selection. Among both TxflSig and TxflSig1 multigene panels are ITGAL, ITGAX, and TMEM119 genes. These three genes were robustly associated with immunosuppressive activities, and their expressions were inhibited by taxifolin. Collectively, this research contributes to improvement in the management of lung cancer patients via patient selection and suggests that taxifolin could be a promising addition to immunotherapy in treating LC patients. ABSTRACT: Using an LL2 cell-based syngeneic mouse LC model, taxifolin suppressed allografts along with the appearance of 578 differentially expressed genes (DEGs). These DEGs were associated with enhancement of processes related to the extracellular matrix and lymphocyte chemotaxis as well as the reduction in pathways relevant to cell proliferation. From these DEGs, we formulated 12-gene (TxflSig) and 7-gene (TxflSig1) panels; both predicted response to ICB (immune checkpoint blockade) therapy more effectively in non-small-cell lung cancer (NSCLC) than numerous well-established ICB biomarkers, including PD-L1. In both panels, the mouse counterparts of ITGAL, ITGAX, and TMEM119 genes were downregulated by taxifolin. They were strongly associated with immune suppression in LC, evidenced by their robust correlations with the major immunosuppressive cell types (MDSC, Treg, and macrophage) and multiple immune checkpoints in NSCLC and across multiple human cancer types. ITGAL, ITGAX, and IIT (ITGAL-ITGAX-TMEM119) effectively predicted NSCLC’s response to ICB therapy; IIT stratified the mortality risk of NSCLC. The stromal expressions of ITGAL and ITGAX, together with tumor expression of TMEM119 in NSCLC, were demonstrated. Collectively, we report multiple novel ICB biomarkers—TxflSig, TxflSig1, IIT, ITGAL, and ITGAX—and taxifolin-derived attenuation of immunosuppressive activities in NSCLC, suggesting the inclusion of taxifolin in ICB therapies for NSCLC.