Abstract
Cancer-associated fibroblasts (CAFs) are a critical component of the tumor microenvironment and play a central role in tumor progression. Previously, we reported that CAFs might induce tumor immunosuppression via interleukin-6 (IL-6) and promote tumor progression by blocking local IL-6 in the tumor microenvironment with neutralizing antibody. Here, we explore whether an anti-IL-6 receptor antibody could be used as systemic therapy to treat cancer, and further investigate the mechanisms by which IL-6 induces tumor immunosuppression. In clinical samples, IL-6 expression was significantly correlated with α-smooth muscle actin expression, and high IL-6 cases showed tumor immunosuppression. Multivariate analysis showed that IL-6 expression was an independent prognostic factor. In vitro, IL-6 contributed to cell proliferation and differentiation into CAFs. Moreover, IL-6 increased hypoxia-inducible factor 1α (HIF1α) expression and induced tumor immunosuppression by enhancing glucose uptake by cancer cells and competing for glucose with immune cells. MR16-1, a rodent analog of anti-IL-6 receptor antibody, overcame CAF-induced immunosuppression and suppressed tumor progression in immunocompetent murine cancer models by regulating HIF1α activation in vivo. The anti-IL-6 receptor antibody could be systemically employed to overcome tumor immunosuppression and improve patient survival with various cancers. Furthermore, the tumor immunosuppression was suggested to be induced by IL-6 via HIF1α activation.