Uncovering metabolic microenvironments modulating tumor immunity in colorectal cancer

Abstract

Colorectal cancer (CRC) is characterized by a complex intricate of molecular changes that accompany morphological alterations, modifying the normal colonic epithelium into carcinogenic tissue. While the underlying genetic alteration of CRC plays a significant role, the interplay between the cancer cells and the tumor microenvironment (TME) is a critical determinant of cancer progression and therapeutic response. In particular, the immune system interacts in a reciprocal manner with the tumor, regulating its growth and immune evasion. In recent years, research interest has grown in gut microbiota as an active component of the TME, highlighting the immunomodulatory role of bacterial- derived metabolites. Although some of these metabolites have been well-studied, some of their functions have not been fully described. In fact, the majority of these studies have been performed in conventional in vitro models, not fully recapitulating the complexity of the TME and the architecture of the colon epithelium. Here, as a proof of concept, we investigated the effects of the two well-described metabolites, being butyrate and deoxycholic acid (DCA), on antigen-specific CD8⁺ T cell function in the context of murine CRC organoids. We employed conventional co-cultures to model the tumor-immune-metabolite axis with increasing levels of complexity. Our results demonstrated that butyrate enhances T cell activation, along with IFN-γ and TNF production. In contrast, DCA suppressed CD8+ T function, decreasing both cytokine levels. We also investigated the role of gallic acid (GA), a not-well described phenolic metabolite. GA exhibited promoting effects on CD8+ T cells, demonstrated by an decrease in T cell activation. To further study the roles of butyrate and DCA in a more physiological approach resembling the TME, we used colon-on-chip. This system mimics the in vivo colon epithelium architecture and functionality. By integrating CRC organoids and immune cells, we observed that butyrate enhanced the migration of the immune cells towards the tumor, whereas DCA exhibited an opposite effect. These findings underscore the necessity of studying immunometabolic interactions in dynamic, tissue-relevant environment, highlighting the potential for metabolites in oncology research.