SMAD7-Associated Glycolytic Regulation Promotes Lactate-Dependent Macrophage Phenotype Modulation in Colorectal...

Colorectal cancer (CRC) progression is shaped by dynamic interactions between tumor-intrinsic metabolic adaptations and immune remodeling within the tumor microenvironment. In CRC, the expression of SMAD7, a classical inhibitor of TGF-β1 signaling, is increased and has been associated with tumor-associated inflammatory responses and malignant progression. In this study, we investigated the potential role of SMAD7 in regulating glycolytic metabolism and macrophage phenotype in CRC. Knockdown of SMAD7 in CRC cell lines resulted in reduced glycolytic activity, as demonstrated by decreased extracellular acidification rate, basal glycolysis, and glycolytic capacity. These metabolic changes were associated with reduced expression of the basal and IL-6- and IL-22-induced glycolytic enzyme hexokinase 2 (HK2), while glucose uptake was increased. Similar reductions in HK2 expression were observed in patient-derived CRC organoids following SMAD7 inhibition, supporting the relevance of this pathway in human tumor-derived models. Functionally, SMAD7 knockdown reduced lactate production by CRC cells and diminished the ability of tumor cell-derived conditioned medium to induce the expression of macrophage-associated immunoregulatory markers, including CD163, CD206, and ARG1. The addition of exogenous lactate restored these effects, indicating that tumor-derived lactate contributes to SMAD7-dependent control of the expression of macrophage-associated immunoregulatory markers. Analysis of human CRC transcriptomic datasets revealed positive associations between SMAD7 expression and macrophage-related signatures, including profiles associated with immunoregulatory tumor-associated macrophages. Together, these findings support a potential role for SMAD7 in controlling tumor metabolism and macrophage-associated immunoregulatory markers in CRC.