Probiotic-Derived Metabolites from Lactiplantibacillus plantarum OC01 Reprogram Tumor-Associated Macrophages to an Inflammatory Anti-Tumoral Phenotype: Impact on Colorectal Cancer Cell Proliferation and Migration

Background: Tumor-associated macrophages (TAMs) are key players in the colorectal cancer (CRC) tumor microenvironment (TME), representing the most abundant immune cells within it. The interplay between the intestinal microbiota, macrophages, and cancer cells significantly impacts tumor progression by driving macrophage polarization. Particularly, the polarization into the pro-tumoral M2-like TAM phenotype promotes the extracellular matrix remodeling, cancer cell proliferation, metastasis, immune suppression, and therapy resistance. Probiotic metabolites can disrupt this crosstalk, possibly reverting the TAM polarization toward a pro-inflammatory anti-tumoral phenotype, thus potentially benefiting the intestinal mucosa and opposing CRC progression. Previously, we showed that Lactiplantibacillus plantarum OC01 metabolites counter interleukin (IL)-6-induced CRC proliferation and migration. Methods: Here, we explore how probiotics affect CRC secretome and how this influences TAM polarization, which then impacts CRC malignancy. Results: The conditioning medium (CM) from CRC cells indeed promoted the polarization of macrophage toward the M2-like phenotype, whereas the CM from CRC pre-treated with L. plantarum OC01 metabolites induced a pro-inflammatory macrophage phenotype, characterized by NLRP3 inflammasome activation and reactive oxygen species (ROS) production, and by decreased expression of the M2 phenotype markers CD206 and CD163. Consistently, the expression of tumor growth factor (TGF)-β, a promoter of M2 macrophage polarization, was reduced in CRC cells treated with L. plantarum OC01. The pro-inflammatory macrophages inhibited CRC proliferation and migration. Conclusions: Overall, our study highlights the potential of metabolites from L. plantarum OC01 to reprogram the metabolism in cancer cells and thus reshape the TME by shifting TAMs toward a more inflammatory and anti-tumoral phenotype, emphasizing the promise of probiotics in advancing novel therapeutic approaches for CRC.