The metabolic dialogue between intratumoural microbes and cancer: implications for immunotherapy

The tumour microenvironment (TME) exerts a profound influence on cancer progression and treatment outcomes. Recent investigations have elucidated the crucial role of intratumoural microbiota and their metabolites in shaping the TME and modulating anti-tumour immunity. This review critically assesses the influence of intratumoural microbial metabolites on the TME and cancer immunotherapy. We systematically analyse how microbial-derived glucose, amino acid, and lipid metabolites modulate immune cell function, cytokine secretion, and tumour growth. The roles of specific metabolites, including lactate, short-chain fatty acids, bile acids, and tryptophan derivatives, are comprehensively examined in regulating immune responses and tumour progression. Furthermore, we investigate the potential of these metabolites to augment the efficacy of cancer immunotherapies, with particular emphasis on immune checkpoint inhibitors. By delineating the mechanisms through which microbial metabolites influence the TME, this review provides insights into novel microbiome-based therapeutic strategies, thereby highlighting a promising frontier in personalised cancer medicine.