Cancer immunotherapy resistance: The impact of microbiome-derived short-chain fatty acids and other emerging metabolites

The landscape of cancer therapy has undergone dramatic changes over the past decade. Immune checkpoint inhibitors (ICIs) among various cancer immunotherapies have transformed the treatment paradigm for cancer therapy and improved the survival of patients. Nevertheless, oncologists are faced with key challenges that need to be overcome, such as the unpredictability of patient response to these therapies and the many immune-related adverse effects (irAEs). One major factor contributing to patient response to treatment is the composition of their gut microbiota. Many studies reported the role of gut microbiota in modulating immunotherapy. In particular, microbiota-derived metabolites, mainly short-chain fatty acids (SCFAs), have been the highlights of many studies exploring the association between the gut microbiome and patient sensitivity to cancer immunotherapy. This review discusses the role of gut microbiota-derived metabolites on patient response to ICIs and their potential use as predictive biomarkers and therapeutic targets to fine-tune, regulate, and enhance cancer immunotherapy.