Fig. 3

Gut microbiota-targeting strategies to boost cancer immunotherapy. There are different approaches that target the gut microbiota to improve the immunotherapy response. (1) Antimicrobial intervention, which uses antibiotics to selectively eradicate gut pathobionts without harming beneficial commensals. (2) Microbial metabolites (e.g., SCFAs, tryptophan derivatives, L-arginine, vitamins, inosine, TMAO), and (3) probiotics, prebiotics, and dietary intervention can activate cytotoxic T lymphocytes (CTLs) to potentiate antitumor immunity. (4) Engineered bacteria develop a bacterial strain to specifically target tumor cells, modulate the host antitumor response, and remodel the tumor microenvironment (TME). (5) Oncolytic viruses utilize engineered viruses to specifically target and destroy tumor cells through direct oncolysis and activation of CTLs and other antitumor immune cells. (6) Antiviral prevention, which utilizes vaccines targeting viruses, including EBV, HPV, HBV and HCV, to abolish their ability to infect tumor cells and elicit a protumorigenic immune response. (7) Bacteriophage therapy, which targets and directly kills gut pathobionts and detrimental bacteria to facilitate antitumor immune responses involving DCs and CTLs. (8) Antifungal treatments deplete protumorigenic fungi such as Candida, Alternaria, and Cladosporium and reduce the number of tumor-promoting immunosuppressive cells (e.g., MDSCs, TAMs, IL2, and Th2). TCR, T-cell receptor. Figure created with BioRender.com