The role of the microbiome in skin cancer development and treatment.

Purpose of review: Recent research underscores the significant influence of the skin and gut microbiota on melanoma and nonmelanoma skin cancer (NMSC) development and treatment outcomes. This review aims to synthesize current findings on how microbiota modulates immune responses, particularly enhancing the efficacy of immunotherapies such as immune checkpoint inhibitors (ICIs).

Recent findings: The microbiota's impact on skin cancer is multifaceted, involving immune modulation, inflammation, and metabolic interactions. Beneficial strains like Bifidobacterium and Lactobacillus have shown potential in supporting anti-PD-1 and anti-CTLA-4 therapies by promoting T-cell activation and immune surveillance. Evidence from preclinical and clinical studies, including fecal microbiota transplantation (FMT), highlights improved response rates in patients with microbiota-rich profiles. Notably, certain bacterial metabolites, such as inosine, contribute to enhanced antitumor activity by stimulating IFN-γ in CD8 + T cells.

Summary: Understanding the interplay between microbiota and skin cancer treatment opens promising avenues for adjunctive therapies. Probiotic and prebiotic interventions, FMT, and microbiota modulation are emerging as complementary strategies to improve immunotherapy outcomes and address treatment resistance in melanoma and NMSC.