High blood levels of the SCFAs butyrate and propionate were associated with resistance to CTLA-4 blockade, reducing the efficacy of immunotherapy by upregulating CD80/CD86 on dendritic cells, ICOS (Inducible T-cell COStimulator) gene expression in T cells, and the accumulation of tumor-specific T cells and memory T cells. This evidence concerns the gene CTLA4 and neoplasm.