CXCL9 and melanoma: METTL3 and METTL14 inhibit mRNA m6A modification, enhancing the response of colorectal cancer and melanoma with good mismatch repair or low microsatellite instability (pMMR-MSI-L) to anti-PD-1 treatment while increasing the infiltration of CD8 + T cells and IFN-γ, Cxcl9, and Cxcl10 in tumor-infiltrating cells [222].