To validate our findings, we employed multiplex IF to asses the expression of REG4, MUC1 and MUC5AC in a cohort of MSI CRC patients (n = 9) who underwent immunotherapy-based treatment and achieved either a complete response (CR; n = 3), a partial response (PR; n = 3) or experienced disease progression (PD; n = 3) (Supplementary Table S2). The gene discussed is REG4; the disease is colorectal carcinoma.