Three meta-analyses have investigated the impacts of PPIs on immune checkpoint inhibitors (including PD-1/PD-L1 inhibitor and CTLA-4 inhibitor), but got different results.[8,19,20] Subgroup analysis has found that concomitant PPIs may have a positive effect on the prognosis of melanoma patients and a negative effect on the prognosis of NSCLC patients.[19] Further analysis found that melanoma patients mainly used CTLA-4 inhibitors, but NSCLC patients only used PD-1/PD-L1 inhibitors.[19] This might portend the different impact of PPI on effect of PD-1/PD-L1 inhibitors and CTLA-4 inhibitor. The gene discussed is CTLA4; the disease is melanoma.