CTLA4 and melanoma: In addition to IFN-γ, the expression of PD1 and CTLA-4, two critical checkpoint molecules that negatively regulate T-cell immune response23,24, were significantly decreased (P < 0.05 in melanoma; P < 0.01 in hepatocarcinoma) in tumor-infiltrating CD8+ T cells by CQ monotreatment but not when CQ was combined with clodronate (Fig. 2g, h).