SIAH2 and neoplasm: The difference of cell susceptibility to T-cell killing between PCCA#2-LV-NC and PCCA#2-LV-Siah2 was reversed by blocking PD-L1 with pembrolizumab (Figures 7C, D), indicating that PD-L1 is required for Siah2-mediated tumor resistance to T-cell antitumor activity.