PDCD1 and neoplasm: In an in vitro study, Chen J et al [33] found that hepatoma cells up-regulate expression of programmed cell death-1 in T cells.Based on the dynamic circulating PD-1/PD-L1 variation after cryoablation and Chen's finding [33], we support the mechanism that PD-1/PD-L1 upregulation may be due to cytokine stimulations in the tumor microenvironment [29].