In the present study, we detected PD-L1/PD-1 expression on circulating peripheral blood mononuclear cells and found PD-L1/PD-1 expression increased with liver tumor progression. Further study revealed that there was a close correlation between the circulating and intratumoral PD-L1 expression. We analyzed the circulating PD-1/PD-L1 expression and the clinical parameters in patients with HCC. The result demonstrated that tumor size, blood vessel invasion and BCLC staging were associated with PD-1/PD-L1 expression. However, no significant relationships were found between PD-1/PD-L1 expression and gender, age, number of tumors, HBV DNA load, AFP level or stage of liver function. Although several publications demonstrated that PD-1/ PD-L1 expression levels correlated with the HBV DNA titers, we did not find any correlations in the present study regarding HCC patients with chronic HBV infection. Besides monocytes, PD-L1 is also expressed in dendritic cells and our previous investigations also revealed a good correlation for PD-L1 expression between these two kinds of cells. However, we abandoned the dendritic cell-associated PD-L1 in the present study due to its more complex detection procedures and more expensive cost. Our observations suggested that BKM120 PI3K inhibitor elevated PD-1/PD-L1 expression during the first week after cryoablation was related to inflammation caused by the therapy and that postoperative fever and liver function impairment were the main manifestations. A previous study reported that inflammation could promote PD-1/ PD-L1 expression. Subsequent reduction of PD-1/PD-L1 expression 4 weeks after therapy was associated with a recovery from stress and the reduction of tumor burden. Additionally, numerous tumor antigens are released from these necrotic cells, resulting in an immune response and reduction in immune tolerance. Interestingly, Campbell et al found that cryopreservation of PBMC led to a marked reduction of PD-1 and PD-L1 expression in CD3+/CD8+ T cells and CD45+/CD14+ monocytes, with no significant effect on CD3+CD4+ T cells. The previous study suggested that intratumoral PD-L1 was closely associated with the recurrence or metastasis of HCC after surgery, and we compared the circulating PD-1/PD-L1 expression before and after tumor recurrence in 11 HCC patients received cryoablation.The result showed that PD-1/PD-L1 expression was elevated after tumor recurrence. In an in vitro study, Chen J et al found that hepatoma cells up-regulate expression of programmed cell death-1 in T cells.