To investigate whether the activation of CaSR by spermine is required for PD-L1 expression, we examined the effects of the CaSR inhibitor NPS2134 and the intracellular Ca2+ chelator BAPTA-AM (each applied to cells at 10 μM) on spermine-induced expression of CD274 mRNA and PD-L1 protein in HCC cells. Here, CD274 is linked to hepatocellular carcinoma.