In tumor cells, Wang et al. recently reported that IFN-γ upregulates HHLA2 expression in hepatocellular carcinoma [15], while Bhatt et al. reported that HHLA2 regulation and PD-L1 regulation may be distinct as HHLA2 is not induced by IFN-γ in renal cell carcinoma (RCC) cell lines [12]. Here, HHLA2 is linked to neoplasm.