PD-1H (VISTA) Expression in Cutaneous Squamous Cell Carcinoma Is Correlated with T-Cell Infiltration and Activation

Cutaneous squamous cell carcinoma (cSCC) is one of the most common human cancers, with an estimated death rate approaching or exceeding that of melanoma. Immune inhibitory receptor antagonism through the blockade of PD-1 or its ligand, PD-L1, has revolutionized the treatment of cSCC; however, approximately half of patients still fail to respond. The inhibitory receptor PD-1H (also known as VISTA) controls T-cell and myeloid cell functions in preclinical cancer studies. Currently, cancer clinical trials using anti-VISTA-blocking antibodies are ongoing. We sought to determine the extent of VISTA expression in cSCCs and to correlate its expression with PD-L1 expression. Using multiplexed quantitative immunofluorescence of primary cSCC tissues (n = 76), we found that VISTA was expressed in 48% of cSCCs and that PD-L1 was expressed in 58% of cSCCs. We found that high VISTA expression, more than PD-L1 expression, correlated with greater T-cell infiltration and activation, as measured by the proliferation marker Ki-67 and the cytotoxic marker granzyme B. Furthermore, there was no significant correlation between VISTA and PD-L1 coexpression within the same cSCCs, suggesting that individual tumors have distinct immunosuppressive microenvironments. These findings provide a rationale for the targeting of VISTA in cSCC immunotherapy.