Expression of the immune checkpoint VISTA in breast cancer

V-domain Ig suppressor of T cell activation (VISTA) is a novel immune checkpoint that is an emerging target for cancer immunotherapy. This study aimed to investigate the expression of VISTA and its association with clinicopathologic parameters as we N ll as with the key immune markers including programmed cell death-1 (PD-1) and PD-1 ligand-1 (PD-L1) in invasive ductal carcinoma (IDC) of the breast. Immunohistochemistry was used to detect VISTA, PD-1, PD-L1, and CD8 in tissue microarrays from 919 patients with IDC ( N = 341 in the exploratory cohort and = 578 in the validation cohort). VISTA was expressed on the immune cells of 29.1% (267/919) of the samples and on the tumor cells of 8.2% (75/919). VISTA was more frequently expressed in samples that were estrogen receptor-negative, progesterone receptor-negative, human epidermal growth factor receptor 2-positive, poorly differentiated, human epidermal growth factor receptor 2-enriched, and consisting of basal-like tumors. VISTA on immune cells correlated with PD-1, PD-L1, stromal CD8, and tumor-infiltrating lymphocyte expression and was an independent prognostic factor for improved relapse-free and disease-specific survival in patients with estrogen receptor-negative, progesterone receptor-negative, and basal-like IDC. These findings support therapeutic strategies that modulate VISTA expression, perhaps in combination with PD-1/PD-L1 blockade, in human breast cancer immunotherapy.