Expression of B7 family checkpoint proteins in cervical cancer

The role of programmed cell death-ligand 1 (PD-L1) in cervical cancer has been widely investigated; however, the influences of other inhibitory B7 family members are poorly understood. We investigated the expression of PD-L1, B7 homolog 3 (B7-H3), B7-H4, and V-domain Ig suppressor of T-cell activation (VISTA) and their association with the clinicopathological features and outcomes of a large cohort of 673 patients with squamous cell carcinoma or adenocarcinoma of the uterine cervix. The positivity rates for PD-L1 (combined positive score ≥1), B7-H3 in tumor cells (TCs), B7-H4 (exclusively in TCs), VISTA in immune cells (ICs), and VISTA in TCs were 57.9%, 62.8%, 44.8%, 92.6%, and 4.8%, respectively, in 606 primary cervical cancer samples. Co-expression of PD-L1 with B7-H3 in TCs and with B7-H4 and VISTA in ICs was observed in 38.8%, 25.4%, and 57.9% of samples, respectively. B7-H3 in TCs and B7-H4 and VISTA in ICs were observed in 58.1%, 46.6%, and 83.1% of PD-L1-negative samples, respectively. These proteins were observed more frequently in squamous cell carcinomas and in moderately to poorly differentiated carcinomas. VISTA (in ICs) and B7-H4 were more frequent in primary tumors than in recurrent counterparts and correlated with improved survival; in contrast, B7-H3 positivity in TCs was less frequent in primary tumors and correlated with short disease-specific survival. Co-expression of B7-H4 and VISTA in ICs was an independent predictor of favorable outcomes overall and among patients with PD-L1-negative tumors. These data indicate that B7 family proteins exhibit differing expression patterns, distributions, and prognostic implications in cervical cancer. Furthermore, the co-expression of PD-L1 with other checkpoint proteins suggests that PD-1/PD-L1 blockade combined with modulating other immune checkpoints may present a novel therapeutic approach for cervical cancer. Future studies are needed to validate prognostic values of B7 family proteins and explore their biological roles in this malignancy.