Clinical Significance of combinatorial blockade of novel immune checkpoint B7-H4 with PD-L1 in Urothelial Carcinoma of Bladder: A rational therapeutic approach

Purpose: Urothelial carcinoma of bladder (UBC) is complex disease with high mortality and recurrence rates. Current standard regimens have exhibited anti-tumor activity however, proportion of patients are non-responsive or ineligible to receive such treatments, which stresses upon identifying new effective options for treating UBC. Immune checkpoints have emerged as potential class of therapeutics to be tested in UBC treatment. Methods: : 40 UBC patients and 30 healthy controls were recruited from whom blood was taken. Histopathologically proven tumors and adjacent normal tissue were obtained from patients. The frequency of T cells and immune checkpoints (B7-H4 and PD-L1) was assessed in circulation. Molecular expression of immune checkpoints has been studied in tumors and normal tissue. In-vitro blocking of B7-H4 alone and in combination with PD-L1 was performed to test for T cell functionality. Finally, these immune checkpoints were correlated with clinico-pathological parameters. Results: : Elevated expression of B7-H4 and PD-L1 were observed in CD8 T cells of UBC patients. Relative mRNA expression and immunohistochemistry displayed upregulation in bladder tumor tissue. Co-blockade enhanced IFN-gand granzyme B of CD-8 T cells. Also, B7-H4 was significantly associated with clinico-pathological parameters. Conclusion: Increased expression of B7-H4 along with PD-L1 in periphery and tumor of UBC patients highlights involvement of B7-H4 in disease progression, showcasing elevated expression with disease progression. Combinatorial blocking enhanced functional T cell immune response in UBC patients. Also, positive association of B7-H4 with clinico-pathological parameters showcase it as potential therapeutic target for treatment of UBC patient in future after further validation.