B7-Family Score in Urothelial Carcinoma

Immunotherapy has been found to confer substantial survival benefits to the patients with higher mutation burdens, which become the first biomarker approved by FDA in urothelial carcinoma (UC). Nevertheless, among the patients with high mutation burdens, some still remained refractory to immunotherapy. The B7 family molecules have long been perceived as vital determinant of immune response and may define dominant molecular subsets associated with immunotherapeutic response. Simultaneously, our previous study (Eur J Cancer. 2022,171:133-142) unveiled the potential of B7-H4 as a candidate biomarker to refine the predictive capability of tumor mutation burden (TMB) in immunotherapeutic efficacy based on its significant correlation with TMB in MIBC. We hypothesized that the integration of B7 family molecules with TMB could better identify patients with better response to checkpoint blockade.

In this retrospective study, a total of 1,084 UC patients from 5 independent cohorts were enrolled. We established the B7 Family Score (BFS) by the expression patterns of three B7 family members: PD-L1 (CD274), B7-H3 (CD276) and B7-H4 (VTCN1) based on protein and transcriptomic level respectively. We further investigated the correlation of BFS with genomic features and therapeutic response in UC. In addition, we integrated the BFS with tumor mutation burden (TMB) to better stratify the clinical benefit from PD-L1 blockade and platinum-based chemotherapy.