Genomic ERBB2/ERBB3 mutations promote PD-L1-mediated immune escape in gallbladder cancer: a whole-exome sequencing analysis

Objectives Patients with gallbladder carcinoma (GBC) lack effective treatment methods largely due to the inadequacy of both molecular characterisation and potential therapeutic targets. We previously uncovered a spectrum of genomic alterations and identified recurrent mutations in the ErbB pathway in GBC. Here, we aimed to study recurrent mutations of genes and pathways in a larger cohort of patients with GBC and investigate the potential mechanisms and clinical significance of these mutations. Design We performed whole-exome sequencing (WES) in 157 patients with GBC. Functional experiments were applied in GBC cell lines to explore the oncogenic roles of ERBB2/ ERBB3 hotspot mutations, their correlation with PD-L1 expression and the underlying mechanisms. ERBB inhibitors and a PD-L1 blocker were used to evaluate the anticancer activities in co-culture systems in vitro and in vivo. Results WES identified ERBB2 and ERBB3 mutations at a frequency of 7%-8% in the expanded cohort, and patients with ERBB2/ ERBB3 mutations exhibited poorer prognoses. A set of in vitro and in vivo experiments revealed increased proliferation/ migration on ERBB2/ ERBB3 mutation. Ectopic expression of ERBB2/ ERBB3 mutants upregulated PD-L1 expression in GBC cells, effectively suppressed normal T-cellmediated cytotoxicity in vitro through activation of the PI3K/ Akt signalling pathway and contributed to the growth and progression of GBC in vivo. Treatment with an ERBB2/ ERBB3 inhibitor or a PD-L1 monoclonal antibody reversed these immunosuppressive effects, and combined therapy revealed promising therapeutic activities. Conclusions ERBB2/ ERBB3 mutations may serve as useful biomarkers in identifying patients who are sensitive to ERBB2/ ERBB3 inhibitors and PD-L1 monoclonal antibody treatment.