Mutational landscape of DNA damage response deficiency-related genes and its association with immune biomarkers in esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) has limited effective treatment strategies. DNA damage response (DDR) genes are of therapeutic interest in multiple cancer types. This study aimed to depict the landscape of DDR mutations in ESCC and evaluate the association between DDR mutations and known immunotherapy biomarkers. We recruited 250 Chinese patients with ESCC and performed next-generation sequencing. A total of 107 patients underwent a PD-L1 examination. Among the 250 patients, 73 (29.2%) harbored at least one DDR gene mutation and were defined as DDR-mut. Among the six functional DDR pathways, homologous recombination (HR) accounted for 12.4% (31/250). DDR-mut patients were significantly associated with higher tumor mutational burden than those in the DDR-wt group (p=7.4e-07). Patients with PDL1-H accounted for 21.2% (36/107) of the patients. PDL1-H was more prevalent in DDR-mut than DDR-wt, although the p-value did not reach a significant level (40.5% vs. 30%, p=0.29). Further analysis revealed that BRCA1, one of the most frequently mutated genes in the HR pathway, was significantly associated with PDL1-H (p=0.01). Our data revealed a subset of patients with ESCC harbored DDR gene mutations. Patients with these DDR gene mutations are significantly associated with immune biomarkers, implying the potential feasibility of combining DDR agents with immunotherapy in patients with DDR deficiency.