The mutational pattern of homologous recombination(HR)-associated genes and its relevance to the immunotherapeutic response in gastric cancer

Objective:Currently,there is an urgent need to identify immunotherapeutic biomarkers to increase the benefit of immune checkpoint inhibitors(ICIs)for patients with gastric cancer(GC).Homologous recombination deficiency(HRD)can modify the tumor immune microenvironment by increasing the presence of tumor-infiltrating lymphocytes and therefore might serve as a biomarker of immunotherapeutic response.We aimed to analyze the mutational pattern of HR-associated genes in Chinese patients with GC and its relevance to the tumor immune profile and clinical immunotherapeutic response.Methods:A panel of 543 cancer-associated genes was used to analyze genomic profiles in a cohort comprising 484 Chinese patients with GC.Correlations between HR gene mutations and tumor immunity or clinical outcomes were identified via bioinformatic analysis using 2 GC genomic datasets(TCGA and MSK-IMPACT).Results:Fifty-one of the 484(10.54%)patients carried at least one somatic mutation in an HR gene;ATM(16/484,3.31%)was among the most frequently mutated HR genes in the Chinese cohort.Mutations in HR genes were associated with elevated tumor mutational burden,enhanced immune activity,and microsatellite instability status.In the MSK-IMPACT cohort comprising 49 patients with stomach adenocarcinoma or gastroesophageal junction adenocarcinoma treated with ICIs,patients with HR-mut GC(n=12)had significantly better overall survival than those with HR-wt GC(n=37)(log-rank test,P<0.05).Conclusions:Our data suggest that detection of somatic mutations in HR genes might aid in identifying patients who might benefit from immune checkpoint blockade therapy.

Alterations in DNA damage response and repair genes as potential biomarkers for immune checkpoint blockade in gastrointestinal cancer

Objective:Immune checkpoint inhibitors(ICIs)have achieved remarkable results in cancer treatments.However,there is no effective predictive biomarker for gastrointestinal(GI)cancer.Methods:We conducted integrative analyses of the genomic and survival data of ICI-treated GI cancer patients from the Memorial Sloan Kettering Cancer Center cohort(MSK-GI,n=227),the Janjigian cohort(n=40),and the Peking University Cancer Hospital&Institute cohort(PUCH,n=80)to determine the possible associations between DNA damage response and repair(DDR)gene mutations and clinical outcomes.Data from The Cancer Genome Atlas database were analyzed to determine the possible correlations between DDR gene mutations and the tumor microenvironment.Results:In the MSK cohort,the presence of≥2 DDR gene mutations was correlated with prolonged overall survival(OS).The Janjigian and PUCH cohorts further confirmed that subgroups with≥2 DDR gene mutations displayed a prolonged OS and a higher durable clinical benefit.Furthermore,the DDR gene mutation load could be considered as an independent prognostic factor,and exhibited a potential predictive value for survival in GI cancer patients treated with ICIs.Mechanistically,we showed that the presence of≥2 DDR gene mutations was correlated with higher levels of tumor mutation burden,neoantigen,and T cell infiltration.Conclusions:The DDR gene mutation status was correlated with favorable clinical outcomes in GI cancer patients receiving ICIs,which could serve as a potential biomarker to guide patient selection for immunotherapy.

Prognostic impact of gene copy number instability and tumor mutation burden in patients with resectable gastric cancer

Dear Editor,Gastric cancer(GC)is a leading cause of cancer-related deaths worldwide,especially in China and other East Asian countries[1,2].Although considerable achievements have been made in its treatment[3]and predictive biomarkers[4]in past decades,the prognosis of GC remains poor[5].Therefore,more effective prognostic markers are needed to improve the prognosis prediction of GCs.Small panels based on next-generation sequencing,such as FoundationOne CDx and MSK-IMPACT,are widely used for selecting appropriate treatment approaches(such as targeted therapies,immunotherapies,and chemotherapies)with the advantages of a higher sequencing depth and more cost-effectiveness than whole-exome sequencing(WES).Previous studies have demonstrated that molecular characteristics based on the designed cancer-related gene panel were consistent with those determined by WES and could be prognostic markers for various cancer types[6-8].As such,we analyzed the molecular features with the designed panel to investigate probable prognostic biomarkers for Chinese patients with GC.