Association of MUC16 Mutation With Response to Immune Checkpoint Inhibitors in Solid Tumors.

Importance:As the third most frequently mutated gene in cancers, the association between MUC16 mutation and response to immune checkpoint inhibitors (ICIs) in solid tumors remains unclear. Objective:To examine whether MUC16 mutation is associated with genomic factors in ICI response in solid tumors and with outcomes in ICI-treated patients. Design, Setting, and Participants:This cohort study used multidimensional genomic data of 10 195 patients from The Cancer Genome Atlas (TCGA) across 30 solid tumor types, 56 patients from a non-small cell lung cancer (NSCLC) cohort, and 145 patients from a melanoma cohort. Genomic factors associated with ICI response covered tumor mutational burden, neoantigens, immune-related gene signatures, and tumor immune microenvironment. Both NSCLC and melanoma cohorts included ICI-treated patients. The TCGA cohort was used to examine the association of MUC16 mutation with genomic factors. Two ICI-treated cohorts were used to explore the significance of outcomes associated with MUC16 mutation, using Kaplan-Meier curves and Cox models with adjusting for potential confounders. Gene set enrichment analysis was used to identify MUC16 mutation-associated biological processes. Data were obtained from October 1 through October 10, 2019, and were analyzed from October 11 through December 31, 2019. Main Outcomes and Measures:Genomic factors associated with ICI response, overall survival, and clinical response. Results:Of the 10 195 patients, 4821 (47.6%) were men (median [interquartile range {IQR}] age, 60 [50-70] years). MUC16 was mutated in 2006 of 10 195 patients (19.68%). In this pan-cancer data set, patients with MUC16 mutation had higher tumor mutational burden (median [IQR], 230 [93-595] mutations vs 48 [25-92] mutations; difference, 182 mutations; 95% CI, 164-199 mutations; P < .001) and neoantigen load (median [IQR], 179 [74-394.5] neoantigens vs 48 [24-89] neoantigens; difference, 131 antigens; 95% CI, 116.5-145 neoantigens; P < .001) than those without mutations. The tumor immune microenvironment with dual-positive CD8A and PD-L1 was overrepresented in MUC16-mutated tumors compared with wild-type ones (43.8% vs 32.4%; odds ratio, 1.63; 95% CI, 1.46-1.80; P < .001). Of the 40 immune-related genes, 37 (92.5%) exhibited differential expression between 2 states. MUC16 mutation was associated with improved overall survival in both the NSCLC (hazard ratio, 0.34; 95% CI, 0.12-0.99; P = .04) and melanoma (hazard ratio, 0.57; 95% CI, 0.36-0.90; P = .02) cohorts. The improvement persisted after adjusting for age, sex, and dominant mutational signatures in the melanoma cohort (hazard ratio, 0.57; 95% CI, 0.33-0.96; P = .04). MUC16 mutation was associated with greater response rates in the NSCLC cohort (odds ratio, 4.03; 95% CI, 1.06-16.43; P = .03) and the melanoma cohort (odds ratio, 3.38; 95% CI, 1.07-14.25; P = .03). Gene set enrichment analysis revealed that gene sets regarding cell proliferation and immune response were enriched in MUC16-mutated tumors (false discovery rate, <.001). Conclusions and Relevance:MUC16 mutation appears to be associated with reported genomic factors associated with response to and improved outcomes for ICI treatment in solid tumors. It may hold promise as a marker for guiding immunotherapeutic responsiveness.

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