Identification of RPTOR mutation as a novel predictor of efficacious immunotherapy in melanoma.

Abstract

9524 Background: mTOR pathway is known to influence cancer immunity by metabolism reprogramming. RPTOR (Regulatory Associated Protein of MTOR Complex 1), one of mTOR pathway genes, which is involving in control of mammalian target of mTORC1 activity for regulating cell growth and survival. Whether mutations of RPTOR are associated with clinical efficacy of immune checkpoint inhibitors (ICIs) in melanoma is still ambiguous. Methods: In discovery cohort, we retrospective analyzed the genomic data of 418 melanoma samples which derived from seven immunotherapy studies ( http://www.cbioportal.org/ ) to evaluate the relationship between RPTOR mutation status and efficacy of immunotherapy. Then in validation cohort, the predictive value of RPTOR mutation was confirmed in 320 melanomas from MSKCC cohort (http://www.cbioportal.org/). TMB was calculated as the total count of nonsynonymous mutations in coding sequence. We used the CIBERSORT to evaluate the 22 types immune cell infiltration status in TCGA melanoma cohort. Results: The TMB level of RPTOR-mutant patients was higher than RPTOR-wildtype patients in both discovery (Median [IQR]: 43.11[23.76-140.15] vs. 6.13[2.07-13.66], P < 0.001) and validation (Median [IQR]: 37.38[20.17-84.95] vs. 8.85[3.35-21.07], P < 0.001) cohort. In discovery cohort, compared to RPTOR-wildtype patients, the RPTOR-mutant patients achieved prolonged OS (median OS: not reach, NR vs 22.7 months, HR (95%CI): 0.47(0.22-0.99), P = 0.043). This result was confirmed in validation cohort (median OS: NR vs. 42; HR (95%CI): 0.34 (0.11-1.0); P = 0.049). According to analysis of immune cell infiltration status, the mechanism of the predictive values of RPTOR mutations to ICI efficacy may be activated CD4 memory T cell more abundant in RPTOR-mutant tumors. Conclusions: RPTOR mutation is associated with higher TMB in ICI-treated melanoma patients. Survival analysis shows RPTOR mutation have a good link with longer OS after immunotherapy. These findings indicate that RPTOR mutation may serve as a potential predictive biomarker for ICIs in melanoma.