Rapamycin-insensitive companion of mTOR (RICTOR) amplification defines a subset of advanced gastric cancer and is sensitive to AZD2014-mediated mTORC1/2 inhibition

Background: Targeting oncogenic genomic aberrations is an established therapeutic strategy in multiple tumor types. Molecular classification has uncovered a number of novel targets, and rapamycin-insensitive companion of mTOR (RICTOR) amplification has been identified in lung cancer. Further investigation assessing the therapeutic potential of RICTOR amplification as a novel target across advanced cancers is needed. Patients and methods: Tumor samples from 640 patients with metastatic solid tumors, primarily gastrointestinal and lung cancers were prospectively subjected to a next-generation sequencing (NGS) assay to identify molecular targets. Samples with NGS-detected RICTOR amplification were confirmed with FISH. A RICTOR-amplified patient-derived cell (PDC) line was generated and used to investigate the effectiveness of selective AKT, mTORC1, and mTORC1/2 inhibition. Results: NGS identified 13 (2%) of 640 patients with RICTOR-amplified tumors (6 gastric, 3 NSCLC, 1 SCLC, 1 CRC, 1 sarcoma, 1 MUO). Of the 13 patients, seven patients had RICTOR protein overexpression by IHC. The prevalence of RICTOR amplification in gastric cancer by NGS was 3.8% (6/160). FISH testing confirmed amplification (RICTOR/control> 2) in 5/13 (38%) of samples, including four gastric cancers and one lung cancer. Treatment of a RICTOR amplified PDC with a selective AKT (AZD5363), selective mTORC1 (everolimus), dual mTORC1/2 (AZD2014), and the multi-target kinase inhibitor pazopanib demonstrated preferential sensitivity to the mTORC1/2 inhibitor (AZD2014). Knockdown of RICTOR reversed PDC sensitivity to AZD2014, validating the importance of RICTOR amplification to the PDC line. Conclusions: RICTOR amplification is a rare but therapeutically relevant genomic alteration across solid tumors. Our results support further pre-clinical and clinical investigation with AZD2014 in RICTOR amplified gastric cancer and highlights the importance of genomic profiling.