Point mutations of the mTOR-RHEB pathway in renal cell carcinoma

• Published in: Oncotarget Vol. 6; no. 20; pp. 17895 - 17910
• Main Authors: Ghosh, Arindam P, Marshall, Christopher B, Coric, Tatjana, Shim, Eun-Hee, Kirkman, Richard, Ballestas, Mary E, Ikura, Mitsuhiko, Bjornsti, Mary-Ann, Sudarshan, Sunil
• Format: Journal Article
• Language: English
• Published: United States Impact Journals LLC 20.07.2015
• Subjects: Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - metabolism; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Carcinoma, Renal Cell - drug therapy; Carcinoma, Renal Cell - genetics; Carcinoma, Renal Cell - metabolism; Carcinoma, Renal Cell - pathology; Cell Proliferation - drug effects; Databases, Genetic; DNA Mutational Analysis; Drug Resistance, Neoplasm - genetics; Genetic Predisposition to Disease; GTPase-Activating Proteins - genetics; GTPase-Activating Proteins - metabolism; HEK293 Cells; Humans; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Kidney Neoplasms - drug therapy; Kidney Neoplasms - genetics; Kidney Neoplasms - metabolism; Kidney Neoplasms - pathology; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; Monomeric GTP-Binding Proteins - genetics; Multiprotein Complexes - genetics; Multiprotein Complexes - metabolism; Neuropeptides - genetics; Phenotype; Point Mutation; Priority Research Paper; Protein Kinase Inhibitors - pharmacology; Protein Structure, Tertiary; Ras Homolog Enriched in Brain Protein; Signal Transduction - drug effects; Sirolimus - pharmacology; TOR Serine-Threonine Kinases - antagonists & inhibitors; TOR Serine-Threonine Kinases - genetics; TOR Serine-Threonine Kinases - metabolism; Transfection; Tumor Suppressor Proteins - genetics; Tumor Suppressor Proteins - metabolism; mTOR; renal cancer; mutations; RHEB; rapamycin
• DOI: 10.18632/oncotarget.4963
• ISSN: 1949-2553

Aberrations in the mTOR (mechanistic target of rapamycin) axis are frequently reported in cancer. Using publicly available tumor genome sequencing data, we identified several point mutations in MTOR and its upstream regulator RHEB (Ras homolog enriched in brain) in patients with clear cell renal cell carcinoma (ccRCC), the most common histology of kidney cancer. Interestingly, we found a prominent cluster of hyperactivating mutations in the FAT (FRAP-ATM-TTRAP) domain of mTOR in renal cell carcinoma that led to an increase in both mTORC1 and mTORC2 activities and led to an increased proliferation of cells. Several of the FAT domain mutants demonstrated a decreased binding of DEPTOR (DEP domain containing mTOR-interacting protein), while a subset of these mutations showed altered binding of the negative regulator PRAS40 (proline rich AKT substrate 40). We also identified a recurrent mutation in RHEB in ccRCC patients that leads to an increase in mTORC1 activity. In vitro characterization of this RHEB mutation revealed that this mutant showed considerable resistance to TSC2 (Tuberous Sclerosis 2) GAP (GTPase activating protein) activity, though its interaction with TSC2 remained unaltered. Mutations in the FAT domain of MTOR and in RHEB remained sensitive to rapamycin, though several of these mutations demonstrated residual mTOR kinase activity after treatment with rapamycin at clinically relevant doses. Overall, our data suggests that point mutations in the mTOR pathway may lead to downstream mTOR hyperactivation through multiple different mechanisms to confer a proliferative advantage to a tumor cell.