Nicotinamide‐N‐methyltransferase is a promising metabolic drug target for primary and metastatic clear cell renal cell carcinoma

• Published in: Clinical and translational medicine Vol. 12; no. 6; pp. e883 - n/a
• Main Authors: Reustle, Anna, Menig, Lena‐Sophie, Leuthold, Patrick, Hofmann, Ute, Stühler, Viktoria, Schmees, Christian, Becker, Michael, Haag, Mathias, Klumpp, Verena, Winter, Stefan, Büttner, Florian A., Rausch, Steffen, Hennenlotter, Jörg, Fend, Falko, Scharpf, Marcus, Stenzl, Arnulf, Bedke, Jens, Schwab, Matthias, Schaeffeler, Elke
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.06.2022; John Wiley and Sons Inc; Wiley
• Subjects: Antibodies; Carcinoma, Renal Cell - drug therapy; Carcinoma, Renal Cell - genetics; Carcinoma, Renal Cell - metabolism; Clinical medicine; Deoxyglucose; DNA methylation; Enzymes; Fatty acids; Gene expression; Genomes; Glucose; Glutamine; Humans; Kidney cancer; Kidney Neoplasms - drug therapy; Kidney Neoplasms - genetics; Kidney Neoplasms - metabolism; Lymphatic system; Metabolism; Metastasis; Niacinamide - pharmacology; NNMT; NNMTi; oxphos; Patients; renal cell carcinoma; Response rates; Tumor Microenvironment; Urology; Germany; renal cell carcinoma; NNMT; metastasis; metabolism; glutamine; oxphos; NNMTi
• ISSN: 2001-1326; 2001-1326
• DOI: 10.1002/ctm2.883

Background The metabolic enzyme nicotinamide‐N‐methyltransferase (NNMT) is highly expressed in various cancer entities, suggesting tumour‐promoting functions. We systematically investigated NNMT expression and its metabolic interactions in clear cell renal cell carcinoma (ccRCC), a prominent RCC subtype with metabolic alterations, to elucidate its role as a drug target. Methods NNMT expression was assessed in primary ccRCC (n = 134), non‐tumour tissue and ccRCC‐derived metastases (n = 145) by microarray analysis and/or immunohistochemistry. Findings were validated in The Cancer Genome Atlas (kidney renal clear cell carcinoma [KIRC], n = 452) and by single‐cell analysis. Expression was correlated with clinicopathological data and survival. Metabolic alterations in NNMT‐depleted cells were assessed by nontargeted/targeted metabolomics and extracellular flux analysis. The NNMT inhibitor (NNMTi) alone and in combination with the inhibitor 2‐deoxy‐D‐glucose for glycolysis and BPTES (bis‐2‐(5‐phenylacetamido‐1,3,4‐thiadiazol‐2‐yl)ethyl‐sulfide) for glutamine metabolism was investigated in RCC cell lines (786‐O, A498) and in two 2D ccRCC‐derived primary cultures and three 3D ccRCC air–liquid interface models. Results NNMT protein was overexpressed in primary ccRCC (p = 1.32 × 10–16) and ccRCC‐derived metastases (p = 3.92 × 10–20), irrespective of metastatic location, versus non‐tumour tissue. Single‐cell data showed predominant NNMT expression in ccRCC and not in the tumour microenvironment. High NNMT expression in primary ccRCC correlated with worse survival in independent cohorts (primary RCC—hazard ratio [HR] = 4.3, 95% confidence interval [CI]: 1.5–12.4; KIRC—HR = 3.3, 95% CI: 2.0–5.4). NNMT depletion leads to intracellular glutamine accumulation, with negative effects on mitochondrial function and cell survival, while not affecting glycolysis or glutathione metabolism. At the gene level, NNMT‐depleted cells upregulate glycolysis, oxidative phosphorylation and apoptosis pathways. NNMTi alone or in combination with 2‐deoxy‐D‐glucose and BPTES resulted in inhibition of cell viability in ccRCC cell lines and primary tumour and metastasis‐derived models. In two out of three patient‐derived ccRCC air–liquid interface models, NNMTi treatment induced cytotoxicity. Conclusions Since efficient glutamine utilisation, which is essential for ccRCC tumours, depends on NNMT, small‐molecule NNMT inhibitors provide a novel therapeutic strategy for ccRCC and act as sensitizers for combination therapies. NNMT is highly expressed in ccRCC primary tumours and metastases, correlating with worse patient survival. Glutamine metabolism is impaired in NNMT‐depleted cells, with negative consequences for cellular fitness. NNMT inhibition reduces cell viability and induces cytotoxicity in 2D/3D ccRCC‐derived tumour models. Beyond NNMT inhibition for the treatment of metabolic diseases, its application for anticancer therapy appears promising.