Abstract LB-099: Metabolic vulnerabilities of mesenchymal-like EGFR-mutant NSCLC cells with acquired resistance to tyrosine kinase inhibitors

Despite the availability of the effective targeted therapies in lung cancer, such as EGFR tyrosine kinase inhibitors (TKIs), drug tolerance and acquired resistance are two common problems that negatively impact lung cancer patient survival. Consequently it is important to understand the molecular basis of the drug tolerance and resistance so that we could formulate effective strategies to ameliorate the efficacy of existing drug and to suppress the emergence of drug resistance. A burgeoning body of literature demonstrated that epigenetic changes by the methylation of DNA and histones are critical in acquired drug resistance, especially in those cancer cells with stem cell-like properties and epithelial to mesenchymal (EMT)-like features. EMT involves multiple and complex changes in the epigenome and therefore in the transcriptome, the proteome and the metabolome. However, in the context of NSCLC, there are no comprehensive studies linking epigenomic and metabolic reprogramming during EMT and the acquisition of drug resistance. One-carbon metabolic pathway is composed of the folate and methionine cycle, generating S-adenosylmethionine (SAM), which is the universal methyl donor for methylation reactions, including histone and DNA methylation. Interestingly, it has been demonstrated that the overexpression of specific methyl-transferases, such as NNMT, which catalyzes the transfer of the methyl group from SAM to nicotinamide, can impact the methylation potential of cancer cells, draining methyl groups from the methionine cycle and thereby decreasing protein and DNA methylation. Strikingly, NNMT depletion has been shown to restore methylation potential and attenuate the aggressive nature of several cancer cell lines with NNMT overexpression. However, its contribution to lung cancer progression and the drug resistance is still unknown. In this work we have discovered that NNMT is a poor prognosis factor and is significantly correlated with mesenchymal-like phenotypes in publicly available NSCLC clinical databases. We have generated multiple EGFR-TKI acquired resistant NSCLC models with EMT phenotype and utilized a multi-omic approach on the clinically-relevant resistant cell lines to identified that NNMT overexpression affects the nicotinamide pathway leading to deficient nicotinamide adenine dinucleotide (NAD) synthesis. This new cancer vulnerability of TKI-resistant, mesenchymal-like NSCLC cells is druggable using NAD depleting agents such as daporinad, a NAMPT inhibitor in phase II clinical trials for the treatment of B-cell chronic lymphocytic leukemia, cutaneous T-cell lymphoma and melanoma. Additionally, the quantitative measurement of the metabolite signature of the nicotinamide pathway in liquid biopsies may correlate with poor prognosis of TKI-treated patients, and emerges as a potential biomarker of TKI response and tumor progression in NSCLC patients. Based on these evidences and tools, we propose that targeting nicotinamide pathway may serve as a therapeutic tool for sensitizing drug-resistant NSCLC cells with an EMT phenotype to currently available treatments. Citation Format: Ines Pulido, Jeff Becker, Miguel Aupi, Juan Carlos Garcia Canaveras, Javier Alcacer, Maria Rodriguez, Paloma Martin, Javier Perales, Salvador Aparisi, Lourdes Chulia, Arantxa Lafuente, Maribel Alcoriza, Salvador Mena, Javier Pereda, Jose Galbis-Carabajal, Amelia Insa, Oscar Juan, Fatima Al-Shahrour, Manuel Sanchez del Pino, Agustin Lahoz, Takeshi Shimamura, Julian Carretero. Metabolic vulnerabilities of mesenchymal-like EGFR-mutant NSCLC cells with acquired resistance to tyrosine kinase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-099.