Research Papers:
Novel NAPRT specific antibody identifies small cell lung cancer and neuronal cancers as promising clinical indications for a NAMPT inhibitor/niacin co-administration strategy
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Abstract
Jonathan Cole1, Marie-Christine Guiot2, Michel Gravel1, Cynthia Bernier1, Gordon C. Shore1 and Anne Roulston1
1Laboratory for Therapeutic Development, Rosalind and Morris Goodman Cancer Research Centre, and Department Biochemistry, McGill University, Montreal, QC, Canada
2Department of Pathology, Montreal Neurological Hospital, Montreal, QC, Canada
Correspondence to:
Anne Roulston, email: [email protected]
Keywords: NAMPT, NAPRT, biomarker, NAMPT inhibitor, NAD+ biosynthesis
Received: April 12, 2017 Accepted: August 17, 2017 Published: September 12, 2017
ABSTRACT
Tumor cells are particularly dependent on NAD+ due to higher rates of metabolism, DNA synthesis and repair. Nicotinamide phosphoribosyltransferase inhibitors (NAMPTis) inhibit NAD+ biosynthesis and represent promising new anti-cancer agents. However, clinical efficacy has been limited by toxicities demonstrating the need for drug combinations to broaden the therapeutic index. One potential combination involves niacin/NAMPTi co-administration. Niacin can rescue NAD+ biosynthesis through a parallel pathway that depends on nicotinic acid phosphoribosyltransferase (NAPRT) expression. Most normal tissues express NAPRT while a significant proportion of malignant cells do not, providing a possible selection marker for patients to achieve NAMPTi efficacy while minimizing toxicities.
Here we identify and validate a novel highly NAPRT-specific monoclonal antibody (3C6D2) that detects functional NAPRT in paraffin embedded tissue sections by immunohistochemistry (IHC). NAPRT detection by 3C6D2 coincides with the ability of niacin to rescue cells from NAMPTi induced cytotoxicity in cell lines and animal xenograft models. 3C6D2 binds to an epitope that is unique to NAPRT among phosphoribosyltransferases. In a series of primary tumor samples from lung and brain cancer patients, we demonstrate that >70 % of human small cell lung carcinomas, glioblastomas and oligodendrogliomas lack NAPRT identifying them as potentially suitable indications for the NAMPT/niacin combination.
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