Serum levels of nicotinamide N-methyltransferase in patients with lung cancer

The aim of this study was to determine if nicotinamide N-methyltransferase (NNMT) is useful as a biomarker of lung cancer (stages I-III). We established an ELISA system for NNMT. We determined the levels of NNMT and carcinoembryonic antigen (CEA) in sera of 113 non-small cell lung cancer (NSCLC) patients undergoing surgery and sera of 50 non-neoplastic lung disease patients with chronic obstructive pulmonary disease (COPD) and of 24 healthy donors. The serum levels of NNMT were significantly higher in lung cancer patients than in COPD patients and healthy donors. The relationship between the specificity and sensitivity of NNMT and CEA measurements for the detection of lung cancer was analyzed by means of receiver-operating characteristic curves. The corresponding areas under the curves were 0.703 for NNMT and 0.621 for CEA, indicating slightly better sensitivity of NNMT. With 90% specificity, the sensitivities of NNMT and CEA as lung cancer markers were 25 and 24%, respectively. There was no significant correlation between NNMT and CEA. Therefore, the sensitivity of NSCLC detection at 90% specificity increased from 25 to 32% when NNMT was used in combination with CEA. The NNMT serum level may have significance in the early detection of NSCLC patients.