Nicotinamide N-methyltransferase protein expression in renal cell cancer.

OBJECTIVE: To understand the function of nicotinamide N-methyltransferase (NNMT) protein as tumor biomarker in renal carcinoma. METHODS: Recombinant NNMT protein was used to prepare monoclonal antibodies by hybridoma technique. The diagnostic and prognostic function of NNMT protein in renal carcinoma was evaluated by analyzing 74 renal cancer tissues through immunohistochemical staining for NNMT by using the prepared antibodies. RESULTS: Two hybridomas named 2F8 and 1E7 stably secreting the monoclonal antibodies were isolated successfully, and characters such as isotypes and specificity were determined. NNMT protein was significantly up-regulated in renal cancer and significantly associated with tumor histology and ages. The univariate survival analysis demonstrated that the pT-status, high levels of NNMT, and distant metastasis were significant prognosticators. CONCLUSION: NNMT is over-expressed in a large proportion in renal cell cancers. High NNMT expression is significantly associated with unfavorable prognosis. However, the prognostic value of NNMT needs further verification in larger sample sizes.

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

PURPOSE: The aim of this study was to determine if nicotinamide N-methyltransferase (NNMT) is useful as a biomarker of lung cancer (stages I-III). METHODS: 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. RESULTS: 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. CONCLUSION: The NNMT serum level may have significance in the early detection of NSCLC patients.

Optimization of diagnostic ELISA-based tests for the detection of auto-antibodies against tumor antigens in human serum.

Colorectal cancer is one of the most common cancer types worldwide and it continues to be a serious public health problem. Early detection and diagnosis are of great importance in cancer management. At present, diagnostic blood tests are based on the detection of tumor-associated markers such as carcino-embryonic antigen (CEA), the cancer antigen CA19-9 for gastrointestinal cancer, CA15-3 for breast cancer or CA125 for ovarian cancer. The lack of sensitivity and specificity of these markers prevents their general use in cancer screening of an average risk population. Therefore, new cancer biomarkers or better screening methods are necessary to improve the diagnostics of the disease. This study was directed to the optimization of a diagnostic, enzyme linked immunosorbent assay (ELISA) based test to identify and validate new serum markers, such as extracellular Protein Kinase A (ecPKA) and Nicotinamide N-Methyltransferase (NNMT). In this type of assay, the cancer antigens are quantified indirectly - by detecting the presence of auto-antibodies against tumor proteins in human serum. The result of the optimization and validation process was in the case of ecPKA a reproducible and stable assay. In case of NNMT the assay was probably not sensitive enough.

Overexpression of nicotinamide N-methyltransferase in gastric cancer tissues and its potential post-translational modification.

Gastric cancer is one of the most common cancers worldwide. The purpose of this study was to find out potential markers for gastric cancer. Tumor and normal tissues from 152 gastric cancer cases were analyzed by two-dimensional gel electrophoresis (2-DE). The images of silver stained gels were analyzed and statistical analysis of spot intensities revealed that spot 4262 showed higher expression (5.7-fold increase) in cancer tissues than in normal tissues (P < 0.001). It was identified by peptide mass fingerprinting as nicotinamide N-methyltransferase (NNMT). A monoclonal antibody with a detection limit down to 10 ng was produced against NNMT in mouse. Using the prepared monoclonal antibody, western blot analysis of NNMT was performed for gastric tissues from 15 gastric cancer patients and two gastric ulcer patients. The results corroborated those of 2-DE experiments. A single spot was detected in gastric ulcer tissues while four to five spots were detected in gastric cancer tissues. In cancer tissues, two additional spots of acidic and basic form were mainly detected on 2-DE gels. This suggests that NNMT receives a post-translational modification in cancer- specific manner.