RESUMO
BACKGROUND: CpG island hypermethylation of gene promoters is a well-known mechanism of epigenetic regulation of tumor related-genes and is directly linked to lung carcinogenesis. Alterations in the pattern of methylation of the NPTX1 gene have not yet been studied in detail in human lung cancer. METHODS: Methylation-specific PCR (MSP) and bisulfite sequencing PCR (BSP) were used to analyze promoter methylation status, and real-time quantitative reverse transcription-PCR (qRT-PCR) examined mRNA levels. Subsequently, we compared the methylation profile of NPTX1 in samples of neoplastic and non-neoplastic lung tissue taken from the same patients by using quantitative methylation specific PCR (QMSP). RESULTS: CpG island hypermethylation in promoter of NPTX1 was confirmed in lung cancer cell lines. A significant increase in NPTX1 methylation was identified in lung cancer specimens compared to adjacent noncancerous tissues and that it was negatively correlated with its mRNA expression. The overall survival time among patients carrying methylated NPTX1 tumors was significantly shorter as compared to those with unmethylated NPTX1 tumors (P = 0.011). Moreover, methylation of NPTX1 gene was found to be an independent prognostic factor for poor overall survival based on multivariate analysis models (p = 0.021), as was age ≥60 years old (p = 0.012) and TNM stage (p < 0.001). CONCLUSIONS: These results suggest that NPTX1 hypermethylation and consequent mRNA changes might be an important molecular mechanism in lung cancer. Epigenetic alterations in NPTX1 may serve as potential diagnostic and prognostic biomarkers in lung cancer.