Lung cancer is one of the most common causes of cancer-related mortality worldwide. Effective early diagnosis and targeted therapies for lung cancer to reduce incidence and mortality would benefit from a better understanding of the key molecular changes that occur from normal to malignant tumor cells during lung cancer initiation and development, but these are largely unknown. Previous studies have shown that DNA methylation, an important mechanism for the regulation of gene expression, plays a key role in lung carcinogenesis. In this study, we screened a novel methylation gene. ANKRD18A, encoding ankyrin repeat domain 18A, to determine whether it is regulated by DNA methylation in lung cancer. Methylation-specific PCR and bisulfite sequencing PCR were used to analyze gene methylation status, and real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) examined mRNA levels. Promoter hypermethylation of ANKRD18A was detected in 68.4% (26/38) of lung cancer tissues but not (0/20) in normal lung tissues (P < 0.01), whereas ANKRD18A mRNA expression was significantly decreased in lung cancer tissues compared with adjacent normal tissues. In addition, we found that ANKRD18A expression was significantly decreased in 9, of 10 lung cancer cell lines. This was associated with hypermethylation of the ANKRD18A promoter region. Moreover, weak expression of ANKRD18A in methylated lung cancer cell lines increased markedly after treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine. These results suggest that ANKRD18A hypermethylation and consequent mRNA alterations might be a vital molecular mechanism in lung cancer. (C) 2012 Elsevier Inc. All rights reserved.