Methylation of the candidate biomarker TCF21 is very frequent across a spectrum of early-stage nonsmall cell lung cancers.

The transcription factor TCF21 is involved in mesenchymal-to-epithelial differentiation and was shown to be aberrantly hypermethylated in lung and head and neck cancers. Because of its reported high frequency of hypermethylation in lung cancer, further characterization of the stages and types of nonsmall cell lung cancer (NSCLC) that are hypermethylated and the frequency of hypermethylation and associated "second hits" were assessed. TCF21 promoter hypermethylation in 105 NSCLC including various stages and histologies in smokers and nonsmokers was determined. In addition, TCF21 loss of heterozygosity and mutational status were examined. Twenty-two cancer cell lines from varied tissue origins were also assayed. The NSCLC results were validated and expanded by examining TCF21 immunohistochemical expression on a tissue microarray containing 300 NSCLC cases. Overall, 81% of NSCLC samples showed TCF21 promoter hypermethylation, and 84% showed decreased TCF21 protein expression. Multivariate analysis showed that TCF21 expression, although below normal in both histologies, was lower in adenocarcinoma than in squamous cell carcinoma and was not independently correlated with sex, smoking, and EGFR mutation status or with clinical outcome. Cell lines from other cancer types also showed frequent TCF21 promoter hypermethylation. Hypermethylation and decreased expression of TCF21 were tumor specific and very frequent in all NSCLCs, even early-stage disease, thus making TCF21 a potential candidate methylation biomarker for early-stage NSCLC screening. TCF21 hypermethylation in a variety of tumor cell lines suggests it may also be a valuable methylation biomarker in other tumor types.