Transcription factor CDX2 up-regulates proto-oncogenic miR-744 via a promoter activation mechanism in non-small-cell lung cancer

BACKGROUND: The role of caudal-related homeobox 2 (CDX2) in the pathogenesis of non-small cell lung cancer (NSCLC) is unclear. The purpose of this study was to investigate the mRNA (message RNA) expression of CDX2 in NSCLC, and to determine its relationship with miR-744 (microRNA744) and its potential as a biomarker of NSCLC. METHODS: MiR-744 is overexpressed in A549, H460, and H1299 cell lines. Real-time quantitative polymerase chain reaction (qRT-PCR) was used to detect the mRNA expression. A chromatin immunoprecipitation (ChIP) essay was performed to determine the CDX2 binding sites. We then conducted a luciferase reporter essay to analyze interaction between MiR-744 and 3'UTRs (the 3' untranslated sequences). The migration and Boyden chamber method were used to study cell mobility. RESULTS: In this study, we found that ectopic CDX2 increased the expression of miR-744, while the attenuation of CDX2 reduced the expression of miR-744 by qRT-PCR. Chromatin immunoprecipitation experiments confirmed that CDX2 directly binds to the promoter of miR-744. The luciferase reporter assay further verified the binding sites of −347 to −358 bp in the most likely promoter like sequence of miR-744. CDX2-induced up-regulation of miR-744 can significantly promote the migration and invasion of NSCLC cells, while overexpression CDX2 is sufficient to rescue the migration and invasion capacity of these cells following knockdown of miR-744. CONCLUSIONS: In summary, our results confirmed for the first time the regulatory mechanism of CDX2 on miR-744 transcription and provided a potential mechanism for CDX2 as an oncogene in lung cancer.