HOXD1 inhibits lung adenocarcinoma progression and is regulated by DNA methylation [TBS]

The homeobox (HOX) family encodes highly conserved transcription factors and plays a crucial role in embryonic development and tumorigenesis. Homeobox D1 (HOXD1) is a member of the HOX family, whose biological functions in lung cancer are unclear. The UALCAN database analysis of HOXD1 expression patterns revealed that HOXD1 is downregulated in lung adenocarcinoma patient samples relative to adjacent normal tissue. Western blotting validated low HOXD1 expression in lung adenocarcinoma (LUAD) cell lines. The Kaplan-Meier plotter database demonstrated that HOXD1 expression reduction in LUAD was found to correlate with worse overall survival. Meanwhile, in vitro study showed that HOXD1 overexpression suppressed LUAD cells proliferation, migration, and invasion. In the mouse tumor model, upregulated HOXD1 retarded tumor growth. In addition, targeted bisulfite sequencing and ChIP assay found that DNA hypermethylation occurred in the promoter region of the HOXD1 gene and was associated with DNA methyltransferases. In additionMoreover, upregulated HOXD1 as a transcriptional factor increased the transcriptional expression of BMP2 and BMP6. Taken together, the dysregulation of HOXD1 mediated by DNA methylation inhibited the initiation and progression of lung adenocarcinoma by regulating the expression of BMP/BMP6. To investigate that the HOXD1 promoter undergoes DNA methylation, targeted bisulfite sequencing (TBS) was performed to detect methylation levels of HOXD1 in BEAS-2B, A549, and H1299 cells.