BACKGROUND: Colorectal cancer (CRC) is a prevalent malignancy worldwide, and epigenetic modifications, particularly methylation of key genes, play a crucial role in its initiation and progression. DNA methyltransferase 1 (DNMT1) is aberrantly overexpressed in CRC; however, its specific mechanisms of action and downstream targets remain unclear. This study aims to elucidate how DNMT1 epigenetically regulates HOXD11 expression and subsequently influences CRC progression. METHODS: The expression and methylation status of HOXD11 in 30 pairs of CRC tissues and adjacent normal tissues were detected by RT-qPCR, Western Blot, and methylation-specific PCR (MSP). HOXD11 overexpression assays were performed in CRC cell lines, and cell proliferation, migration, invasion, and apoptosis were evaluated using CCK-8, colony formation, wound healing, Transwell assays, and flow cytometry. To identify the key enzyme regulating HOXD11, we conducted specific shRNA knockdown screening of DNA methyltransferase family members (DNMT1, DNMT3A, and DNMT3B). The regulatory effect of DNMT1 on HOXD11 was then verified using the demethylating agent 5-AzaC. Finally, a nude mouse subcutaneous xenograft model was established to validate the therapeutic potential of targeting the DNMT1/HOXD11 axis in vivo. RESULTS: HOXD11 was significantly downregulated in CRC tissues, accompanied by promoter hypermethylation. Overexpression of HOXD11 markedly inhibited CRC cell proliferation, migration, and invasion, while inducing apoptosis. Mechanistic studies revealed that among the three DNMTs screened, only DNMT1 knockdown significantly upregulated HOXD11 expression, confirming DNMT1 as the specific methyltransferase mediating HOXD11 promoter hypermethylation and transcriptional silencing. Treatment with 5-AzaC restored HOXD11 expression and suppressed malignant phenotypes, whereas simultaneous knockdown of HOXD11 reversed these tumor-suppressive effects. In vivo experiments further confirmed that targeted inhibition of DNMT1 significantly curbed tumor growth by upregulating HOXD11. CONCLUSION: This study reveals that DNMT1-mediated promoter hypermethylation of HOXD11 is a critical mechanism driving the malignant progression of CRC. The DNMT1/HOXD11 axis may serve as a potential therapeutic target of CRC.
Wang et al. (Tue,) studied this question.