Colorectal cancer (CRC) has a high mortality rate among cancers worldwide. To reduce this mortality rate, chemotherapy (5-fluorouracil, oxaliplatin, and irinotecan) or targeted therapy (bevacizumab, cetuximab, and panitumumab) has been used to treat CRC. However, due to various side effects and poor responses to CRC treatment, novel therapeutic targets for drug development are needed. In this study, we identified the overexpression of EHMT1 in CRC using RNA sequencing (RNA-seq) data derived from TCGA, and we observed that knocking down EHMT1 expression suppressed cell growth by inducing cell apoptosis in CRC cell lines. In Gene Ontology (GO) term analysis using RNA-seq data, apoptosis-related terms were enriched after EHMT1 knockdown. Moreover, we identified the CHOP gene as a direct target of EHMT1 using a ChIP (chromatin immunoprecipitation) assay with an anti-histone 3 lysine 9 dimethylation (H3K9me2) antibody. Finally, after cotransfection with siEHMT1 and siCHOP, we again confirmed that CHOP-mediated cell apoptosis was induced by EHMT1 knockdown. Our findings reveal that EHMT1 plays a key role in regulating CRC cell apoptosis, suggesting that EHMT1 may be a therapeutic target for the development of cancer inhibitors.

The epigenetic regulation of oncogenes and tumor suppressor genes by histone methyltransferases is an important process for colon cancer growth and metastasis. Although various epigenetic modifiers have been recognized as attractive therapeutic targets for colon cancer treatment, alternative epigenetic regulation in colon cancer for reducing side effects and increasing the effectiveness of treatments has not been thoroughly explored. In this study, we identified CDKN1A as a direct target for EHMT2 by RNA-sequencing and found increased growth suppression via upregulation of CDKN1A by EHMT2 knockdown. In addition, using a 3-dimensional culture system for spheroid formation with an ultralow attachment plate, we confirmed EHMT2-related growth suppression and CDKN1A regulation. Thus, we suggest that EHMT2 may be a therapeutic target for colon cancer treatment, and an EHMT2 inhibitor should be developed for the effective treatment of colon cancer.