KDM4A promotes the migration and invasion of breast cancer cell line MDA-MB-231 by downregulating BMP9

Abstract

Background and purpose: Exogenous bone morphogenetic protein 9 (BMP9) inhibits the malignant progression of human breast cancer, but its expression is often abnormally low in breast cancer. In this study, we intended to explore the expression and role of epigenetically-modified histone lysine-specific demethylase 4A (KDM4A) in breast cancer, and to investigate the relationship between KDM4A and BMP9 and its possible regulatory mechanism. Methods: The expression of KDM4A in breast cancer and its relationship with BMP9 were analyzed by bioinformatics and verified by real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) and Western blot. Chromatin immunoprecipitation (ChIP) verified the regulatory role of KDM4A on BMP9, and RNA stability experiments and CHX protein stability experiments verified the effect of KDM4A in BMP9 expression. Exogenous recombinant MDA-MB-231 cells transfected with KDM4A small interfering RNA (siKDM4A) or infected with siBMP9 adenovirus (Ad-siBMP9) were constructed using RNA interference technology and adenoviruses knocking down BMP9, and the migratory and invasive abilities of the cells were detected by scratch healing assay and transwell assay, respectively. Results: Bioinformatics analysis showed that the expression of KDM4A was significantly higher in breast cancer than in normal tissues, and there was a negative correlation between the expression of KDM4A and that of BMP9 in breast cancer; RTFQ-PCR and Western blot showed that KDM4A was highly expressed in different breast cancer cell lines, and the knockdown of KDM4A significantly up-regulated BMP9. ChIP experiment confirmed that KDM4A could be significantly enriched in the promoter region of BMP9 gene, reducing its histone lysine 36 position instead of position 4 methyl status, thus silencing the expression of BMP9. RNA stability assay and CHX protein stability assay confirmed that KDM4A had no significant effect on the mRNA of BMP9, but could affect its protein degradation. After knocking down KDM4A, the migration and invasion abilities of breast cancer cells MDA-MB-231 were significantly inhibited, and this effect could be partially reversed by knocking down BMP9. Conclusion: KDM4A is highly expressed in breast cancer and breast cancer cell MDA-MB-231, and can silence its expression by down-regulating the level of histone methylation in the promoter region of the BMP9 gene, as well as affecting the stability of BMP9 at the protein level rather than at the level of mRNA, and promoting the migration and invasion of breast cancer.

Keywords

• |breast cancer|lysine-specific demethylase 4a|histone demethylation|bone morphogenetic protein 9