Demethylase KDM4A Down-regulates Estrogen Receptor α-mediated Gene Transcription In Papillary Thyroid Carcinoma

Objective: Thyroid cancer was a non-reproductive cancer with a significant high incidence in women,of which thyroid papillary carcinoma(PTC)accounted for more than 80%.The incidence of PTC was similar between boys and girls before adolescence and increases significantly in women from adolescence onwards.The research indicated that estrogen receptor α(ERα)played an important role in the occurrence and development of PTC.However,the role of the regulation of ERα signaling pathway in PTC was still unclear.Histone demethylase KDM4 A was commonly involved in the demethylation of histones H3K9 me and H3K36 me,and exerted its biological functions by regulating gene transcription.In addition,KDM4 A also recruited protein complexes to participate in gene transcription regulation in an enzyme activity-independent manner.This paper aims to investigate the biological functions of KDM4 A in PTC cells,and analyze the role and molecular mechanism of KDM4 A in ERα-mediated gene transcription regulation of PTC,in an attempt to provide a theoretical basis and new targets for the treatment and prognosis judgment of PTC.Methods: The protein expression of KDM4 A in PTC tissues was detected by Western Blot assay and statistical analysis was performed based on clinical data.The interaction of KDM4 A with ERα was confirmed by Co-Immunoprecipitation(Co-IP)and GST pulldown assays.The intracellular localization of KDM4 A and ERα was analyzed by immunofluorescence confocal assay(confocal).The regulatory effects of KDM4 A on ERα-mediated gene transcription were analyzed by double luciferase reporter gene assay,real-time fluorescent quantitative PCR(q PCR)and Western Blot assays.The effects of KDM4 A on the biological function of PTC cells were detected by colony formation assay,MTS cell proliferation assay,cell cycle assay and wound-healing assay.Results: 1.The protein expression of KDM4 A was significantly low in PTC tissues(p< 0.001).2.In PTC patients,the low expression of KDM4 A was significantly associated with a higher proportion of lymph node metastases(p=0.038).3.The results of Co-IP assays confirmed the interaction between KDM4 A and ERα in PTC cells.The results of GST pull-down assay showed that KDM4 A bound to ERα AF-1 region.The confocal assays confirmed that KDM4 A and ERα were co-located in the nucleus.4.Assays such as double luciferase reporter gene detection confirmed that KDM4 A down-regulated ERα-mediated downstream gene transcription in PTC cells,and knocking down KDM4 A promoted the expression of endogenous ERα downstream gene.5.The results of colony formation assay showed that knocking down KDM4 A promoted the proliferation of PTC cells,MTS cell proliferation assay showed that overexpression of KDM4 A significantly inhibited cell proliferation,cell cycle assay showed that knocking down KDM4 A promoted the transformation of PTC cells in S/G2 phase,and wound-healing assay showed that overexpression of KDM4 A significantly inhibited cell migration.Conclusion: Histone demethylase KDM4 A was significantly low in PTC tissues,and the low expression of KDM4 A was significantly and positively correlated with PTC lymph node metastasis.2.KDM4 A interacted with ERα in PTC cells to down-regulate ERα-mediated downstream gene transcription.3.KDM4 A regulates the cell cycle of PTC cells and inhibits cell proliferation and migration.