The Mechanism Of DNMT1 Promoting The Growth And Metastasis Of Hypopharyngeal Carcinoma Fadu Cells By Inhibiting The Expression Of DAPK1

Hypopharyngeal carcinoma is one of the most malignant tumors of head and neck squamous cell carcinoma.In the past decades,domestic and foreign experts have continuously explored novel ideas and mechanisms for the treatment of hypopharyngeal cancer,while the prognosis of patients with hypopharyngeal cancer has not been significantly improved.However,the pathological mechanism leading to highly malignant hypopharyngeal carcinoma and poor prognosis has not been fully clarified,and there is an urgent need to explore new research directions and therapeutic targets.Studies have shown that epigenetic modification plays an important role in tumorigenesis.DNA methylation was the most common epigenetic modification catalyzed by DNA methyltransferases(DNMTs).Among DNMTs,DNMT1 was a key enzyme responsible for accurate replication and maintenance of DNA methylation patterns.Hypermethylation of tumor suppressor gene promoter could lead to transcriptional inactivation of tumor suppressor genes,and thus participating in tumorigenesis.Overexpression of DNMT1 and its role in promoting tumor growth have been demonstrated in gastric cancer,bladder cancer,and cervical cancer cells.Since DNMT1 was a key enzyme that mediates methylation,determining the role of this enzyme in hypopharyngeal carcinoma and its relationship with the tumor suppressor gene is helpful to understand the underlying pathological mechanism of the occurrence and development of hypopharyngeal carcinoma.As a tumor suppressor gene,death associated protein kinase 1(DAPK1)was involved in multiple internal and external apoptotic stimulation-induced cell death processes.However,inhibiting the expression of DAPK1 may lead to tumor genesis and metastasis.Studies have shown that the decreased expression of DAPK1 was associated with the hypermethylation of the gene promoter.Hypermethylation of DAPK1 promoter has been detected in gastric cancer,esophageal cancer,laryngeal cancer and other malignant tumors,but the mechanism that mediates its methylation has not been fully clarified.Studies have shown that DNMT1 could inhibit the expression of tumor suppressor genes by promoting methylation of tumor suppressor gene promoters such as GSTP1,CDH1 and P16 in various tumors.However,the mechanism that whether DNMT1 was involved in the occurrence and development of hypopharyngeal cancer by regulating methylation in the promoter region of DAPK1 gene has not been studied.Objective The purpose of this study is to explore the role of DNMT1 in the growth and metastasis of hypopharyngeal cancer Fadu cells and the mechanism of the regulation of DNMT1 and DAPK1 expression.Methods DNMT1 was transfected with DNMT1-siRNA to silence the expression of DNMT1 in hypopharyngeal cancer Fadu cells,and then low expression of DNMT1 cells were constructed.PCR and Western Bolt were used to detect the expression levels of DNMT1 and DAPK1.Then the effects of DNMT1 on proliferation,apoptosis,cell cycle,migration and invasion of hypopharyngeal carcinoma Fadu cells were detected by CCK8 assay,flow cytometry analysis,scratch assay and Transwell assay.Finally,the methylation status of DAPK1 promoter was detected by Methylation-Specific PCR(MS-PCR).Results1.Silencing the expression of DNMT1 in hypopharyngeal cancer Fadu cells inhibits cell proliferation;2.Silencing the expression of DNMT1 in hypopharyngeal cancer Fadu cells promoted cell apoptosis;3.Silencing the expression of DNMT1 in hypopharyngeal cancer Fadu cells blocked cell cycle;4.Silencing the expression of DNMT1 in hypopharyngeal cancer Fadu cells decreased the migration and invasion ability of cells;5.The expression of DAPK1 was low in hypopharyngeal cancer Fadu cells,and the expression level of DAPK1 was significantly increased after the silenced expression of DNMT1 in hypopharyngeal cancer Fadu cells;6.Silencing the expression of DNMT1 in hypopharyngeal cancer Fadu cells resulted in demethylation of the DAPK1 promoter region.Conclusion In this study,we found that DNMT1 could inhibit the expression of DAPK1 by promoting the methylation of the promoter region of DAPK1,thus promoting the growth and metastasis of hypopharyngeal cancer Fadu cells,enriching the basic research on the pathogenesis and development of hypopharyngeal cancer and the potential molecular mechanism leading to its highly malignant,and providing a scientific basis for the discovery of new therapeutic targets for hypopharyngeal cancer.