Expression Of SGK1 And Its Effect On The Biological Function Of Nasopharyngeal Carcinoma Cells

BackgroundNasopharyngeal carcinoma(NPC)is one of the most common head and neck tumors that originating from nasopharyngeal mucosa.NPC frequently occurs in Southern China and Southeast Asia,due to its features of regional distribution and familial aggregation.Most of the pathological types of NPC are low differentiated squamous cell carcinoma,which have been high degree of malignancy and cervical lymph node metastasized at early stage.NPC is almost highly sensitive to radiotherapy.Although the local control rate has been greatly improved thanked to concurrent chemo-radiotherapy,the distant metastasis rate was no significantly decreased.Local recurrence and distant metastasis are still the main reasons leading to the failure of NPC treatment.Various pathogenic factors,including family history,genetic dysregulation,environmental alteration,Epstein-Barr virus(EBV)infection and trace elements,correspond to NPC development.However,the molecular processes involved in the NPC pathogenesis have not yet been fully explained.Therefore,it is of great significance to further study in the occurrence and development of NPC,in order to seek new therapeutic approaches and improve the survival of NPC patients.Serum and glucocorticoid-induced kinase 1(SGK1)belongs to the serine/threonine kinase family and is stimulated by serum and glucocorticoid transcription.Insulin and growth factors induce the expression of SGK1 through PI3K,3-phosphoinositide dependent kinase-1(PDK1)or mTORC-2 complex.In mammals,SGK1 is expressed in all examined tissues and regulates a variety of cellular molecules,including cell proliferation,metastasis and apoptosis,ion channels and so on.However,the relationship between SGK1 and nasopharyngeal carcinoma has not been reported at home and abroad.The purpose of this study was to study the expression of SGK1 in nasopharyngeal carcinoma tissues,and the effect of SGK1 on the biological characteristics of nasopharyngeal carcinoma cells,and to explore the relationship between the expression of SGK1 and the occurrence and development of nasopharyngeal carcinoma.Materials and methods1.Immunohistochemical analyses were performed to assess the SGK1 protein expression in formalin-fixed,paraffin-embedded specimens from various nasopharyngeal tissues,including 21 NPC samples and 13 normal nasopharyngeal epithelial samples.The difference between two groups was compared by the chi-square test.2.Lipofectamine 2000 was used to transient transfect HNE-1 cell lines.Fluorescence microscope determined the success of transfection according to the degree of green fluorescent protein(GFP)after 24 hours and western blot detected the expression of SGK1 protein after 48 hours.The siRNA with the most significant SGK1 silencing effect was selected to construct the nasopharyngeal carcinoma cells silencing SGK1.3.Cell biological function test:the proliferation ability of nasopharyngeal carcinoma cells after silencing SGK1 was detected by CCK8 method;the level of apoptosis was detected by flow cytometry;the migration ability of Transwell migration test was detected by Transwell migration test.The survival rate,apoptosis rate and Transwell migration test were compared between groups by variance analysis of factorial design.Results1.The immunohistochemical results showed that the protein expression of SGK1 was mainly found in the cytoplasm.In 21 cases of nasopharyngeal carcinoma,the positive expression rate of SGK1 protein was 76.19%,and in 13 cases of chronic nasopharyngitis,the positive expression rate of SGK1 protein was 15.38%.There was significant difference between the two groups(P<0.01).2.The successful construction of nasopharyngeal carcinoma cell line HNE-1/siSGK1,silencing SGK1 confirmed that down-regulation of SGK1 expression could significantly inhibit the proliferation,survival and migration of nasopharyngeal carcinoma cells in vitro,and promote the level of apoptosis.Conclusion1.SGK1 expression in nasopharyngeal carcinoma and chronic nasopharyngitis tissues is significantly different,and it is highly expressed in nasopharyngeal carcinoma tissues.2.Silencing SGK1 expression in nasopharyngeal carcinoma cells significantly inhibits the proliferation and migration of nasopharyngeal carcinoma cells and promotes apoptosis.