Function And Regulation Mechanism Of SGK1 In The Chemoresistance Of Pancreatic Cancer

BackgroundPancreatic cancer is a malignant tumor of the digestive system which has a poor prognosis.Gemcitabine,as a first-line chemotherapy agent for pancreatic cancer,performs a good efficacy and tolerable side effect in some patients.However,the overall response rate and the ability to prolong survival are limited,as many patients develop acquired resistance to gemcitabine during chemotherapy.Deciphering the molecular mechanism of gemcitabine resistance is of great significance for finding new therapeutic targets to break the current therapeutic bottleneck.SGK1 was found to be associated with gemcitabine resistance based on the PDTX model.SGK1 is a member of the serine/threonine kinase family and is correlated to the occurrence and development of glioblastoma,breast cancer,colorectal cancer,prostate cancer,ovarian cancer,non-small cell lung cancer,and other malignant tumors.SGK1 can induce tumor chemoresistance to AKT inhibitors,paclitaxel,and temozolomide.However,the function and mechanism of SGK1 in pancreatic cancer have not been reported,and the relationship between SGK1 and gemcitabine chemoresistance is not clear.ObjectiveTo identify the expression of SGK1 in pancreatic cancer tissue,pancreatic cancer cell lines,and gemcitabine-resistant pancreatic cancer cell lines.To detect the effect of SGK1 on biological behavior,such as colony formation,proliferation,drug resistance,migration,and apoptosis.To explore the mechanism of SGK1 in regulating the gemcitabine sensitivity in pancreatic cancer.We aim to provide a new idea for deciphering the mechanism of chemotherapy resistance in pancreatic cancer,which may shed light on novel treatment targets for pancreatic cancer.MethodsFirstly,the expression level of SGK1 in pancreatic cancer tissues was detected by immunohistochemical staining,the SGK1 level in pancreatic cancer cell lines was detected by RT-qPCR and Western Blot.Secondly,SGK1 knockdown and overexpression cell line models were constructed.The effects of SGK1 on drug resistance,proliferation,apoptosis,and migration of pancreatic cancer cells were detected by colony formation,CCK-8,Annexin V,Transwell migration,and wound healing assay.Then,the transcriptome sequencing and bioinformatics analysis were performed to explore the possible downstream targets of SGK1.The effect of the candidate downstream target on cell proliferation and drug resistance was verified in vitro.Finally,we confirmed the downstream pathway of SGK1 regulating gemcitabine sensitivity in pancreatic cancer by Western Blot.ResultsImmunohistochemical staining indicated that SGK1 expression in pancreatic cancer tissues was higher than that in adjacent normal tissues,and SGK1 high expression was associated with a poor prognosis of pancreatic cancer.RT-qPCR indicated that SGK1 expression in gemcitabine-resistant cell lines was higher than that in wild type cell lines,and SGK1 expression level was increased under the induction of gemcitabine.Further experiments showed that knockdown of SGK1 could inhibit the proliferation,survival,and migration ability,while overexpression of SGK1 could promote the colony formation,proliferation,survival,and migration capabilities.Based on transcriptome sequencing and bioinformatics analysis,HMGB2 may be the downstream target of SGK1.In vitro experiments have shown that knockdown of HMGB2 can reduce the proliferation ability of pancreatic cancer cells and increase the sensitivity to gemcitabine chemotherapy.Rescue experiment showed that simultaneous knockdown of HMGB2 could rescue the gemcitabine sensitivity suppressed by SGK1.Western Blot showed that the phosphorylation levels of mTOR and NF-?B were significantly changed after SGK1 knockdown or overexpression,and the phosphorylation levels of NF-?B were significantly changed after HMGB2 knockdown.ConclusionThe expression of SGK1 in pancreatic cancer tissues is higher than that in adjacent normal tissues,which is associated with poor prognosis and acquired resistance to gemcitabine.SGK1 can increase the expression level of HMGB2,and then induce the phosphorylation of NF-?B,thereby promoting gemcitabine resistance.SGK1 can also enhance the phosphorylation level of mTOR,and thereby promote the proliferation,migration,and survival ability of pancreatic cancer cells.