Effect Of STAT1 On Apoptosis Of Esophageal Cancer Cells Induced By NDV Infection

Cancer proliferates indefinitely and avoids apoptosis by controlling the genetic,transcriptional and epigenetic changes in the signal pathways of cell cycle,apoptosis and cell growth.At present,it is difficult to prevent early esophageal cancer because of the special anatomical structure of esophagus,atypical early symptoms of esophageal cancer and the lack of screening methods.The high invasiveness of esophageal cancer causes poor prognosis to patients who are treated with traditional cures such as surgery and drug therapy.The majority of patients also do not benefit from the currently available targeted therapy and immunotherapy.Newcastle disease virus(NDV)selectively replicates in malignant cells.In addition to causing direct damage of host cells through viral infection,NDV activates multiple signaling pathways and antitumor immune responses,triggering apoptosis and autophagy.However,the antitumor molecular mechanisms of NDV-induced esophageal cancer(EC)cells apoptosis are not well-understood.NDV infection induces the apoptosis of tumor cells through mitochondrial pathway is related to the activation of caspase,while signal transducer and activator of transcription1(STAT1)regulates anti-tumor function characterized by elevated caspase family members.Therefore,we hypothesize that the apoptosis by NDV-induced is related to STAT1.The bulk of evidence reveals that STAT1 functions as a tumor suppressor involved in cell proliferation,apoptosis,differentiation and immune responses mainly through interacting and regulating target genes at multiple levels.The majority of studies have also evaluated the clinical significance of STAT1 as a improved prognostic marker.However,it has been reported that STAT1 promotes tumor cell invasion,radioresistance,angiogenesis and immunosuppression.STAT1 whether performs as an oncoprotein or tumor suppressor role in EC cells and functions as a synergistic or antagonistic factor in oncolytic virotherapy by NDV.Using different online available databases and bioinformatics tools,we studied the role of STAT1 across cancer.STAT1 expression in EC were analyzed using GEPIA2,GENT2 and Human Protein Atlas.Furthermore,the potential prognostic values were evaluated through KM plotter.Moreover,a correlational analysis between STAT1 expression and immune cells analysis was performed using GEPIA2021.Then,STRING wasutilized to examine the STAT1 interacting protein,while gene enrichment analysis was performed using GSEA.Gene enrichment analysis indicated that STAT1 participates in signaling pathways and involved in regulation of cell cycle and apoptosis,while a correlations were also documentedbetween STAT1 expression and CD8~+T immune cells infiltration.According to NDV infection or treated with fludarabine,a specific inhibitor of STAT1,ECA109 cells were classified into four groups:cells with NDV infectionwas taken as positive control group,cells treated with fludarabine serve as negative control group,experimental group added fludarabine before NDV infection,while cells without treatment serve as controlcheck group.Western blot was used to detected the expression of STAT1 in each group,results showed that with the infection of NDV,expression of STAT1 in positive control group increased significantly,however the effect wasdecreased after the treatment of fludarabine(P<0.05).Cells treated with fludarabine were observed to have a more obvious apoptosis under phase-contrast microscope when compared to the experimental group.CCK-8was used to determine the proliferation,flow cytometry and DNA ladder in order to determine the apoptosis rate,compared to the positive control,the rate was significantly decreased in the experimental group(P<0.05).Electron micrographs were used to identify potential active viral infections within ECA109 cells,widespread apoptosis was observed in the infected cells including organelle swelling and increased formation of apoptoticbodies.Our results indicate that NDV induces apoptosis of ECA109 tumor cells and this intrinsic mechanism is related to STAT1,reveale thatSTAT1-dependent pathway might be required in the induction of apoptosis by NDV.