Effect Of Antisense Glucose Transporter-1on Enhancement Of Radiosensitivity Of Laryngeal Carcinoma Hep-2Cell In Vitro

BackgroundTreatment options for laryngeal carcinoma, one of the most common head and neck malignancies, consist of radiotherapy,surgery,chemotherapy or a combination thereof. The functional treatment of laryngeal carcinoma poses a considerable challenge because of its resistance to chemo-and radiotherapy and local recurrences, and finding ways to inhibit theenergy supply of malignant tumours is becoming increasingly attractive.The glucose transporter-1(GLUT-1)is the main transporter of glucose in solid carcinomas and has become a focus of cancer research.Recently, we showed that the increased expression of GLUT-1in head and neck carcinomas is correlated with lymph node metastasis, poor survival and clinical stage,and revealed that suppression of GLUT-1expression by antisense oligodeoxynucleotides decreased glucose uptake and inhibited the proliferation of Hep-2cells.Therefore,we propose that suppression of Glut-1expression is a new therapeutic target for laryngeal carcinoma.In this study, we determined whether suppression of GLUT-1expression by antisense oligodeoxynucleotides(AS-ODNs) may affect on the radiosensitivity of laryngeal carcinoma Hep-2cell.Materials and methodsLaryngeal carcinoma Hep-2cells divided into five groups:control group(OGy), group of2Gy radiation dose,group of4Gy radiation dose, group of8Gy radiation dose, group of12Gy radiation dose before transfection of GLUT-1AS-ODNs or transfected GLUT1AS-ODNs, respectively. After radiation for24hours,48hours,72hours,cell survival rate was assessed by the MTS assay, expression of GLUT-1mRNA was measured by reverse transcription polymerase chain reaction(RT-PCR),cell cycle distribution and apoptosis were monitored by flow cytometry(FCM).Results1Before transfection:The resullts of MTS assay showed that there were no significant cytotoxic effects of X-ray radiation on Hep-2cells24h after irradiation,whereas the survival rate of4gy radiation group was higher than control group(p<0.05);There were no significant differences between the survival rates of2Gy groups during different culture time(24h,48h,72h)(p>0.05) while survival rates of4Gy and8Gy doses increased after radiation for24h;Compared to the control group, GLUT-1mRNA expression of Hep-2cells exposed to X-ray increased(p<0.05);The results of FCM demonstrated that Hep-2cells exposed to X-ray arrested at G2/M phase,while the apoptosis rate of Hep-2cells increased with the prolongation of culture time and the increment of radiation dose(p<0.05).2After transfection:MTS assay showed the survival rates of radiation groups (2Gy,4Gy,8Gy,12Gy)were gradually reduced with the prolongation of culture time (p<0.05);At the same time,cell survival rates were significantly reduced along with the increasing of radiation dose.Expression of GLUT-1mRNA of transfected groups was much lower than that of untransfected groups. However, compared to the control group, GLUT-1mRNA expression of radiation groups transfected GLUT-1AS-ODN was not significantly reduced.FCM showed G2/M phase arrest in transfected cells after radiation, which is similar to the untrantsfected cells(p>0.05).Apoptosis rates of transfected cells were much higher than these of untrantsfection cells(p<0.05). Differences of apoptosis rates between transfected groups and untransfected groups became more apparent with prolonged culture time and the increase of irradiation dose.Conclusion:The laryngeal carcinoma Hep-2cell is insensitive or resistant to the radiation of X-ray, which may be associated with overexpression of GLUT-1mRNA. GLUT-1AS-ODNs can increase the sensitivity of Hep-2cells to the radiation.The mechanism may be promoting cell apoptosis.