The Radiosensitivity Effect Of E1A Gene On Human Cervical Carcinoma Cell In Vitro

Objective:Human cervical carcinoma is a common malignant tumor and asignificant cause of morbidity and mortality among women in the world.Radiotherapy is the chief treatment in advanced cervical cancer. However,most patients of cervical cancer in late stages of disease will experiencerecurrence with a poor prognosis and limited treatment options. Therefore,there is an unmet need for an exploration of a new approach to improvethe radiosensitivity and survival of cervical cancer. Our study is toinvestigate the radiosensitivity effect of E1A gene to human cervicalcarcinoma cell in vitro and its mechanism of action, these in vitro resultsalso offer us a prospect for the continued in vivo experiment andpreclinical development of E1A as a novel gene therapeutic agent forhuman cervical cancer.MethodHuman cervical carcinoma cell line of HeLa were cultured at 37℃in a humidified atmosphere of 95% air and 5% CO₂. Then these cells in85%-90% confluence were divided into three groups in random: blankcontrol group(HeLa group); blank-vector group (HeLa-vector group) and E1A group(HeLa-E1A group). The three groups were transfected withE1A gene or blank-vector followed by an irradiation by 6MV X-ray at thedose of 0, 2, 4, 6, 8 Gy respectively. The expression of the E1A andHer-2 gene was detected by RT-PCR. Radiosensitivity was determined bycolony formation assay and quantified by calculating the cell survival rateand the sensitization enhancement ratio(SER). Cell cycle distribution wasmonitored by flow cytometry.ResultsRT-PCR showed that E1A gene had a stable transfection in HeLacells and obviously down-regulated Her-2 expression; Colony formationassay demonstrated the survival rate of HeLa cell colony in HeLa-E1Agroup is significantly lower than that in the control groups. There is nosignificant difference between HeLa and HeLa-vector groups. D₀calculated from the dose-response curve in HeLa-E1A, HeLa andHeLa-vector groups were 1.23, 2.51 and 2.59 respectively, andcorresponding SER was 2.04; Flow cytometry revealed that E1Atransfection induced S stage suppression and G₂ stage arrest in HeLacells.ConclusionE1A gene can effectively enhance the radiosensitivity of humancervical carcinoma cells and its mechanisms of action may relate to thesuppression of Her-2 expression and a redistribution of cell cycles regulated by E1A gene.