The Effect Of E1A Gene On The Radiosensitivity Of Xenograft Tumor Models Of Cervical Cancer

Objective:1．To explore the effect of E1A gene to the radiotherapy sensitivity of xenograft tumor models of cervical carcinoma and its relevant mechanism.2．To afford the experimental evidence for improvement of cervical carcinoma's radiotherapy effect, and to provide primary theory evidence for gene therapy of tumor.Methods:Cell culture: HeLa cells were inoculated in RPMI-1640 blended with 10% foetus cattle serum, and maintained in a humidified incubator at 37℃containing 5% CO₂．2 x10⁶ human cervical cancer HeLa cells were implanted into nude mice to get the tumor model of HeLa cell line. The transplanted tumors were observed every day. And measure the tumors' length (a) and width (b) every three days. V=1/2×ab²ï¼ŽAfter the tumors' average diameter reached about 10mm, the mice were divided into three groups in random. E1A-experimental group:0．2ml E1A-PEI-Fe₃O₄ solution was injected into the tumor. Empty vector control group: 0．2ml PEI-Fe₃O₄ empty vector solution was injected into the tumor. Blank control group: 0．2ml asepsis liquor natrii chloridi isotonicus was injected into the tumor. Radiotherapy was applied to mice of each group, 6-MV X-ray, distance 100cm, 2Gy/min×5day, 10Gy in total. The decrease of tumor volumes were observed every day, and the tumor volumes were calculated after the radiotherapy was over. Tumor decrease rate=(mean tumor volume before radiotherapy-mean tumor volume after radiotherapy)/ mean tumor volume before radiotherapy×100%. The mean tumor weights were measured, respectively. After the mice were killed, the tumors were made sections. The apoptosis rate of cells in tumor tissues were measured by TUNEL test, and the expression of survivin protein were measured by immunohistochemistry.Results:1．Tumors started to form in the seventh day after HeLa cells injection. And in the twenlfth day, tumor formation rate reached 100%.2．Before radiotherapy the tumor volumes of E1A group, empty vector control group and control group were 302．28±37．48 mm³, 326．57±57．34 mm³, 317．95±86．93 mm³ï¼ŽWhen the radiotherapy was over and before the kill of mice, the tumor volumes of E1A group, empty vector control group and control group were 46．50±29．04mm , 222．4±37．47 mm³, and 202．83±67．51 mm³, respectively. The tumor decrease rates were 84．62±14．25%, 31．90±8．42%, 36．21±7．76%, respectively. The tumor weights were 148．1±69．7mg, 434．9±38．7mg, 394．3±88．6mg, respectively. And they were all statistically significant(p<0．05) . 3．The apoptosis rate of cells in tumor tissues were measured by TUNEL test. Significantly, E1A group had more apoptosis cells, AI was 32．07+4．48%, while the empty vector group and control group had few apoptosis cells. AI were 13．93±1．31% and 14．02±0．98%. They were statistically significant (p<0．05) .4．The expression of survivin protein were measured by immunohistochemistry. The expression of survivin protein was weak in E1A group, but were strong in the empty vector group and control group. And they were statistically significant (p<0．05) .Conclusions:1．E1A gene can obviously increase the radiotherapy sensitivity of xenograft tumor models of cervical carcinoma HeLa cell.2．E1A gene can down-regulate the expression of survivin in HeLa cells' xenograft tumor models. It may be the mechanism of increased radiotherapy sensitivity by E1A gene.