595. Combination Tissue Specific SCC Antigen Promoter with CD/5-FC Gene Therapy Enhances Killing of Human Uterine Cervical Cancer Cells by Radiation

Background: Cervical caner is the leading cause of female cancer death worldwide. The squamous cell carcinoma (SCC) antigen was isolated first from uterine cervical SCC tissue in 1977. SCC antigen is a serologic tumor marker for patients with squamous cell carcinoma of the cervix. Serum concentrations of this marker correlate well with stage of disease, the presence or absence of risk factors, the effect of treatment, and the course of the disease. Moreover, the measurement of posttreatment SCC antigen levels is useful for monitoring the response to therapy and for predicting tumor recurrence and metastasis. In advance or recurrence cervical cancer, radiation with chemotherapy including 5-FU is used clinically. However, the morbidity is relative high. Gene therapy combined with radiation represents a new approach to cervical cancer treatment. In the present study, we investigated whether adenovirally directed, SCC antigen promoter with cytosine deaminase (CD)/5-fluorocytosine (5-FC) gene therapy could induce cell toxicity and radiosensitization through the intracellular production of 5-fluorouracil (5-FU) in uterine cervical cancer.Methods: Primary culture normal cervical cells as well as a series of human cervical cancer cell lines, including SiHa, Cx, SKG IIIb, were evaluated for the SCC antigen expression levels by Quantitative-PCR. Human uterine cervical cancer tissues were immunostained by monoclonal SCC antibody. Also, To determine the infectability of uterine cervical cells by adenovirus, normal cervical cells and cervical cancer cell lines were infected with various doses of Ad/LacZ, incubated for 48 h, stained for β-gal activity. Based on these results, Ad-SCC-CD, a recombinant replication-defective Ad was prepared, purified and titrated. Cervical cancer cells were infected with Ad-SCC-CD and treated with 5-FC. After infection, the cells were irradiated and a colorimetric assay using WST-8 was used to assess cell viability.Results: Immunohistochemistry showed only tumor cells expressing SCC antigen in human cervical tumor tissues. Adenovirus infected all test cervical cancer cells about 10-fold increase than normal cervical cells at MOI of 10. All cervical cancer cell lines, both SCC antigen 1 and antigen 2 were overexpressed for 3 to 4 fold increasing comparing to normal cervical cell by Quantitative-PCR. Ad-SCC-CD/5-FC-treated tumor cells showed significantly lower cell numbers than no treatment groups (all p value