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Abstract
Human Papillomavirus (HPV) is one of the most common causes of sexually transmitted disease worldwide. Infections by high-risk HPVs, such as HPV-18, have been associated etiologically with cervical cancer. The successful development of HPV vaccines may be beneficial to the HPV-naïve population, but women that have already been exposed to the virus are still at risk of developing HPV-associated malignancies. A need for a systemic cure for HPV-infection therefore still exists. Gene therapies using tissue-specific promoters have been reported to be a promising tool for treating cancers; however, few studies have explored this possibility for cervical cancer.
The aim of this project is to construct a gene expression vector that can specifically target HPV-infected cervical cancer cells, by making use of the activity and selectivity of the P105 promoter which is determined by transcription control elements within the HPV-18 long control region (LCR). The first part of this study involved the construction of LCR deletion plasmids, and examining the subsequent level of gene expression induced within different mammalian cell lines. The results suggest the LCR to be capable in achieving cervical cancer-specific gene expression. The 3′-end of the viral L1 gene upstream of the LCR appeared to have a repressive effect on the promoter and therefore should be excluded for maximum LCR promoter activity. The second part of the project involved site-directed mutagenesis studies performed on selected transcription factor binding sites with an attempt to further increase the level of LCR promoter activity and specificity towards HPV-infected cervical cancer cells. The results suggest that a GRE/YY1 mutation may significantly enhance promoter activity. In terms of promoter regulation, the E2BSs appeared to be responsible for promoter activation in the absence of viral E2 proteins.
The findings of this study suggest a possible gene therapy approach towards the treatment of cervical cancer. By making use of the activity and specificity of the HPV-18 P105 promoter to induce cervical carcinoma-specific expression of appropriate therapeutic genes, suicidal phenotypes can be introduced selectively within HPV-positive cervical cancer cells while normal HPV-negative cells are unaffected.