Molecular Approaches to Cervical Cancer Therapy

Cervical cancer is the second most common malignancy in women worldwide. Two HPV strains, HPV-16 and 18, occur in the 70% of untreated cancers. Expression of viral oncogenes E6 and E7 disrupt the cell cycle by interfering with p53 and p107Rb. It is known that HPV infection is necessary but insufficient to cause malignancy. Furthermore, persistence of HPV-16 or 18 in women does not necessarily result in cancer. Persistence indicates the importance of other factors for malignant conversion of high-grade HPV infection. The multi-step cervical carcinogenesis process is amendable to molecular therapeutics such as therapeutic nucleic acids (TNAs). TNA-based therapies for cervical carcinoma include ribozymes, antisense oligonucleotides (AS-ODNs) and small interfering RNAs (siRNAs). In vitro experiments with TNAs successfully inhibited E6/E7 expression and caused induction of apoptosis and/or senescence in cervical carcinoma cells. Early ribozyme and AS-ODN approaches showed promise as therapeutic moieties for cervical cancer. Despite the very high in vitro efficiency of siRNA-based therapies they present the same issues that burdened clinical development of ribozymes and AS-ODNs. These issues include intracellular target accessibility, specificity and delivery. Ribozymes are useful for functional genomic studies including diagnosis. Moreover, AS-ODNs appear better suited for clinical protocols because recent advances in nucleic acid chemistry allow higher cell uptake with very low off-target effects leading to actual AS-ODNs clinical applications. By using combined treatments with multiple targets it will be possible to apply TNAs directly to the cancerous cervix to destroy viral RNA and obliterate the tumor.