Preclinical study on gene therapy of cervical carcinoma using adeno-associated virus vectors

Approximately 90% of cervical carcinomas are causally linked to infections with high-risk human papillomaviruses (HPVs), whose oncogenicity has been a ssigned to the continued expression of two early genes, E6 and E7. Reversal of the transformed phenotype by inhibiting E6/E7 gene expression therefore provides a suitable goal for future tumor therapy. Using recombinant adeno -associated virus type 2 (AAV-2) vectors, two types of therapeutic genes we re expressed in cervical carcinoma cells with the aim of suppressing the E6 /E7 oncogenes: (a) antisense E6/E7 and ribozyme genes and (b) the monocyte chemoattractant protein-1 (MCP-1) gene encoding MCP-1. Previous studies hav e shown that the MCP-1 protein is able to indirectly repress E6/E7 gene exp ression and is consistently absent in tumorigenic HPV-positive cervical car cinoma cell lines. Here, the effect of these therapeutic genes on tumor for mation is analyzed in nude mice after ex vivo gene transfer into a HPV16- o r HPV18-positive cervical carcinoma cell line (HeLa or SiHa respectively). Whereas AAV-2 vector-mediated transfer of antisense or even ribozyme genes did not significantly influence tumor formation from implanted SiHa cells, the transfer and expression of human MCP-1 strongly inhibited the developme nt of tumors derived from either HeLa or SiHa cells. Similar results were a lso obtained after in vivo delivery of these genes into SiHa-derived tumors . This suggests that transfer of therapeutic genes mediating a systemic eff ect via recombinant AAV-2 vectors offers a promising approach for the devel opment of gene therapies directed against papillomavirus-induced human canc ers.