Nucleoside Phosphonate Analogs and HPV Positive Cancers

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Cidofovir (CDV) is a broad spectrum antiviral with activity against most double-stranded DNA viruses. A number of DNA viruses have been implicated as essential factors in viral-induced malignancy. The concept of using antivirals for treating cancers is in its infancy and worth exploring. This proposal seeks to evaluate new, highly active analogs of CDV that are substantially more active against DNA viruses while having reduced nephrotoxicity, a limiting factor in the utilization of cidofovir. We have synthesized and tested alkyoxyalkyl analogs of CDV that were at least 10 fold more potent than unmodified CDV. Our preliminary results in testing such agents against the human papilloma positive cell lines, Me-180 and HeLa, demonstrated that the cells were undergoing apoptosis and S phase arrest. This effect was 200-300 times more prominent in cervical cancer cells than in normal HFF or PHK cells. This may be due to p53 dependent or p53 independent factors. In early structure-activity studies we have identified that alkoxyethyl esters of cidofovir are more more potent antiproliferatives to cervical cancer cells than are alkoxypropyl CDV esters. Furthermore, the presence of one double bond in the aikyl chain seems to enhance the antiproliferative activity against cervical cancer cells such as Me-180 and HeLa. OleyloxyethyI-CDV is 15 to 80 times more active than HDP-CDV, the first compound we evaluated. We plan to continue structure-activity work, assessing antiproliferative effects of the new compounds and their effect on the cell cycle in normal cells and a panel HPV DNA+ cell lines expressing high risk subtypes. The most active and selective compounds will be selected for testing in athymic nude mice implanted with tumors. The mechanism of action will be explored by evaluating gene and protein expression and cell cycle effects. We believe that the structure-activity and molecular analysis approach may yield success and could be broadly applicable to a other types of cancer where HPV oncogenes interfere with the levels and function of p53 and pRb. This proposal could lead to new agents for treatment of cervical cancer and other HPV-associated cancers.