Use of a safety recombinant adenovirus vector for selective bone marrow purging carrying the chemosensitization gene cytosine deaminase
We are developing a genetic method for purging of breast cancer (BC) cells, which is totally selective for the neoplastic cells that contaminate autologous hematopoietic cells (HC) used for transplant. Adenoviral vectors (AW) carrying the non mammalian cytosine deaminase (CD) gene specifically infects breast cancer but not HC. The adenoviral vector CD converts the non toxic drug 5 Fluorocytosine (5FC) to 5-Fluorouracil (5FU) within the BC cells. In vitro toxîcity studies performed in BC cell lines (MCF-7, MDA-453), in expiants of normal ductal epithelial cells, and in mixtures of human CD34+ cells and MCF-7 BC cells (l%-0.1/o), showed that the AVV CD exposure sensitized the BC cells to the toxic effects of 5FC. Plating efficiency assays of CFU-GM in methylcellulose and limiting dilution (LDA) breast cancer colony assays on these cells showed little or no reduction of the plating efficiency of the HC following AVV CD/5FC exposure, whereas this exposure generated a dramatic reduction in the proliferative capacity of the BCcells in the LDA assay. 19-F NMR spectroscopy showed interconversion of 5FC into 5FU and its phosphorylated metabolites in the AVV CD exposed BC cells but not in the AVV CD exposed CD34+ cells. This genetic purging approach will therefore be of potential utility in improving the outcome of autotransplants in BC patients.