Adenoviral-mediated gene therapy with Ad5CMVp53 and Ad5CMVp21 in combination with standard therapies in human breast cancer cell lines

Our objective was to determine the efficacy of adenoviral-mediated gene the rapy with wild-type p53 or p21 in human breast cancer cells and investigate interactions with radiation and chemotherapy. Two human breast cancer cell lines, MDA-MB-231 and MDA-MB-435, both with p53 mutations, were transduced with adenoviral vectors containing wild-type p53 (Ad5CMV-p53) or p21/WAF1/ Cip1 (Ad5CMV-p21), and the effects on growth were determined. Infection was combined with low-dose (1.4 - 3.7 Gy) irradiation to see if this would imp rove transduction efficiency and enhance numbers of cells killed. Transduct ion with either vector resulted in expression of p21(WAF1/cip1) and growth inhibition, although Ad5CMV-p53 transduction produced greater growth inhibi tion than did Ad5CMV-p21. The cell lines differed in sensitivity to the vec tors. The Ad5CMV-p53 vector in a multiplicity of infection (MOI) of 125 res ulted in 50% to 80% inhibition of MDA-MB-231, while MOI 250 of the same vec tor resulted in 27% inhibition of MDA-MB-435. Infection with Ad5CMV-p21 pro duced modest growth inhibition in both cell lines (less than or equal to 40 % at MOI 200), although protein expression was detected at lower viral dose s. Low dose gamma-irradiation (1.4 to 3.7 Gy) was used to try and improve t he rate of gene transfer. Modest increases in transduction efficiency and d uration of expression of a vector containing beta-galactosidase occurred in irradiated breast cancer cells. Radiation 24 hr before transduction with A d5CMV-p53 increased the proportions of apoptotic MDA-MB-231 cells. The cell s transduced with Ad5CMV-p21 were arrested in G(1), yet when they were irra diated before adenoviral transduction, the overexpression of p21 protected the cells from the cytotoxic effects of me radiation. Clonogenic assays sho wed that Ad5CMV-p21 reduced the sensitivity of MDA-MB-231 to VP-16 and pacl itaxel. Combining these drugs with Ad5CMV-p53 did not consistently or signi ficantly decrease clonogenic survival.