We recently completed a phase I trial of E1A gene therapy for patients with advanced breast or ovarian cancers. The trial's rationale was that E1A gene would downregulate HER-2/neu expression by repressing the gene's transcription, thus reversing the malignant phenotype. Our preclinical studies showed that i) transfection capabilities were not reduced in preparing E1A/cationic liposome complexes, ii) samples after ex vivo transfection, and iii) HER-2/neu gene expression could be quantified by quantitative imaging analysis. These results facilitated the translation of our basic research findings into a clinical trial and to obtain final approval from the National Institutes of Health Recombinant DNA Advisory Committee.