The tumor suppression activity of E1A in HER-2/neu-overexpressing breast cancer

Preclinical and clinical study of HER-2/neu-targeting cancer gene therapy

Cationic liposomes have been used in many gene therapy approaches. The advantages of low toxicity, lack of immunological response, and easy preparation using cationic liposomes make multiple administrations possible, which may overcome the disadvantage of low transfection efficiency. Cationic liposomes, therefore, provide a promising procedure for delivering a therapeutic gene into cancer patients. Amplification or overexpression of the HER-2/neu oncogene is frequently found in breast and ovarian cancers and correlates with poor clinical prognosis. We have found that the adenovirus 5 E1A and the nontransforming simian virus 40 (SV40) large-T antigen mutant can inhibit HER-2/neu overexpression and reverse the HER-2/neu-mediated malignant phenotypes. By using the cationic liposome 3beta[N-(N',N'dimethylamino)ethanecarbamoyl]-cholesterol (DC-Chol), we successfully transferred E1A and/or large-T mutant into established orthotopic breast and ovarian cancer models. The survival of a treated group of mice was significantly prolonged and the expression of HER-2/neu oncogene was down-regulated in vivo. A subsequent toxicity assay indicated that no significant toxicity was associated with the liposome-DNA complex administration even when we used ten times the dose needed to achieve a therapeutic effect. Based on these data, a phase I clinical trial of DC-Chol-mediated E1A gene therapy for ovarian and breast cancers that overexpress HER-2/neu has been initiated in our institute. In this article, we will review the development of HER-2/neu-targeting gene therapy using cationic liposomes.

Inhibition of nuclear factor-kappaB activity is involved in E1A-mediated sensitization of radiation-induced apoptosis

The adenoviral E1A protein has been implicated in the potentiation of apoptosis induced by various external stimuli, but the exact mechanism of that potentiation is not clear. In this study, we compared the sensitivity to ionizing gamma-irradiation of E1A transfectants with that of parental cells in a human ovarian cancer cell line (SKOV3.ip1); we found that the E1A transfectants became sensitive to radiation-induced apoptosis. Recently, activation of the transcription factor nuclear factor-kappaB (NF-kappaB) has been shown to play a key role in the anti-apoptotic pathway of radiation-induced apoptosis. In an attempt to determine whether NF-kappaB was involved in the E1A-mediated sensitization of radiation-induced apoptosis, we found that radiation-induced activation of NF-kappaB occurred in the parental cells but was blocked in the E1A transfectants. Furthermore, parental cells cotransfected with NF-kappaB and E1A were better protected from undergoing apoptosis upon irradiation than those transfected with E1A alone. Thus, our results suggest that inhibition of NF-kappaB activation by E1A is a plausible mechanism for E1A-mediated sensitization of radiation-induced apoptosis.