1. ¹Department of Thoracic and Cardiovascular Surgery, Houston, TX, USA
2. ²Department of Introgen Therapeutics Inc., Houston, TX, USA
3. ³Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA

Correspondence: Dr A Pataer, Department of Thoracic and Cardiovascular Surgery, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Box 445, Houston, TX 77030, USA. E-mail: apataer@mdanderson.org

Received 4 October 2005; Revised 1 April 2006; Accepted 22 July 2006; Published online 6 October 2006.

Abstract

Our previous studies demonstrated that adenovirus-mediated overexpression of melanoma differentiation-associated gene-7 (Ad-mda7) leads to rapid induction of double-stranded RNA-dependent protein kinase (PKR) and activation of its downstream targets, resulting in apoptosis induction in human lung cancer cells. Here, we report that Ad-mda7 and the benzoquinone ansamycin geldanamycin (GA) interact in a highly synergistic manner to induce cell death in human lung cancer cells. Co-administration of Ad-mda7 and GA did not modify expression of MDA-7, and was not associated with further PKR induction and activation; instead the enhanced cytotoxicity of this combination was associated with inactivation of AKT by GA. By surface staining using anti-E-cadherin monoclonal antibody and flow cytometry, we found that treatment with the combination of Ad-mda7 and GA increased E-cadherin levels in these cancer cells. Ad-mda7 and GA cotreatment also inhibited lung cancer cell motility by increasing the |[beta]|-catenin|[sol]|E-cadherin association. Moreover, combination of GA derivative 17-allyl-amino, 17-demethoxygeldanamycin (17AAG), with Ad-mda7 resulted in enhancement of cell death in A549 and H460 human lung cancer cells.