Chemotherapeutic agents enhance AAV2-mediated gene transfer into breast cancer cells promoting CD40 ligand-based immunotherapy

Bernd Koppold1, Georg Sauer1, Hildegard Buening2, Michael Hallek2, Rolf Kreienberg1, Helmut Deissler1 and Christian Kurzeder1

(1) Department of Obstetrics and Gynecology, University of Ulm Medical School, Frauensteige 14, 89075 Ulm, Germany
(2) Department of Internal Medicine (Clinic I), University of Cologne, Cologne, Germany

Received: 27 January 2006 Accepted: 19 May 2006 Published online: 23 June 2006

Abstract
Purpose Supplementing conventional treatment with gene therapy to induce an immune response might be beneficial to cancer patients. In this study, we evaluated the efficiency of transduction of breast cancer cells with recombinant adeno-associated virus (rAAV) and effects of cytotoxic agents used in chemotherapy. Furthermore, the capacity of tumor cells expressing transgenic CD40 ligand (CD40L) to stimulate dendritic cells was measured.
Methods Breast cancer cell lines were infected with a rAAV encoding the enhanced green fluorescent protein (EGFP) or murine CD40L and transgene expression was analyzed by flow cytometry. Stimulation of isolated human dendritic cells by CD40L-expressing tumor cells was quantified by measuring secreted interleukin 12.
Results Infection with an EGFP-encoding rAAV resulted in variable fractions (14–93%, mean 42%) of transgene-expressing cells. Pre-incubation of MM 157, MM 231, and MCF7 cells with epirubicin or carboplatin substantially increased AAV-mediated transgene expression. rAAV/CD40L was used to generate CD40L-transgenic tumor cells, which specifically activated immature dendritic cells, as confirmed by blocking with an antibody binding to CD40L.
Conclusions The efficiency of rAAV-mediated gene transfer into breast cancer cells is significantly higher than previously reported and can be further enhanced by co-administration of chemotherapeutic agents. We also confirmed that breast cancer cells can activate human dendritic cells after infection with a CD40L-encoding rAAV.
Keywords Adeno-associated virus - Gene therapy - Breast cancer - CD40 ligand