Differential expression of a recombinant adeno-associated virus 2 vector in human CD34⁺ cells and breast cancer cells

Abstract

The use of autologous hematopoietic stem cell (HSC) grafts after high-dose chemotherapy protocols may be hampered by contamination of the grafts with tumor cells. Because epithelial cells seem to be the natural hosts of adeno-associated virus 2 (AAV-2), we speculated that epithelial tumor cells in HSC grafts might be selective targets for AAV-2-based vectors. To test this hypothesis, the breast cancer cell lines T47D and MCF-7 were infected with a recombinant AAV-2 vector expressing the green fluorescent protein (GFP) gene; in addition, human CD34⁺ mobilized peripheral progenitor cells were infected with the same vector. At a multiplicity of infection of 100, only 1.39% ± 0.51% CD34⁺ cells expressed the GFP gene whereas, 36.06% ± 6.53% of the infected T47D cells and 41.52% ± 3.16% of the infected MCF-7 cells expressed the transduced GFP gene. After further optimizing the transduction procedure by using higher multiplicities of infection (100–500) and preincubation of samples with the tyrosine kinase inhibitor genistein, up to 82.52% and 85.35% GFP⁺ T47D and MCF-7 cells, respectively, were observed. The GFP fluorescence intensity in transduced mammary tumor cells was up to 3 logs higher than that of transduced CD34⁺ cells. The differential expression of recombinant AAV-2 vectors in hematopoietic and epithelial tumor cells warrants further research with this vector system, including the use of suicide genes for the purging of autologous HSC grafts.