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

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 H SC 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) g ene; 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 c ells expressed the transduced GFP gene. After further optimizing the transd uction procedure by using higher multiplicities of infection (100-500) and preincubation of samples with the tyrosine kinase inhibitor genistein, up t o 82.52% and 85.35% GFP(+) T47D and MCF-7 cells, respectively, were observe d. The GFP fluorescence intensity in transduced mammary tumor cells was up to 3 logs higher than that of transduced CD34(+) cells. The differential ex pression 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.