Superior gene transfer into solid tumour cells than into human mobilised peripheral blood progenitor cells using helpervirus-free adeno-associated viral vector stocks.

Autologous peripheral blood progenitor cell (PBPC) grafts can be contaminated with tumour cells that potentially give rise to relapse following myeloablative therapy and PBPC transplantation. Adeno-associated virus (AAV)-based vectors produced by a new adenovirus-free technique are a gene delivery system which may be applicable for tumour cell purging. To test for the host range of these vectors, solid tumours of clinical relevance and normal CD34+ PBPC were selected as target cells for an AAV-vector, encoding the green-fluorescent protein (GFP) as the indicator gene. At a multiplicity of infection (MOI) of 100: 79.94% +/- 14.36% (mean +/- SEM) of the connective tissue sarcoma cell line (HS-1) and 64.84% +/- 6.91% of the cervical carcinoma cell line cells (HeLa-RC) expressed GFP while the other cell lines tested (1 ovarian tumour, 1 germ cell tumour, 1 osteosarcoma, 2 small cell lung cancer) ranged between 2.82% and 11.94%. Optimising the transduction protocol by use of higher MOIs of up to 500 and by pretreatment with the tyrosine kinase inhibitor, genistein, resulted in up to 95.97% and 94.10% green-fluorescent HS-1 and HeLa-RC cells, respectively. In contrast, only 1.39% +/- 0.51% of the normal haematopoietic CD34+ progenitor cells expressed GFP at a MOI of 100. The differential infectivity between HS-1 and CD34+ cells was maintained after tumour cell spiking in leucapheresis products. Our observations suggest that AAV-based vectors may prove useful for purging of autologous PBPC grafts from solid tumour cells.