Purging of human breast cancer cells from stem cell products with an adenovirus containing p53

Tumor cell contamination of stem cell products can contribute to tumor rela pse following high-dose chemotherapy and stem cell rescue, Numerous techniq ues have been used to remove the tumor cells from stem cell products with t he objective of prolonging relapse-tree survival. However, to elate these t echniques have been relatively ineffectual and/or toxic to hematopoietic st em and progenitor cells. The differential infectivity of adenovirus (Adv) v ectors for breast cancer cells, compared with hematopoietic cells, has sugg ested that Adv-p53 might provide an effective purging strategy. To facilita te the use of Adv-p53 as a clinical strategy, we undertook studies to deter mine the parameters necessary for optimal stem cell product purging. The pa rameters studied were the particle number to nucleated cell ratio, the dura tion of coincubation, the incubation volume, and the presence or absence of hematopoietic progenitor cells. We have found that these parameters are in terdependent and conclude that a 4-hour coincubation with an Adv-p53 partic le to nucleated cell ratio of 2000:1 with 2 x 10(8) nucleated cells/mL is o ptimal for tumor cell purging. Furthermore, this appeared to be a safe proc edure, with total loss of clonogenic growth of breast cancer cells as well as no significant effect on progenitor cell function as determined by granu locyte-macrophage colony-forming unit assays.