Hematopoietic potential of IL-2-cultured peripheral blood stem cells from breast cancer patients

Patients receiving autologous transplants for various malignancies generally experience an increased incidence of relapse compared with patients receiving unmanipulated allogeneic transplants. We initiated a protocol for IL-2 activation of peripheral blood stem cells (PBSC) for induction of in vitro and in vivo autologous graft-versus-tumor (GVT) activity in patients with breast cancer. In this study we analyzed the effects of 24 h of IL-2 incubation on the hematopoietic potential of PBSC from these patients. Cells collected by leukapheresis were first cryopreserved and stored in liquid nitrogen, then thawed rapidly and incubated with IL-2 in a serum-free system for 24 h, with samples analyzed before and after incubation. Although there was a significant drop in mononuclear cells (MNC) (from 4.5 to 3.7 x 10⁸/kg) and CD34⁺ cells (from 12.3 to 7.5 x 10⁶/kg) after 24 h in culture, there was no significant change in colony-forming units (CFU) (from 12.5 to 11.5 x 10⁵/kg). Time to engraftment (neutrophils: < 0.5 x 10⁹/l; platelets: > 20 x 10⁹/l) was comparable to a cohort of similar patients receiving non-cultured PBSC transplants. These results indicate that mobilized frozen/thawed PBSC which have been cultured in IL-2 for 24 h retain adequate potential for hematopoietic reconsistution in this group of patients.