Ex-vivo expansion of hematopoietic progenitor cells: preliminary results in breast cancer

Ex-vivo expanded progenitor cells have been proposed as a source of cells t o support high-dose chemotherapy and to decrease or eliminate the period of neutropenia following transplantation. To date, no clinical studies using ex vivo expanded cells, have demonstrated any decrease in the time to neutr ophil or platelet recovery, although a number of clinical studies have been performed using a variety of growth factor cocktails and culture condition s. Over the past 6 years we have developed a static culture system that res ults in optimal expansion of myeloid progenitor cells. We have initiated a clinical study to evaluate this culture system in breast cancer patients re ceiving peripheral blood progenitor cells (PBPC) to support high-dose chemo therapy. CD34 selected cells were cultured for 10 days in 800 ml of defined media (Amgen Inc.) containing 100 ng/ml each of rhSCF, rhG-CSF and rhMGDF in 1L teflon bags (American Fluoroseal) at 20,000 to 50,000 cells per ml. A fter culture the cells were washed with 3 volumes of PBS to remove all medi a and growth factors and reinfused on day 0 of transplant followed by daily administration of rhG-CSF. On day +1 the patients received an unexpanded P BPC product to ensure the durability of the graft. Patients transplanted wi th expanded PBPC cells recovered neutrophil counts (ANC > 500/mu l) as earl y as day 4 post transplant with a median of 6 days (range 4 to 14 days). In comparison, our historical control group of patients (N = 175) had a media n time to neutrophil engraftment of 9 days (range 7 to 24 days). A second c ohort of patients were transplanted with expanded cells alone and a similar rapid engraftment was obtained. The first patients are now over 70 days po st transplant with durable engraftment. No effect on platelet recovery has been observed in any patients to date. These data demonstrate that PBPC exp anded under the conditions defined can significantly shorten the time to en graftment of neutrophils.