American Fluoroseal Corporation

Ex vivo expanded PBPC have been shown to provide rapid neutrophil engraftment and in some patients eliminates neutropenia following transplantation to support high dose chemotherapy. However, the effect of expansion culture on stem cell content and potential loss of stem cells due to induction of differentiation remains a concern.

We have transplanted 11 breast cancer patients with expanded (autologous) PBPC as their sole hematopoietic cell source. In these studies the CD34 selected cells were cultured for 10 days in 800 m1of defined media (Arngen Inc. ) containing 100 ng/ml each of rhSCF, rhG-SCF and rhMGDF in1.L1L Teflon bags (American Fluoroseal) at 20,000 to 50,000 cells per ml.

After culture the cells were washed with 3 volumes of PBS to remove all media and growth factors and reinfused 48 hours after high dose chemotherapy followed by daily administration of rhG-CSF. Engraftment of neutrophils [(ANC)>500/ul] occurred in 4 to 6 days in many of the patients.

All 11 patients have durable engraftment at more than 18 months; neutrophil and platelet levels remain stable.

It is possible that the long term cell production in these patients resulted from endogenous recovery of stem cells.

Conclusion: This study demonstrates that it is safe to transplant patients with ex vivo expanded PBPC cells that provide I) rapid neutrophil engraftment, ii) sufficient progenitor cells to bridge the time until stem cells repopulate the hematopoietic system and iii) possibly sufficient stem cells to enable long term cell production.