[Future perspectives of bone marrow and stem cell activation for autologous transplantation]

Autologous bone marrow transplantation has gained an increasing role in modern oncology. The use of circulating progenitors from the peripheral blood as autografts might have some important advantages, since leukaphereses are better tolerable than a BM harvest, could be done immediately following chemotherapy, are possible in patients with previous irradiation to the pelvis and might be less contaminated with malignant progenitor cells. We have shown that monitoring transplants with the relatively simple in vitro assay for myeloid progenitor cells is predictive for hematopoietic recovery in animal models as well as in the clinical setting. Moreover, stem cells harvested during repeated leukapheresis were able to repopulate permanently the irradiated BM. Using recombinant human granulocyte/macrophage colony stimulating factor, large quantities of progenitor cells can be mobilized into the peripheral blood and collected for autotransplantation, in particular if used directly following chemotherapy. Cell separation studies showed that a bone marrow/blood barrier retains some subpopulations of progenitor cells which might lead to the preferential circulation of normal stem cells following chemotherapy. Methods are described to distinguish normal and leukemic progenitor cells which will help in the future to assay autografts both for their repopulating ability and their contamination with tumor cells.