In vitro effects of etoposide purging on natural killer cells.

Autologous bone marrow transplantation (ABMT) is widely used to treat hematologic and non-hematologic malignancies. In an attempt to reduce potential neoplastic contamination of the graft, pharmacologic purging with cyclophosphamide derivatives and etoposide (VP16) is often used. Trilineage hemopoietic engraftment is seen following ABMT with VP16-purged bone marrow (BM), but little is known about immune reconstitution in this setting. We studied the in vitro development of natural killer (NK) cells from VP16-purged BM. These cells, defined by phenotypic and functional criteria, undergo rapid regeneration, expansion, and maturation in the presence of interleukin 2 (IL-2). VP16 seems to spare subsets of NK cells, and this cell lineage develops rapidly in VP16-treated BM cultures from patients with acute myelogenous leukemia (AML) and healthy donors. Since relapse rates remain high, immunotherapy following ABMT with purged BM may be useful and should be considered in these patients.