Modification of the clonogenic capacity of bone marrow cells from normal individuals by the tyrosine kinase inhibitor STI571.

STI571 shows clinical activity in the treatment of chronic myelogenous leukemia, Philadelphia positive acute lymphoblastic leukemia and gastrointestinal stromal tumors. Resistance of normal progenitor cells to STI571 is essential when determining the optimal therapeutic window for patients with cancer without bone marrow involvement, and for patients with chronic myeloid leukemia who achieved complete cytogenetic remission. The effect of graded concentrations of STI571 on the clonogenic potential of normal fresh bone marrow hematopoetic progenitor cells from 13 normal individuals was analyzed. It was shown that lower concentrations of STI571 (0.1 and 0.5 microM/l) may increase colony numbers, whereas higher concentrations (>1 microM/l) may reduce normal colony formation.