Interferon-alpha-treated patients with chronic myelogenous leukemia show BCR/ABL-positive peripheral blood progenitor cells surviving long-term culture

Several groups have shown that Ph-progenitors reappear in LTC of CML bone m arrow or PBMNC when the cell preparations were derived from newly diagnosed Ph-positive patients or after induction chemotherapy. We have tested the hypothesis whether LTC may further decrease CML progenit ors if the cells to be cultured were from IFN-treated patients. In our expe riments, PBMNC were cultured from 7 IFN- and 5 HU-treated patients in stabl e chronic phase of the disease, and from 9 patients at diagnosis. Progenito r cells in PBMNC were quantitatively analyzed before and after 35 days of L TC by combining the clonogenic assay in semisolid medium with dual-color in terphase FISH for identification of the? BCR/ABL status of colony-forming p rogenitor cells. A median of 22 colonies (range 7-88) before and 30 colonie s (5-71) after LTC were analyzed per patient. Our results show that the num ber of BCR/ABL-positive CFC before and after LTC was approximatetly the sam e. This was independent of IFN or HU therapy. In the IFN group there were 5 8% (median) BCR/ABL-positive CFC before and 54% (median) after LTC of PBMNC . In the HU group, 80% of CFC were BCR/ABL-positive before and 85% after LT C, A complete elimination of BCR/ABL-positive cells was not achieved, We co nclude that CML early progenitors In PBMNC of IFN-treated CML patients may survive LTC.