HYPERSENSITIVITY OF BCR-ABL-POSITIVE PROGENITORS TO HYPERTHERMIA IN PATIENTS WITH CHRONIC MYELOID-LEUKEMIA

In this study, we evaluated the effect of hyperthermia on hematopoieti c progenitors from six chronic myeloid leukemia (CML) bone marrow (BM) samples at diagnosis and four peripheral blood stem cell (PBSC) sampl es from CML patients after stem cell mobilisation. CD34-positive cells , isolated from these samples, were incubated for 2 h at 37, 42 or 43 degrees C and were plated in the colony-forming unit granulocyte-macro phage (CFU-GM) and the long-term culture initiating cell (LTCIC) assay . To evaluate purging, individual colonies from these assays were anal yzed for the presence of the bcr-abl gene with interphase fluorescence in situ hybridization (FISH) and/or RT-PCR. BM samples showed a signi ficant higher sensitivity both at the CFU-GM and LTCIC level, after tr eatment at 42 degrees C, as compared to the control BM samples obtaine d from healthy volunteers. The four BM samples of CML patients with a low leukocyte number at diagnosis harbored a mixture of bcr-abl-negati ve and positive colonies and an increase in the percentage of bcr-abl- negative colonies was observed in all cases. CML patients with a high leukocyte count at diagnosis, however, showed only bcr-abl-positive pr ogenitors even after hyperthermia. PBSCs showed a significant higher s ensitivity at the LTCIC level but not at the CFU-GM level, after treat ment at 42 degrees C, as compared to the control PBSC samples obtained from nonhematologic cancer patients. Molecular analysis of individual colonies demonstrated an increase of bcr-abl-negative progenitors aft er thermic treatment in two out of three samples. When comparing both stem cell sources, PBSCs showed a decreased thermic sensitivity as com pared to the BM samples at the CFU-GM level, whereas at the LTCIC leve l an increased thermic sensitivity was observed, both for the controls and the CML samples. In conclusion, both for BM and PBSCs samples, CM L progenitors are more sensitive to hyperthermia than control cells, e specially at the LTCIC level. In agreement with these results, an incr ease of bcr-abl-negative progenitors in six out of seven samples could be demonstrated either at the CFU-GM level, LTCIC level or both. Hype rthermia should be explored further as a possible purging modality in CML.