Sft. Thijsen et al., HYPERSENSITIVITY OF BCR-ABL-POSITIVE PROGENITORS TO HYPERTHERMIA IN PATIENTS WITH CHRONIC MYELOID-LEUKEMIA, Leukemia, 11(10), 1997, pp. 1762-1768
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.