Glucose availability in hypoxia regulates the selection of chronic myeloid leukemia progenitor subsets with different resistance to imatinib-mesylate.
BACKGROUND
Incubation of chronic myeloid leukemia cells in hypoxia inhibits growth and selects BCR/Abl-independent cells with stem cell properties which are refractory to imatinib-mesylate. This study aimed to characterize the relationship of this refractoriness with glucose availability in the environment.


METHODS
K562 or primary chronic myeloid leukemia cells were cultured at 0.1% O(2), different cell densities and glucose concentrations. The stem and progenitor cell potential of these cultures at different times of incubation in relation to BCR/Abl(protein) expression and sensitivity to imatinib-mesylate was explored by transferring cells to growth-permissive secondary cultures in normoxia, according to the Culture-Repopulating Ability assay methodology.


RESULTS
Hypoxia-resistant cells maintained BCR/Abl(protein) expression until glucose was no longer available in primary hypoxic cultures, where glucose availability appeared to regulate cell number and the balance between the enrichment of cells with kinetic properties typical of stem or progenitor cells. Cells surviving merely hypoxic conditions were, upon transfer to secondary cultures, immediately available for numerical expansion due to the maintained BCR/Abl(protein) expression, and were consequently sensitive to imatinib-mesylate. Instead, BCR/Abl(protein)-negative cells selected in primary cultures under oxygen/glucose shortage underwent a delayed numerical expansion in secondary cultures, which was completely refractory to imatinib-mesylate. Cells with the latter properties were also found in primary chronic myeloid leukemia explants.


CONCLUSIONS
Glucose shortage in hypoxia was shown to represent the condition selecting BCR/Abl(protein)-negative cells refractory to imatinib-mesylate from either chronic myeloid leukemia lines or patients. These cells, exhibiting stem cell properties in vitro, are metabolically suited to home to stem cell niches in vivo and so may represent the chronic myeloid leukemia cell subset responsible for minimal residual disease.
Dipartimento di Patologia e Oncologia Sperimentali, Università degli Studi di Firenze and Istituto Toscano Tumori, Viale G.B. Morgagni 50, I-50134, Firenze, Italia.
Serena
S
Giuntoli
Michele
M
Tanturli
Federico
F
Di Gesualdo
Valentina
V
Barbetti
Elisabetta
E
Rovida
Persio
P
Dello Sbarba
D017209:Apoptosis; D001549:Benzamides; D049109:Cell Proliferation; D019008:Drug Resistance, Neoplasm; D016044:Fusion Proteins, bcr-abl / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology; D010879:Piperazines / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D013549:Sweetening Agents / Q000378:metabolism; D014407:Tumor Cells, Cultured
D001549:Benzamides; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D013549:Sweetening Agents; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl; D005947:Glucose