Identification of a subset of patients with acute myeloid leukemia characterized by long-term in vitro proliferation and altered cell cycle regulation of the leukemic cells

Abstract

Objective: The malignant cell population of acute myeloid leukemia (AML) includes a small population of stem/progenitor cells with long-term in vitro proliferation. We wanted to compare long-term AML cell proliferation for unselected patients, investigate the influence of endothelial cells on AML cell proliferation and identify biological characteristics associated with clonogenic capacity.

Methods: Cells were cultured in medium supplemented with recombinant growth factors FMS-like tyrosine kinase-3 ligand, stem cell factor, IL-3, G-CSF and thrombopoietin. The colony-forming unit assay was used to estimate the number of progenitors in AML cell populations after 35 days of culture, and microarray was used to study global gene expression profiles between AML patients.

Results: Long-term cell proliferation was observed in 7 of 31 patients, whereas 3 additional patients showed long-term proliferation after endothelial cell coculture. Patient-specific differences in constitutive cytokine release were maintained during cell culture. Patients with long-term proliferation showed altered expression in six cell cycle-related genes (HMMR, BUB1, NUSAP1, AURKB, CCNF, DLGAP5), two genes involved in DNA replication (TOP2A, RFC3) and one gene with unknown function (LHFPL2).

Conclusion: We identified a subset of AML patients characterized by long-term in vitro cell proliferation and altered expression of cell cycle regulators that may be potential candidates for treatment of AML.

Keywords::

• acute myeloid leukemia
• cell cycle
• colony-forming unit assay
• cytokines
• endothelial cells
• progenitor cells

Acknowledgment

Ø Bruserud, conception and design of study, interpretation of experimental data, manuscript writing, provision of study material; H Reikvam, analysis and interpretation of data; KJ Hatfield, conception and design, performed the experiments, analysis and interpretation of experimental data, manuscript writing.

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