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Severe functional alterations in vitro in CD34(+) cell subpopulations from patients with chronic myeloid leukemia
Antonieta Chávez-González1, Alejandro Rosas-Cabral, Jorge Vela-Ojeda
1Oncolgical Research Unit, Oncology Hospital, National Medical Center, IMSS, Mexico City, Mexico.
Insights
Chronic myeloid leukemia (CML) CD34(+) cells show functional defects. Immature CML stem cells exhibit the most severe proliferation and expansion abnormalities in vitro.
Area of Science:
- Hematology
- Stem Cell Biology
- Oncology
Background:
- Chronic myeloid leukemia (CML) originates from malignant hematopoietic stem cells (HSCs).
- Both HSCs and their progeny (HPCs) are found within CD34(+) cells in bone marrow (BM).
- CML HSCs produce functionally impaired progeny, affecting both primitive and mature progenitor cells.
Purpose of the Study:
- To investigate the functional capacity of distinct CD34(+) cell subpopulations from CML patients.
- To compare the proliferation and expansion potential of CML-derived CD34(+) cells with normal counterparts in vitro.
- To identify which CML CD34(+) cell subpopulation exhibits the most significant functional abnormalities.
Main Methods:
- Separation of two CD34(+) cell subpopulations from CML and normal bone marrow: Population I (CD34(+) Lin(-)) and Population II (CD34(+) CD36(-) CD38(-) CD45RA(-) Lin(-)).
- Assessment of progenitor cell content (CFC) in both populations.
- Long-term liquid cultures using hematopoietic cytokines in serum- and stroma-free conditions to evaluate proliferation and expansion capacity.
Main Results:
- Population II (more immature) CD34(+) cells were four-fold amplified in CML compared to normal BM.
- No significant difference in the absolute number of colony-forming cells (CFC) was observed between CML and normal populations.
- CML CD34(+) cells demonstrated markedly deficient proliferation and expansion potential compared to normal cells, especially in the immature Population II.
Conclusions:
- Bone marrow-derived CD34(+) cells from CML patients exhibit significant in vitro functional abnormalities.
- The most immature CML CD34(+) subpopulation (Population II) displayed the most severe functional deficits.
- These findings highlight intrinsic defects in CML stem and progenitor cells impacting their regenerative capacity.
Abstract:
Chronic myeloid leukemia (CML) arises from the malignant transformation of a hematopoietic stem cell (HSC) that gives rise to functionally defective progeny, including primitive and relatively mature progenitor cells (HPC). Both HSC and HPC are comprised within the population of CD34(+) cells, normally present in bone marrow (BM). In the present study, we have separated two different subpopulations of CD34(+) cells from CML marrow: Population I, enriched for CD34(+) Lin(-) cells; and Population II, enriched for CD34(+) CD36(-) CD38(-) CD45RA(-) Lin(-) cells, and assessed their progenitor cell content as well as their capacity to proliferate and expand in response to a combination of hematopoietic cytokines in serum- and stroma-free long-term liquid cultures. The absolute cell numbers recovered in Population I from normal and CML samples were similar; in contrast, we found that Population II from CML was amplified four-fold, as compared to normal. In spite of this latter observation, no significant differences were observed in terms of the absolute number of CFC when comparing Populations I and II from CML patients and normal subjects. Interestingly, the proliferation and expansion potentials of CML cells were clearly deficient as compared to their normal counterparts. Indeed, in cultures of Population I cells the maximum fold increase in total and progenitor cell numbers corresponded to 30 and 8%, respectively, of those observed in cultures of normal marrow-derived Population I cells. Such functional deficiencies were even more evident in Population II cells in which the maximum fold increase in total and progenitor cell numbers corresponded to 3 and 0.5%, respectively, of the levels found in cultures of Population II cells from normal marrow. The present study demonstrates that bone marrow-derived CD34(+) cells from CML patients possess functional abnormalities, clearly evident in the in vitro system used by us. Among the two CML subpopulations studied here, the more immature one (Population II; enriched for CD34(+) CD36(-) CD38(-) CD45RA(-) Lin(-) cells) was the one that showed the most severe abnormalities, as compared to its relatively more mature counterpart (Population I; enriched for CD34(+) Lin(-) cells).
