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Monocytically differentiating HL60 cells proliferate rapidly before they mature
G Brown1, M A Choudhry, J Durham
1LRF Differentiation Programme, Division of Immunity & Infection, University of Birmingham, Birmingham, B15 2TT, United Kingdom. G.Brown@bham.ac.uk
Experimental Cell Research
|December 10, 1999
Summary
Vitamin D3 (D(3)) initially accelerates HL60 cell proliferation before inducing monocytic differentiation. This complex process involves several cell divisions, challenging previous assumptions about immediate growth arrest.
Area of Science:
- Cell Biology
- Hematology
- Endocrinology
Background:
- 1alpha,25-Dihydroxyvitamin D(3) (D(3)) is known to induce growth arrest and monocytic differentiation in myeloid cells.
- Previous assumptions suggested immediate cellular events leading to growth arrest upon D(3) addition.
- Conflicting evidence indicated D(3) could also promote proliferation-related gene expression and accelerate cell division.
Purpose of the Study:
- To clarify the relationship between proliferation and maturation in D(3)-induced monocytic differentiation of HL60 cells.
- To investigate the timing of growth arrest and differentiation following D(3) exposure at different cell cycle stages.
Main Methods:
- HL60 cells were cultured individually.
- D(3) was administered at various cell cycle phases.
- Cell progeny counts and proportions of mature monocytes were determined.
- The effect of indomethacin on D(3)-induced differentiation was assessed.
Main Results:
- D(3)-treated cells initially proliferated at an accelerated rate before maturation.
- Cells encountering D(3) early in G1 divided 2-4 times before maturing.
- Later cell cycle exposure to D(3) resulted in an additional division.
- Indomethacin-treated cells matured later and underwent fewer divisions post-D(3) exposure.
Conclusions:
- Promyeloid cells do not immediately arrest growth or mature upon D(3) exposure.
- D(3) initiates a complex program involving 2-3 days of rapid proliferation, followed by growth arrest and maturation.
- A single D(3)-treated cell can yield over 10 mature monocytes.
- The process of D(3)-induced monocytic differentiation is more intricate than previously understood.