F. Zhang et al., INCREASED STRINGENCY OF THE 1,25-DIHYDROXYVITAMIN-D-3-INDUCED G1-PHASE TO S-PHASE BLOCK IN POLYPLOID HL-60 CELLS, Journal of cellular physiology, 168(1), 1996, pp. 18-25
Treatment of mammalian cells with 1,25-dihydroxyvitamin D-3 (1,25D(3))
produces a G1 to S (G1/S) phase cell cycle block. In addition, it has
been noted that a smaller proportion of cells accumulates in the G2/M
compartment in 1,25D(3)-treated cultures. Since cyclins have a major
influence on the regulation of cell cycle progression, we determined t
he expression of cyclins A and B as markers of the G2 phase and of cyc
lin E as the marker of G1/S transition. No increase in the steady-stat
e levels of cyclin A or cyclin B mRNA was detected in the total cell p
opulation or in the cyclin B1 protein in the G2/M cell cycle compartme
nt. In contrast, immunodetectable cyclin E protein was increased in ce
ll cultures as a whole and specifically in the G2/M compartment cells.
Determination of BrdU incorporation into DNA by flow cytometry showed
marked inhibition of DNA replication in cells with DNA content higher
than 4C, and autoradiography of H-3-TdR-pulsed cells showed that poly
nucleated cells did not replicate DNA after 96 h of treatment with 1,2
5D(3) or analogs. Taken together, these experiments show that at least
a portion of the G2/M compartment in 1,25D(3)-arrested cultures of HL
60 cells represents G1 cells at a higher ploidy level, which are block
ed from entering the high ploidy S phase. (C) 1996 Wiley-Liss, Inc.