Increased stringency of the 1,25-dihydroxyvitamin D3-induced G1 to S phase block in polyploid HL60 cells.
Treatment of mammalian cells with 1,25-dihydroxyvitamin D3 (1,25D3) 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 1,25D3-treated cultures. Since cyclins have a major influence on the regulation of cell cycle progression, we determined the expression of cyclins A and B as markers of the G2 phase and of cyclin E as the marker of G1/S transition. No increase in the steady-state levels of cyclin A or cyclin B mRNA was detected in the total cell population or in the cyclin B1 protein in the G2/M cell cycle compartment. In contrast, immunodetectable cyclin E protein was increased in cell 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 3H-TdR-pulsed cells showed that polynucleated cells did not replicate DNA after 96 h of treatment with 1,25D3 or analogs. Taken together, these experiments show that at least a portion of the G2/M compartment in 1,25D3-arrested cultures of HL60 cells represents G1 cells at a higher ploidy level, which are blocked from entering the high ploidy S phase.
Zhang
F
F
Department of Pathology and Laboratory Medicine, UMD-New Jersey Medical School, Newark 07103, USA.
Rathod
B
B
Jones
J B
JB
Wang
Q M
QM
Bernhard
E
E
Godyn
J J
JJ
Studzinski
G P
GP
D002117:Calcitriol / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018922:HL-60 Cells; D006801:Humans; D011123:Polyploidy; D012333:RNA, Messenger / Q000235:genetics; D016196:S Phase
D016213:Cyclins; D012333:RNA, Messenger; D002117:Calcitriol