1,25-dihydroxyvitamin D(3)-induced retardation of the G(2)/M traverse is associated with decreased levels of p34(cdc2) in HL60 cells.
Cellular differentiation of neoplastic cells after exposure to 1, 25-dihydroxyvitamin D(3) (1,25 D(3)) is accompanied by altered cell cycle regulation. In previous studies, blocks in both G(1)/S and G(2)/M checkpoints have been observed in 1,25D(3)-treated HL60 cells, but the mechanism of the 1,25D(3)-induced G(2)/M block has not been previously reported. In this study, we show by cell cycle analysis, using bromodeoxyuridine pulse-chase labeling, that the G(2)/M block in 1,25D(3)-treated HL60 cells is incomplete. We also demonstrate that although the 1,25D(3)-treated cells exhibit elevated levels of cyclin B1, Cdc25C, and Cdk7, which are positive regulators of the G(2)/M traverse, these cells have decreased protein levels of p34(cdc2) and decreased p34(cdc2) kinase activity. This provides potential mechanisms for the observed accumulation of cells in the G(2) cell cycle compartment and occasional polyploidization following treatment of HL60 cells with 1,25D(3). The data also suggest that the ability of some cells to traverse this block may be the result of cellular compensatory mechanisms responding to decreased p34(cdc2) activity by increasing the levels of other regulators of the G(2) traverse, such as cyclin B1, Cdc25C, and Cdk7.
Harrison
L E
LE
Department of Surgery, UMDNJ-New Jersey Medical School, Newark, New Jersey 07103, USA.
Wang
Q M
QM
Studzinski
G P
GP
D001973:Bromodeoxyuridine / Q000378:metabolism; D016203:CDC2 Protein Kinase / Q000187:drug effects / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects*; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D018844:Cyclin-Dependent Kinases; D005434:Flow Cytometry; D016195:G2 Phase / Q000187:drug effects*; D018922:HL-60 Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008938:Mitosis / Q000187:drug effects*; D008954:Models, Biological; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation; D020687:cdc25 Phosphatases / Q000378:metabolism; D000095043:Cyclin-Dependent Kinase-Activating Kinase
C534699:CCNB1 protein, human; D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D006657:Histones; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D018844:Cyclin-Dependent Kinases; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases; D002117:Calcitriol; D001973:Bromodeoxyuridine; D000095043:Cyclin-Dependent Kinase-Activating Kinase; C000722416:CDK7 protein, human