Lowering of p27Kip1 levels by its antisense or by development of resistance to 1,25-dihydroxyvitamin D3 reverses the G1 block but not differentiation of HL60 cells.
Cyclin-dependent kinase inhibitors are proteins with functions which appear to involve regulation of cell cycle traverse, and have been suggested to have a role in cell differentiation. However, there is as yet no rigorous proof that this is the case. We have addressed the participation of one of these inhibitors, p27Kip1, in the induction of differentiation and the subsequent G1 block induced in HL60 cells by 1,25-dihydroxyvitamin D3 (1,25D3). First, it was noted that sublines of HL60 cells able to grow rapidly in the presence of 1,25D3 have protein levels of p27Kip1 lower than the levels in cells subjected to 1,25D3-induced growth inhibition, but higher than in untreated parental cells. In contrast, there was no discernible relationship between the levels of p27Kip1 and the expression of differentiation markers. Further, HL60 cells treated with 1,25D3 and an oligonucleotide antisense, but not mismatched, to p27Kip1 showed an almost complete elimination of the 1,25D3-induced G1 block, but no decrease in the expression of differentiation markers. Similar results were obtained following transient transfection with an expression vector bearing the entire p27Kip1 coding sequence in the anti-sense orientation. This is the first direct demonstration that p27Kip1 plays a role in the 1,25D3-induced G1 arrest, and that partial reduction in its levels has no effect on the induction of differentiation in HL60 cells.
Department of Pathology and Laboratory Medicine, UMD - New Jersey Medical School, Newark 07103, USA.
Q M
QM
Wang
F
F
Chen
X
X
Luo
D C
DC
Moore
M
M
Flanagan
G P
GP
Studzinski
D002117:Calcitriol / Q000627:therapeutic use*; D018797:Cell Cycle Proteins; D002454:Cell Differentiation / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000378:metabolism; D016193:G1 Phase; D016147:Genes, Tumor Suppressor; D018922:HL-60 Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D013997:Time Factors; D014162:Transfection; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D008869:Microtubule-Associated Proteins; D016376:Oligonucleotides, Antisense; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases; D002117:Calcitriol