p27Kip1 is essential for the antiproliferative action of 1,25-dihydroxyvitamin D3 in primary, but not immortalized, mouse embryonic fibroblasts.
1alpha,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) inhibits the growth of numerous cancer cell types. The intracellular proteins that mediate 1,25(OH)(2)D(3)-induced growth inhibition are poorly defined, although it is speculated that p21 and p27 are involved. We tested the requirement of p21 and p27 by treating primary wild-type, p21(-/-), and p27(-/-) mouse embryonic fibroblasts (MEFs) with 100 nm 1,25(OH)(2)D(3). In response to treatment, the wild-type and p21(-/-) MEFs exhibited 54 and 60% growth inhibition (p < 0.05), respectively, whereas the growth of p27(-/-) MEFs was unaffected. Western analyses indicated that p27 expression is induced by 1,25(OH)(2)D(3) treatment in wild-type and p21(-/-) MEFs. p21 expression is also induced by 1,25(OH)(2)D(3) treatment in wild-type and p27(-/-) MEFs, although the effect is less robust than for p27. Next, we spontaneously immortalized each MEF strain, which resulted in a gain of responsiveness to 1,25(OH)(2)D(3) by the p27(-/-) MEFs, as exhibited by 87% growth inhibition (p < 0.05). Both wild-type and p21(-/-) MEFs retained responsiveness (43 and 72% growth inhibition (p < 0.05), respectively). These data from primary and immortalized MEFs demonstrate that there are both p27-dependent and -independent pathways that mediate the antiproliferative action of 1,25(OH)(2)D(3).
Wade
Wendy N
WN
Department of Cancer Biology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
Willingham
Mark C
MC
Koumenis
Constantinos
C
Cramer
Scott D
SD
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D016147:Genes, Tumor Suppressor; D051379:Mice; D018345:Mice, Knockout; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism
C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D002117:Calcitriol