Up-regulation and functional role of p21Waf1/Cip1 during growth arrest of human breast carcinoma MCF-7 cells by phenylacetate

Cell Growth Differ. 1996 Dec;7(12):1609-15.


Phenylacetate (PA) and related aromatic fatty acids constitute a novel class of relatively nontoxic antineoplastic agents. These compounds induce tumor cytostasis and growth inhibition and differentiation of cancer cells, but little is known regarding the molecular events mediating these biological effects. Using human breast carcinoma MCF-7 cells as a model, we show here that PA-induced growth arrest is associated with enhanced expression of the cyclin-dependent kinase inhibitor p21Waf1/Cip1 and dephosphorylation of the retinoblastoma protein (pRB). The induction of p21WAF1/CIP1 mRNA by PA was independent of the cellular p53 status. To directly assess the contribution of p21Waf1/Cip1 to PA-mediated cytostasis, we compared the effects of PA in parental MCF-7 cells and cells expressing reduced levels of p21Waf1/Cip1 protein (clones AS.3 and AS.4), accomplished through constitutive expression of antisense p21Waf1/Cip1 transcripts. In contrast to parental cells, AS.3 and AS.4 cells did not show reduced pRB phosphorylation following PA treatment, indicating that p21Waf1/Cip1 induction by PA is required for dephosphorylation (inactivation) of pRB, a known mediator of cell cycle control. A prominent role for p21Waf1/Cip1 in mediating PA-induced growth arrest was further supported by the demonstration that embryonal fibroblasts derived from a p21WAF1/CIP1 knockout mouse (p21-/- mouse embryonal fibroblasts) did not growth arrest following PA treatment, whereas PA effectively induced p21WAF1/CIP1 mRNA and growth inhibition of the wild-type mouse embryonal fibroblasts. Taken together, our findings strongly support a role for p21Waf1/Cip1 in the PA-mediated inhibition of cell growth.

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / pharmacology*
  • Antisense Elements (Genetics)
  • Breast Neoplasms
  • CDC2-CDC28 Kinases*
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Cell Division / drug effects
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclin-Dependent Kinases / genetics
  • Cyclin-Dependent Kinases / metabolism
  • Cyclins / genetics
  • Cyclins / metabolism*
  • Enzyme Inhibitors / metabolism*
  • Female
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Fibroblasts / enzymology
  • Gene Expression Regulation, Neoplastic / physiology
  • Humans
  • Mice
  • Mice, Knockout
  • Phenylacetates / pharmacology*
  • Phosphorylation
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism
  • RNA, Messenger / metabolism
  • Retinoblastoma Protein / metabolism
  • Signal Transduction / physiology
  • Tumor Cells, Cultured / cytology
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / enzymology
  • Up-Regulation / drug effects


  • Antimetabolites, Antineoplastic
  • Antisense Elements (Genetics)
  • CDKN1A protein, human
  • Cdkn1a protein, mouse
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • Enzyme Inhibitors
  • Phenylacetates
  • RNA, Messenger
  • Retinoblastoma Protein
  • Protein Serine-Threonine Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • CDC2-CDC28 Kinases
  • CDK2 protein, human
  • Cdk2 protein, mouse
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases
  • phenylacetic acid