P21(WAF1/CIP1) is dispensable for G1 arrest, but indispensable for apoptosis induced by sodium butyrate in MCF-7 breast cancer cells

Oncogene. 2004 Jan 8;23(1):21-9. doi: 10.1038/sj.onc.1207020.


Sodium butyrate (NaB) has been proposed as a potential anticancer agent. However, its mechanism of action is not totally elucidated. Here, we showed that NaB-induced cell cycle arrest and apoptosis were associated with an increase of P21(waf1/cip1) in MCF-7 breast cancer cells. This increase was more important in the nuclei, as revealed by immunofluorescence analysis. Transient transfections of MCF-7 cells with p21 deficient for interaction with CDK, but not with p21 deficient for interaction with PCNA (p21PCNA-), abrogated NaB-induced cell cycle arrest. This indicated that cell cycle blockage involved the interaction of P21(waf1/cip1) with CDK. However, P21(waf1/cip1) was dispensable, since p21 antisense did not modify cell cycle arrest. On the other hand, NaB-induced apoptosis was abolished by p21 antisense or p21PCNA-. In addition, NaB decreased PCNA levels, but increased the association of PCNA with P21(waf1/cip1). These results suggested that NaB-induced apoptosis required P21(waf1/cip1) and its interaction with PCNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Breast Neoplasms / pathology
  • Butyrates / pharmacology*
  • Cell Line, Tumor
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclin-Dependent Kinases / antagonists & inhibitors
  • Cyclins / analysis
  • Cyclins / physiology*
  • DNA Repair
  • Female
  • G1 Phase / drug effects*
  • Humans
  • Plasmids
  • Proliferating Cell Nuclear Antigen / analysis


  • Butyrates
  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • Proliferating Cell Nuclear Antigen
  • Cyclin-Dependent Kinases