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The plant alkaloid cryptolepine induces p21WAF1/CIP1 and cell cycle arrest in a human osteosarcoma cell line

Taka-aki Matsui1, Yoshihiro Sowa, Hiroaki Murata

  • 1Department of Molecular-Targeting Cancer Prevention, Kyoto Prefectural University of Medicine, Kyoto, Japan.

International Journal of Oncology
|September 6, 2007
PubMed

Insights

Cryptolepine (CLP), derived from Sida cordifolia, inhibits osteosarcoma cell growth by activating p21(WAF1/CIP1) expression. This compound induces cell cycle arrest in a p53-independent manner, suggesting potential as a chemotherapeutic agent.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Pharmacology

Background:

  • p21(WAF1/CIP1) is a key inhibitor of cyclin-dependent kinases.
  • A bioassay was previously developed to identify p21(WAF1/CIP1) promoter activators.
  • Cryptolepine (CLP) is an indoloquinoline alkaloid from Sida cordifolia.

Purpose of the Study:

  • To investigate the anti-cancer properties of cryptolepine (CLP).
  • To determine if CLP activates p21(WAF1/CIP1) promoter activity in a p53-independent manner.
  • To explore CLP's potential as a chemotherapeutic agent for osteosarcoma.

Main Methods:

  • Screening for compounds activating p21(WAF1/CIP1) promoter activity.
  • Treating p53-mutated MG63 osteosarcoma cells with CLP.
  • Analyzing cell growth, cell cycle phase, and p21(WAF1/CIP1) expression (mRNA and protein).
  • Utilizing mutant p21(WAF1/CIP1) promoter constructs to identify response elements.
  • Employing p21(WAF1/CIP1) gene knockout in HCT116 cells to assess CLP's mechanism.

Main Results:

  • CLP induced p21(WAF1/CIP1) expression and caused G2/M-phase arrest in MG63 cells.
  • CLP inhibited MG63 cell growth completely at 4 micromolar.
  • CLP up-regulated p21(WAF1/CIP1) mRNA and protein in a dose-dependent manner.
  • The Sp1 site at -82 of the p21(WAF1/CIP1) promoter was identified as the CLP-responsive element.
  • CLP-mediated cell cycle arrest was partially dependent on p21(WAF1/CIP1) induction.

Conclusions:

  • CLP arrests MG63 cell growth by activating the p21(WAF1/CIP1) promoter via the Sp1 site, independent of p53.
  • CLP's cell cycle arrest is at least partially mediated by inducing p21(WAF1/CIP1) expression.
  • CLP shows potential as a chemotherapeutic agent for osteosarcoma treatment.

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