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Suppression of oncogenic transformation by hypothemycin associated with accelerated cyclin D1 degradation through

H Sonoda1, K Omi, K Hojo

  • 1Shionogi Research Laboratories, Shionogi & Co., Ltd., Osaka, Japan. hikaru.sonoda@shionogi.co.jp

Life Sciences
|July 27, 1999
PubMed

Insights

Hypothemycin, an antifungal compound, halts cancer cell growth by targeting cyclin D1 degradation. It inhibits malignant phenotypes by activating the ubiquitin-proteasome pathway, offering potential therapeutic strategies.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Molecular Oncology

Background:

  • Hypothemycin is an antifungal metabolite from Hypomyces trichothecoides.
  • Ras-transformed cells exhibit malignant phenotypes, including uncontrolled proliferation.
  • Cyclin D1 is a key regulator of the cell cycle, often dysregulated in cancer.

Purpose of the Study:

  • To investigate the mechanism of hypothemycin's action on cancer cells.
  • To determine hypothemycin's effect on cyclin D1 protein levels and cell cycle progression.
  • To explore hypothemycin's potential to inhibit malignant transformation via the ubiquitin-proteasome pathway.

Main Methods:

  • Treatment of v-K-ras-transformed NIH3T3 (DT) cells with hypothemycin.
  • Analysis of cyclin D1 protein levels and cell cycle phase distribution.
  • Studies using hypothemycin-resistant Schizosaccharomyces pombe mutants to identify targets.
  • Experiments with lactacystin, a proteasome inhibitor, to assess ubiquitination and degradation pathways.

Main Results:

  • Hypothemycin treatment decreased cyclin D1 protein and prolonged the G1 phase in DT cells.
  • Hypothemycin targets S. pombe rhp6+ and mammalian ubc2, involved in ubiquitin conjugation.
  • Hypothemycin enhanced multi-ubiquitination of cyclin D1 in the presence of lactacystin, indicating facilitation of its degradation.
  • Hypothemycin inhibited anchorage-independent growth and reverted malignant morphology of DT cells, an effect abolished by lactacystin.

Conclusions:

  • Hypothemycin facilitates the ubiquitin-proteasome pathway, leading to cyclin D1 degradation.
  • Cyclin D1 is a crucial downstream mediator of ras-induced transformation.
  • Hypothemycin demonstrates potential as an anti-cancer agent by targeting the ubiquitin-proteasome pathway and inhibiting malignant phenotypes.

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