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4-Hydroxytamoxifen induces autophagic death through K-Ras degradation

Latika Kohli1, Niroop Kaza, Tatjana Coric

  • 1Departments of Pathology, Cell Biology, and Pharmacology and Toxicology, and Medical Scientist Training Program, University of Alabama at Birmingham, Birmingham, AL 35294, USA.

Cancer Research
|June 1, 2013
PubMed

Insights

4-hydroxytamoxifen (OHT) kills cancer cells, including estrogen receptor-negative types like MPNST, through a novel autophagic cell death pathway. This mechanism involves K-Ras degradation and offers potential for broader clinical cancer treatment applications.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Death Pathways

Background:

  • Tamoxifen is a standard treatment for estrogen receptor-positive breast cancer.
  • Emerging evidence shows tamoxifen and 4-hydroxytamoxifen (OHT) have estrogen receptor-independent cytotoxic effects.
  • Clinical trials are exploring OHT for estrogen receptor-negative cancers, including malignant peripheral nerve sheath tumors (MPNST).

Purpose of the Study:

  • To elucidate the estrogen receptor-independent cytotoxic mechanisms of OHT in MPNST cells.
  • To identify the specific cell death pathways involved in OHT-induced cell death.
  • To investigate the role of K-Ras in OHT's anti-cancer effects.

Main Methods:

  • Investigated OHT's effects on MPNST cell viability and death.
  • Assessed caspase activation and inhibition.
  • Analyzed OHT's impact on autophagy induction and autophagic vacuole formation.
  • Examined K-Ras degradation following OHT treatment using genetic and molecular techniques.
  • Validated OHT's effects on K-Ras in other cancer cell lines (breast, colon, glioma, pancreatic).

Main Results:

  • OHT induced cell death in MPNST cells independently of estrogen receptors.
  • Caspase activation was observed, but caspase inhibition did not protect cells from OHT-induced death.
  • OHT treatment led to the induction of autophagy.
  • Inhibition of autophagic vacuole formation attenuated OHT-induced cell death.
  • OHT stimulated the autophagic degradation of K-Ras, a protein crucial for MPNST cell survival.
  • OHT also induced K-Ras degradation in breast, colon, glioma, and pancreatic cancer cells.

Conclusions:

  • OHT triggers a novel form of cancer cell death via autophagy, independent of estrogen receptor signaling.
  • The mechanism involves the autophagic degradation of the survival protein K-Ras.
  • This OHT-induced autophagic death pathway holds promise for broader clinical applications in treating various cancers.

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