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Silymarin induces apoptosis primarily through a p53-dependent pathway involving Bcl-2/Bax, cytochrome c release, and

Santosh K Katiyar1, Anshu M Roy, Manjeshwar S Baliga

  • 1Department of Dermatology, University of Alabama at Birmingham, 1670 University Boulevard, Volker Hall 557, P.O. Box 202, Birmingham, AL 35294, USA. skatiyar@uab.edu

Molecular Cancer Therapeutics
|February 17, 2005
PubMed

Insights

Silymarin, a plant flavonoid, induces apoptosis in preneoplastic skin cells, primarily through a p53-dependent pathway. This mechanism involves caspase activation and shifts the balance towards programmed cell death, offering potential for skin cancer prevention.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Dermatology

Background:

  • Silymarin, a flavonoid from plants, exhibits anti-skin carcinogenic properties in mice.
  • The precise molecular mechanisms underlying silymarin's anti-skin cancer effects remain unclear.
  • Understanding silymarin's action is crucial for developing novel chemopreventive strategies against skin cancer.

Purpose of the Study:

  • To elucidate the mechanism of silymarin's anti-skin carcinogenic effects.
  • To investigate the role of the p53 tumor suppressor protein in silymarin-induced apoptosis.
  • To determine the involvement of apoptotic signaling pathways in silymarin-treated preneoplastic cells.

Main Methods:

  • Treatment of JB6 C141 cells and p53+/+ fibroblasts with silymarin and silibinin.
  • Assessment of cell viability, apoptosis (fluorescence staining, flow cytometry), and p53 expression/phosphorylation.
  • Analysis of apoptotic protein expression (Bcl-2, Bcl-xl, Bax), cytochrome c release, and caspase-3 activation.

Main Results:

  • Silymarin and silibinin dose-dependently inhibited cell viability and induced apoptosis.
  • Apoptosis was significantly greater in p53-expressing cells compared to p53-deficient cells, indicating p53 dependence.
  • Silymarin treatment increased p53 expression and phosphorylation, decreased anti-apoptotic proteins (Bcl-2, Bcl-xl), increased pro-apoptotic Bax, and activated caspase-3.

Conclusions:

  • Silymarin-induced apoptosis in preneoplastic epidermal keratinocytes is primarily p53-dependent.
  • The mechanism involves modulation of Bcl-2 family proteins, cytochrome c release, and caspase-3 activation.
  • These findings highlight silymarin's potential as a chemopreventive agent against skin carcinogenesis via apoptosis induction.

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