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Keywords:

  • Shikonin;
  • oral squamous cell carcinoma (OSCC);
  • growth inhibition;
  • apoptosis;
  • NF-κB;
  • caspase family

Abstract

Shikonin, a naphthoquinone pigment isolated from the Chinese herbal therapeutic, Zicao, has been shown to exhibit antioxidant and anticancer effects. In this study, its ability to induce apoptosis in cultured Tca-8113 oral cancer cells was studied. Treatment of the Tca-8113 cells with a variety of concentrations of Shikonin (10–40 µm) resulted in dose- and time-dependent sequences of events marked by apoptosis, as shown by the loss of cell viability, chromatin condensation, internucleosomal DNA fragmentation and sub-G1 phase accumulation. Furthermore, apoptosis in the Tca-8113 cells was accompanied by the activation of protease caspase-8, -9, -3 and low expression of Bcl-2 protein. Interestingly, inactivation of the NF-κB pathway was found in shikonin-induced apoptosis in Tca-8113 cells. These results raise the possibility that the anti-tumor effects of Shikonin in Tca-8113 cells are at least partly through the inactivation of the NF-κB pathway and subsequent activation of protease caspase family. Pharmacological inhibition of the NF-κB activity by Shikonin might be a powerful treatment option for OSCC in which activation of NF-κB plays a critical role in tumor growth and progression. Copyright © 2007 John Wiley & Sons, Ltd.