Polymethoxylated flavones induce Ca2+-mediated apoptosis in breast cancer cells

Igor N. Sergeev, Shiming Li, Julie Colby, Chi Tang Ho, Slavik Dushenkov

Research output: Contribution to journalArticlepeer-review

80 Scopus citations


Flavonoids, polyphenolic phytochemicals which include flavones and isoflavones, are present in the common human diet. It has been suggested that these compounds may exert anticancer activity; however, the mechanisms involved remain unknown. We have recently shown (Sergeev, 2004, Biochem Biophys Res Commun 321: 462-467) that isoflavones can activate the novel apoptotic pathway mediated by cellular Ca2+. Here, we report that polymethoxyflavones (PMFs) derived from sweet orange (Citrus sinensis L.) inhibit growth of human breast cancer cells via Ca2+-dependent apoptotic mechanism. The treatment of MCF-7 breast cancer cells with 5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone (5-OH-HxMF) and 3′-hydroxy-5,6,7,4′-tetramethoxyflavone (3′-OH-TtMF) induced a sustained increase in concentration of intracellular Ca2+ ([Ca2+]i) resulting from both depletion of the endoplasmic reticulum Ca2+ stores and Ca2+ influx from the extracellular space. This increase in [Ca2+]i was associated with the activation of the Ca2+-dependent apoptotic proteases, μ-calpain and caspase-12, as evaluated with the calpain and caspase-12 peptide substrates and antibodies to active (cleaved) forms of the enzymes. Corresponding non-hydroxylated PMFs, 3,5,6,7,8,3′,4′-heptamethoxyflavone (HpMF) and 5,6,7,3′,4′-pentamethoxyflavone (PtMF), were dramatically less active in inducing Ca2+-mediated apoptosis. Our results strongly suggest that the cellular Ca2+ modulating activity of flavonoids underlies their apoptotic mechanism and that hydroxylation of PMFs is critical for their ability to induce an increase in [Ca2+]i and, thus, activate Ca2+-dependent apoptotic proteases.

Original languageEnglish (US)
Pages (from-to)245-253
Number of pages9
JournalLife Sciences
Issue number3
StatePublished - Dec 23 2006

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)


  • Apoptosis
  • Breast cancer
  • Calpain
  • Caspase-12
  • Flavones
  • Flavonoids
  • Intracellular calcium
  • MCF-7 cells
  • Methoxyflavones
  • Polymethoxyflavones
  • Sweet orange (Citrus sinensis L.)


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