β-Caryophyllene oxide inhibits growth and induces apoptosis through the suppression of PI3K/AKT/mTOR/S6K1 pathways and ROS-mediated MAPKs activation

Cancer Lett. 2011 Dec 22;312(2):178-88. doi: 10.1016/j.canlet.2011.08.001. Epub 2011 Aug 26.

Abstract

Both PI3K/AKT/mTOR/S6K1 and mitogen activated protein kinase (MAPK) signaling cascades play an important role in cell proliferation, survival, angiogenesis, and metastasis of tumor cells. In the present report, we investigated the effects of β-caryophyllene oxide (CPO), a sesquiterpene isolated from essential oils of medicinal plants such as guava (Psidium guajava), oregano (Origanum vulgare L.), cinnamon (Cinnamomum spp.) clove (Eugenia caryophyllata), and black pepper (Piper nigrum L.) on the PI3K/AKT/mTOR/S6K1 and MAPK activation pathways in human prostate and breast cancer cells. We found that CPO not only inhibited the constitutive activation of PI3K/AKT/mTOR/S6K1 signaling cascade; but also caused the activation of ERK, JNK, and p38 MAPK in tumor cells. CPO induced increased reactive oxygen species (ROS) generation from mitochondria, which is associated with the induction of apoptosis as characterized by positive Annexin V binding and TUNEL staining, loss of mitochondrial membrane potential, release of cytochrome c, activation of caspase-3, and cleavage of PARP. Inhibition of ROS generation by N-acetylcysteine (NAC) significantly prevented CPO-induced apoptosis. Subsequently, CPO also down-regulated the expression of various downstream gene products that mediate cell proliferation (cyclin D1), survival (bcl-2, bcl-xL, survivin, IAP-1, and IAP-2), metastasis (COX-2), angiogenesis (VEGF), and increased the expression of p53 and p21. Interestingly, we also observed that CPO can significantly potentiate the apoptotic effects of various pharmacological PI3K/AKT inhibitors when employed in combination in tumor cells. Overall, these findings suggest that CPO can interfere with multiple signaling cascades involved in tumorigenesis and used as a potential therapeutic candidate for both the prevention and treatment of cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects*
  • Cell Division / drug effects*
  • Cell Line, Tumor
  • Enzyme Activation
  • Humans
  • Immunohistochemistry
  • In Situ Nick-End Labeling
  • Mitogen-Activated Protein Kinases / metabolism*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Polycyclic Sesquiterpenes
  • Proto-Oncogene Proteins c-akt / metabolism
  • Reactive Oxygen Species / metabolism*
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • Sesquiterpenes / pharmacology*
  • Signal Transduction
  • TOR Serine-Threonine Kinases / metabolism

Substances

  • Polycyclic Sesquiterpenes
  • Reactive Oxygen Species
  • Sesquiterpenes
  • caryophyllene
  • TOR Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa
  • ribosomal protein S6 kinase, 70kD, polypeptide 1
  • Mitogen-Activated Protein Kinases