Antimetastatic effect and mechanism of ovatodiolide in MDA-MB-231 human breast cancer cells

Cancer metastasis is a primary cause of cancer death. Ovatodiolide, a bioactive cembrane-type diterpenoid isolated from Anisomeles indica (L) Kuntze (Labiatae), has been shown to inhibit the growth and proliferation of cancer cells. However, the anti-metastatic effects of ovatodiolide on highly metastatic human breast cancer MDA-MB-231 cells remain unclear. In this study, we first noted that ovatodiolide inhibited MDA-MB-231 cell migration and invasion by wound-healing assay and Boyden chamber assay. Western blot, gelatin zymography and reversed transcription-PCR analysis showed that ovatodiolide significantly and selectively suppressed the expression, activation, and mRNA of matrix metalloproteinase-9 (MMP-9) in a concentration-dependent manner. Ovatodiolide significantly decreased the nuclear level of nuclear factor kappaB (NF-kappa B), increased inhibitor of kappaB alpha (I kappa B alpha) through preventing phosphorylation of upstream signal I kappa B kinase (IKK). Pretreatment with a specific NF-kappa B inhibitor (PDTC) and an I kappa B protease inhibitor (TPCK) also reduced MMP-9 activity, cell migration and cell invasion. Moreover, ovatodiolide can suppress activation of c-Jun N-terminal kinase, p38 mitogen-activated protein kinase, phosphatidylinositol 3-kinase and Akt, while it did not affect phosphorylation of extracellular signal regulating kinases (ERK)1/2. Additionally, the treatment of inhibitors specific for PI3K (wortmannin), JNK (SP600125) or p38 MAPK (SB203580) to MDA-MB-231 cells could result in a reduced activation of MMP-9, concomitantly with a marked inhibition on cell migration and invasion. Taken together, these results demonstrate that ovatodiolide inhibits the metastatic ability of MDA-MB-231 cells by reducing MMP-9 activity through suppressing JNK, p38 MAPK and PI3K/Akt signaling pathways and inhibiting NF-kappa B activity. These results are the first to reveal the function of ovatodiolide in tumor metastasis and its underlying molecular mechanism, thus suggesting ovatodiolide to be a promising antimetastatic agent. (C) 2011 Elsevier Ireland Ltd. All rights reserved.