Melittin prevents liver cancer cell metastasis through inhibition of the Rac1-dependent pathway

Abstract

Melittin, a water-soluble toxic peptide derived from bee venom of Apis mellifera was reported to have inhibitory effects on hepatocellular carcinoma (HCC). However, its role in antimetastasis and the underlying mechanism remains elusive. By utilizing both HCC cell lines and an animal model based assay system, we found that Rac1, which has been shown to be involved in cancer cell metastasis, is highly expressed in aggressive HCC cell lines and its activity correlated with cell motility and cytoskeleton polymerization. In addition, Rac1-dependent activity and metastatic potential of aggressive HCC cells are remarkably high in both cellular and nude mouse models. We provide evidence here that melittin inhibits the viability and motility of HCC cells in vitro, which correlates with its suppression of Rac1-dependent activity, cell motility, and microfilament depolymerization. Furthermore, melittin suppresses both HCC metastasis and Rac1-dependent activity in nude mouse models. The specificity of the effect of melittin on Rac1 was confirmed in HCC cells both in vitro and in vivo. Conclusion: Melittin inhibits tumor cell metastasis by reducing cell motility and migration via the suppression of Rac1-dependent pathway, suggesting that melittin is a potential therapeutic agent for HCC. (HEPATOLOGY 2008;47:1964-1973 H epatocellular carcinoma (HCC) is one of the most aggressive malignant tumors highly prevalent in Asia and Africa. 1 Recent studies show that the incidence of HCC in the United States and the United Kingdom has increased substantially in the past 2 decades. 2,3 Despite intense efforts to improve its prognosis, the overall survival rate of patients with HCC is very low. [4][5][6] The major obstacles to survival are metastasis and recurrence after HCC resection. 7 However, the molecular mechanism for HCC metastasis remains unclear, and the means to inhibit HCC metastasis are limited.It has been shown that HCC cell invasiveness and metastasis are regulated by multiple cues, including extracellular molecules such as cell adhesion molecules, proteases, angiogenesis factors, cytokines, and growth factors, and the underlying signaling transduction components such as Rac1. Rac1, a member of the Ras superfamily of small GTP (guanosine triphosphate)-binding protein is known to play important roles in the regulation of distinct microfilament-based structures, which is required for cell adhesion, migration, and invasion. It has been demonstrated that Rac1 can promote tumor cell migration and invasion for multiple types of cancer such as renal, breast, and liver carcinomas. Rac1 is involved in the activation of c-Jun N-terminal kinase (JNK) and JNK-dependent cell motility. 8,9 A dominant-negative form of Rac1 (Rac12 DN or Rac1 N17) blocks the changes in cell shape and the formation of adhesion complexes induced by growth factors. Conversely, microinjection of a constitutively active form of Rac1 (Rac1 DA or Rac1 V12) into fibroblasts induces changes in cytoskeleton and cell morphology in the absence of growth factors. 10 T...

Mea6 controls VLDL transport through the coordinated regulation of COPII assembly

“…Bel7402 and HEK293 cells were cultured and transfected, western blotting and co-IP were performed as we described previously [47,48]. Immunofluorescence staining was performed as described previously [49].…”

Loss of microRNA-205 expression is associated with melanoma progression

“…Western blots were performed as previously described 32 using monoclonal mouse anti-human E-cadherin antibody (1:500 dilution, Dako) and rabbit polyclonal anti-human ZEB2 IgG polyclonal antibody (Santa Cruz Biotechnology, sc-48789, 1:200 dilution).…”

Biotoxins for Cancer Therapy

“…Authors also concluded that BV takes effect by blocking the tyrosine phosphorylation of VEGFR-2 so as exerting anti-angiogenic activity, and validate the application of BV in lung cancer treatment (Huh et al, 2010). A recent study by Liu et al found that melittin derived from the venom of the bee inhibits cell motility drastically and prevents HCC metastasis via inhibition of Rac1 (Liu et al, 2008). Ip et al found that BV-induced apoptosis occurs through multiple pathways in human bladder cancer TSGH-8301 cells by inducing the release of reactive oxygen species and Ca2+and ER stress-mediated apoptotic death, and promoting the activation of initiator caspases and effector caspase with adaptor proteins (Fas/CD95) act as a receptor for BV (Ip et al, 2012).…”

“…It contains at least 18 kinds of active compounds, including melittin (a major component of BV), apamin, adolapin, the mast-cell-degranulating (MCD) peptide, enzymes (phospholipase A2, and hyaluronidase) as well as non-peptide components, such as histamine, dopamine, and norepinephrine which have a variety of pharmaceutical properties . Recent studies reported several effects of bee venom such as induction of apoptosis and necrosis and effects on proliferation, cytotoxicity, and growth inhibition of different types of cancer cells, including prostate cancer (Park et al, 2011), breast cancer (Ip et al, 2008), ovarian cancer (Jo et al, 2012), lung cancer (Huh et al, 2010), liver cancer (Liu et al, 2008), bladder cancer (Ip et al, 2012) as well as leukemia (Moon et al, 2006). BV induces apoptotic cell death through several cancer cell death mechanisms, among them the activation of PLA2 by melittin is the critical mechanism for the anti-cancer activity of BV.…”