Nedd4L modulates the transcription of metalloproteinase-1 and -13 genes to increase the invasive activity of gallbladder cancer

Gallbladder cancer is an aggressive cancer, often with high invasive activity, and therefore difficult to cure by conventional treatments. It is well known that the prognosis of patients with gallbladder cancer depends on the extent of surrounding tissue invasion of cancer cells. Despite the recent advances in cancer treatment, gallbladder cancer continues to carry a poor prognosis with the overall survival rate being less than 10% (Gourgiotis et al. 2008). Therefore, new therapeutic approaches based on pathobiological features of gallbladder carcinogenesis are needed. It is believed that genotoxic stress, in association with chronic inflammation, is one of the major aetiological factors in gallbladder cancer (Zatonski et al. 1997; Schottenfeld & Beebe-Dimmer 2006). Many studies have linked early steps in gallbladder carcinogenesis to genetic mutations of p53 (Takagi et al. 1994; Wee et al. 1994; Diamantis et al. 1995), mutational activation of the K-ras proto-oncogene (Malats et al. 1995) and loss of cell-cycle regulation by mutations in CDK-INK4A (Yoshida et al. 1995). By contrast, the molecular mechanisms that are responsible for the robust invasive activity of gallbladder cancer are still largely unclear. A few studies examined the role of invasion-associated matrix metalloproteinase (MMP)-2 in gallbladder carcinogenesis; however, their results were not consistent with each other (Fan et al. 2002; Wu et al. 2009). Neural precursor cell expressed, developmentally down-regulated 4-like (Nedd4L) (a homologue of the mouse Nedd4–2) is a HECT (homologous to E6-AP carboxyl terminus)-family ubiquitin ligase (Kamynina et al. 2001). It is well known that Nedd4L targets ENaC (epithelial Na+ channel) for proteasome degradation (Snyder et al. 2002). A mutation in the Nedd4L interacting region of ENaC increases the expression of ENaC on the cell membrane surface to cause an inherited form of hypertension, Liddle's syndrome (Schild et al. 1996; Staub et al.1996). Interestingly, recent studies have revealed that Nedd4L targets a broad range of molecules along with ENaC, and is thus thought to be involved in various biological properties other than regulating ion channels (Persaud et al. 2009; see review Yang & Kumar 2010). Nedd4, a ubiquitin ligase closely related to Nedd4L, is ubiquitously expressed in a broad range of tissues. By contrast, Nedd4L expression is restricted to the heart, brain, liver, kidney, and to a lesser extent to the lung (Kamynina et al. 2001). Interestingly, various cancer cell cultures expressed abundant Nedd4L (Chen & Matesic 2007); thus, Nedd4L might have an oncogenic property. In the present study, we attempted to reveal the expression status of Nedd4L in gallbladder cancer cells, and subsequently identified the pathobiological property of Nedd4L in gallbladder carcinogenesis. The findings indicate that Nedd4L is over-expressed in many invasive gallbladder cancers, and may regulate the transcription of collagenase genes through its oncogenic properties. We believe that Nedd4L could be a novel target molecule for abrogating the invasion of gallbladder cancer.