Regulation of Cullin 2 ubiquitin ligase expression by HGF/C-Met signaling pathway

Hepatocellular carcinoma is developing in cirrhotic ground. Cirhosis induces fibrogenesis which leads to formation of a hypoxic environment. In these hypoxic environment HIF1 accumulates. HIF1 activates the expression of many genes related with glucose metabolism, cell survival, invasion, metastasis and angiogenesis. In HCC HIF1 accumulation is related with poor prognosis. HIF1 is composed of two subunits: alpha and ß. While ß subunit is constantly stable in cell,alpha subunit stability is dependent on oxygen concentration. CUL2 E3 ligases participates in degradation of HIF1-alpha subunit so prevents HIF1 accumulation in cell. In our study we showed that Cobalt chloride (CoCl2) is used to mimic hypoxic environment. CoCl2 is known to induce HIF1 in HCC cells. In our study we used RT-PCR and western blot techniques. In our study we showed that CoCl2 induces CUL2 expression in dose and time dependent manner. In addition we used CoCl2 to induce cell death in HCC cell lines. We used MTT technique to study CoCl2 effect on SK-Hep1 and HuH7 cell viability on time and dose dependent manner. We showed that CoCl2 induces apoptosis at high doses in HCC cell lines. In hepatocarcinogenesis HGF/c-Met pathway is highly activated. HGF/c-Met pathway contirbutes cell survival, motility, invasion and angiogenesis. We studied HGF or Heparin effect on CUL2 expression in HCC cell lines with RT-PCR and western blot techniques. In our study we showed that while Heparin or HGF induces CUL2 transcription separately, they suppress CUL2 transcription together. Furthermore we showed that HGF or Heparin induces CUL2 protein expression in dose and time dependent manner To sum up HIF1, Heparin and HGF contrbutes hepatocarciogenesis. In our study we showed that HIF1, Heparin, and HGF increase CUL2 expression. It can be concluded that CUL2 can have an essential role in hepatocarcinogenesis. Key words: CUL2, HIF1, hypoxia, Heparin, HGF, HCC