**8. References**

284 Hepatocellular Carcinoma – Basic Research

migration by interacting with actin through the zonula occludens. On the contrary of connexin overexpression experiments, these data were observed in an RNA interference knockdown screen. Interactions between Cx43 and ZO-1 or ZO-2, both zonula occludens proteins, were demonstrated in several studies. They bind to the same region of Cx43 in a cell cycle dynamic process, so Cx43-ZO-1 interaction occurs mainly in G0 and while Cx43-

A different kind of interaction with actin seems to occur in HTC-Cx43/GFP cells treated with geodiamolides, natural peptides from marine sponge usually involved with microfilament disruption. We observed that low geodiamolides concentration for short time (2 or 4 hours) treatment did not alter the organization of actin filaments but induces larger GJ plaques (Rangel et al., 2010). The effect could be related to the stabilization of GJ plaques due to both (i) improvement in the connexon exportation or (ii) inhibition of the degradation pathway. To uncouple events leading to GJ assembly from those related to GJ removal, HTC-CX43/GFP cells were treated with geodiamolides in combination or not with fungal antibiotic BrefeldinA, a drug that disrupts the Golgi and protein trafficking to plasma membrane. BrefeldinA drastically reduced the GJ plaques formation, and the same response was obtained when the cells were treated with BrefeldinA and geodiamolides simultaneously. These data indicate that the peptide affects mainly the delivery pathway of Cx43 protein, suggesting that geodiamolide increases the length of GJ plaques mainly because it improves the delivery pathway of

Disruption of GJIC is closed associated to hepatocarcinogenesis process despite of hepatocarcinoma cells rarely present mutation in connexin genes. Epigenetic events can be involved with to lose functional GJ. Change in connexin expression profile (from Cx32 to Cx43) is frequently observed in liver tumor cells. Abnormal localization of connexin (cytoplasmatic instead plasma membrane) also is characteristic de tumor cells. Thus, many studies were employed in the past to verify if connexin could be target of therapeutic approaches. The studies about connexin biosynthesis, traffic, docking at plasma membrane and degradation were very important to understand as functional channels are formed as well as the possible protein partners related with delivery and removal of connexin at plasma membrane. The phosphorylation status of connexin is very critical in relation this issue, likewise the participation of many proteins (signaling pathways, cytoskeleton and cell-to-cell adhesion). The attention for connexins was reinforced when it was observed that functional GJIC was restored in tumor cells by forced expression of connexin. Fortunately along of time a lot of information were collected and today we know that connexins exert tumor suppressor activity on hepatocarcinoma cells dependent and independent-functional GJIC. So, in the future it is possible that connexin will be used as therapeutic target for

ZO-2 in G0 and S phases.

Cx43 protein.

**7. Conclusion** 

hepatocarcinoma.

**6. Acknowledgments**  Supported by CNPq, Brazil.


**14** 

*USA* 

Mark A. Feitelson et al.\*

**Mechanisms of HBx Mediated Liver Cancer:** 

Chronic hepatitis B virus (HBV) infection is associated with a high risk for the development of chronic liver diseases (CLDs) which include hepatitis, cirrhosis and hepatocellular carcinoma (HCC). HCC is among the top five most prevalent tumor types worldwide, has few effective treatment options, and is highly lethal. The pathogenesis of CLD and HCC is immune mediated, and the virus has developed a number of defense mechanisms that essentially prevent infected cells from being effectively eliminated by the immune system. This, in part, involves the sustained, high level expression of the virus encoded protein, hepatitis B x antigen (HBx). Recent work has shown that HBx blocks pathways of innate immunity (Kumar et al., 2011; Wei et al., 2010), thereby blunting the development of adaptive immunity that is central to virus elimination. In addition, HBx inhibits immune mediated apoptosis by multiple pathways, including those mediated by Fas and tumor necrosis factor alpha (TNF). In this context, HBx has been shown to up-regulate TNF expression (Lara-Pezzi et al., 1998), which is thought to kill uninfected hepatocytes more readily than infected cells, thereby promoting expansion of the virus within the liver, since virus infected hepatocytes would preferentially regenerate following a bout of chronic hepatitis. HBx also switches the growth signals mediated by elevated transforming growth factor beta 1 (TGF1) from that of negative growth regulation to that of positive growth regulation. TGF1 is a transcriptional target of HBx (Yoo et al., 1996), suggesting that HBx expression in the liver promotes fibrogenesis and the development of cirrhosis. Within the infected hepatocyte, HBx blocks the action of tumor suppressors, such as p53 and Rb (Feitelson et al., 2008), and up-regulates the expression of selected host genes that strongly promote hepatocarcinogenesis even in the absence of HBx (see below). Recent work has also

Alla Arzumanyan1, Tiffany Friedman1, N. Lale Tufan2, Zhaorui Lian1, Marcia M. Clayton1, Joyce Kang3,

*3Division of Medical Microbiology, Guiyang Medical College, Guizhou Province, People's Republic of China 4MIT Portugal Program, Av. Antonio Jose de Almeida, Lisboa, Portugal 5Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, USA 6Department of Digestive Diseases of Huashan Hospital, Fudan University, Shanghai, P. R. China 7Molecular Hepatology Research Unit, Department of Medicine, University of the Witwatersrand, Johannesburg,* 

Helena M. G. P. V. Reis4, Jingbo Pan5, Jie Liu6, Patrick Arbuthnot7 and Michael Kew7

*2Department of Medical Biology, Pamukkale University School of Medicine, Kinikli Denizli, Turkey* 

*1Department of Biology, Temple University, Philadelphia, PA, USA* 

**1. Introduction** 

 \*

*South Africa* 

**Multiple Pathways and Opportunities** 

*Department of Biology, Temple University, Philadelphia, PA* 

