Xuanyong Lu Assistant Professor, Microbiology and Immunology Drexel Institute for Biotechnology and Virology Research Ph.D., 1989, Goettingen University, Goettingen, Germany 3805 Old Easton Road Doylestown, PA 18902 Tel: 215-489-4906 Fax: 215-489-4920 Email: Xuanyong.Lu@DrexelMed.edu

Keywords:

Hepatitis B virus, HBV entry, viral attachment, fusion, protease, apoptosis, serine protease inhibitor, apoptosis inhibitor, cancer, virology

Research Interests

We have previously reported that, limited digestion of human and woodchuck hepatitis viruses with the Staphylococcal protease V8 rendered the viruses “infectious” in cultured HepG2 cells. The infected HepG2 cells were shown to produce progeny viruses. The reason that V8 protease treatment induces viral infectivity is not clear. Our studies suggest that the proteolysis of V8 has exposed a region that contains a hydrophobic motif associated with membrane fusion that probably results in virus-cell membrane fusion, permitting viral genome entry into the cytosol, and then triggering HBV infection (above). The fusogenesis of this motif was supported by the fact that synthetic peptides corresponding to this motif induced fusion of bio-membranes, and of HepG2 cells from without in vitro (our unpublished observations). Other evidence supports this assumption comes from that similar motif with the identical sequence has been found in the other viral envelope polypeptides associated with fusion, including Human Immunodeficiency Virus (HIV) and influenza virus. Accordingly, the resistance of HepG2 cells to HBV infection is a possible result of the lack of a proteolysis that induces virus-cell fusion. The observation that supports this hypothesis is the finding of the over-expressing of a kind of protease inhibitor named serine protease inhibitor (SPI) in HepG2 cells. The probable mechanism is that the SPI by inactivating vital proteases in the virus-cell fusion process prevents infecting and gives immunity to the HepG2 cells. Further support for this hypothesis is provided when an anti-sense oligo was used to down regulate the SPIK gene expression led to a potential HBV infection of HepG2 cells in vitro. Logically following this, a permanent cell line that can be infected by HBV could be established by silencing the over-expressed SPI in the HepG2 cell line. Those studies are carrying on in our laboratory now.

The second field, in which I am interested, is controlling cancer growth, particularly hepatocellular carcinoma (HCC), by silence of over-expressed apoptosis inhibitors in cancer cells (Figure below). Recent studies suggest that the life and death of cells must be balanced if tissue homeostasis is to be maintained, too much growth and too little death can lead to a severe disturbance that might, ultimately, result in cancer. Cells have an intrinsic mechanism of self destruction called programmed cell death or apoptosis. In multi-cellular organisms, many of the mechanisms that control tissue homeostasis are linked to apoptosis. Defects in the apoptosis-inducing pathways can eventually lead to expansion of a population of neoplastic cells. Resistance to apoptosis can also augment the escape of tumor cells from surveillance by the immune system. In the chronic HBV/HCV infection, chronic hepatitis and inflammation usually leads to escape of infected cell from the body’s immune surveillance including CTL and NK cell induced cell apoptosis, which allows the build up of cells carrying mutated genes, integrated viral DNA, and unregulated proliferation within the infected liver, eventually triggering development of HCC. However, the resistance of the cell to apoptosis believably is achieved through over-expression of proteins known as apoptosis inhibitors. For example, the over expression of apoptosis inhibitors was found in pancreatic, gastric, colon, esophageal and colorectal cancer. Recently our studies suggest that the apoptosis inhibitors such as cIAP1and cIAP2, particularly serine protease inhibitor (SPIK), are over-expressed in hepatoma cell lines as well as in liver cancer cells. Furthermore, we have demonstrated that over-expression of such apoptosis inhibitors, for example SPIK, leading to the resistance of the cell to apoptosis. In contrast, suppressing the over-expressed SPIK in Huh 7T (a liver cancer cell line) results in the reinstatement of cell sensitivity to the apoptotic death. More interestingly, virus infection such as HBV or HCV infection closely correlates with cell over-expression of SPIK. Therefore, we hypnotize that HBV/HCV infections trigger the over-expression of apoptosis inhibitor such as SPIK, resulting in the cell resistance to apoptotic death, consequently cell carcinogenesis. If it were true, down regulation of over-expressed apoptosis inhibitor, reinstating the apoptosis of cancer cell probably could be used to control the cancer development. This new strategy to cancer therapy is developing in our laboratory now.

Selected Research Publications

1. Block, T., X. Lu, F.M. Platt., G.R. Foster, W.H. Gerlich, B.S. Blumberg, and R.A. Dwek. The secretion of human hepatitis B virus is inhibited by the imino sugar, N-butyldeoxynojirimycin. PNAS USA, 91: 2235-2239, 1994.
   
   
2. Bruss, V., X. Lu, R. Thomssen, and W.H. Gerlich. Posttranslational alterations in transmenbrance topology of the hepatitis B virus large envelope protein. EMBO J., 13: 2273-2279, 1994.
   
   
3. Lu, X., A. Metha, R. Dwek, T. Butters, and T. Block. Evidence the N-linked glycosylation is necessary for hepatitis B virus secretion. Virology 213: 660-665, 1995.
   
   
4. Lu, X., T. Block, and W.H. Gerlich. Protease-induced infectivity of hepatitis B virus for a human hepatoma cell line. J. Virol. 70: 2277-2285, 1996.
   
   
5. Lu, X., A. Metha, D.M. Dwek, B. Blumberg, and T. Block. Aberrant trafficking of hepatitis b virus glycoproteins in which N-glycan processing is inhibited. PNAS USA 94: 2380-2385, 1997.
   
   
6. Block, T.M., X. Lu, A. Mehta, B.S. Blumburg, B. Tennant, M. Ebling, B. Korba, D. Lansky, G.S. Jacob, and R. Dwek. Treatment of Hepatitis virus in chronically infected woodchucks with folding and trafficking inhibitor. Nature Medicine 4(5): 610-614, 1998.
   
   
7. Block, T.M., X. Lu, A. Mehta, J. Park, B.S. Blumberg, and R. Dwek. Role of glycan processing in hepatitis B virus envelope protein trafficking. Advances in Experimental Medicine & Biology, 435: 207-16, 1998.
   
   
8. Lu, X., T. Hazboun, and T. Block. Limited proteolysis induces woodchuck hepatitis virus infectivity for human HepG2 cells. Virus Research, 73(1): 27-40, 2001.
   
   
9. Lu, X., Y. Lu, R. Geschwindt, R.A. Dwek, and T.M. Block. The hepatitis B virus MHBs antigen is selectively sensitive to glucosidase mediated processing in the endoplasmic reticulum. DNA and Cell Biology, 20(10): 647-656, 2001.
   
   
10. Lu, X., T. Tran, E. Semick, and T. Block. The alkylated imino sugar, n- (n-nonyl)-deoxygalactonojirimycin, reduces the amount of hepatitis B virus (HBV) nucleocapsid in tissue culture. J. Virol., 77(22): 11933-11940, 2003.
    
    
11. Norton, P., Q. Gong, A. Mehta, X. Lu, and T. Block. Hepatitis B Virus-mediated changes of apolipaprotein mRNA abundance in cultured hepatoma cells. J. Virol., 77(9): 5503-5506, 2003.
    
    
12. Lu, X., P. Weiss, and T. Block. A phage with high affinity for hepatitis B surface antigen for detection of HBsAg. J. Virolog. Meth., 119(1): 51-54, 2004.
    
    
13. Lu, X., and T. Block. Study of the early steps of the Hepatitis B Virus life cycle. Int. J. Med. Sci. 1(1): 21-33, 2004.
    
    
14. Lu, X, Matthew Lee, Trang Tran, and Timothy Block. High level expression of apoptosis inhibitor in hepatoma cell line expressing Hepatitis B virus. Int. J. Med. Sci. 2(1), 44-51, 2005.
    
    
15. Huang T, Lu C, Tsai J, Yao W, Lu X, Lai M, Liu H, Shiau A. Novel autoregulatory function of hepatitis B virus M protein on surface gene expression. J Biol. Chem. 280: 27742-27754, 2005.