Prospects for hepatitis B virus eradication and control of hepatocellular carcinoma

Tackling hepatitis B virus-associated hepatocellular carcinoma--the future is now

Hepatocellular carcinoma (HCC) is one of the most lethal and prevalent cancers in many developing countries including India. Among the various etiological factors being implicated in the cause of HCC, the most important cause, however, is hepatitis B virus (HBV) infection. Among all HBV genes, HBx is the most critical carcinogenic component, the molecular mechanisms of which have not been completely elucidated. Despite its clinical significance, there exists a very elemental understanding of the molecular, cellular, and environmental mechanisms that drive disease pathogenesis in HCC infected with HBV. Furthermore, there are only limited therapeutic options, the clinical benefits of which are insignificant. Therefore, the quest for novel and effective therapeutic regimen against HBV-related HCC is of paramount importance. This review attempts to epitomize the current state of knowledge of this most common and dreaded liver neoplasm, highlighting the putative treatment avenues and therapeutic research strategies that need to be implemented with immediate effect for tackling HBV-related HCC that has plagued the medical and scientific fraternity for decades. Additionally, this review proposes a novel "five-point" management algorithm for HBV-related HCC apart from portraying the unmet needs, principal challenges, and scientific perspectives that are relevant to controlling this accelerating global health crisis.

Antibodies to the envelope glycoprotein of human T cell leukemia virus type 1 robustly activate cell-mediated cytotoxic responses and directly neutralize viral infectivity at multiple steps of the entry process

Infection of human cells by human T cell leukemia virus type 1 (HTLV-1) is mediated by the viral envelope glycoproteins. The gp46 surface glycoprotein binds to cell surface receptors, including heparan sulfate proteoglycans, neuropilin 1, and glucose transporter 1, allowing the transmembrane glycoprotein to initiate fusion of the viral and cellular membranes. The envelope glycoproteins are recognized by neutralizing Abs and CTL following a protective immune response, and therefore, represent attractive components for a HTLV-1 vaccine. To begin to explore the immunological properties of potential envelope-based subunit vaccine candidates, we have used a soluble recombinant surface glycoprotein (gp46, SU) fused to the Fc region of human IgG (sRgp46-Fc) as an immunogen to vaccinate mice. The recombinant SU protein is highly immunogenic and induces high titer Ab responses, facilitating selection of hybridomas that secrete mAbs targeting SU. Many of these mAbs recognize envelope displayed on the surface of HTLV-1-infected cells and virions and several of the mAbs robustly antagonize envelope-mediated membrane fusion and neutralize pseudovirus infectivity. The most potently neutralizing mAbs recognize the N-terminal receptor-binding domain of SU, though there is considerable variation in neutralizing proficiency of the receptor-binding domain-targeted mAbs. By contrast, Abs targeting the C-terminal domain of SU tend to lack robust neutralizing activity. Importantly, we find that both neutralizing and poorly neutralizing Abs strongly stimulate neutrophil-mediated cytotoxic responses to HTLV-1-infected cells. Our data demonstrate that recombinant forms of SU possess immunological features that are of significant utility to subunit vaccine design.

Hepatitis B vaccination: disease and cancer prevention-a Taiwanese experience

Prevention is most cost effective toward successful control of hepatitis B virus (HBV) infection and its complications. It is particularly urgent where HBV infection and hepatocellular carcinoma (HCC) are prevalent. To achieve better results of primary HCC prevention globally, higher world coverage rates of HBV vaccine, better strategies against breakthrough infection/nonresponder, and good long-term protection are needed. With the universal hepatitis B vaccination program starting from neonates in most countries, HBV infection and its complications will be further reduced in this century. An effective decline in the incidence of HCC in adults is expected in the near future. The concept of a cancer preventive vaccine, using HBV as an example, can be applied further to other infectious agents and their related cancers.

[Hepatitis B vaccination: a major player in the control of primary liver cancer]

In worst cases, chronic hepatitis B ultimately leads to primary liver cancer. Populations the more at risk to develop hepatocellular carcinoma (HCC), i.e. patients infected perinatally, reside essentially in Asia. A quarter of century after its introduction in medical practice, data coming from Eastern Asia demonstrate a strong impact of the vaccine on HCC incidence. Strikingly, universal immunization of Taiwanese newborns reduced fourfold pediatric HCC incidence. However, residual cases still appear though among children infected at birth by HBe antigen-carrying mothers. Epidemiologic models indicate that the continuation of universal vaccination policy will reduce chronic hepatitis B endemicity 50-fold in three generations. Recently, mutant forms of HBV potentially escaping to vaccine appeared as a potential consequence of large-scale vaccination. Finally, lack of early immunization of newborns in developing countries still represents a major limitation to the progresses against liver cancer.

Hepatitis B virus pre-S2 mutant upregulates cyclin A expression and induces nodular proliferation of hepatocytes

Naturally occurring mutants with a deletion in the pre-S2 region of the large surface protein (Delta S2-LHBs) are prevalent in serum and livers of patients with chronic hepatitis B virus (HBV) infection associated with cirrhosis. The Delta S2-LHBs protein is retained in the endoplasmic reticulum (ER) and may induce ER stress. One interesting observation is the consistently clustered distribution of hepatocytes expressing Delta S2-LHBs. In this study, complementary DNA microarray analysis identified cyclin A and several groups of genes as being significantly upregulated by Delta S2-LHBs in the HuH-7 cell line. This observation was confirmed in liver tissues. The induction of cyclin A expression may occur via the specific transactivator function of Delta S2-LHBs independent of ER stress. In the presence of Delta S2-LHBs, hepatocytes sustained cyclin A expression and cell cycle progression under ER stress and displayed increased BrdU incorporation with multinuclear formation. Furthermore, Delta S2-LHBs could enhance anchorage-independent cell growth in a nontransformed human hepatocyte line and induced nodular proliferation of hepatocytes in transgenic mice. In conclusion, these in vitro and in vivo data support a role for Delta S2-LHBs in the hepatocyte hyperplasia and a likely role in the process of HBV-related tumorigenesis.

Preventive effect of Ganfujian granule on experimental hepatocarcinoma in rats

AIM: To investigate the inhibitory effect of dietary and medicinal formula Ganfujian granule on diethylnitrosamine (DEN)-induced hepatocarcinoma in rats.

METHODS: Male SD rats had free access to water containing 0.1 g/L DEN for 16 weeks, during which the rats fed with standard diet or administration of Ganfujian granule (30.4 g/Kg in diet). At weeks 4, 8, 12 and 16 of hepatocarcinogenesis 5 rats of each group were sacrificed, and at week 20 another 30 rats were sacrificed from each group. The end point for survival observation was at week 28.Immunochemistry methods were used to examine the effect of Ganfujian granule on the process of hepatocarcinogenesis including proliferation of hepatocytes and cell cycle modulation.

RESULTS: Ganfujian granule could reduce and delay the incidence of hepatocarcinoma in rats and prolong the survival of animals. In addition, Ganfujian granule had a marked inhibitory effect on high expression of cyclin dependent kinase (CDK4) during the whole process of hepatocarcinogenesis and cyclin D1 at week 16 and the number of proliferating cell nuclear antigen (PCNA) positive cells in different stages of hepatocarcinogenesis.

CONCLUSION: Ganfujian granule can reduce and delay the incidence of hepatocarcinoma in rats by exerting direct or indirect effects on cell cycle and inhibiting uncontrolled proliferation of hepatocytes.

Susceptibility and biomarker knowledge for improvement of environmental health

At the international level, environmental health problems are usually most serious in countries that have the least resources to deal with the problems. Therefore, international efforts have been initiated to achieve equitable environmental health globally. One approach is to conduct international collaborative studies. This approach has been successful in the building of scientific infrastructure in these countries so that they can address their own environmental health concerns and to sustain the environmental health programs. Using liver and oral cancers as models for discussion, examples of success in the identification of etiology and the mechanisms for the diseases are provided. For example, biomarkers are used to provide early warning signals for the disease. In addition, the application of the collected information for developing disease prevention and intervention programs is presented. Expertise in genetic susceptibility is used to provide a more precise understanding of the cancer process. With the precise knowledge, the information can potentially be used to screen for high-risk individuals and to develop "designer" intervention procedures against specific biochemical defects. Success in disease prevention is dependent upon multidisciplinary collaborations at the local and international levels.