Natural killing activities in chronic liver diseases and hepatocellular carcinoma

Adoptive immunotherapy for postoperative hepatocellular carcinoma: a systematic review

The high risk of recurrence in post-operative hepatocellular carcinoma (HCC) highlights the need for an effective adjuvant treatment. A systematic review of randomised controlled trials (RCTs) was performed to evaluate the clinical efficacy of adjuvant adoptive immunotherapy (AIT) for post-operative HCC patients. Electronic (MEDLINE, EMBASE and Cochrane Library databases) and manual searches were conducted throughout May 2011 to identify RCTs evaluating postoperative AIT for patients with HCC. Methodological quality was assessed in accordance with the QUOROM statement. Four RCTs totalling 423 patients met the eligibility criteria. All RCTs reported significantly improved disease-free survival rate or reduced recurrence rate after treating with adjuvant AIT (p < 0.05). The overall survival rates of AIT group are slightly higher than those of the control group in one study. Moreover, AIT was a safe treatment, with fever as the main adverse effects. This study adds to the evidence that postoperative HCC patients treated with adjuvant AIT show an improvement in disease-free survival rate or recurrence rate.

Association between polymorphisms of the T cell immunoglobulin musin-3 gene and outcome of hepatitis B virus infection

AIM: To investigate the relationship between single nucleotide polymorphisms (SNPs) of the T cell immunoglobulin musin-3 (Tim-3) gene and outcome of hepatitis B virus (HBV) infection in a Chinese Han population.

METHODS: Two tagSNPs of the Tim-3 gene (rs11741184 and rs13170556) were genotyped using the SNaPshot method in 996 patients with chronic HBV infection group and 301 patients with acute self-limiting HBV infection. The genotypes, allele frequencies and haplotypes of the two Tim-3 tagSNPs were compared between the two groups of patients.

RESULTS: The frequencies of CC, CG and GG genotypes at the rs11741184 locus were 84.39% (254/301), 15.28% (46/301) and 0.3% (1/301) in patients with acute self-limiting HBV infection, and 86.04% (857/996), 13.65% (136/996) and 0.3% (3/996) in patients with chronic HBV infection, respectively. There were no statistical differences in the genotype frequencies at the rs11741184 locus between the two groups of patients (all P > 0.05). The frequencies of AA, GA and GG genotypes at the rs13170556 locus were 68.77% (207/301), 28.57% (6/301) and 2.66% (8/301) in patients with acute self-limiting HBV infection, and 68.07% (678/996), 28.41% (283/996) and 3.51% (35/996) in patients with chronic HBV infection, respectively. There were also no statistical differences in the genotype frequencies at the rs13170556 locus between the two groups of patients (all P > 0.05). Three haplotypes for Tim-3 tagSNPs (C-A, C-G, G-A) were found in the Chinese Han population, and their haplotype frequencies were similar between patients with acute self-limiting HBV infection (75.08%, 16.94%, 7.97%) and those with chronic HBV infection (75.08% vs 75.15%, 16.94% vs 17.72%, 7.97% vs 7.13%, all P > 0.05).

CONCLUSION: The two Tim-3 tagSNPs may not be associated with outcome of HBV infection in Chinese Han population.

T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) mediates natural killer cell suppression in chronic hepatitis B

BACKGROUND & AIMS

T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) has been shown to influence autoimmune diseases; however, its function in viral infection has not been well-defined. We therefore investigated the expression and regulatory function of Tim-3 in natural killer (NK) cells in chronic Hepatitis B (CHB) infection.

METHODS

Seventy-six CHB patients, 38 healthy controls, and 18 patients with fatty liver disease (FLD) were tested for Tim-3 expression on peripheral blood mononuclear cells (PBMCs) and in the liver tissue by flow cytometry and immunohistochemical stainning. The effects of HBV infection on Tim-3 expression in NK cells and the roles of Tim-3 in regulation of NK-cell function were also studied.

RESULTS

There was a significant increase of Tim-3 expression in PBMCs, circulating NK cells and liver infiltrating lymphocytes (LILs) from CHB patients compared to that of healthy controls and FLD patients. Increased Tim-3 expression was also detected in NK92 cells that had been transfected with a HBV expression vector and NK cells isolated from the liver of HBV transgenic mice. Importantly, blockage of Tim-3 signaling with anti-Tim-3 antibodies or Tim-3-Fc fusion proteins resulted in an increased cytotoxicity for NK92 cells compared to HepG2 and HepG2.2.15 cells, as well as an elevated interferon-gamma (IFN-gamma) production. Similarly, enhanced cytotoxicity was also observed in PBMCs or NK cells from CHB patients treated with the Tim-3 blockade ex vivo.

CONCLUSION

HBV infection can up-regulate Tim-3 expression in NK cells, which may in turn suppress NK-cell functions in CHB patients.

HLA antigen changes in malignant cells: epigenetic mechanisms and biologic significance

Changes in classical and nonclassical HLA class I as well as HLA class II antigens have been identified in malignant lesions. These changes, which are described in this review are believed to play a major role in the clinical course of the disease since both HLA class I and class II antigens are critical to the interaction between tumor cells and components of both innate and adaptive immune system. Abnormalities in HLA antigen expression in malignant cells, which range in frequency from 0-90%, are caused by distinct mechanisms. They include defects in beta(2)-microglobulin (beta(2)m) synthesis, loss of the gene(s) encoding HLA antigen heavy chain(s), mutations, which inhibit HLA antigen heavy chain transcription or translation, defects in the regulatory mechanisms, which control HLA antigen expression and/or abnormalities in one or more of the antigen processing, machinery (APM) components. More recently, epigenetic events associated with tumor development and progression have been found to underlie changes in HLA antigen, APM component, costimulatory molecule and tumor antigen (TA) expression in malignant cells. The types of epigenetic modifications that may occur in normal and malignant cells as well as their role in changes in HLA antigen expression by malignant cells have been reviewed. The epigenetic events associated with alterations in HLA antigen expression may be clinically relevant as, in some cases, they have been shown to impair the recognition of tumor cells by components of the adaptive immune system. The functional relevance and potential clinical significance of these epigenetic alterations have been addressed. Finally, unlike genetic alterations, epigenetic modifications can, in some cases, be reversed with pharmacologic agents that induce DNA hypomethylation or inhibit histone deacetylation. Therefore, strategies to overcome epigenetic modifications underlying changes in HLA antigen expression in malignant cells have been discussed.

NK and NKT cells in liver injury and fibrosis

The innate immune mechanisms of the liver represent an important first line of defense against bacterial products, toxins, and food antigens coming from the intestine. Natural Killer (NK) and Natural Killer T cells (NKT) are components of the innate immune system with increased presence in the liver compared to other organs and have been reported to participate in the inflammatory processes during hepatic diseases. However significant confusion has been noted in this field mainly due to changes in the characterization of these cells as new knowledge accumulates and due to differences in the approaches used for their study. Both cell types can mediate hepatic injury in several models but studies in human liver diseases have not managed to fully explain their functions. However accumulating evidence supports an antifibrotic role of NK cells mainly via an inhibitory effect on hepatic stellate cells by inducing apoptosis and via production of interferon-gamma. Therefore, downregulation of NK cells during most types of liver injury may facilitate liver fibrosis. Data about the role of NKT cells in liver fibrosis are limited. This review will summarize the studies about the role of NK and NKT cells in liver diseases with a special interest in hepatic injury and liver fibrosis.

Classical and nonclassical HLA class I antigen and NK Cell-activating ligand changes in malignant cells: current challenges and future directions

Changes in classical and nonclassical HLA class I antigen and NK cell-activating ligand expression have been identified in malignant lesions. These changes, which are described in this chapter, are believed to play a major role in the clinical course of the disease since both HLA class I antigens and NK cell-activating ligands are critical to the interaction between tumor cells and components of both innate and adaptive immune systems. Nevertheless, there is still debate in the literature about the biologic and functional significance of HLA class I antigen and NK cell-activating ligand abnormalities in malignant lesions. The reasons for this debate are reviewed. They include (i) the incomplete association between classical HLA class I antigen changes and the clinical course of the disease; (ii) the relatively limited number of malignant lesions that have been analyzed for nonclassical HLA class I antigen and NK cell-activating ligand expression; and (iii) the conflicting data regarding the role of immunoselection in the generation of malignant cells with HLA antigen and NK cell-activating ligand abnormalities. The technical limitations associated with the assessment of HLA antigen and NK cell-activating ligand expression in malignant lesions as well as the immunological and nonimmunological variables that may confound the impact of HLA antigen and NK cell-activating ligand changes on the clinical course of the disease are also discussed. Future studies aimed at overcoming these limitations and characterizing these variables are expected to provide a solution to the current debate regarding the significance of HLA class I antigen and NK cell-activating ligand abnormalities in malignant lesions.

The role of psychosocial factors in the progression of hepatocellular carcinoma

The number of deaths per year from hepatocellular carcinoma (HCC) exceeds 250000, placing it sixth as the cause of death from cancer worldwide. The primary etiology of most cases of HCC in the US is hepatitis B and/or C. Extensive research has demonstrated that the relationship between hepatitis B infection and the progression to HCC is mediated by the immune system. A substantial, but unrelated literature, describes the relationship between psychosocial factors (e.g., stress, psychiatric morbidity), immune system reactivity, and disease progression in patients with cancer. However, the role of these factors in the progression of HBV-HCC has not been explored. An understanding of the relationship among virology, immunology, and behavior in the development and recurrence of HCC may provide alternative methods for secondary prevention of HCC (e.g., behavioral) until a vaccine and/or pharmacological treatments are developed, feasible, and affordable.

Perforin and Fas/Fas ligand-mediated cytotoxicity in acute and chronic woodchuck viral hepatitis

The Fas ligand (FasL)/Fas and the perforin-granzyme cytotoxic pathways presumably play a central role in the development of hepatocellular injury in viral hepatitis. To recognize the potential contribution of FasL and perforin-based cell killing in hepadnaviral infection, we adopted a cytotoxic assay using murine Fas+ P815 and human Fas- K562 cells as targets. Freshly isolated peripheral blood mononuclear cells (PBMC) from woodchucks with newly acquired woodchuck hepatitis virus (WHV) infection (n = 6), with chronic WHV hepatitis (n = 9), and from healthy animals (n = 11) were used as effector cells. We have found that woodchuck lymphoid cells kill cell targets via both the FasL/Fas and the perforin death pathways. The contribution of Fas-dependent cytolysis was ascertained in blocking experiments with anti-Fas antibody and by incubation of PBMC with cyclohexamide to prevent de novo synthesis of FasL. The involvement of the perforin pathway was confirmed by treatment of K562 cells with colchicine to inhibit the microtubule-dependent perforin release. Comparative analysis showed that peripheral lymphoid cells from acute WHV hepatitis, but not those from chronic WHV infection, are more cytotoxic and that this increase seems to be entirely due to activation of perforin-mediated killing. The data indicate that acute infection in woodchucks is associated with the augmented capacity of lymphoid cells to elicit perforin-dependent killing, but in chronic infection, independent of the severity of liver disease and duration of chronicity, these cells have the same or lower cytotoxic potential as PBMC from healthy controls. These findings suggest a role for non-specific cellular immunity, presumably natural killer (NK) cells, in the control of early WHV infection and in the progression of chronic hepatitis.

Clinical significance of natural killing activity in patients with advanced lymphoma

Using a newly described analysis of natural killing activity employing an "individual effector/target cell ratio" according to the number of effector cells in blood, we recently determined that patients with spontaneous lymphoma regression had elevated natural killing activity prior to regression. To clarify the clinical significance of natural killing activity in patients with advanced lymphoma, a prospective study was performed at a single institution in 43 untreated patients. Survival was analyzed to detect prognostic variables. Among factors chosen initially by univariate analyses, multivariate analysis selected three prognostic factors: chemotherapy response (P < 0.0001), low-grade lymphoma (P = 0.0005), and natural killing activity (P = 0.0052). Within the chemotherapy response, natural killing activity was a unique correlative factor (P < 0.0001) selected by a multivariate regression analysis using forward selection method. In patients with advanced lymphoma, natural killing activity is a valuable prognostic factor and may also predict the response to chemotherapy.

Natural killing activity in patients with spontaneous regression of malignant lymphoma

Previously, we proposed a new analysis of natural killing activity, for comparison, employing an "individual effector/target cell ratio" according to the number of effector cells in blood. The activity could be measured in four patients with spontaneous regression of malignant lymphoma. Despite the absence of episodes suggesting viral infections, patients with spontaneous regression had significantly higher activities prior to their regressions than either controls or patients without regression. In one patient who had a spontaneous regression accompanied by a high level of natural killing activity, subsequent exacerbation of the disease with a reduced activity was never followed by a regression and became life-threatening. In another patient, a spontaneous regression was accelerated after greater augmentation of natural killing activity was induced by a superimposed viral infection. These facts suggest that highly elevated natural killing activity may be one of the possible mechanisms responsible for spontaneous regression of malignant lymphoma.