Cirrhotic patients with or without hepatocellular carcinoma harbour AFP-specific T-lymphocytes that can be activated in vitro by human alpha-fetoprotein

A Pathophysiological Approach To Current Biomarkers

Biomarkers are necessary for screening and diagnosing numerous diseases, predicting the prognosis of patients, and following-up treatment and the course of the patient. Everyday new biomarkers are being used in clinics for these purposes. This section will discuss the physiological roles of the various current biomarkers in a healthy person and the pathophysiological mechanisms underlying the release of these biomarkers. This chapter aims to gain a new perspective for evaluating and interpreting the most current biomarkers.

Alpha-Fetoprotein- and CD40Ligand-Expressing Dendritic Cells for Immunotherapy of Hepatocellular Carcinoma

Simple Summary

In first clinical trials, vaccinations against tumor-associated antigens (TAA), such as Alpha-Fetoprotein (AFP) using antigen presenting cells, such as dendritic cells (DC), failed to achieve effective immune responses towards hepatocellular carcinoma (HCC). CD40Ligand is a potent immune checkpoint, which can increase the antitumoral immune response of DC. In this study, a subcutaneous vaccination with DCs, which were transduced with AFP-coding adenoviruses and an intratumoral treatment with DCs, which were transduced with CD40L-coding adenoviruses, induced an antitumoral immune response and led to complete remissions and long-term survival in 62% of mice with established HCC. Combined strategy causes rapid and profound changes in the tumor environment with enhanced Th1-cytokine expression, strong tumor infiltration of cytotoxic T lymphocytes and DC, and higher tumor apoptosis, leading to effective tumor regression of HCC. Thus, intratumoral CD40L co-stimulation represents a promising tool for improving tumor-antigen DC-based immunotherapy of HCC.

Abstract

Dendritic cells (DC) as professional antigen presenting cells are able to prime T-cells against the tumor-associated antigen α-fetoprotein (AFP) for immunotherapy of hepatocellular carcinoma (HCC). However, a strong immunosuppressive tumor environment limits their efficacy in patients. The co-stimulation with CD40Ligand (CD40L) is critical in the maturation of DC and T-cell priming. In this study, the impact of intratumoral (i.t.) CD40L-expressing DC to improve vaccination with murine (m)AFP-transduced DC (Ad-mAFP-DC) was analyzed in subcutaneous (s.c.) and orthotopic murine HCC. Murine DC were adenovirally transduced with Ad-mAFP or Ad-CD40L. Hepa129-mAFP-cells were injected into the right flank or the liver of C3H-mice to induce subcutaneous (s.c.) and orthotopic HCC. For treatments, 10⁶ Ad-mAFP-transduced DC were inoculated s.c. followed by 10⁶ CD40L-expressing DC injected intratumorally (i.t.). S.c. inoculation with Ad-mAFP-transduced DC, as vaccine, induced a delay of tumor-growth of AFP-positive HCC compared to controls. When s.c.-inoculation of Ad-mAFP-DC was combined with i.t.-application of Ad-CD40L-DC synergistic antitumoral effects were observed and complete remissions and long-term survival in 62% of tumor-bearing animals were achieved. Analysis of the tumor environment at different time points revealed that s.c.-vaccination with Ad-mAFP-DC seems to stimulate tumor-specific effector cells, allowing an earlier recruitment of effector T-cells and a Th1 shift within the tumors. After i.t. co-stimulation with Ad-CD40L-DC, production of Th1-cytokines was strongly increased and accompanied by a robust tumor infiltration of mature DC, activated CD4⁺-, CD8⁺-T-cells as well as reduction of regulatory T-cells. Moreover, Ad-CD40L-DC induced tumor cell apoptosis. Intratumoral co-stimulation with CD40L-expressing DC significantly improves vaccination with Ad-mAFP-DC in pre-established HCC in vivo. Combined therapy caused an early and strong Th1-shift in the tumor environment as well as higher tumor apoptosis, leading to synergistic tumor regression of HCC. Thus, CD40L co-stimulation represents a promising tool for improving DC-based immunotherapy of HCC.

Recombinant heat shock protein 70 functional peptide and alpha-fetoprotein epitope peptide vaccine elicits specific anti-tumor immunity

Alpha-fetoprotein (AFP) is a marker of hepatocellular carcinoma (HCC) and serves as a target for immunotherapy. However, current treatments targeting AFP are not reproducible and do not provide complete protection against cancer. This issue may be solved by developing novel therapeutic vaccines with enhanced immunogenicity that could effectively target AFP-expressing tumors. In this study, we report construction of a therapeutic peptide vaccine by linking heat shock protein 70 (HSP70) functional peptide to the AFP epitope to obtain HSP70-P/AFP-P. This novel peptide was administered into BALB/c mice to observe the effects. Quantification of AFP-specific CD8 ⁺ T cells that secrete IFN-γ in these mice via ELISPOT revealed the synergistic effects of HSP70-P/AFP-P with increased numbers of AFP-specific CD8 ⁺ T cells. Similarly, ELISA analysis showed increased granzyme B and perforin released by natural killer cells. Moreover, in vitro cytotoxic T-lymphocyte assays and in vivo tumor preventive experiments clearly showed the higher antitumor effects of HSP70-P/AFP-P against AFP-expressing tumors. These results show that treatment of BALB/c mice with HSP70-P/AFP-P induced stronger T-cells responses and improved protective immunity. Our data suggest that HSP70-P/AFP-P may be used as a therapeutic approach in the treatment of AFP-expressing cancers.

Physiology of Alpha-Fetoprotein as a Biomarker for Perinatal Distress: Relevance to Adverse Pregnancy Outcome

The many physiologic roles of human alpha-fetoprotein (HAFP) and its correlation with perinatal distress/pregnancy outcome are rarely addressed together in the biomedical literature, even though HAFP has long been used as a biomarker for fetal birth defects. Although the well being of the fetus can be monitored by the measurement of gestational age–dependent HAFP in biologic fluid levels (serum, amniotic fluid, urine, and vaginal fluids) throughout pregnancy, the majority of clinical reports reflect largely second trimester and (less likely) first trimester testing due to regulatory clinical restrictions. However, reports of third-trimester and pregnancy term measurement of HAFP levels performed in clinical research and/or investigational settings have gradually increased over the years and have expanded our base knowledge of AFP-associated pregnancy disorders during these stages. The different structural forms of HAFP (isoforms, epitopes, molecular variants, etc.) detected in the various biologic fluid compartments have been limited by antibody recognition of specific epitopic sites developed by the kit manufacturers based on antibody specificity, sensitivity, and precision. Concomitantly, the advances in elucidating the various biologic actions of AFP are opening new vistas toward understanding the physiologic roles of AFP during pregnancy. The present review surveys HAFP as a biomarker for fetal distress during the perinatal period in view of its structural and functional properties. An attempt is then made to relate the AFP fluid levels to adverse pregnancy complications and outcomes. Hence, the present review was divided into two major sections: (I) AFP structure and function considerations and (II) the relationship of AFP levels to the distressed fetus during the third trimester and at term.

Immunotherapy of hepatocellular carcinoma

Newer immunotherapy agents may break the barrier that tumors create to evade the attack from the immune system. Dendritic cell vaccination has shown encouraging clinical activity and a favorable safety profile in advanced tumor stages. However, optimal cell maturation status, choice of tumor antigens and route of administration have not been established. Single or multiple peptides derived from tumor-associated antigens may also be used for cancer vaccination. Intratumoral delivery of oncolytic viruses expressing immunostimulating cytokines like GM-CSF have produced stimulating clinical results that need further verification. But it is probably T-cell checkpoint modulation with monoclonal antibodies that has attracted the highest expectations. Promising activity has been reported for tremelimumab, a CTLA-4 inhibitor, and a clinical trial testing the PD-1 antibody nivolumab is underway. Future progress will probably come from a better understanding of the mechanisms of cancer-related immunosuppression, improvement in agents and strategies and combination of the available therapeutic tools.

Glycoprotein 96 and α-fetoprotein cross-linking complexes elicited specific antitumor immunity

Hepatocellular carcinoma (HCC) is one of the most common malignant gastroenterological cancers over the world. α-fetoprotein (AFP) is an oncofetal protein produced during HCC development that could generate weaker and less reproducible antitumor protection, and it may serve as a target for immunotherapy. Therefore, it is imperative to enhance its immunogenicity and develop therapeutic vaccines to eliminate AFP-expressing tumors. In this study, by way of glutaraldehyde cross-linking, we constructed a potential therapeutic protein vaccine, glycoprotein 96 (gp96)/AFP. Our results demonstrated that AFP and gp96 synergistically exhibited significant increase in AFP-specific CD8⁺ T-cell responses and impressive cytotoxic antitumor effect against AFP-expressing tumors. Priming mice with the reconstructed vaccine, we elicited robust strong protective immunity. Our study suggests that tumor vaccine by cross-linking tumor antigen and gp96 is a promising approach to cancer therapy.

HSP72 and gp96 in gastroenterological cancers

Heat shock protein 72 (HSP72) and glycoprotein 96 (gp96) are highly expressed in cancer tissues. Recent studies indicate the possible roles of HSP72 and gp96 in the development and progression of gastrointestinal carcinomas but detailed mechanisms are still ambiguous. Human esophageal cancer, gastric cancer, colon cancer and liver cancer are common gastrointestinal malignant carcinomas in the world. The studies indicated that there existed a significant correlation between the expression of HSP72, gp96 and the development and progression of digestive carcinomas. HSP72 and gp96 expression were significantly associated with the presence of tumor infiltration, lymph node and remote metastasis. Interestingly, studies have found that HSP72 chaperoned alpha-fetoprotein (AFP), HBx in hepatocellular carcinoma, and CD44 in colonic carcinomas. The further researches demonstrated that HSP72-AFP or gp96-AFP recombined vaccine could elicit specific anti-tumor immunity. The high-level expression of HSP72 and gp96 may be not only used as diagnostic or prognostic markers for gastrointestinal carcinomas but also as better immunotherapeutic vaccines in the cancers.

YB-1 immunization combined with regulatory T-cell depletion induces specific T-cell responses that protect against neuroblastoma in the early stage

Neuroblastoma is the most common extracranial solid cancer in childhood and the most common cancer in infancy. Currently, no effective clinical treatments are available for advanced neuroblastoma. In a previous study, we screened Y Box protein 1 (YB-1) as a potential neuroblastoma-associated antigen from sera of AGN2a-immunized mice by serological analysis of recombinant cDNA expression libraries technique. The aim of this study is to explore if YB-1 immunization in the context of Treg depletion could induce protective immune response against the neuroblastoma in mice. YB-1 was expressed and purified by pET-15b prokaryotic expression system. It was demonstrated that anti-YB-1 CD8(+) T-cell responses could be induced by AGN2a immunization, and the strongest CD8(+) T-cell responses against AGN2a were induced by YB-1-immunized mice in the context of Treg depletion compared with YB-1 only immunization group and control group. Importantly, the survival rate of mice treated with YB-1 immunization combined with Treg depletion was 80% when challenged by 1 × 10(4) AGN2a cells, significantly higher than that of mice immunized with YB-1 alone (P < 0.01). Furthermore, T-cell adoptive therapy showed that the neuroblastoma growth was inhibited when T cells or splenic cells from YB-1-immunized mice with Treg depletion were transferred to AGN2a bearing mice. Both CD4(+) and CD8(+) T cells were involved in the anti-neuroblastoma responses induced by YB-1 immunization combined with Treg depletion. These results indicated that YB-1 immunization combined with Treg depletion could induce specific T-cell responses against neuroblastoma and could be a potential strategy for the prevention and treatment of neuroblastoma in the early stage.

Alpha-fetoprotein specific CD4 and CD8 T cell responses in patients with hepatocellular carcinoma

The presence of CD8 T cell responses to tumor associated antigens have been reported in patients with different malignancies. However, there is very little information on a comparable CD8 and CD4 T cell response to a tumor antigen in liver cancer patients. Here, we re-examine the kinetic and the pattern of T helper 1 and cytotoxic T lymphocyte responses to alpha-fetoprotein (AFP), a tumor rejection antigen in hepatocellular carcinoma (HCC). Then, we discuss the possibility of using AFP-based immunotherapy in combination with necrotizing treatments in HCC patients.

Cell-mediated immune responses to alpha-fetoprotein and other antigens in hepatocellular carcinoma

Cell-mediated immune responses play an important role in the control of tumour growth. CD4 and CD8 T cells recognise tumour antigens presented via major histocompatibility complex molecules of antigen presenting cells and develop into effector cells with the ability to identify and kill tumour cells. Here, we re-examine the adaptive immune response to tumour antigens expressed by hepatocellular carcinoma (HCC) and discuss approaches that could be applied in future T-cell-based immunotherapy schedules to induce a potent and effective antitumour immunity. Moreover, we discuss cytotoxic T lymphocyte and Th1 responses to tumour antigens in patients with HCC and evaluate the effects of conventional treatments on antitumour T-cell responses.

A novel immunotherapy to hepatocellular carcinoma: CD40-activated B lymphocytes transfected with AFPmRNA

Alpha-fetoprotein (AFP) is overexpressed in the majority of hepatocellular carcinomas (HCCs), and thus may offer attractive target for immunotherapy against this neoplasm. CD40 ligand (CD40L) is the major signal that induces B cells to efficiently present antigen to T cells, and CD40-activated B (CD40-B) lymphocyte cells may boost cytotoxic T lymphocytes (CTLs) when they are pulsed with tumour antigens. CTL is considered to be a promising therapeutic means for the treatment of cancers. Here, we intend to build a plasmid pGEM4Z/AFP/A64 and to prepare AFPmRNA, then separate B lymphocyte cells. These CD40-B cells are pulsed with AFPmRNA, and they may boost robust T-cell responses, but more importantly, they also may prime naive T-cell responses against hepatocarcinoma. These CD40-B cells will be a powerful source of APCs generated by simple and reliable technology that may be applied to antigen responses, immune treatment for cancer, vaccination approaches, and ex vivo T-cell expansion for adoptive therapy. AFPmRNA-transfected B cells may represent a broadly applicable vaccine strategy to induce potentially therapeutic CTL responses against AFP-positive target cells in HCC. Vaccine strategies such as these may contribute to the effective future treatment of HCC.

Strategies for Successful Vaccination against Hepatocellular Carcinoma

Current therapies against hepatocellular carcinoma (HCC) are not curative in the majority of patients. In the past, immunotherapy approaches aimed to non-specifically stimulate immune response were quite ineffective. New treatments based on stimulation of specific anti-tumor immune response are currently proposed and appear more promising. Tumor-specific antigens identified in HCC demonstrated immunogenicity both in preclinical and clinical trials. Effectiveness in animal studies raised interest in the clinical applicability of non-specific adoptive immunotherapy that prevented disease recurrence after tumor resection. Dendritic cell (DC)-based tumor vaccines achieved encouraging results, and cellular vaccines based on DCs have already entered clinical trials. Preventive and therapeutic DNA vaccination have been proposed, all based on tumor-associated antigens (TAAs), either modified or not, an example being alpha-fetoprotein (AFP). The concomitant expression of co-stimulatory molecules and cytokines was used to increase tumor immunogenicity. Syngeneic or nude mice models indicated that immunotherapy for HCC could stimulate an anti-tumor T-cell response leading to clinical benefit devoid of significant toxicity. The use of DNA-based vaccination raises exciting possibilities in preventing HCC in high-risk individuals such as those with cirrhosis. Novel immunotherapy strategies may contribute in the future to prevention and treatment of HCC.

Alpha-fetoprotein (AFP)-derived peptides as epitopes for hepatoma immunotherapy: a commentary

The various immunological roles of human alpha-fetoprotein (HAFP), and its correlation with hepatomas, that is, hepatocellular carcinomas (HCCs), are not often addressed together in biomedical reports considering that HAFP is an established biomarker for hepatomas. Studies reporting measurement of HAFP serum levels in hepatoma patients in basic/clinical research settings has greatly increased over the years. Recent reports have now expanded our base knowledge in the mounting of an immune response against AFP, a self antigen, during hepatoma tumorigenesis. Advances in the detection and identification of AFP-derived peptide epitopes are opening new vistas of knowledge regarding the immunological role of AFP-peptides as T cell stimulating antigens in the course of hepatoma growth and progression. The present commentary addresses HAFP-derived peptides as immunologic responders in HCC and their use in the study and generation of AFP-peptide sensitized T cells directed against hepatoma cells. Attempts were further made to relate the AFP-derived peptide epitopes to T cell activities during the course of hepatoma immunotherapies and to profile the traits and properties of the peptides themselves. Hence, the present commentary was divided into two sections; (1) the characterization, properties, and traits of AFP peptide epitopes, and (2) the use of AFP-derived peptides in the therapeutic induction of T cells primed against hepatoma cells using both in vivo and in vitro models.

A phase II study of adoptive immunotherapy using dendritic cells pulsed with tumor lysate in patients with hepatocellular carcinoma

This is a phase II clinical trial investigating the safety and efficacy of intravenous vaccination with mature autologous dendritic cells (DCs) pulsed ex vivo with a liver tumor cell line lysate (HepG2) in patients with advanced hepatocellular carcinoma (HCC). HCC is an attractive target for immunotherapy as evidenced by an active recruitment of tumor-infiltrating lymphocytes that are capable of lysing autologous tumor cells in ex vivo studies. DCs are the most potent antigen-presenting cells, with the capacity to take up, process, and present tumor antigens to T cells and stimulate an immune response, thus providing a rational platform for vaccine development. Thirty-five patients with advanced HCC and not suitable for radical or loco-regional therapies received a maximum of six DC vaccinations each at 3-week intervals. In total, 134 DC infusions were administered with no significant toxicity and no evidence of autoimmunity. Twenty-five patients who received at least three vaccine infusions were assessed clinically for response. The radiologically determined disease control rate (combined partial response and stable disease >or=3 months) was 28%. In 17 patients the baseline serum alpha-fetoprotein (AFP) was >or= 1,000 ng/mL; in four of these patients, it fell to <30% of baseline following vaccination. In one patient there was a radiological partial response associated with a fall in AFP to <10% of baseline. Immune responses were assessed using an ELIspot assay of interferon-gamma (IFN-gamma) release. In several cases there was induction of T cell responses to the vaccine and/or AFP following vaccination.

CONCLUSION

Autologous DC vaccination in patients with HCC is safe and well tolerated with evidence of antitumor efficacy assessed radiologically and serologically, with generation of antigen-specific immune responses in some cases.

Comprehensive analysis of the alpha-fetoprotein-specific CD8+ T cell responses in patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide, with a poor prognosis and limited therapeutic options. Therefore, the development of novel therapeutic strategies is of high priority. alpha-Fetoprotein (AFP) is overexpressed in the majority of HCCs. Priming of immune responses against AFP results in significant protective antitumoral T cell responses in the mouse model. Little information is available about the hierarchy, breadth, frequency, and peripheral versus intrahepatic distribution of AFP-specific CD8(+) T cell responses in patients with HCC. To address these important issues we comprehensively analyzed CD8(+) T cell responses against full-length AFP in peripheral blood, tumor liver tissue, and nontumor liver tissue from patients with HCC using overlapping AFP peptides. The AFP-specific CD8(+) T cell response was also tested in peripheral blood and liver from patients chronically infected with hepatitis C virus (HCV) and compared to the HCV-specific CD8(+) T cell response. The majority of patients with HCC showed AFP-specific responses, with many responses directed against previously unreported epitopes. These responses were primarily detectable in the HCC tissue and mainly targeted the C-terminus of AFP. Interestingly, AFP-specific T cells were not only found in patients with HCC but also in patients with chronic HCV infection, other liver diseases, and less frequently in healthy subjects.

CONCLUSION

In patients with HCC, a high frequency of AFP-specific CD8(+) T cells directed against different epitopes suggest that AFP has a strong and broad immunogenicity. Further, CD8(+) T cells specific for the self-antigen AFP are present in the normal T cell repertoire and are not centrally or peripherally deleted. Our results provide support for strategies to boost AFP-specific CD8(+) T cell responses in patients with HCC but also demonstrate a diversity of immune responses that may be needed for protection.

Identification of new cytotoxic T-lymphocyte epitopes from cancer testis antigen HCA587

The cancer testis (CT) antigen HCA587 is highly expressed in human hepatocellular carcinoma (HCC) and induces specific T-cell responses in a significant proportion of HCC patients. To explore its potential in cancer immunotherapy, a reverse immunology approach was adopted to identify HCA587-derived HLA-A( *)0201-restricted epitopes. Multiple peptides with a top ranking in various prediction programs were thus synthesized and three of them-p248-256, p140-149 and p144-152-were found to bind to HLA-A(*)0201 molecules with a high affinity and effectively induced a recall response of CD8+ T cells, which were either primed in vitro with the HCA587 antigen or directly isolated from HCC patients bearing HCA587+ tumors. Notably, these peptide-specific CD8+ T cells exhibited potent cytotoxic activity over HCA587+ tumor cells. Taken together, the present study has identified three new HLA-A(*)0201-restricted cytotoxic T cell epitopes in the CT antigen HCA587, which may serve as targets for peptide-based immunotherapy for HCC patients.

Alpha-fetoprotein and other tumour-associated antigens for immunotherapy of hepatocellular cancer

BACKGROUND

Hepatocellular carcinoma (HCC) is a leading cause of cancer death, with few treatment options for advanced disease.

OBJECTIVES

Here, we review the aetiology of HCC and focus on recent data on tumour-associated antigens (TAA) for HCC, their functions and potential use as immunological targets for immune-based therapy for HCC. In addition, we examine some aspects of antigen presentation within the liver.

RESULTS/CONCLUSIONS

alpha-Fetoprotein (AFP) has been investigated for many years as a TAA, and has been tested in recent clinical trials. More recently, additional TAA have been identified and new therapeutic approaches have been investigated which may be testable clinically in this difficult disease setting.

Spontaneous and vaccine induced AFP-specific T cell phenotypes in subjects with AFP-positive hepatocellular cancer

We are investigating the use of Alpha Fetoprotein (AFP) as a tumor rejection antigen for hepatocellular carcinoma (HCC). We recently completed vaccination of 10 AFP+/HLA-A2.1+ HCC subjects with AFP peptide-pulsed autologous dendritic cells (DC). There were increased frequencies of circulating AFP-specific T cells and of IFNgamma-producing AFP-specific T cells after vaccination. In order to better understand the lack of association between immune response and clinical response, we have examined additional aspects of the AFP immune response in patients. Here, we have characterized the cell surface phenotype of circulating AFP tetramer-positive CD8 T cells and assessed AFP-specific CD4 function. Before vaccination, HCC subjects had increased frequencies of circulating AFP-specific CD8 T cells with a range of naïve, effector, central and effector memory phenotypes. Several patients had up-regulated activation markers. A subset of patients was assessed for phenotypic changes pre- and post-vaccination, and evidence for complete differentiation to effector or memory phenotype was lacking. CD8 phenotypic and cytokine responses did not correlate with level of patient serum AFP antigen (between 74 and 463,040 ng/ml). Assessment of CD4+ T cell responses by ELISPOT and multi-cytokine assay did not identify any spontaneous CD4 T cell responses to this secreted protein. These data indicate that there is an expanded pool of partially differentiated AFP-specific CD8 T cells in many of these HCC subjects, but that these cells are largely non-functional, and that a detectable CD4 T cell response to this secreted oncofetal antigen is lacking.

A transgenic mouse with beta-Galactosidase as a fetal liver self-antigen for immunotherapy studies

BACKGROUND/AIMS

To optimise vaccination strategies for immunotherapy in the liver, we have generated a line of transgenic mice expressing beta-Galactosidase downstream of the alpha-fetoprotein promoter (AFP/betaGal).

METHODS

betaGal expression was documented by qRT-PCR, enzyme activity and immunohistochemistry. betaGal-specific CD8+ T-cell activation in mice immunised with various vectors was measured by interferon-gamma ELISpot.

RESULTS

Like AFP, betaGal expression was detected in fetal hepatocytes and disappeared around birth. In adult mice, a CD8+ T-cell response to betaGal was observed after immunisation with betaGal adenovirus or plasmid DNA but not with betaGal protein or after retroviral infection. When betaGal was re-expressed in adult hepatocytes, immunisation with betaGal adenovirus triggered T-cell mediated elimination of betaGal-expressing hepatocytes. However, the response was weaker than in AFP/betaGal animals in which betaGal was only present around birth.

CONCLUSIONS

In AFP/betaGal mice, betaGal is a fetal liver self-antigen. Interestingly, the basal tolerance to betaGal displayed by these animals is increased during liver re-expression of the self-antigen in adulthood. Adenoviral immunisation allows complete elimination of betaGal-expressing hepatocytes in spite of this increased peripheral tolerance. These results highlight the importance of tolerance against self-antigens and validate the AFP/betaGal mice as a good background to test immunotherapy strategies in hepatocarcinogenesis models.

The alpha-fetoprotein-derived growth inhibitory peptide 8-mer fragment: review of a novel anticancer agent

This review describes the antigrowth and anticancer activities of the alpha-fetoprotein (AFP)-derived growth inhibitory peptide (GIP) 8-mer fragment. The 8-amino acid peptide (GIP-8) comprises the carboxy-terminal portion of a 34-amino acid peptide (GIP-34) previously identified as an occult epitopic segment of the full-length human AFP molecule. The GIP-8 segment has been chemically synthesized, purified, characterized, and bioassayed. The purified 8-mer segment was characterized as a random coil (disordered) structure extending from a C-terminal beta-hairpin that forms a horseshoe-shaped partially cyclic octapeptide; this structure can be formulated into a fully cyclic form by the addition of asparagine or glutamine residues. The pharmacophore of the octo- and nanopeptide forms is largely composed of a PXXP motif known to interact with Src-3 (SH3) domains of serine/theronine kinases. The GIP-8 has been shown to be growth-suppressive largely in estradiol (E2)-dependent neonatal and tumor-cell proliferation models and to inhibit tumor-cell adhesion to extracellular matrices. The 8-mer GIP displays antigrowth properties in immature mouse uterine cells and anticancer cell proliferation traits in estrogen receptor positive (ER(+)), but not (ER()) negative breast tumor cells. Even though its mechanism of action has not been fully elucidated, GIP-8 has been shown by computer modeling to dock with the extracellular loops of G-coupled seven transmembrane helical-like receptors, which could possibly interfere with signal transduction through MAP kinase pathways. It was apparent that the GIP-8 derived from the 34-mer GIP fragment of HAFP represented an E2-sensitive growth inhibitory motif, which allows the participation in cellular events, such as receptor binding, contact inhibition, extracellular matrix adhesion, angiogenesis, and T-cell activation. Thus, it was proposed that the 8-mer fragment derived from GIP could potentially serve as a lead compound for targeted cancer therapeutic agents of the biologic-response modifier type.

AFP-specific CD4+ helper T-cell responses in healthy donors and HCC patients

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and is often diagnosed at an advanced stage. We have investigated alpha-fetoprotein (AFP) as a tumor-associated antigen for HCC. We identified major histocompatibility complex class I-restricted peptide epitopes derived from AFP and studied CD8 T-cell responses in vivo and in vitro in ongoing immunotherapy studies. Helper T cells are of critical importance in shaping the immune response; therefore, we investigated the frequency and function of AFP-specific CD4 T cells in the general population and among HCC patients. CD4 T-cell responses were assessed by direct ex vivo multicytokine enzyme-linked immunospot assay and by measurement of cytokine levels using a multicytokine assay. Our analysis indicates that healthy donors have very low frequencies of AFP-specific CD4 T-cell responses, which are of TH1 type, detectable ex vivo. In contrast, these T cells were either reduced or eliminated in HCC patients at advanced stages of disease. To better activate these cells, we compared the stimulatory capacity of both AFP protein-fed and AdVhAFP-engineered dendritic cells (DC). Healthy donors have CD4 T-cell responses, which were activated in response to AFP protein-fed DC whereas HCC patients do not demonstrate significant responses to AFP protein. AdVhAFP-transduced DC were capable of activating higher frequency TH1 CD4 responses to AFP in both healthy donors and AFP-positive HCC patients. Importantly, CD4 T-cell cytokine expression profiles were skewed towards interleukin-2 and interferon-gamma production when activated by adenovirally engineered DC, which has therapeutic implications for vaccination efforts.

Unmasking of alpha-fetoprotein-specific CD4(+) T cell responses in hepatocellular carcinoma patients undergoing embolization

Necrosis of tumor cells can activate both innate and adaptive antitumor immunity. However, there is little information on the effects of necrosis-inducing cancer treatments on tumor-specific T cell immune responses in humans. We studied the effects of a necrosis-inducing treatment (embolization) on anti-alpha-fetoprotein (AFP)-specific CD4(+) T cell responses in hepatocellular carcinoma (HCC) patients and controls using an array of AFP-derived peptides. In this study, we show that AFP-specific CD4(+) T cell responses to three immunodominant epitopes in HCC patients were significantly expanded during (p < 0.0001) and after embolization (p < 0.002). The development of higher frequencies of AFP-specific CD4(+) T cells after treatment were significantly associated with the induction of >50% necrosis of tumor and an improved clinical outcome (p < 0.007). In addition, we identified two novel HLA-DR-restricted AFP-derived CD4(+) T cell epitopes (AFP(137-145) and AFP(249-258)) and showed that the CD4(+) T cells recognizing these epitopes produce Th1 (IFN-gamma and TNF-alpha) but not Th2 (IL-5)-type cytokines. AFP(137-145)-, AFP(249-258)-, and AFP(364-373)-specific CD4(+) T cells were detected in HCC patients but not in patients with chronic liver diseases or healthy donors. In conclusion; our study shows that induction of tumor necrosis by a conventional cancer treatment can unmask tumor rejection Ag cell-mediated immunity and provides a rationale for combining embolization with immunotherapy in HCC patients.

Aberrant composition of the dendritic cell population in hepatic lymph nodes of patients with hepatocellular carcinoma

Patients with hepatocellular carcinoma (HCC) are characterized by a weak T-cell response to their tumor, and chronic carriers of hepatitis B virus or hepatitis C virus have a poor T-cell response against the virus. These inadequate T-cell responses may be due to insufficient activation of the T cells by dendritic cells (DCs). Because lymph nodes (LNs) are the primary site of antigen-specific T-cell activation, we hypothesized that hepatic LNs of patients with HCC and/or chronic viral hepatitis might have aberrant compositions of their DC populations. To address this hypothesis, we enumerated mature myeloid DCs (MDCs) and plasmacytoid DCs (PDCs) in hepatic LNs by quantitative immunohistochemistry. Patients with HCC and chronic viral hepatitis and patients with chronic viral hepatitis without HCC were compared with patients with liver inflammation of nonviral etiology and with organ donors with healthy livers. The numbers of PDCs and mature MDCs in hepatic LNs of patients with chronic viral hepatitis did not differ from those of patients with liver inflammation of nonviral etiology nor from individuals with healthy livers. However, hepatic LNs of patients with HBV or HCV infection complicated by HCC showed a 1.5-fold reduction in numbers of mature MDCs and a 4-fold increase in numbers of PDCs in their T-cell areas compared with those of patients with viral hepatitis only (P <.01). In conclusion, patients with HCC have an aberrant composition of the DC population in their hepatic LNs. This may be one of the causes of the inadequate T-cell response against HCC in these patients.

Patient-derived dendritic cells transduced with an a-fetoprotein-encoding adenovirus and co-cultured with autologous cytokine-induced lymphocytes induce a specific and strong immune response against hepatocellular carcinoma cells

BACKGROUND/AIMS

Breaking immunologic tolerance towards the hepatocellular carcinoma (HCC)-associated alpha-fetoprotein (AFP) antigen is possible. The use of this potential for the treatment of immunocompromised HCC patients is limited. In this study, we analyzed whether dendritic cells (DCs) from HCC patients transduced with a human AFP (hAFP)-expressing adenovirus and co-cultured with cytokine-induced killer (CIK) cells can induce a strong specific immune response against HCC-cells.

METHODS

An hAFP-encoding adenovirus (Ad-hAFP) was generated. DCs from healthy donors or patients were transduced at a very high efficacy. Afterwards, DCs were co-cultured with autologous CIK-cells, and their ability to lyse HCC-cells was analyzed.

RESULTS

AFP-transduced DCs stimulated CIK cells strongly to lyse about 70% of AFP-expressing HCC cells. Cytotoxicity was significantly higher when lymphocytes were co-cultured with Ad-hAFP-transduced DCs than with Ad-mock-transduced DCs, indicating an AFP-specific immune response. More interestingly, CIK cells from patients with AFP-positive HCC could be stimulated to lyse AFP-expressing HCC cells as effectively as CIK cells from healthy individuals and stronger than CIK cells from patients without AFP-expressing HCC.

CONCLUSIONS

The data demonstrate that patient-derived DCs that were transduced with an AFP-expressing adenovirus and co-cultured with autologous CIK cells induce an AFP-specific, strong immune response against HCC cells. Therefore, this approach may have a potential for an adoptive and/or DC-based immunotherapy for HCC patients.

Analysis of CD4+ T-Cell responses to a novel alpha-fetoprotein-derived epitope in hepatocellular carcinoma patients

PURPOSE

Alpha-fetoprotein (AFP) is a tumor-associated antigen in hepatocellular carcinoma and is a target for the development of cancer vaccine. Four immunodominant AFP-derived HLA-A*0201-restricted peptides have been identified and the administration of these peptides with an adjuvant has stimulated AFP-specific CTL responses in hepatocellular carcinoma patients. However, no AFP-derived CD4 T-cell epitope has yet been reported and the status of AFP-specific CD4(+) T-cell responses in hepatocellular carcinoma patients is not fully understood. The aim of this study was to analyze naturally occurring CD4(+) T-cell responses to AFP.

EXPERIMENTAL DESIGN

We analyzed the ability of CD4(+) T cells to recognize an HLA-DR-restricted AFP-derived epitope in 41 hepatocellular carcinoma patients and 24 non-hepatocellular carcinoma control patients using intracellular cytokine assays for IFN-gamma.

RESULTS

Here, for the first time, we report the identification of an AFP-derived CD4(+) T-cell epitope that is recognized by circulating lymphocytes from hepatocellular carcinoma patients in association with HLA-DR. The absence of detectable responses in healthy donors and patients with chronic liver disease suggests that AFP-specific CD4(+) T cells in the responder patients had been previously expanded in vivo in response to the tumor. The anti-AFP CD4(+) T-cell response was only detected in hepatocellular carcinoma patients with normal or mildly elevated serum AFP levels who were in the early stage of disease.

CONCLUSION

Our data will be instrumental in the development of cancer vaccine using AFP-derived immunogens.

Activation of dendritic cells by local ablation of hepatocellular carcinoma

BACKGROUND/AIMS

Local ablation methods are an effective treatment for hepatocellular carcinoma (HCC). The rate of recurrence or development of intra-hepatic metastases may be lowered by antitumoral immune responses. Since HCCs are in general only weakly immunogenic, cell injury induced by local tumor ablation (PEI/RFTA) may increase HCC immunogenicity and may release endogenous adjuvants that activate dendritic cells (DC). The aim of the study, therefore, was the analysis whether PEI or RFTA induced injury results in an adjuvant effect for immune responses to HCCs.

METHODS

Eight HCC patients were treated with PEI or RFTA and serially analyzed for 4 weeks. Plasmocytoid (PDC) and myeloid dendritic cells (MDC) were analyzed directly ex vivo and in vitro using FACS and proliferation assays.

RESULTS

HCC ablation induced a functional transient activation of MDC but not of PDC associated with increased serum levels of TNF-alpha and IL-1beta.

CONCLUSIONS

These findings suggest that the combination of PEI or RFTA and active antigen specific immunotherapeutic approaches using DCs is a promising approach for the induction of sustained antitumoral immune responses aiming at the reduction of tumor recurrence and metastases in HCC patients.

Alpha-fetoprotein triggers hepatoma cells escaping from immune surveillance through altering the expression of Fas/FasL and tumor necrosis factor related apoptosis-inducing ligand and its receptor of lymphocytes and liver cancer cells

AIM: To investigate the mechanism of α-fetoprotein (AFP) in escaping from the host immune surveillance of hepatoc-ellular carcinoma.

METHODS: AFP purified from human umbilical blood was administrated into the cultured human lymphoma Jurkat T cell line or hepatoma cell line, Bel7402 in vitro. The expression of tumor necrosis factor related apoptosis-inducing ligand (TRAIL) and its receptor (TRAILR) mRNA were analyzed by Northern blot and Western blot was used to detect the expression of Fas and Fas ligand (FasL) protein.

RESULTS: AFP (20 mg/L) could promote the expression of FasL and TRAIL, and inhibit the expression of Fas and TRAILR of Bel7402 cells. For Jurkat cell line, AFP could suppress the expression of FasL and TRAIL, and stimulate the expression of Fas and TRAILR. AFP also could synergize with Bel7402 cells to inhibit the expression of FasL protein and TRAIL mRNA in Jurkat cells. The monoclonal antibody against AFP (anti-AFP) could abolish these functions of AFP.

CONCLUSION: AFP is able to promote the expression of FasL and TRAIL in hepatoma cells and enhance the expression of Fas and TRAILR in lymphocytes. These could elicit the escape of hepatocellular carcinoma cells from the host’s lymphocytes immune surveillance.

Spontaneous tumor-specific humoral and cellular immune responses to NY-ESO-1 in hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is the fifth most common cancer around the world. Although several therapeutic approaches for treatment of HCC are available, survival rates for HCC patients are still very poor because of inefficient treatment options. For HCC, as well as other tumors, antigen-specific immunotherapy remains a viable approach that is dependent on the definition of tumor-associated antigens. NY-ESO-1, a member of the cancer testis antigen family, is one possible candidate for a tumor-specific antigen in HCC. The aim of this study was to show the relevance of NY-ESO-1 in hepatocellular carcinoma.

EXPERIMENTAL DESIGN

Sera samples from 189 HCC patients were analyzed for NY-ESO-1-specific antibodies. Forty-nine HCC patients were screened for NY-ESO-1 mRNA expression in HCC tissue. Selected patients were followed for up to 3 years to correlate their immune response with their clinical course of events. NY-ESO-1-specific CD4+ and CD8+ T-cell responses from NY-ESO-1 seropositive patients were analyzed and a NY-ESO-1+ specific cytotoxic T-cell line was generated.

RESULTS

Twelve of 49 analyzed tumor samples expressed NY-ESO-1 mRNA and 23 of 189 patients showed NY-ESO-1-specific antibody responses. These humoral immune responses were accompanied by NY-ESO-1-specific functional CD4+ and CD8+ T-cell responses. Finally, NY-ESO-1 humoral responses were dependent on the presence of NY-ESO-1-expressing tumors.

CONCLUSIONS

This is the first report of a spontaneous immune response in HCC patients to a known tumor-specific antigen, NY-ESO-1 protein. Our data favor the possibility of immunotherapeutic strategies for the treatment of HCC.

Immunoregulation of dendritic and T cells by alpha-fetoprotein in patients with hepatocellular carcinoma

BACKGROUND/AIMS

Novel immunotherapeutic and other strategies are being explored for the treatment of hepatocellular carcinoma (HCC). Alpha-fetoprotein (AFP) may be a target antigen for immunotherapy. Little is known, however, about the immunobiology of AFP. Therefore, the impact of AFP on dendritic cells (DC), CD4+ and CD8+ T cells was studied in detail.

METHODS

Immune cells from peripheral blood of 27 HCC patients were studied using FACS, ELISPOT, and proliferation assays.

RESULTS

The in vitro generation, maturation, and T cell stimulatory capacity of DCs were not altered by AFP up to concentrations of 20 microg/ml. Higher AFP concentrations (> 20 microg/ml) resulted in phenotypic changes on DCs without impairing their capacity to stimulate CD4+ T cells. Frequencies and function of DCs and AFP specific T cells were not reduced in HCC patients independent on serum AFP levels. Finally, T lymphocytic infiltrations in the liver were not dependent on AFP serum levels.

CONCLUSIONS

These studies clearly demonstrate that (i) DC-based immunotherapeutic approaches are a promising approach for HCC treatment and (ii) AFP-reactive T cell clones have not been deleted from the human T cell repertoire establishing AFP as a potential target for T cell based immunotherapy of HCC.

Antitumor immunity induced by DNA vaccine encoding alpha-fetoprotein/heat shock protein 70

AIM: To construct a DNA vaccine encoding human alpha-fetoprotein (hAFP)/heat shock protein 70 (HSP70), and to study its ability to induce specific CTL response and its protective effect against AFP-expressing tumor.

METHODS: A DNA vaccine was constructed by combining hAFP gene with HSP70 gene. SP2/0 cells were stably transfected with pBBS212-hAFP and pBBS212-hAFP/HSP70 eukaryotic expression vectors. Mice were primed and boosted with DNA vaccine hAFP/HSP70 by intramuscular injection, whereas plasmid with hAFP or HSP70 was used as controls. ELISPOT and ELISA were used to detect IFN-γ - producing splenocytes and the level of serum anti-AFP antibody from immunized mice respectively. In vivo tumor challenge was measured to assess the immune effect of the DNA vaccine.

RESULTS: By DNA vaccine immunization, the results of ELISPOT and ELISA showed that the number of IFN-γ - producing splenocytes and the level of serum anti-AFP antibody were significantly higher in rhAFP/HSP70 group than in hAFP and empty plasmid groups (95.50 ± 10.90 IFN-γ spots/10⁶ cells vs 23.60 ± 11.80 IFN-γ spots/10⁶ cells, 7.17 ± 4.24 IFN-γ spots/10⁶ cells, P < 0.01; 126.50 ± 8.22 μg/mL vs 51.72 ± 3.40 μg/mL, 5.83 ± 3.79 μg/mL, P < 0.01). The tumor volume in rhAFP/HSP70 group was significantly smaller than that in pBBS212-hAFP and empty plasmid groups (37.41 ± 7.34 mm³vs 381.13 ± 15.48 mm³, 817.51 ± 16.25 mm³, P < 0.01).

CONCLUSION: Sequential immunization with a recombinant DNA vaccine encoding AFP and heat shock protein70 could generate effective AFP-specific T cell responses and induce definite antitumor effects on AFP-producing tumors, which may be suitable for some clinical testing as a vaccine for HCC.

Immunotherapeutic strategies for hepatocellular carcinoma

There is a continuing need for innovative, alternative therapies for hepatocellular carcinoma (HCC). Immunotherapy for cancer is attractive because of the exquisite specificity of the immune response. Activation of an HCC-specific response can be accomplished by strategies targeting tumor-associated self-antigens (for example, alpha-fetoprotein [AFP]). Gene array studies have added to the list of HCC-specific gene products that can be targeted. Alternatively, the immune response can be targeted against viral antigens in those patients infected with hepatitis B or C virus. Uncharacterized and mutated antigens can also be targeted with whole tumor cell or tumor lysate-based immunization strategies or with vectors coding for genes that make the tumor immunogenic, allowing the immune system to naturally evolve specificity against immunogenic target antigens. Strategies being investigated in animal models include increasing tumor immunogenicity by targeting cytokines or costimulatory molecules to tumor; immunization with tumor cells fused with antigen-presenting cells; adoptive transfer of viral antigen-specific T cells; and targeting AFP-expressing HCC cells by DNA, adenovirus, peptide, and dendritic cell (DC) strategies. Strategies that have been tested in human clinical trials include adoptive transfer of lymphocytes and autologous tumor-pulsed DC as well as 2 AFP-based strategies: AFP-derived peptides in Montanide and AFP peptides pulsed onto autologous DC. These trials, testing novel immune-based interventions in HCC subjects, have resulted in immunologic responses and have impacted recurrence and survival in HCC subjects.

Requirements for adeno-associated virus-derived non-viral vectors to achieve stable and site-specific integration of plasmid DNA in liver carcinoma cells

BACKGROUND AND AIMS

Adeno-associated virus (AAV) is the only known virus capable of site-specific genomic integration in human cells. Thus, AAV-based vectors may be an attractive option to achieve prolonged transgene expression in human cells. We therefore studied the minimal elements of gene therapy vectors necessary for stable integration and tested the effectiveness of this approach in hepatoma cells.

METHODS

Plasmids were constructed that contained a GFPneo fusion transgene with or without the AAV-inverted terminal repeats (ITRs). In addition, Rep protein was either encoded in CIS or supplied in TRANS by co-transfections. Stable clones were analyzed by Southern blotting for site-specific integration.

RESULTS

The ITRs alone conferred neither stable nor site-specific transgene integration. Expression of Rep protein in CIS or TRANS resulted in an increased frequency of integration regardless of the presence of ITRs. It was shown that in the absence of the ITRs, other Rep-binding site (RBS) like sequences such as the ColE1 sequence present in plasmid backbones can function as RBS. Site-specific integration was achieved in up to 26% of clones derived from hepatoma cells.

CONCLUSION

Both expression of Rep proteins and inclusion of a RBS are necessary for enhanced and stable integration of AAV-based non-viral vectors. A novel two-plasmid system capable of achieving stable and site-specific gene transfer in hepatoma cells is introduced.

HCA587 antigen expression in normal tissues and cancers: correlation with tumor differentiation in hepatocellular carcinoma

The HCA587 gene, identified by serological analysis of recombinant cDNA expression library (SEREX) from a hepatocellular carcinoma (HCC) patient, encodes a new member of cancer-testis antigens. HCA587 mRNA expression in normal tissues and cancers has been previously reported. To estimate its immunogenicity to induce immune response, it is essential to analyze HCA587 expression at the protein level. In this study anti-HCA587 polyclonal antibody, termed "TC-1," was generated, and the expression of HCA587 protein was assessed by immunohistochemical staining in a panel of normal and tumor tissue sections. No HCA587 protein was shown in normal tissues except germ cells in testis and Purkinji cells in cerebellum. In HCC specimens the HCA587 protein was expressed in 37.1% (26 of 70) samples. The expressed protein was either located in the cytoplasm or nucleus depending on the individual samples. More importantly, there appears to be correlation between the tumor differentiation of HCC and HCA587 protein expression, ie, the lower differentiation, the higher percentage of protein expression. Coincidentally, seroreactivity showed that the Ab specific to recombinant HCA587 protein was detected only in the sera of three patients with poorly differentiated HCCs. HCA587 antigen was also expressed in different proportions in melanoma, lymphoma, pancreatic cancer, and lung cancer.