Expression of cancer-testis antigen (CTA) in tumor tissues and peripheral blood of Chinese patients with hepatocellular carcinoma

Application of cancer-testis antigens in immunotherapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a worldwide common malignancy with poor prognosis. Several studies have aimed at identification of appropriate biomarkers for early detection of this cancer. Cancer-testis antigens (CTAs) as a novel group of tumor-associated antigens have been demonstrated to be expressed in HCC samples as well as peripheral blood samples from these patients but not in the corresponding adjacent noncancerous samples. Such pattern of expression has provided them an opportunity to be used as immunotherapeutic targets. The detection of spontaneous immune responses against CTAs in HCC patients has prompted design of CTA-based immunotherapeutic protocols in these patients. The results of some clinical trials have been promising in a subset of patients.

Tumour antigen expression in hepatocellular carcinoma in a low-endemic western area

Background:

Identification of tumour antigens is crucial for the development of vaccination strategies against hepatocellular carcinoma (HCC). Most studies come from eastern-Asia, where hepatitis-B is the main cause of HCC. However, tumour antigen expression is poorly studied in low-endemic, western areas where the aetiology of HCC differs.

Methods:

We constructed tissue microarrays from resected HCC tissue of 133 patients. Expression of a comprehensive panel of cancer-testis (MAGE-A1, MAGE-A3/4, MAGE-A10, MAGE-C1, MAGE-C2, NY-ESO-1, SSX-2, sperm protein 17), onco-fetal (AFP, Glypican-3) and overexpressed tumour antigens (Annexin-A2, Wilms tumor-1, Survivin, Midkine, MUC-1) was determined by immunohistochemistry.

Results:

A higher prevalence of MAGE antigens was observed in patients with hepatitis-B. Patients with expression of more tumour antigens in general had better HCC-specific survival (P=0.022). The four tumour antigens with high expression in HCC and no, or weak, expression in surrounding tumour-free-liver tissue, were Annexin-A2, GPC-3, MAGE-C1 and MAGE-C2, expressed in 90, 39, 17 and 20% of HCCs, respectively. Ninety-five percent of HCCs expressed at least one of these four tumour antigens. Interestingly, GPC-3 was associated with SALL-4 expression (P=0.001), an oncofetal transcription factor highly expressed in embryonal stem cells. SALL-4 and GPC-3 expression levels were correlated with vascular invasion, poor differentiation and higher AFP levels before surgery. Moreover, patients who co-expressed higher levels of both GPC-3 and SALL-4 had worse HCC-specific survival (P=0.018).

Conclusions:

We describe a panel of four tumour antigens with excellent coverage and good tumour specificity in a western area, low-endemic for hepatitis-B. The association between GPC-3 and SALL-4 is a novel finding and suggests that GPC-3 targeting may specifically attack the tumour stem-cell compartment.

XAGE-1b expression is associated with the diagnosis and early recurrence of hepatocellular carcinoma

XAGE-1b is a 470 bp transcript of the XAGE-1 gene, which belongs to the cancer-testis antigens that exhibit a restricted pattern of expression in normal tissues. Recently, the expression of XAGE-1b has been shown to be frequent in patients with hepatocellular carcinoma (HCC). However, the underlying mechanism is not fully understood. To investigate the role of XAGE-1b in HCC diagnosis and postoperative evaluation, the expression level of XAGE-1b was first examined in the tissue and peripheral blood of HCC patients and controls by using quantitative polymerase chain reaction. Subsequently, the associations between XAGE-1b and the clinical variables were assessed using χ² or Kaplan-Meier tests. The data showed that HCC tissues had increased XAGE-1b expression when compared to paired non-tumorous tissues. The blood samples from the HCC patients showed upregulated XAGE-1b mRNA, as compared to non-HCC patients. The patients with portal vein tumor thrombus or higher tumor-node metastasis stages (II~IV) were more likely to have increased levels of XAGE-1b mRNA. Furthermore, the 1-year recurrence rate of the patients with a high level of XAGE-1b mRNA was significantly greater compared to the patients with a low level. All these findings indicate that XAGE-1b is associated with the aggressive biological behavior of HCC cells and it may be a potential biomarker for HCC diagnosis and prognosis.

RNA interference against cancer/testis genes identifies dual specificity phosphatase 21 as a potential therapeutic target in human hepatocellular carcinoma

Cancer/testis (CT) antigens have been considered therapeutic targets for treating cancers. However, a central question is whether their expression contributes to tumorigenesis or if they are functionally irrelevant by-products derived from the process of cellular transformation. In any case, these CT antigens are essential for cancer cell survival and may serve as potential therapeutic targets. Recently, the cell-based RNA interference (RNAi) screen has proven to be a powerful approach for identifying potential therapeutic targets. In this study we sought to identify new CT antigens as potential therapeutic targets for human hepatocellular carcinoma (HCC), and 179 potential CT genes on the X chromosome were screened through a bioinformatics analysis of gene expression profiles. Then an RNAi screen against these potential CT genes identified nine that were required for sustaining the survival of Focus and PLC/PRF/5 cells. Among the nine genes, the physiologically testis-restricted dual specificity phosphatase 21 (DUSP21) encoding a dual specificity phosphatase was up-regulated in 39 (33%) of 118 human HCC specimens. Ectopic DUSP21 had no obvious impact on proliferation and colony formation in HCC cells. However, DUSP21 silencing significantly suppressed cell proliferation, colony formation, and in vivo tumorigenicity in HCC cells. The administration of adenovirus-mediated RNAi and an atelocollagen/siRNA mixture against endogenous DUSP21 significantly suppressed xenograft HCC tumors in mice. Further investigations showed that DUSP21 knockdown led to arrest of the cell cycle in G1 phase, cell senescence, and expression changes of some factors with functions in the cell cycle and/or senescence. Furthermore, the antiproliferative role of DUSP21 knockdown is through activation of p38 mitogen-activated protein kinase in HCC.

CONCLUSION

DUSP21 plays an important role in sustaining HCC cell proliferation and may thus act as a potential therapeutic target in HCC treatment.

Downstream and intermediate interactions of synovial sarcoma-associated fusion oncoproteins and their implication for targeted therapy

Synovial sarcoma (SS), an aggressive type of soft tissue tumor, occurs mostly in adolescents and young adults. The origin and molecular mechanism of the development of SS remain only partially known. Over 90% of SS cases are characterized by the t(X;18)(p11.2;q11.2) translocation, which results mainly in the formation of SS18-SSX1 or SS18-SSX2 fusion genes. In recent years, several reports describing direct and indirect interactions of SS18-SSX1/SSX2 oncoproteins have been published. These reports suggest that the fusion proteins particularly affect the cell growth, cell proliferation, TP53 pathway, and chromatin remodeling mechanisms, contributing to SS oncogenesis. Additional research efforts are required to fully explore the protein-protein interactions of SS18-SSX oncoproteins and the pathways that are regulated by these partnerships for the development of effective targeted therapy.

Progress in research of tumor markers for diagnosis of hepatocellular carcinoma in AFP-negative patients

Alpha-fetoprotein (AFP) is an important marker for hepatocellular carcinoma (HCC), and the detection of serum AFP is currently the principal method for the diagnosis of HCC. About on-e-third of HCC patients have normal serum AFP concentration, and the diagnosis of HCC in these patients is challenging. In recent years, many studies have been done to seek other tumor markers for HCC. In this paper, we review the recent progress in research of tumor markers for the diagnosis of HCC in AFP-negative patients.

Recovering circulating extracellular or cell-free RNA from bodily fluids

The presence of extracellular circulating or cell-free RNA in biological fluids is becoming a promising diagnostic tool for non invasive and cost effective cancer detection. Extracellular RNA or miRNA as biological marker could be used either for the early detection and diagnosis of the disease or as a marker of recurrence patterns and surveillance. In this review article, we refer to the origin of the circulating extracellular RNA, we summarise the data on the biological fluids (serum/plasma, saliva, urine, cerebrospinal fluid and bronchial lavage fluid) of patients suffering from various types of malignancies reported to contain a substantial amount of circulating extracellular (or cell-free) RNAs and we discuss the appropriate reagents and methodologies needed to be employed in order to obtain RNA material of high quality and integrity for the majority of the experimental methods used in RNA expression analysis. Furthermore, we discuss the advantages and disadvantages of the RT-PCR or microarray methodology which are the methods more often employed in procedures of extracellular RNA analysis.

Biological treatment for liver tumor and new potential biomarkers

The search for effective and efficacious therapy for liver tumor was started many years ago and is still ongoing. Despite all of the surgical advances, much work needs to be done to improve understanding of the biology of the tumor and its treatment. The rules of hepatic surgery are changing because of two recent major trends: (1) technical simplification, and (2) the endeavor to treat an increasing number of patients. T lymphocytes are potent cellular effectors of the immune system and possess a memory that responds to rechallenge by the same antigen. Being more specific and less toxic than chemotherapy, tumor infusion could be an ideal adjuvant therapy for patients with primary and secondary liver malignancies. Moreover, tumor cell vaccines have demonstrated efficacy in terms of minimal residual disease and are being investigated, but the requirement for an adequate supple of autologos tumor may limit the general applicability of these approaches. Various studies have demonstrated the aberrant expression of germ-cell proteins called cancer-testis (CT) antigens in liver neoplastic cells. Their selective normal-tissue expression makes them ideal antigens for immune targeting of malignant disease. Specific expression of CT antigens also suggests their application as tumor markers to detect circulating hepatocellular carcinoma (HCC) cells, as an adjuvant diagnostic tool, and as indicators for recurrence and prognosis. Biological therapy is now generating more clinical trials. More studies need to be performed and further experiments need to be done, although currently this seems a valid pathway for the treatment of liver cancer. Cytoreduction treatment of liver tumor and the vaccine might be the future of the treatment of primary and secondary liver tumor.

Proteomic characterization of Sophoraflavone J-induced apoptosis in HepG2 cells

Chinese herb Radix sophorae is widely applied as an anticarcinogenic/antimetastatic agent against liver cancers. In the current study, Sophoraflavone J, a flavonoid constituent enriched in the root of Radix sophorae, induced apoptosis in human hepatoma HepG2 cells via the intrinsic mitochondrial death pathway. The molecular mechanism of the cytotoxic effect was further investigated by a comparative proteomic approach. Differentially expressed proteins identified included membrane proteins/antigens, structural proteins, transcriptional factors, glycolytic enzymes, heat-shock chaperon proteins, ROS-related proteins and proteosomes, etc. These findings were further validated by Western blot analysis and real-time PCR. Preliminary experiments to characterize the roles of these proteins were conducted. Our data suggested that Sophoraflavone J treatment triggered nutrient depletion and generation of ROS in cells, which subsequently led to mitochondrial dysfunction and apoptosis.

Usefulness of cancer-testis antigens as biomarkers for the diagnosis and treatment of hepatocellular carcinoma

Despite advances in our cellular and molecular knowledge, hepatocellular carcinoma (HCC) remains one of the major public health problems throughout the world. It is now known to be highly heterogeneous: it encompasses various pathological entities and a wide range of clinical behaviors, and is underpinned by a complex array of gene alterations that affect supra-molecular processes.

Four families of HCC tumour markers have been recently proposed: a) onco-fetal and glycoprotein antigens; b) enzymes and iso-enzymes; c) cytokines and d) genes. A category of tumour-associated antigens called cancer-testis (CT) antigens has been identified and their encoding genes have been extensively investigated. CT antigens are expressed in a limited number of normal tissues as well as in malignant tumors of unrelated histological origin, including the liver. Given that cancers are being recognized as increasingly complex, we here review the role of CT antigens as liver tumour biomarkers and their validation process, and discuss why they may improve the effectiveness of screening HCC patients and help in determining the risk of developing HCC.