Multiple antigenic peptides of human heparanase elicit a much more potent immune response against tumors

The influence of component structural arrangement on peptide vaccine immunogenicity

Peptide-based subunit vaccines utilise minimal immunogenic components (i.e. peptides) to generate highly specific immune responses, without triggering adverse reactions. However, strong adjuvants and/or effective delivery systems must be incorporated into such vaccines, as peptide antigens cannot induce substantial immune responses on their own. Unfortunately, many adjuvants are too weak or too toxic to be used in combination with peptide antigens. These shortcomings have been addressed by the conjugation of peptide antigens with lipidic/ hydrophobic adjuvanting moieties. The conjugates have shown promising safety profiles and improved immunogenicity without the help of traditional adjuvants and have been efficient in inducing desired immune responses following various routes of administration, including subcutaneous, oral and intranasal. However, not only conjugation per se, but also component arrangement influences vaccine efficacy. This review highlights the importance of influence of the vaccine chemical structure modification on the immune responses generated. It discusses a variety of factors that affect the immunogenicity of peptide conjugates, including: i) self-adjuvanting moiety length and number; ii) the orientation of epitopes and self-adjuvanting moieties in the conjugate; iii) the presence of spacers between conjugated components; iv) multiepitopic arrangement; and v) the effect of chirality on vaccine efficacy.

Peptide Multimerization as Leads for Therapeutic Development

Multimerization of peptide structures has been a logical evolution in their development as potential therapeutic molecules. The multivalent properties of these assemblies have attracted much attention from researchers in the past and the development of more complex branching dendrimeric structures, with a wide array of biocompatible building blocks is revealing previously unseen properties and activities. These branching multimer and dendrimer structures can induce greater effect on cellular targets than monomeric forms and act as potent antimicrobials, potential vaccine alternatives and promising candidates in biomedical imaging and drug delivery applications. This review aims to outline the chemical synthetic innovations for the development of these highly complex structures and highlight the extensive capabilities of these molecules to rival those of natural biomolecules.

Heparanase in Acute Pancreatitis

Acute pancreatitis (AP) is one of the most common diseases in gastroenterology, affecting 2% of all hospitalized patients. Nevertheless, neither the etiology nor the pathophysiology of the disease is fully characterized, and no specific or effective treatment has been developed. Heparanase (Hpa) is an endoglycosidase that cleaves heparan sulfate (HS) side chains of heparan sulfate proteoglycans (HSPGs) into shorter oligosaccharides, activity that is highly implicated in cell invasion associated with cancer metastasis and inflammation. Given that AP is a typical inflammatory disease, we investigated whether Hpa plays a role in AP. Our results provide keen evidence that Hpa expression and activity are significantly increased following cerulein-induced AP in wild type mice. In parallel to the classic manifestations of AP, namely elevation of amylase and lipase levels, pancreas edema and inflammation as well as induction of cytokines and signaling molecules, have been detected in this experimental model of the disease. Noteworthy, these features were far more profound in transgenic mice overexpressing heparanase (Hpa-Tg), suggesting that these mice can be utilized as a model system to reveal the molecular mechanism by which Hpa functions in AP. Further support for the involvement of Hpa in the pathogenesis of AP emerged from our observation that treatment of experimental AP with PG545 or SST0001(= Ronepastat), two potent Hpa inhibitors, markedly attenuated the biochemical, histological and immunological manifestations of the disease. Hpa, therefore, emerges as a potential new target in AP, and Hpa inhibitors are hoped to prove beneficial in AP along with their promising efficacy as anti-cancer compounds.

Involvement of Heparanase in Gastric Cancer Progression and Immunotherapy

Heparanase is upregulated in various tumors, and its expression is closely associated with tumor growth, angiogenesis and metastasis, which accomplishes this mainly through degrading heparan sulfate and releasing heparin-binding growth factors thereby influencing multiple signaling pathways. In addition to its enzymatic degrading activity, heparanase can act via its non-enzymatic mechanisms that directly regulate various signaling. This review mainly focuses on the expression levels and role of heparanase in gastric cancer, and multiple genes and mechanisms regulating heparanase expression in gastric cancer. Furthermore, the development of heparanase-targeted immunotherapy and its potential application for treating gastric cancer are discussed.

Enhanced antitumor effect of cytotoxic T lymphocytes induced by dendritic cells pulsed with colorectal cancer cell lysate expressing α-Gal epitopes

Colorectal cancer (CRC) is one of the most common types of gastrointestinal malignancy. Traditional therapeutic options for CRC exhibit a limited effect. Adoptive cellular therapy has emerged as a new treatment strategy for CRC. Dendritic cells (DCs) are potent antigen-presenting cells. Specific cytotoxic T lymphocytes (CTLs) activated by DCs pulsed with tumor lysate have been reported to be a safe and promising treatment approach for CRC. However, the antitumor effect of specific CTLs remains limited. The low immunogenicity of tumor-associated antigens (TAAs) is the main reason for this limited therapeutic effect. In the present study, α-gal epitopes were synthesized on the CRC cell line SW620 to increase the immunogenicity of TAAs. DCs were pulsed with α-gal-expressing tumor lysate and CTLs were activated by these DCs. The cytotoxicity of CTLs was measured in vitro. The results demonstrated that DCs pulsed with α-gal-expressing tumor lysate can increase the frequency of CD3⁺CD8⁺ CTLs and natural killer T cells, increase the level of tumor necrosis factor-α produced by CTLs and enhance the cytotoxicity of CTLs against tumor cells. Therefore, this novel approach may be an effective treatment strategy for patients with CRC.

Leukocyte Heparanase: A Double-Edged Sword in Tumor Progression

Heparanase is a β-D-endoglucuronidase that cleaves heparan sulfate, a complex glycosaminoglycan found ubiquitously throughout mammalian cells and tissues. Heparanase has been strongly associated with important pathological processes including inflammatory disease and tumor metastasis, through its ability to promote various cellular functions such as cell migration, invasion, adhesion, and cytokine release. A number of cell types express heparanase including leukocytes, cells of the vasculature as well as tumor cells. However, the relative contribution of heparanase from these different cell sources to these processes is poorly defined. It is now well-established that the immune system plays a critical role in shaping tumor progression. Intriguingly, leukocyte-derived heparanase has been shown to either assist or impede tumor progression, depending on the setting. This review covers our current knowledge of heparanase in immune regulation of tumor progression, as well as the potential applications and implications of exploiting or inhibiting heparanase in cancer therapy.

Geometry of a TLR2-Agonist-Based Adjuvant Can Affect the Resulting Antigen-Specific Immune Response

Targeted delivery of otherwise nonimmunogenic antigens to Toll-like receptors (TLRs) expressed on dendritic cells (DCs) has proven to be an effective means of improving immunogenicity. For this purpose, we have used a branched cationic lipopeptide, R₄Pam₂Cys, which is an agonist for TLR2 and enables electrostatic association with antigen for this purpose. Here, we compare the immunological properties of ovalbumin formulated with different geometrical configurations of R₄Pam₂Cys. Our results demonstrate that notwithstanding the presence of the same adjuvant, branched forms of R₄Pam₂Cys are more effective at inducing immune responses than are linear geometries. CD8⁺ T-cell-mediated responses are particularly improved, resulting in significantly higher levels of antigen-specific cytokine secretion and cytolysis of antigen-bearing target cells in vivo. The results correlate with the ability of branched R₄Pam₂Cys conformations to encourage higher levels of DC maturation and facilitate superior antigen uptake, leading to increased production of proinflammatory cytokines. These differences are not attributable to particle size because both branched and linear lipopeptides associate with antigen-forming complexes of similar size, but rather the ability of branched lipopeptides to induce more efficient TLR2-mediated cell signaling. Branched lipopeptides are also more resistant to trypsin-mediated proteolysis, suggesting greater stability than their linear counterparts. The branched lipopeptide facilitates presentation of antigen more efficiently to CD8⁺ T cells, resulting in rapid cell division and upregulation of early cell surface activation markers. These results as well as cognate recognition of Pam₂Cys by TLR2 indicate that the adjuvant's efficiency is also dependent on its geometry.

Branched multipeptide immunotherapy for glioblastoma using human leukocyte antigen-A*0201-restricted cytotoxic T-lymphocyte epitopes from ERBB2, BIRC5 and CD99

We investigated the use of cytotoxic T-lymphocyte (CTL) epitopes in peptide immunotherapy for glioblastoma. Three peptides (ERBB2, BIRC5 and CD99) were selected based on their peptide-T2 cell binding affinities and combined in a multipeptide cocktail or a branched multipeptide synthesized with mini-polyethylene glycol spacers. Dendritic cells (DCs) pulsed with the multipeptide cocktail or branched multipeptide were compared based on their immunophenotype and cytokine secretion. FACS analysis of alpha-type 1 polarized dendritic cells (αDC1s) revealed that both groups highly expressed CD80, CD83 and CD86, indicating that both treatments efficiently generated mature αDC1s with the expected phenotype. Production of IL-12p70, IL-12p40 and IL-10 also increased upon αDC1 maturation in both groups. CTLs stimulated by either αDC1 group (“DC-CTLs”) included numerous IFN-γ-secreting cells against T2 cells loaded with the corresponding multipeptides. Large numbers of IFN-γ-secreting cells were observed when human glioblastoma cell lines and primary cells were treated with multipeptide-pulsed DC-CTLs. Both multipeptide-pulsed DC-CTL groups exhibited cytotoxic activity of 40-60% against the U251 cell line and 60-80% against primary cells. Branched multipeptide from ERBB2, BIRC5 and CD99 stably bound with T2 cells, and its cytotoxicity toward target cells was similar to that of the multipeptide cocktail. Thus, branched multipeptides could be promising candidates for immunotherapeutic glioblastoma treatment.

The Role of Heparanase in the Pathogenesis of Acute Pancreatitis: A Potential Therapeutic Target

Acute pancreatitis (AP) is one of the most common diseases in gastroenterology. However, neither the etiology nor the pathophysiology of the disease is fully understood and no specific or effective treatment has been developed. Heparanase is an endoglycosidase that cleaves heparan sulfate (HS) side chains of HS sulfate proteoglycans into shorter oligosaccharides, activity that is highly implicated in cellular invasion associated with cancer metastasis and inflammation. Given that AP involves a strong inflammatory aspect, we examined whether heparanase plays a role in AP. Here, we provide evidence that pancreatic heparanase expression and activity are significantly increased following cerulein treatment. Moreover, pancreas edema and inflammation, as well as the induction of cytokines and signaling molecules following cerulein treatment were attenuated markedly by heparanase inhibitors, implying that heparanase plays a significant role in AP. Notably, all the above features appear even more pronounced in transgenic mice over expressing heparanase, suggesting that these mice can be utilized as a sensitive model system to reveal the molecular mechanism by which heparanase functions in AP. Heparanase, therefore, emerges as a potential new target in AP, and heparanase inhibitors, now in phase I/II clinical trials in cancer patients, are hoped to prove beneficial also in AP.

Inhibition of tumor growth and metastasis by EMMPRIN multiple antigenic peptide (MAP) vaccination is mediated by immune modulation

Previously, we have identified a new epitope in EMMPRIN, a multifunctional protein that mediates tumor cell-macrophage interactions and induces both MMP-9 and VEGF. Here, we synthesized this epitope as an octa-branched multiple antigenic peptide (MAP) to vaccinate mice implanted with subcutaneous syngeneic colon (CT26), prostate (TRAMP-C2) or renal (RENCA) cell line carcinomas. Vaccination inhibited, and sometimes regressed, tumor growth in a dose-dependent manner, reaching 94%, 71% and 72% inhibition, respectively, at a 50 μg dose (p < 0.01). Mice with regressed tumors demonstrated immune memory, preventing tumor recurrence upon re-implantation (p < 0.001). When tumor cells were administered through the tail vein to generate lung metastases, vaccination reduced the number of metastatic foci (by 15- and 23-folds, p < 0.001), and increased the median survival time by 25% and 53% in RENCA and CT26 metastases, respectively (p < 0.01) relative to scrambled-MAP controls. No significant adverse responses were observed in all experiments. We show that the tumor microenvironment was immune modulated, as vaccination induced production of EMMPRIN-specific antibodies, increased CD8⁺ T cells infiltration and cytotoxicity, alleviated immune suppression by decreasing TGFβ concentrations, reduced angiogenesis and cell proliferation, and enhanced apoptosis. Thus, our successful active peptide vaccination strategy differs from previous, unsuccessful attempts, both in the selected target (the EMMPRIN epitope) and in the use of a modified, MAP configuration, and demonstrates that this may be an efficient approach for the treatment and prevention of some types of cancer.

Heparanase: From basic research to therapeutic applications in cancer and inflammation

Heparanase, the sole heparan sulfate degrading endoglycosidase, regulates multiple biological activities that enhance tumor growth, angiogenesis and metastasis. Heparanase expression is enhanced in almost all cancers examined including various carcinomas, sarcomas and hematological malignancies. Numerous clinical association studies have consistently demonstrated that upregulation of heparanase expression correlates with increased tumor size, tumor angiogenesis, enhanced metastasis and poor prognosis. In contrast, knockdown of heparanase or treatments of tumor-bearing mice with heparanase-inhibiting compounds, markedly attenuate tumor progression further underscoring the potential of anti-heparanase therapy for multiple types of cancer. Heparanase neutralizing monoclonal antibodies block myeloma and lymphoma tumor growth and dissemination; this is attributable to a combined effect on the tumor cells and/or cells of the tumor microenvironment. In fact, much of the impact of heparanase on tumor progression is related to its function in mediating tumor-host crosstalk, priming the tumor microenvironment to better support tumor growth, metastasis and chemoresistance. The repertoire of the physio-pathological activities of heparanase is expanding. Specifically, heparanase regulates gene expression, activates cells of the innate immune system, promotes the formation of exosomes and autophagosomes, and stimulates signal transduction pathways via enzymatic and non-enzymatic activities. These effects dynamically impact multiple regulatory pathways that together drive inflammatory responses, tumor survival, growth, dissemination and drug resistance; but in the same time, may fulfill some normal functions associated, for example, with vesicular traffic, lysosomal-based secretion, stress response, and heparan sulfate turnover. Heparanase is upregulated in response to chemotherapy in cancer patients and the surviving cells acquire chemoresistance, attributed, at least in part, to autophagy. Consequently, heparanase inhibitors used in tandem with chemotherapeutic drugs overcome initial chemoresistance, providing a strong rationale for applying anti-heparanase therapy in combination with conventional anti-cancer drugs. Heparin-like compounds that inhibit heparanase activity are being evaluated in clinical trials for various types of cancer. Heparanase neutralizing monoclonal antibodies are being evaluated in pre-clinical studies, and heparanase-inhibiting small molecules are being developed based on the recently resolved crystal structure of the heparanase protein. Collectively, the emerging premise is that heparanase expressed by tumor cells, innate immune cells, activated endothelial cells as well as other cells of the tumor microenvironment is a master regulator of the aggressive phenotype of cancer, an important contributor to the poor outcome of cancer patients and a prime target for therapy.

Heparanase: a rainbow pharmacological target associated to multiple pathologies including rare diseases

In recent years, heparanase has attracted considerable attention as a promising target for innovative pharmacological applications. Heparanase is a multifaceted protein endowed with enzymatic activity, as an endo-β-D-glucuronidase, and nonenzymatic functions. It is responsible for the cleavage of heparan sulfate side chains of proteoglycans, resulting in structural alterations of the extracellular matrix. Heparanase appears to be involved in major human diseases, from the most studied tumors to chronic inflammation, diabetic nephropathy, bone osteolysis, thrombosis and atherosclerosis, in addition to more recent investigation in various rare diseases. The present review provides an overview on heparanase, its biological role, inhibitors and possible clinical applications, covering the latest findings in these areas.

Guiding principles in the design of molecular bioconjugates for vaccine applications

Antigen- and adjuvant-based bioconjugates that can stimulate the immune system play an important role in vaccine applications. Bioconjugates have demonstrated unique physicochemical and biological properties, enabling vaccines to be delivered to key immune cells, to target specific intracellular pathways, or to mimic immunogenic properties of natural pathogens. In this Review we highlight recent advances in such molecular immunomodulators, with an emphasis on the structure-function relationships that provide the foundation for rational design of safe and effective vaccines and immunotherapies.

Hepatocyte growth factor (HGF) upregulates heparanase expression via the PI3K/Akt/NF-κB signaling pathway for gastric cancer metastasis

Heparanase (HPA) is an endoglucuronidase that can promote the shedding of associated cytokines in several types of tumors. However, little is known about what controls the expression of HPA or its role in gastric cancer. In this study, we report for the first time that HGF regulates HPA expression to promote gastric cancer metastasis. In this study, HGF and HPA were found to be significantly expressed in 58 gastric cancer patients. High expression of both HGF and HPA was positively associated with TNM stage, invasion depth and poor prognosis. In MKN74 cells, exogenous HGF significantly increased HPA expression at both the mRNA and protein levels. Further study revealed that HGF first activated PI3K/Akt signaling. NF-κB signaling was activated downstream of PI3K/Akt and promoted HPA expression. However, when c-met, PI3K/Akt or NF-κB signal inhibitors were used, HPA expression was significantly decreased. All of these results indicate that HGF regulates HPA expression by PI3K/Akt and downstream NF-κB signaling. Using bioinformatics and the ChIP assay, p65 was observed to bind to the HPA promoter. Furthermore, HGF significantly induced tumor cell migration, whereas treatment with an NF-κB inhibitor decreased migration. Moreover, when HPA was overexpressed in MKN74 cells, migration was significantly enhanced, and the HGF concentration was increased. However, when HPA was down-regulated in MKN45 cells, migration and HGF levels decreased. Together, these results demonstrate that HGF/c-met can activate PI3K/Akt and downstream NF-κB signaling to promote HPA expression and subsequent tumor metastasis.

In vitro and ex vivo evaluation of a multi-epitope heparinase vaccine for various malignancies

Previous studies have indicated that heparanase (Hpa) might represent a candidate universal tumor-associated antigen. However, vaccine therapy targeting only one cytotoxic T lymphocyte (CTL) epitope is suboptimal in preventing cancer. In the present study, we designed heparanase multi-epitope vaccines to increase the immune response to standard single heparanase epitopes. The results showed that multi-epitope vaccines Hpa525 + 277 + 405 + 16 and Hpa8 + 310 + 315 + 363 induced higher Hpa-specific lysis of various cancer cells from different tissues in a HLA-A2-restricted and heparanase-specific manner compared with the single epitope vaccines Hpa525, Hpa277, Hpa405, Hpa16, Hpa8, Hpa310, Hpa315 and Hpa363, both in vitro and ex vivo. Heparanase multi-epitope vaccines not only induced the heparanase-specific CTL to lyse tumor cells but also increased CTL secretion of interferon-γ. However, these heparanase-specific CTL did not lyse heparanase-expressing autologous lymphocytes and dendritic cells, which confirms the safety of these multi-epitope vaccines. Therefore, the present study provides theoretical evidence for the use of heparanase multi-epitope vaccines for clinical application.

Heparan sulfate and heparanase as modulators of breast cancer progression

Breast cancer is defined as a cancer originating in tissues of the breast, frequently in ducts and lobules. During the last 30 years, studies to understand the biology and to treat breast tumor improved patients' survival rates. These studies have focused on genetic components involved in tumor progression and on tumor microenvironment. Heparan sulfate proteoglycans (HSPGs) are involved in cell signaling, adhesion, extracellular matrix assembly, and growth factors storage. As a central molecule, HSPG regulates cell behavior and tumor progression. HS accompanied by its glycosaminoglycan counterparts regulates tissue homeostasis and cancer development. These molecules present opposite effects according to tumor type or cancer model. Studies in this area may contribute to unveil glycosaminoglycan activities on cell dynamics during breast cancer exploring these polysaccharides as antitumor agents. Heparanase is a potent tumor modulator due to its protumorigenic, proangiogenic, and prometastatic activities. Several lines of evidence indicate that heparanase is upregulated in all human sarcomas and carcinomas. Heparanase seems to be related to several aspects regulating the potential of breast cancer metastasis. Due to its multiple roles, heparanase is seen as a target in cancer treatment. We will describe recent findings on the function of HSPGs and heparanase in breast cancer behavior and progression.

Diepitope multiple antigen peptide of hTERT trigger stronger anti-tumor immune responses in vitro

Rapid advances in immune system knowledge have led to the exploration of immunologic approaches for eliminating tumor cells. Human telomerase reverse transcriptase (hTERT) is considered to be an ideal universal target for novel immunotherapies against cancers. Thus far, studies of effective antitumor immunotherapies have focused on the quantity and quality of the effector function of the CD8 compartment. However, increasing evidence has demonstrated that CD4+ T cells play important roles in generating and maintaining antitumor immune responses in animal models. The aim of this work was to verify whether diepitope multiple antigen peptides (MAPs) that were composed of the cytotoxic T lymphocyte (CTL) epitope of hTERT and the T-helper epitope of hTERT could improve upon the immunogenicity of a monoepitope MAP of hTERT. Dendritic cells (DCs) pulsed with diepitope MAPs composed of the CTL epitope hTERT-540 and the T-helper epitope hTERT-766 were used to evaluate immune responses against various tumor cells. A standard in vitro 4-h ⁵¹Cr-release assay was employed in this study. The results demonstrated that CTLs activated by the diepitope MAP that consisted of hTERT-540 and hTERT-766 could cause 8.56% more lysis than CTLs activated by the monoepitope MAP containing hTERT-540. Moreover, the activated CTLs could kill neither hTERT-negative tumor cells, such as U2OS cells, nor HLA-A2 negative cells, such as HepG2 cells. Our results indicate that diepitope MAPs that are generated from hTERT can be exploited for cancer immunotherapy.

Production of polyclonal antibodies directed to recombinant methionyl bovine somatotropin

The administration of recombinant methionyl bovine somatotropin (rMbST) to dairy cows to increase milk yield remains a common practice in many countries including the USA, Brazil, Mexico, South Africa and Korea, whereas it has been forbidden within the European Union (EU) since 1999. A rapid screening immunoanalytical method capable of the unequivocal determination of rMbST in milk would be highly desirable in order to effectively monitor compliance with the EU-wide ban for home-made or imported dairy products. For decades, the production of specific antibodies for this recombinant isoform of bovine somatotropin (bST) has remained elusive, due to the high degree of sequence homology between both counterparts (e.g. methionine for rMbST in substitution of alanine in bST at the N-terminus). In this study, we compared several immunizing strategies for the production of specific polyclonal antibodies (pAbs), based on the use of the full-length recombinant protein, an rMbST N-terminus peptide fragment and a multiple antigen peptide (MAP) which consists of an oligomeric branching lysine core attached to the first two N-terminus amino acids of rMbST, methionine and phenylalanine (MF-MAP). The immunization with KLH-conjugated MF-MAP led to the production of the pAb with the highest rMbST/bST recognition ratio amongst the generated battery of antibodies. The pAb exhibited a specific binding ability to rMbST in a competitive antigen-coated ELISA format, which avidity was further improved after purification by rMbST N-terminus peptide-based affinity chromatography. These results suggest that immunodiscrimination between structurally related proteins can be achieved using immuno-enhanced immunogens such as MAPs.

Antitumor effect of new multiple antigen peptide based on HLA-A0201-restricted CTL epitopes of human telomerase reverse transcriptase (hTERT)

The development of peptide vaccines aimed at enhancing immune responses against tumor cells is becoming a promising area of research. Human telomerase reverse transcriptase (hTERT) is an ideal universal target for novel immunotherapies against cancers. The aim of this work was to verify whether the multiple antigen peptides (MAP) based on HLA-A0201-restricted CTL epitopes of hTERT could trigger a better and more sustained CTL response and kill multiple types of hTERT-positive tumor cells in vitro and ex vivo. Dendritic cells (DC) pulsed with MAP based on HLA-A0201-restricted CTL epitopes of hTERT (hTERT-540, hTERT-865 and hTERT-572Y) were used to evaluate immune responses against various tumors and were compared to the immune responses resulting from the use of corresponding linear epitopes and a recombinant adenovirus-hTERT vector. A 4-h standard (51) Cr-release assay and an ELISPOT assay were used for both in vitro and ex vivo analyses. Results demonstrated that targeting hTERT with an adenovector was the most effective way to stimulate a CD8(+) T cell response. When compared with linear hTERT epitopes, MAP could trigger stronger hTERT-specific CTL responses against tumor cells expressing hTERT and HLA-A0201. In contrast, the activated CTL could neither kill the hTERT-negative tumor cells, such as U2OS cells, nor kill HLA-A0201 negative cells, such as HepG2 cells. We also found that these peptide-specific CTL could not kill autologous lymphocytes and DC with low telomerase activity. Our results indicate that MAP from hTERT can be exploited for cancer immunotherapy.

Significance of heparanase in cancer and inflammation

Heparan sulfate proteoglycans (HSPGs) are primary components at the interface between virtually every eukaryotic cell and its extracellular matrix. HSPGs not only provide a storage depot for heparin-binding molecules in the cell microenvironment, but also decisively regulate their accessibility, function and mode of action. As such, they are intimately involved in modulating cell invasion and signaling loops that are critical for tumor growth, inflammation and kidney function. In a series of studies performed since the cloning of the human heparanase gene, we and others have demonstrated that heparanase, the sole heparan sulfate degrading endoglycosidase, is causally involved in cancer progression, inflammation and diabetic nephropathy and hence is a valid target for drug development. Heparanase is causally involved in inflammation and accelerates colon tumorigenesis associated with inflammatory bowel disease. Notably, heparanase stimulates macrophage activation, while macrophages induce production and activation of latent heparanase contributed by the colon epithelium, together generating a vicious cycle that powers colitis and the associated tumorigenesis. Heparanase also plays a decisive role in the pathogenesis of diabetic nephropathy, degrading heparan sulfate in the glomerular basement membrane and ultimately leading to proteinuria and kidney dysfunction. Notably, clinically relevant doses of ionizing radiation (IR) upregulate heparanase expression and thereby augment the metastatic potential of pancreatic carcinoma. Thus, combining radiotherapy with heparanase inhibition is an effective strategy to prevent tumor resistance and dissemination in IR-treated pancreatic cancer patients. Also, accumulating evidence indicate that peptides derived from human heparanase elicit a potent anti-tumor immune response, suggesting that heparanase represents a promising target antigen for immunotherapeutic approaches against a broad variety of tumours. Oligosaccharide-based compounds that inhibit heparanase enzymatic activity were developed, aiming primarily at halting tumor growth, metastasis and angiogenesis. Some of these compounds are being evaluated in clinical trials, targeting both the tumor and tumor microenvironment.

Heparanase: a universal immunotherapeutic target in human cancers

Heparanase has been identified as a particularly important player in metastasis, and its expression directly correlates with the metastatic spread of various tumors. Ideal targets for immunotherapy are gene products that are silenced in normal tissues but overexpressed in cancer, and that are directly involved in tumor cell survival and progression. Metastasis is the culmination of neoplastic progression. The importance of the role of heparanase in metastasis implies that immune escape by downregulation of heparanase expression could reduce the mortality of the cancer. These characteristics of heparanase make it an attractive universal target for cancer immunotherapy. Here, we review current knowledge about heparanase and its involvement in tumor metastasis, with an emphasis on recent results from heparanase-targeted cancer immunotherapy studies.