Role of galectin-3 in the pathogenesis of bladder transitional cell carcinoma

Galectins constitute an evolutionary conserved family that binds to β-galactosides. There is growing evidence that galectins are implicated in essential biological processes such as cellular communication, inflammation, differentiation and apoptosis. Galectin-3 is one of the best-known galectins, which is found in vertebrates. Galectin-3 has been shown to be expressed in some cell lines and plays important roles in several physiological and pathological processes, including cell adhesion, cell activation and chemoattraction, cell cycle, apoptosis, cell growth, and differentiation. Moreover, this galectin is of interest due to its involvement in regulation of cancer. Changes in galectin-3 expression are commonly seen in cancerous and pre-cancerous conditions and galectin-3 may be involved in the regulation of cancer cell activities that contribute to tumourigenesis, cancer progression and metastasis. Finally, galectin-3 seems to be involved in cell events in tumor microenvironment, and therefore it could be considered as a target in transitional cell carcinoma therapies. This review aims to describe recent progress in understanding the role of galectin-3 in cancer biology, with emphasis on bladder tumor progression and metastasis.     

Inhibiting galectin-1 reduces murine lung metastasis with increased CD4(+) and CD8 (+) T cells and reduced cancer cell adherence

Galectin-1 is a β-galactoside-binding protein overexpressed by cancer cells. The primary roles of galectin-1 in cancer progression and metastasis are attributed to suppression of T cell immune responses, promotion of tumor angiogenesis and increased tumor cell adhesion and invasion. Using pulmonary metastasis models of murine breast (4T1) and colon (CT26) cancer, we demonstrate that targeting galectin-1 with thiodigalactoside (TDG) or shRNA galectin-1 knockdown (G1KD) results in a significant reduction in lung metastasis. Increased numbers of CD4(+) helper T cells and CD8(+) cytotoxic T lymphocytes were found in the peripheral blood of both TDG-treated and G1KD cell challenged mice. The levels of TUNEL(+) apoptotic cancer cells and the presence of CD3(+) T cells were also increased in lung metastases. Furthermore, galectin-1 was found to bind to the adhesion molecules, CD44 and CD326, which are also known as markers of breast and colon cancer stem cells, and TDG likely blocks galectin-1 binding to these molecules. The TDG-mediated inhibition of galectin-1 binding reduced 4T1 cell adhesion to the basement membrane protein laminin, Matrigel and EAhy926 endothelial cell surfaces. These findings establish possible mechanisms for the anti-metastatic effect of galectin-1 inhibition and suggest that targeting galectin-1 may represent a promising and effective anti-metastatic therapy.     

活化T 细胞核因子与肿瘤生物学行为的研究进展

NFAT 蛋白的相关信号传导通路对于细胞功能的调节起到十分重要的作用,如对细胞的增殖、分化、侵袭、转移、血管形成和肿瘤微环境的调节,同时,其在胚胎发育、器官发生、免疫反应及炎症反应中均扮演着重要角色。虽然NFAT 家族已被证明在肿瘤的发生发展中有重要的调节功能,但由于其家族中不同亚型在不同细胞中起的作用不同,故进一步了解NFAT 家族在肿瘤演变过程中的作用机制,将有利于确定靶向NFAT 的肿瘤治疗新策略     

Immunohistochemical Expression of the Intracellular Component of Galectin-8 in Squamous Cell Metaplasiaof the Bronchial Epitheliumin Neoplastic and Benign Processes

Specified galectins are known to play a role in regulating cell proliferation, differentiation, adhesion and migration. Po66, a mouse IgG1 monoclonal antibody produced by immunization against squamous cell cancer, reacts against a carbohydrate-binding protein (Po66-CBP), recently shown to be a member of the galectin family with a strong homology with galectin-8 (PCTA-1), identified as a human tumor-associated antigen.

We studied Po66 in squamous metaplasia of the bronchi in order to determine whether it could be specifically involved in neoplastic conditions and if so, if it would be helpful in distinguishing metaplasia at risk of cancer.

Twenty-eight formalin-fixed, paraffin-embedded archival tissues of 17 metaplasias with SCC, 3 metaplasia with distant neoplastic disease and 8 metaplasias with an inflammatory process, were immunostained using a streptavidin biotin peroxydase method.

The squamous metaplasias were positively stained in non-neoplastic disease as well as in neoplastic processes. Expression was also observed in stromal and normal cells.

Po66-CBP was not associated with a pre-neoplastic character. We discussed the expression of this intra-cellular component of galectin-8 according to the functions of galectins in cellular differentiation, host reaction against tumor, and inflammation.     

Racl与肿瘤的研究进展

Rho家族在细胞的一些基本功能中起着分子开关的作用,参与了细胞运动性、肌动蛋白重组、肿瘤的恶性转型、侵袭转移、转录因子的调节及肿瘤的血管生成等.Ras相关的C3肉毒素底物1作为Rho家族成员之一,在肿瘤细胞的增殖分化与凋亡、细胞运动、侵袭与转移及肿瘤血管生成方面发挥重要的作用.     

Galectin-3 Protects Human Breast Carcinoma Cells against Nitric Oxide-Induced Apoptosis : Implication of Galectin-3 Function during Metastasis

Galectin-3 is a beta-galactoside-binding protein which regulates many biological processes including cell adhesion, migration, cell growth, tumor progression, metastasis, and apoptosis. Although the exact function of galectin-3 in cancer development is unclear, galectin-3 expression is associated with neoplastic progression and metastatic potential. Since studies have suggested that tumor cell survival in microcirculation determines the metastatic outcome, we examined the effect of galectin-3 overexpression in human breast carcinoma cell survival using the liver ischemia/reperfusion metastasis model. While the majority of control cells died by hepatic ischemia/reoxygenation, nearly all of galectin-3 overexpressing cells survived. We showed that galectin-3 inhibits nitrogen free radical-mediated apoptosis, one of the major death pathways induced during hepatic ischemia/reperfusion. Galectin-3 inhibition of apoptosis involved protection of mitochondrial integrity, inhibition of cytochrome c release and caspase activation. Taking these results together with the previous observation that galectin-3 inhibits apoptosis induced by loss of cell adhesion, we propose that galectin-3 is a critical determinant for anchorage-independent and free radical-resistant cell survival during metastasis.     

Roles of galectin-3 in immune responses

Galectins are a family of animal lectins with conserved carbohydrate-recognition domains for beta-galactoside. Galectin-3 is the only family member that is composed of a glycine/prolinerich N-terminal repeated sequence and a C-terminal carbohydrate-binding domain.Multiple functions of galectin-3 have been reported, depending on its location. Extracellular galectin-3 can bind to cell surface through glycosylated proteins and thereby trigger or modulate cellular responses such as mediator release or apoptosis. Intracellular galectin-3 has been reported to inhibit apoptosis, regulate the cell cycle, and participate in the nuclear splicing of pre-mRNA. Recent studies have revealed that galectin-3 is expressed in a variety of cell types in the immune system, constitutively or in response to microbial invasion. These studies implicate galectin-3 in both innate and adaptive immune responses, where it participates in the activation or differentiation of immune cells. This review summarizes the roles of galectin-3 in the immune system and discusses the possible underlying mechanisms.     

Hyaluronan and Human Endothelial Cell Behavior

Hyaluronan (HA) is the only nonsulphated glycosaminoglycan of extracellular matrix. In mammals HA is synthesised by three homologues HA synthases: HAS1, HAS2, and HAS3. The HA is daily catabolized by the hyaluronidase enzymes to either oligosaccharides or larger polymer. Despite its simple structure, HA is involved in a great number of biological functions, such as cell proliferation and migration, morphogenesis, wound healing, inflammation, angiogenesis, and tumor growth. Moreover, an important biological role is related to HA oligosaccharides that stimulate cytokine secretion and endothelial cell proliferation. Nevertheless no data about HA presence in endothelium are reported in literature. Several studies underline HA involvement in endothelial cell proliferation, migration, new vessels formation, and leucocytes recruitment. We review the role of HA in endothelial cell in normal condition and during vascular injury.     

Hyaluronan and human endothelial cell behavior

Hyaluronan (HA) is the only nonsulphated glycosaminoglycan of extracellular matrix. In mammals HA is synthesised by three homologues HA synthases: HAS1, HAS2, and HAS3. The HA is daily catabolized by the hyaluronidase enzymes to either oligosaccharides or larger polymer. Despite its simple structure, HA is involved in a great number of biological functions, such as cell proliferation and migration, morphogenesis, wound healing, inflammation, angiogenesis, and tumor growth. Moreover, an important biological role is related to HA oligosaccharides that stimulate cytokine secretion and endothelial cell proliferation. Nevertheless no data about HA presence in endothelium are reported in literature. Several studies underline HA involvement in endothelial cell proliferation, migration, new vessels formation, and leucocytes recruitment. We review the role of HA in endothelial cell in normal condition and during vascular injury.     

Infection of human brain vascular pericytes (HBVPs) by Bartonella henselae

Angiogenesis is an important physiological and pathological process. Bartonella is the only genus of bacteria known to induce pathological angiogenesis in the mammalian host. Bartonella-induced angiogenesis leads to the formation of vascular tumors including verruga peruana and bacillary angiomatosis. The mechanism of Bartonella-induced angiogenesis is not completely understood. Pericytes, along with endothelial cells, play an important role in physiological angiogenesis, and their role in tumor angiogenesis has been extensively studied. Abnormal signaling between endothelial cells and pericytes contributes to tumor angiogenesis and metastasis; however, the role of pericytes in Bartonella-induced angiogenesis is not known. In this study, after infecting human brain vascular pericytes (HBVPs) with Bartonella henselae, we found that these bacteria were able to invade HBVPs and that bacterial infection resulted in decreased pericyte proliferation and increased pericyte production of vascular endothelial growth factor (VEGF) when compared to the uninfected control cells. In the context of pathological angiogenesis, reduced pericyte coverage, accompanied by increased VEGF production, may promote endothelial cell proliferation and the formation of new vessels.     

Identification of genes involved in VEGF-mediated vascular morphogenesis using embryonic stem cell-derived cystic embryoid bodies

The vasculature forms during development via two processes, vasculogenesis and angiogenesis, in which vessels form de novo from angioblast precursors or as sprouts from pre-existing vessels, respectively. A common and critical aspect of both processes is vascular morphogenesis, which includes branching of endothelial cell cords and lumen formation. Although ample evidence support the central role of vascular endothelial growth factor (VEGF) in both vasculogenesis and angiogenesis, the role of VEGF in vascular morphogenesis is unclear and little is known about the regulation of vascular morphogenesis, in general. We have used the in vitro vessel differentiation system of embryonic stem (ES) cell-derived cystic embryonic bodies (CEB) as a model for studying VEGF-mediated vessel formation. Whereas CEB formed from wild-type ES cells make well-formed vessel-like structures, CEB derived from VEGF-null ES cells contain PECAM-1-positive endothelial cells, but these cells do not participate in vascular morphogenesis. Using gene expression microarray analysis to compare gene expression in these two systems, we have been able to identify many genes and novel ESTs that are downstream of VEGF function, and which may be involved in VEGF-mediated vascular morphogenesis including caveolin-1 and HEY-1. These results support using the CEB model, in combination with gene knockout ES cells, for studying vascular morphogenesis.     

Endothelial cells expressing Bcl-2 promotes tumor metastasis by enhancing tumor angiogenesis, blood vessel leakiness and tumor invasion

Metastatic spread of tumor cells to vital organs is the major cause of mortality in cancer patients. Bcl-2, a key antiapoptotic protein, is expressed at high levels in a number of human tumors. We have recently shown that Bcl-2 is also overexpressed in tumor-associated blood vessels in head-and-neck cancer patients. Interestingly, enhanced Bcl-2 expression in tumor blood vessels is directly correlated with metastatic status of these cancer patients. In addition, endothelial cells (ECs) expressing Bcl-2 showed increased production of interleukin-8 (IL-8) resulting in significantly enhanced tumor cell proliferation and tumor cell invasion. Therefore, we hypothesized that Bcl-2 expression in tumor-associated ECs may promote tumor metastasis by enhancing tumor cell invasiveness and release in the circulation. To test our hypothesis, we coimplanted tumor cells along with ECs expressing Bcl-2 (EC-Bcl-2) in the flanks of SCID mice. Our results demonstrate that incorporation of EC-Bcl-2 in primary tumors significantly enhanced tumor cell metastasis to lungs and this EC-Bcl-2-mediated tumor metastasis was independent of primary tumor size. In addition, Bcl-2-mediated tumor metastasis directly correlated with increased tumor angiogenesis. Bcl-2 expression in ECs also promoted transendothelial cell permeability, blood vessel leakiness and tumor cell invasion. EC-Bcl-2-mediated tumor cell proliferation and tumor cell invasion were significantly mediated by IL-8. These results suggest that Bcl-2, when expressed at higher levels in tumor-associated ECs, may promote tumor metastasis by enhancing tumor angiogenesis, blood vessel leakiness and tumor cell invasiveness.     

The role of the extracellular matrix in angiogenesis in malignant glioma tumors

Angiogenesis is a promising target for the development of effective strategies for the treatment of malignant brain tumors in that it has the potential to starve large tumors and prevent the regrowth of residual margins. Two critical steps in angiogenesis, the proliferation of activated endothelial cells and their migration into the perivascular space (sprouting), require adherence of the endothelial cells to the extracellular matrix (ECM). Thus, the availability of the appropriate ligands within the ECM contributes to the regulation of angiogenesis. In addition, several components of the ECM can act through other mechanisms to further promote angiogenesis or inhibit it. Current evidence suggests that the regulation of angiogenesis is a dynamic process in which the endothelial cells can promote angiogenesis by secreting proteases that remodel the ECM, tumor cells can further promote angiogenesis by secreting ECM components and actively remodeling their environment, and stromal cells may respond to angiogenesis associated with tumors and inflammatory reactions by secreting inhibitory molecules. Here, we provide a critical review of the protein and proteoglycan components of the ECM that have been implicated in angiogenesis with an emphasis on their role in promoting or inhibiting angiogenesis in brain tumors.     

Therapeutic potential of renin angiotensin system inhibitors in cancer cells metastasis

Metastasis is a complex process which contributes to the dissemination of cancer cells to other organs and forms new tumor sites. The proliferation of tumor cells is a necessary step for the initiation and progression of cancers and is associated with the formation of new vessels.In the latter stages of metastasis, cancer cells may spread into the extracellular matrix and may form metastatic nodules. Despite efforts to prevent this, effective therapies are limited in the treatment of some malignancies. Among the different tumor properties which could be usefully employed as a cancer target, metastasis may be one suitable target.The renin- angiotensin system is a physiological pathway that contributes to the proliferation of tumor cells, angiogenesis and the inflammatory response in tumor tissue. Angiotensin II (ANGII), a key peptide of this pathway, induces cell proliferation through the activation of two cellular pathways (mitogen-activated protein kinase (MAPK)-STAT3 and phosphoinositide 3-kinase (PI3K) –AKT pathway). AT1-R increases angiogenesis via the elevation of angiogenic factors expression (vascular endothelial growth factor (VEGF) and matrix metallopeptidases (MMPs)). The local activation of the RAS pathway increases the expression of ICAM, VCAM and MMPs genes that are involved in the late steps of the metastasis process.There is some evidence that RAS components are expressed in metastatic tumors and RASIs (renin-angiotensin system inhibitors) could be used to reduce cancer metastasis by affecting the mechanisms involved in several different cancers. Therefore, we have summarized the effects of RASIs, observed in pre-clinical and clinical studies of cancer cell metastasis.     

血管内皮生长因子的生物学及其在临床的初步应用

血管内皮生长因子(VEGF)是内皮细胞特异性的有丝分裂原。它诱导内皮细胞增殖、促进内皮细胞迁移，并抑制内皮细胞凋亡，在调节血管和淋巴管新生中起重要作用。VEGF也是胚胎发育、软骨内骨形成、女性生殖系统、以及肿瘤和眼球内血管新生所必需的。另外，VEGF也可诱导血小板粘附于血管内皮细胞而出现高凝状态。目前，有许多临床实验正在评价VEGF在血管新生依赖性疾病的促血管新生作用和抗血管新生药物用于治疗的效果。     

Altered melanoma cell surface glycosylation mediates organ specific adhesion and metastasis via lectin receptors on the lung vascular endothelium

Adhesive interactions between the molecules on cancer cells and the target organ are one of the key determinants of the organ specific metastasis. In this communication we show that b1,6 branched N-oligosaccharides which are expressed in a metastasis-dependent manner on B16-melanoma metastatic cell lines, participate in the adhesion process. We demonstrate that high metastatic cells show significantly increased translocation of one of the major carriers of these oligosaccharides, lysosome associated membrane protein (LAMP1), to the cell surface. LAMP1 on high metastatic cells, carry very high levels of these oligosaccharides, which are further substituted with poly N-acetyl lactosamine (polylacNAc), resulting in the expression of high density of very high affinity ligands for galectin-3 on the cell surface. We show that galectin-3 is expressed in highest amount in the lungs as compared to other representative organs. Blocking galectin-3 by pre-incubating the frozen sections of the lungs with 100 mM lactose, substantially inhibited the adhesion of high metastatic cells, while pre-incubation with sucrose had no effect. Finally, by in situ labeling and immunoprecipitation experiment, we demonstrated that the lung vascular endothelial cells express galectin-3 constitutively on their surface. Galectin-3 on the organ endothelium could thus serve as the first anchor for the circulating cancer cells, expressing high density of very high affinity ligands on their surface, and facilitate organ specific metastasis.     

Regulation of endothelial cell differentiation and arterial specification by VEGF and Notch signaling

Analysis of molecular and cellular mechanisms underlying vascular development in vertebrates indicates that initially vasculogenesis occurs when a primary capillary plexus forms de novo from endothelial cell precursors derived from nascent mesodermal cells. Transplantation experiments in avian embryos demonstrate that embryonic endothelial cells originate from two different mesodermal lineages: splanchnic mesoderm and somites. Genetic analysis of mouse and zebrafish reveals that vascular endothelial growth factor (VEGF)/Flk1 and Notch signaling play crucial roles throughout embryonic vascular development. VEGFA plays a major role in endothelial cell proliferation, migration, survival, and regulation of vascular permeability. Flk1, the primary VEGFA receptor, is the earliest marker of the developing endothelial lineage and is essential for endothelial differentiation during vasculogenesis. Notch signaling has been demonstrated to directly induce arterial endothelial differentiation. Recent studies suggest that Notch signaling is activated downstream of VEGF signaling and negatively regulates VEGF-induced angiogenesis and suppresses aberrant vascular branching morphogenesis. In addition to altering endothelial cell fate through Notch activation, VEGFA directly guides endothelial cell migration in an isoform-dependent manner, modifying vascular patterns. Interestingly, genetic studies in mice show that many molecules involved in VEGF or Notch signaling must be tightly regulated for proper vascular formation. Taken together, VEGF and Notch signaling apparently coordinate vascular patterning by regulating each other.     

Small interfering RNAs induce target-independent inhibition of tumor growth and vasculature remodeling in a mouse model of hepatocellular carcinoma

RNA interference mediated by small interfering RNAs (siRNAs) has emerged as a potential therapeutic approach to treat various diseases, including cancer. Recent studies with several animal models of posttraumatic revascularization demonstrated that synthetic siRNAs may produce therapeutic effects in a target-independent manner through the stimulation of the toll-like receptor-3 (TLR3)/interferon pathway and suppression of angiogenesis. To analyze the impact of siRNAs on tumor angiogenesis, we injected transgenic mice developing hepatocellular carcinoma (HCC) with either control siRNAs or siRNA targeting neuropilin-1. We found that treatment with these siRNAs led to a comparable reduction in tumor liver volume and to inhibition of tumor vasculature remodeling. We further determined that TLR3, which recognizes double-stranded siRNA, was up-regulated in mouse HCC. Treatment of HCC mice with polyinosinic-polycytidylic acid [poly(I:C)], a TLR3 agonist, led to both a reduction of tumor liver enlargement and a decrease in hepatic arterial blood flow, indicating that TLR3 is functional and may mediate both anti-angiogenic and anti-tumor responses. We also demonstrated that siRNAs increased interferon-γ levels in the liver. In vitro, interferon-γ inhibited proliferation of endothelial cells. In addition, we found that siRNAs inhibited endothelial cell proliferation and morphogenesis in an interferon-γ-independent manner. Our results suggest that synthetic siRNAs inhibit target-independently HCC growth and angiogenesis through the activation of the innate interferon response and by directly inhibiting endothelial cell function.     

Immunohistochemical galectin-3 expression in non-melanoma skin cancers

Galectin-3 is a ss-galactoside-binding lectin. It participates in a variety of normal and pathologic processes, including cancer progression. In this study, we evaluated the pattern of expression of galectin-3 in cutaneous squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), and its correlation with the grade of differentiation in SCC and tumor size. Galectin-3 expression was evaluated by immunohistochemistry in 31 SCCs, 30 BCCs, and 29 non-tumoral skin samples. Galectin-3 expression was higher in normal epidermis than in non-melanoma skin cancers, except for cytoplasmic immunoreactivity in SCC. Cytoplasmic galectin-3 immunoreactivity was significantly higher than nuclear immunoreactivity in non-melanoma skin cancers. Cytoplasmic galectin-3 immunoreactivity was significantly higher in SCC than in both circumscribed and infiltrative BCCs, but no difference was detected between these two types of BCC. Cytoplasmic galectin-3 immunoreactivity predominated within SCCs (p=0.000), and a positive correlation was detected between tumor size and cytoplasmic immunoreactivity (r=0.385, p=0.043). There was no correlation between galectin-3 staining and tumor differentiation and lymph node metastasis. Decreased nuclear galectin-3 expression and cytoplasmic immunoreactivity in tumors are important factors in the progression from the normal to the cancerous state in non-melanoma skin cancers. We speculate that cytoplasmic galectin-3 expression may be one of the factors that contribute to tumor aggressiveness in SCC.