Caveolin-1 as a potential new therapeutic target in multiple myeloma

Caveolae are specialized flask-shaped lipid rafts enriched in cholesterol, sphingolipids, and structural marker proteins termed caveolins. Caveolins are highly conserved hairpin loop-shaped, oligomeric proteins of 22-24 kDa. Besides the plasma cell membrane, caveolins are also present in mitochondria, the endoplasmatic reticulum, the Golgi/trans-Golgi network, and secretory vesicles. They play a critical role in normal vesicular transport, cholesterol homeostasis, and signal transduction. Conversely, dysregulation of caveolin-1 has been associated with several human diseases including multiple myeloma, an incurable malignancy characterized by excess monoclonal plasma cells within the bone marrow. In this mini-review, we characterize the functional role of caveolin-1 in multiple myeloma, and present the preclinical rationale for novel potential therapeutic approaches targeting caveolin-1 in multiple myeloma.     

Identification of a novel membrane protein, HP59, with therapeutic potential as a target of tumor angiogenesis.

CM101, a polysaccharide isolated from the culture medium of Group B streptococcus, a neonatal pathogen, targets pathological angiogenesis and inhibits tumor growth in mice and humans. CM101 also targets neonatal lung and adult sheep lung endothelial cells. A gene encoding a transmembrane protein that interacts with CM101 was isolated from a sheep lung endothelial cell cDNA library. The gene, termed sp55, encodes a 495-amino acid polypeptide. COS-7 cells transfected with a vector containing sp55 express the SP55 protein-bound CM101 in a concentration-dependent manner. Stably transfected CHO cells also bound CM101. The corresponding human gene, hp59, was isolated from a human fetal lung cDNA library and had a predicted identity to SP55 of 86% over 495 amino acids. HP59 protein was shown by immunohistochemistry to be present in the pathological tumor vasculature of the lung, breast, colon, and ovary, but not in the normal vasculature, suggesting that the protein may be critical to pathological angiogenesis. The hp59 gene and/or the HP59 protein was not expressed in a variety of normal tissues, but was significantly expressed in human fetal lung, consistent with the pathophysiology of Group B streptococcus infections in neonates. Mice immunized with HP59 and SP55 peptides showed significant attenuation of tumor growth. Immunization effectively inhibited both the tumor angiogenesis and vasculogenesis processes, as evidenced by lack of both HP59- and CD34-positive vessels. These results and the immunohistochemistry data suggest a therapeutic potential for the CM101 target protein HP59 both as a drug target and as a vaccine against pathoangiogenesis.     

CS1, a potential new therapeutic antibody target for the treatment of multiple myeloma.

PURPOSE: We generated a humanized antibody, HuLuc63, which specifically targets CS1 (CCND3 subset 1, CRACC, and SLAMF7), a cell surface glycoprotein not previously associated with multiple myeloma. To explore the therapeutic potential of HuLuc63 in multiple myeloma, we examined in detail the expression profile of CS1, the binding properties of HuLuc63 to normal and malignant cells, and the antimyeloma activity of HuLuc63 in preclinical models. EXPERIMENTAL DESIGN: CS1 was analyzed by gene expression profiling and immunohistochemistry of multiple myeloma samples and numerous normal tissues. HuLuc63-mediated antimyeloma activity was tested in vitro in antibody-dependent cellular cytotoxicity (ADCC) assays and in vivo using the human OPM2 xenograft model in mice. RESULTS: CS1 mRNA was expressed in >90% of 532 multiple myeloma cases, regardless of cytogenetic abnormalities. Anti-CS1 antibody staining of tissues showed strong staining of myeloma cells in all plasmacytomas and bone marrow biopsies. Flow cytometric analysis of patient samples using HuLuc63 showed specific staining of CD138+ myeloma cells, natural killer (NK), NK-like T cells, and CD8+ T cells, with no binding detected on hematopoietic CD34+ stem cells. HuLuc63 exhibited significant in vitro ADCC using primary myeloma cells as targets and both allogeneic and autologous NK cells as effectors. HuLuc63 exerted significant in vivo antitumor activity, which depended on efficient Fc-CD16 interaction as well as the presence of NK cells in the mice. CONCLUSIONS: These results suggest that HuLuc63 eliminates myeloma cells, at least in part, via NK-mediated ADCC and shows the therapeutic potential of targeting CS1 with HuLuc63 for the treatment of multiple myeloma.     

Neuropilin-1与肿瘤血管新生和生长转移

神经纤毛蛋白-1（Neuropilin-1）最早是作为轴突导向分子collapsin／semaphorin的受体被发现，在神经发育过程中引导轴突选择正确途径以成功到达靶区，与此同时又可作为血管内皮生长因子受体-2（VEGFR-2）的共受体表达于血管内皮细胞，在血管新生中发挥作用。近来的研究表明NRP-1可通过依赖于VEGF和独立于VEGF的方式参与调节肿瘤血管新生，在肿瘤生长转移中发挥作用。     

Laminin isoforms in tumor invasion,angiogenesis and metastasis

Laminins are a growing family of alphabetagamma heterotrimeric proteins, commonly found in basement membranes (BMs). These large molecules promote cell adhesion and migration via integrins and other cell-surface receptors. Over 12 laminin isoforms are presently known. The various isoforms have a cell- and tissue-specific expression and are differentially recognized by integrins. Expression of laminin isoforms in tumors usually reflects expression in their normal counterparts. However, during tumor invasion, loss of the BM barrier occurs and a discontinuous pattern of laminin staining is observed. In carcinomas, tumor cells at the invading front strongly express intracellularly the gamma2 chain, a component of laminin-5. Remodeling of the vascular BM is observed during angiogenesis, and penetration of several BMs occurs during tumor dissemination and metastasis. Thus, disregulated cell-laminin interactions are major traits of malignant disorders.     

MEDI3617, a human anti-angiopoietin 2 monoclonal antibody, inhibits angiogenesis and tumor growth in human tumor xenograft models

Angiopoietin 2 (Ang2) is an important regulator of angiogenesis, blood vessel maturation and integrity of the vascular endothelium. The correlation between the dynamic expression of Ang2 in tumors with regions of high angiogenic activity and a poor prognosis in many tumor types makes Ang2 an ideal drug target. We have generated MEDI3617, a human anti-Ang2 monoclonal antibody that neutralizes Ang2 by preventing its binding to the Tie2 receptor in vitro, and inhibits angiogenesis and tumor growth in vivo. Treatment of mice with MEDI3617 resulted in inhibition of angiogenesis in several mouse models including: FGF2-induced angiogenesis in a basement extract plug model, tumor and retinal angiogenesis. In xenograft tumor models, treatment with MEDI3617 resulted in a reduction in tumor angiogenesis and an increase in tumor hypoxia. The administration of MEDI3617 as a single agent to mice bearing human tumor xenografts resulted in tumor growth inhibition against a broad spectrum of tumor types. Combining MEDI3617 with chemotherapy or bevacizumab resulted in a delay in tumor growth and no body weight loss was observed in the combination groups. These results, combined with pharmacodynamic studies, demonstrate that treatment of tumor-bearing mice with MEDI3617 significantly inhibited tumor growth as a single agent by blocking tumor angiogenesis. Together, these data show that MEDI3617 is a robust antiangiogenic agent and support the clinical evaluation and biomarker development of MEDI3617 in cancer patients.     

The role of tumor angiogenesis as a therapeutic target in colorectal cancer

Introduction: Angiogenesis is a complex process regulated by several pro- and anti-angiogenic factors, thus the loss of its fine equilibrium plays a key role in colorectal cancer (CRC) development and progression. Therapeutic agents targeting VEGF/VEGFR signaling, the main regulator of this process, proved to be effective across different treatment lines in metastatic CRC (mCRC) and contributed greatly to improve patients’ survival in recent years.

Areas covered: This review aimed to summarize the actual body of knowledge available on the VEGF pathway in CRC, including currently available anti-angiogenic drugs and treatment challenges, mechanisms of resistance, promising predictive biomarkers and future perspectives.

Expert commentary: Angiogenesis inhibition in subsequent lines of treatment is a valid strategy in the continuum of care of mCRC patients. In this scenario, the availability of multiple agents warrants to tailor therapy to an individualized approach. However, the validation of predictive biomarkers to aid therapeutic decisions remains an issue. Intrinsic and adaptive resistance to anti-angiogenic agents comprises distinct and intertwined processes, eventually leading to treatment failure and disease progression. The expanding knowledge on the mechanisms underlying the angiogenesis pathway, different potential treatment targets and mechanisms of tumor resistance, may lead to promising new perspectives in this field.     

Monoclonal antibody to vascular endothelial-cadherin is a potent inhibitor of angiogenesis, tumor growth, and metastasis

Vascular endothelial-cadherin (VE-cad) is an endothelial cell-specific adhesion molecule that is crucial for proper assembly of vascular tubes. Here we show that a monoclonal antibody (BV13) directed to the extracellular region of VE-cad inhibits formation of adherens junctions and capillary-like structures by endothelial cells and blocks angiogenesis in the mouse cornea and in Matrigel plugs in vivo. Systemic administration of BV13 markedly decreases the growth of s.c. Lewis lung or human A431 epidermoid tumors and strongly suppresses the growth of Lewis lung metastases. These data demonstrate that VE-cad is essential for postnatal angiogenesis and thus validate VE-cad as a novel target for antiangiogenesis agents.     

Brain tumor hypoxia: tumorigenesis,angiogenesis, imaging,pseudoprogression, and as a therapeutic target

Hypoxia is implicated in many aspects of tumor development, angiogenesis, and growth in many different tumors. Brain tumors, particularly the highly aggressive glioblastoma multiforme (GBM) with its necrotic tissues, are likely affected similarly by hypoxia, although this involvement has not been closely studied. Invasion, apoptosis, chemoresistance, resistance to antiangiogenic therapy, and radiation resistance may all have hypoxic mechanisms. The extent of the influence of hypoxia in these processes makes it an attractive therapeutic target for GBM. Because of their relationship to glioma and meningioma growth and angiogenesis, hypoxia-regulated molecules, including hypoxia inducible factor-1, carbonic anhydrase IX, glucose transporter 1, and vascular endothelial growth factor, may be suitable subjects for therapies. Furthermore, other novel hypoxia-regulated molecules that may play a role in GBM may provide further options. Emerging imaging techniques may allow for improved determination of hypoxia in human brain tumors to better focus therapeutic treatments; however, tumor pseudoprogression, which may be prompted by hypoxia, poses further challenges. An understanding of the role of hypoxia in tumor development and growth is important for physicians involved in the care of patients with brain tumors.     

Gabexate mesilate inhibits colon cancer growth, invasion, and metastasis by reducing matrix metalloproteinases and angiogenesis.

Gabexate mesilate (GM), a synthetic protease inhibitor, has an antiproteinase activity on various types of plasma serine proteases. However, its role on matrix metalloproteinases (MMPs) has not been identified. In this study, we investigated the effect of GM on MMPs and on the invasion and metastasis of human colon cancer cell lines and neoangiogenesis. The activities of MMPs secreted from these cells were significantly reduced by GM but unaffected by the serine protease inhibitor aprotinin. GM directly inhibited purified progelatinase A derived from T98G human glioblastoma cells. In vitro, GM significantly reduced the invasive ability of colon cancer cells but not cellular motility, whereas aprotinin affected neither. Liver metastatic ability and tumorigenic potential in nude mice were remarkably reduced on treatment with GM. Immunohistochemical analysis of GM-treated tumors in mice showed a marked increase in apoptosis and a significant reduction in tumor angiogenesis. Human umbilical vein endothelial cell proliferation, tube formation, and neoangiogenesis in the rabbit cornea and Matrigel implanted in mice were significantly inhibited by GM. These results suggest that GM is a novel inhibitor of MMPs and that it may inhibit the invasion and metastasis of human colon cancer cells by blocking MMPs and neoangiogenesis.     

Novel anti-denatured collagen humanized antibody D93 inhibits angiogenesis and tumor growth: An extracellular matrix-based therapeutic approach

Matrix metalloproteases (MMPs) secreted by both tumor and endothelial cells proteolytically degrade collagen during tumor growth and neo-vascularization. This exposes cryptic binding sites on collagen with functional relevance for angiogenesis. In this report, we characterized a novel humanized monoclonal IgG1 antibody, D93. After humanization, the antibody retained the binding specificity of the parental murine IgM antibody for denatured (dn) collagen. D93 recognized dn-collagen but not native (nat) collagen of different species, including mouse, chicken, and human, indicating that its cryptic binding site(s) is conserved across species. In immunohistochemistry (IHC) studies, D93 stained the basement membrane of blood vessels in several xenograft human tumors or in surgically removed tumor tissues from patients with different types of malignancies. D93 staining was rarely or not present in normal blood vessels of healthy tissues. In in vivo experiments, D93 significantly inhibited basic fibroblast growth factor (bFGF)-induced angiogenesis in chick embryo chorioallantoic membrane (CAM) and the tumor growth of pre-established orthotopic human breast (MDA-MB-435) tumors in mice. D93 i.v. administered in mice was subsequently detected in the subendothelial basement membrane of tumor blood vessels but not blood vessels of normal tissues. Inhibition of growth of pre-established orthotopic human breast MDA-MB-435 tumors was more effective when D93 was combined with Taxol, than either treatment alone. In addition, tumors from animals treated with D93 and/or Taxol showed significantly reduced levels of the endothelial cell-marker CD31. Our data suggest that blockade of cryptic epitopes exposed on collagen IV during angiogenesis and tumor growth by a monoclonal antibody may provide a novel therapeutic modality for treatment of cancer and pathogenic neo-vascularization.     

Lipopolysaccharide-induced metastatic growth is associated with increased angiogenesis,vascular permeability and tumor cell invasion

Endotoxin/lipopolysaccharide (LPS), a cell wall component of Gram-negative bacteria, is a potent inflammatory stimulus. We previously reported that LPS increased the growth of experimental metastases in a murine tumor model. Here, we examined the effect of LPS exposure on key determinants of metastasis-angiogenesis, tumor cell invasion, vascular permeability, nitric oxide synthase (NOS) and matrix metalloproteinase 2 (MMP2) expression. BALB/c mice bearing 4T1 lung metastases were given an intraperitoneal (i.p.) injection of 10 microg LPS or saline. LPS exposure resulted in increased lung weight and incidence of pleural lesions. LPS increased angiogenesis both in vivo and in vitro. Vascular permeability in lung tissue was increased 18 hr after LPS injection. LPS increased inducible nitric oxide synthase (iNOS) and MMP2 expression in lung tumor nodules. 4T1 cells transfected with green fluorescent protein (4T1-GFP) were injected via lateral tail vein. LPS exposure resulted in increased numbers of 4T1-GFP cells in mouse lung tissue compared to saline controls, an effect blocked by the competitive NOS inhibitor, N(G) methyl-L-arginine (NMA). LPS-induced growth and metastasis of 4T1 experimental lung metastases is associated with increased angiogenesis, vascular permeability and tumor cell invasion/migration with iNOS expression implicated in LPS-induced metastasis.     

CANSTATIN, A ENDOGENOUS INHIBITOR OF ANGIOGENESIS AND TUMOR GROWTH

Canstatin is a novel inhibitor of angiogenesis and tumor growth, derived from the C-terminal globular non-collageneous (NCI) domain of the α2 chain of type Ⅳ collagen. It inhibits endothelial cell proliferation and migration in a dose-dependent manner, and induces endothelial cell apoptosis. In vivo experiments show that canstatin significantly inhibits solid tumor growth. The canstatin mediated inhibition of tumor is related to apoptosis. Canstatin- induced apoptosis is associated with phosphatidylinositol 3-kinase/Akt inhibition and is dependend upon signaling events transduced trough membrane death receptor.     

Endocannabinoids as emerging suppressors of angiogenesis and tumor invasion (review)

The medicinal properties of extracts from the hemp plant Cannabis sativa have been known for centuries but only in the 90s membrane receptors for the Cannabis major principle were discovered in mammalian cells. Later on the endogenous ligands for the cannabinoid receptors were identified and the term 'endocannabinoid system' was coined to indicate the complex signaling system of cannabinoid receptors, endogenous ligands and the enzymes responsible for their biosynthesis and inactivation. The 'endocannabinoid system' is involved in a broad range of functions and in a growing number of pathological conditions. There is increasing evidence that endocannabinoids are able to inhibit cancer cell growth in culture as well as in animal models. Most work has focused on the role of endocannabinoids in regulating tumor cell growth and apoptosis and ongoing research is addressed to further dissect the precise mechanisms of cannabinoid antitumor action. However, endocannabinoids are now emerging as suppressors of angiogenesis and tumor spreading since they have been reported to inhibit angiogenesis, cell migration and metastasis in different types of cancer, pointing to a potential role of the endocannabinoid system as a target for a therapeutic approach of such malignant diseases. The potential use of cannabinoids to retard tumor growth and spreading is even more appealing considering that they show a good safety profile, regarding toxicity, and are already used in cancer patients as palliatives to stimulate appetite and to prevent devastating effects such as nausea, vomiting and pain.     

The role of matrix metalloproteinases in tumor invasion, metastasis, and angiogenesis

Tumor invasion and metastasis formation are the hallmarks of malignant cancer. Metastatic spread of cancer cells is a result of a complex cascade of cellular events. This article discusses the matrix metalloproteinase family, the regulation of matrix metalloproteinase activity, and the functions of matrix metalloproteinases in tumor progression.