Cell adhesion molecule expression within the microvasculature of human colorectal malignancies

The First Step in Adoptive Cell Immunotherapeutics: Assuring Cell Delivery via Glycoengineering

Despite decades of intensive attention directed to creation of genetically altered cells (e.g., as in development of chimeric antigen receptor (CAR) T-cells) and/or to achieve requisite in vitro accumulation of desired immunologic effectors (e.g., elaboration of virus-specific T cells, expansion of NK cells, differentiation of dendritic cells, isolation, and propagation of Tregs, etc.), there has been essentially no interest in the most fundamental of all hurdles: assuring tissue-specific delivery of administered therapeutic cells to sites where they are needed. With regards to use of CAR T-cells, the absence of information on the efficacy of cell delivery is striking, especially in light of the clear association between administered cell dose and adverse events, and the obvious fact that pertinent cell acquisition/expansion costs would be dramatically curtailed with more efficient delivery of the administered cell bolus. Herein, based on information garnered from studies of human leukocytes and adult stem cells, the logic underlying the use of cell surface glycoengineering to enforce E-selectin ligand expression will be conveyed in the context of how this approach offers strategies to enhance delivery of CAR T-cells to marrow and to tumor beds. This application of glycoscience principles and techniques with intention to optimize cell therapeutics is a prime example of the emerging field of “translational glycobiology.”

Mutually Supportive Mechanisms of Inflammation and Vascular Remodeling

Chronic inflammation is often accompanied by angiogenesis, the development of new blood vessels from existing ones. This vascular response is a response to chronic hypoxia and/or ischemia, but is also contributory to the progression of disorders including atherosclerosis, arthritis, and tumor growth. Proinflammatory and proangiogenic mediators and signaling pathways form a complex and interrelated network in these conditions, and many factors exert multiple effects. Inflammation drives angiogenesis by direct and indirect mechanisms, promoting endothelial proliferation, migration, and vessel sprouting, but also by mediating extracellular matrix remodeling and release of sequestered growth factors, and recruitment of proangiogenic leukocyte subsets. The role of inflammation in promoting angiogenesis is well documented, but by facilitating greater infiltration of leukocytes and plasma proteins into inflamed tissues, angiogenesis can also propagate chronic inflammation. This review examines the mutually supportive relationship between angiogenesis and inflammation, and considers how these interactions might be exploited to promote resolution of chronic inflammatory or angiogenic disorders.

Pro-apoptotic activities of polyphenolics from açai (Euterpe oleracea Martius) in human SW-480 colon cancer cells

This study aimed to evaluate the cell growth inhibition activity of açai (Euterpe oleracea Mart.) polyphenolic extract against colon cancer HT-29 and SW-480 cells and the nonmalignant CCD-18Co colon fibroblast cells. Results showed that açai polyphenolic extract (5-20 mg/L) inhibited preferentially the growth of SW-480 cells with no toxicity in CCD-18Co cells, and this was accompanied by reduction of H2O2-induced reactive oxygen species (ROS) generation. The mechanisms involved in SW-480 cell growth-inhibition by açai polyphenolic extract included the downregulation of NF-κB proinflammatory transcription factor and the nuclear factor-kappa B targets intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Furthermore, prooncogenic specificity proteins (Sp) were downregulated as well as Sp-targets Bcl-2, vascular endothelial growth factor, and survivin. This was accompanied by activation of mitochondrial proapoptotic pathway involving increase of cytochrome c, cleavage of caspase-3, and decrease of PARP-1. Results strongly suggest that açai polyphenolic extract has antiinflammatory and cytotoxic activities in colon cancer cells and can be effective as natural colon cancer chemopreventive agents.

Complex structure of engineered modular domains defining molecular interaction between ICAM-1 and integrin LFA-1

Intermolecular contacts between integrin LFA-1 (α(L)β(2)) and ICAM-1 derive solely from the integrin α(L) I domain and the first domain (D1) of ICAM-1. This study presents a crystal structure of the engineered complex of the α(L) I domain and ICAM-1 D1. Previously, we engineered the I domain for high affinity by point mutations that were identified by a directed evolution approach. In order to examine α(L) I domain allostery between the C-terminal α7-helix (allosteric site) and the metal-ion dependent adhesion site (active site), we have chosen a high affinity variant without mutations directly influencing either the position of the α7-helix or the active sites. In our crystal, the α(L) I domain was found to have a high affinity conformation to D1 with its α7-helix displaced downward away from the binding interface, recapitulating a current understanding of the allostery in the I domain and its linkage to neighboring domains of integrins in signaling. To enable soluble D1 of ICAM-1 to fold on its own, we also engineered D1 to be functional by mutations, which were found to be those that would convert hydrogen bond networks in the solvent-excluded core into vdW contacts. The backbone structure of the β-sandwich fold and the epitope for I domain binding of the engineered D1 were essentially identical to those of wild-type D1. Most deviations in engineered D1 were found in the loops at the N-terminal region that interacts with human rhinovirus (HRV). Structural deviation found in engineered D1 was overall in agreement with the function of engineered D1 observed previously, i.e., full capacity binding to α(L) I domain but reduced interaction with HRV.

Vascular density and endothelial cell expression of integrin alpha v beta 3 and E-selectin in murine tumours

The endothelial cell adhesion molecules, including the integrin alpha v beta 3 (αvβ3) and E-selectin, are involved in the process of angiogenesis required for tumour growth, cell migration and metastasis. The purpose of this study was to assess and compare widely used tumour models to select the ones most suitable for angiogenesis research. Fifteen murine tumours were selected including melanoma (B16), colon (C26, C38, C51), mammary (MA13, MA16, MA16/Adr, MA17, MA17/Adr, MA25, MA44), pancreatic (PO2, PO3), Glasgow osteogenic sarcoma (GOS) and Lewis lung carcinoma (LLC). The tumour vascular density, assessed using the platelet endothelial cell adhesion molecule 1 (PECAM-1; CD31) immunostaining, revealed that B16 melanoma was poorly vascularized (<5 %), whereas the colon and mammary tumours were well vascularized (5-15 %). The most vascularized tumours (>15 %) were the pancreatic tumours (PO2 and PO3), the sarcoma (GOS) and the lung tumour (LLC). The integrin αvβ3 and E-selectin, evaluated by immunohistology, showed that 7/15 tumours expressed the αvβ3 integrin which was homogeneously distributed on all tumour sections (B16, C26, MA17/Adr, MA25, MA44, PO2, LLC). E-selectin was expressed in 4/15 tumours and its expression was restricted to the tumour periphery. Only 2/15 tumours (B16 and C26) were shown to express both integrin αvβ3 and E-selectin. In conclusion, these data not only contribute to a better understanding of the tumour biology of murine tumours but can also guide the choice of appropriate models for antiangiogenic therapy, for selective drug delivery to tumours and the validation of tumour imaging modalities targeting these endothelial cell adhesion molecules.

Inflamed leukocyte-mimetic nanoparticles for molecular imaging of inflammation

Dysregulated host inflammatory response causes many diseases, including cardiovascular and neurodegenerative diseases, cancer, and sepsis. Sensitive detection of the site of inflammation will, therefore, produce a wide-ranging impact on disease diagnosis and treatment. We hypothesized that nanoprobes designed to mimic the molecular interactions occurring between inflamed leukocytes and endothelium may possess selectivity toward diverse host inflammatory responses. To incorporate inflammation-sensitive molecular interactions, super paramagnetic iron oxide nanoparticles were conjugated with integrin lymphocyte function-associated antigen (LFA)-1 I domain, engineered to mimic activated leukocytes in physiology. Whole body optical and magnetic resonance imaging in vivo revealed that leukocyte-mimetic nanoparticles localized preferentially to the vasculature within and in the invasive front of the tumor, as well as to the site of acute inflammation. This study explored in vivo detection of tumor-associated vasculature with systemically injected inflammation-specific nanoparticles, presenting a possibility of tumor detection by inflamed tumor microenvironment.

Carcinoembryonic antigen-stimulated THP-1 macrophages activate endothelial cells and increase cell–cell adhesion of colorectal cancer cells

The liver is the most common site for metastasis by colorectal cancer, and numerous studies have shown a relationship between serum carcinoembryonic antigen (CEA) levels and metastasis to this site. CEA activates hepatic macrophages or Kupffer cells via binding to the CEA receptor (CEA-R), which results in the production of cytokines and the up-regulation of endothelial adhesion molecules, both of which are implicated in hepatic metastasis. Since tissue macrophages implicated in the metastatic process can often be difficult to isolate, the aim of this study was to develop an in vitro model system to study the complex mechanisms of CEA-induced macrophage activation and metastasis. Undifferentiated, human monocytic THP-1 (U-THP) cells were differentiated (D-THP) to macrophages by exposure to 200 ng/ml phorbol myristate acetate (PMA) for 18 h. Immunohistochemistry showed two CEA-R isoforms present in both U- and D-THP cells. The receptors were localized primarily to the nucleus in U-THP cells, while a significant cell-surface presence was observed following PMA-differentiation. Incubation of D-THP-1 cells with CEA resulted in a significant increase in tumor necrosis factor-alpha (TNF-alpha) release over 24 h compared to untreated D-THP-1 or U-THP controls confirming the functionality of these cell surface receptors. U-THP cells were unresponsive to CEA. Attachment of HT-29 cells to human umbilical vein endothelial cells significantly increased at 1 h after incubation with both recombinant TNF-alpha and conditioned media from CEA stimulated D-THP cells by six and eightfold, respectively. This study establishes an in vitro system utilizing a human macrophage cell line expressing functional CEA-Rs to study activation and signaling mechanisms of CEA that facilitate tumor cell attachment to activated endothelial cells. Utilization of this in vitro system may lead to a more complete understanding of the expression and function of CEA-R and facilitate the design of anti-CEA-R therapeutic modalities that may significantly diminish the metastatic potential of CEA overexpressing colorectal tumors.

Hurdles to lymphocyte trafficking in the tumor microenvironment: implications for effective immunotherapy

An important consideration in the development of T cell-based cancer immunotherapy is that effector T cells must efficiently traffic to the tumor microenvironment in order to control malignant progression. T cell trafficking to target tissues is orchestrated by dynamic interactions between circulating lymphocytes and endothelial cells lining blood vessels. It is informative, in this regard, to compare and contrast the molecular mechanisms governing lymphocyte extravasation at distinct vascular sites: (1) high endothelial venules (HEV) of secondary lymphoid organs, which are portals for efficient trafficking of naive and central memory T lymphocytes; (2) non-activated endothelium of normal tissues that mediate relatively low basal levels of trafficking but are rapidly transformed into HEV-like vessels in response to local inflammatory stimuli; and (3) vessels within the intratumoral region and the surrounding peritumoral areas. These vessels can be distinguished by differential expression of hallmark trafficking molecules that function as molecular beacons directing lymphocyte migration across vascular barriers. This article reviews evidence that recruitment of effector T cells to the intratumoral microenvironment is impeded by sub-threshold expression of trafficking molecules on tumor microvessels. Emerging data support the thesis that when considered from the perspective of extravasation, vessels embedded within the intratumoral microenvironment of established tumors do not exhibit stereotypical characteristics of a chronic inflammatory state. A major challenge will be to develop therapeutic approaches to improve trafficking of effector T lymphocytes to tumor sites without skewing the balance in favor of a chronic inflammatory milieu that facilitates tumor maintenance and progression.

Detection of vascular expression of E-selectin in vivo with MR imaging

PURPOSE

To develop a contrast agent for targeting E-selectin expressed on activated vascular endothelium and to evaluate detection of the agent with magnetic resonance (MR) imaging in an in vivo mouse model of inflammation.

MATERIALS AND METHODS

All animal experiments were approved according to animal welfare and local ethics committee regulations. An anti-murine E-selectin F(ab')2 monoclonal antibody, MES-1, was conjugated with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles. Flow cytometry, Perl Prussian blue staining for iron, and MR imaging were performed by using Chinese hamster ovary (CHO) cells expressing mouse E-selectin to detect binding of the conjugate in vitro, and a mouse model of contact hypersensitivity to oxazolone in the ear was used to investigate the in vivo characteristics of the MES-1-USPIO. Serial imaging was performed by using a 9.4-T MR imaging system with a custom receive-only coil. Tissue slices were stained to define distribution of E-selectin expression and localization of the MES-1-USPIO conjugate.

RESULTS

MES-1-USPIO was shown to bind to CHO cells expressing mouse E-selectin in vitro. After injection of MES-1-USPIO in vivo, distinct changes in R2 relaxation rate (1/T2) characteristics were detected in inflamed ears when they were compared with control ears. Histologic analysis confirmed the vascular endothelial distribution of MES-1-USPIO.

CONCLUSION

E-selectin expression in vivo can be selectively and directly imaged noninvasively with MR. This has the potential to be useful in the study of inflammatory disease.

Characteristics of tumor-associated endothelial cells derived from glioblastoma multiforme

Glioblastomas multiforme (GBMs) are highly vascular brain tumors characterized by abnormal vessel structures in vivo. This finding supports the theory that glioma-associated endothelial cells (ECs) have intrinsically different properties from ECs in normal human brain. Therefore, identification of the functional and phenotypic characteristics of tumor-associated ECs is essential for designing a rational antiangiogenic therapy. The GBM-associated ECs have a large, flat, and veil-like appearance, in contrast to normal ones, which are small and plump. Although the tumor ECs have the typical markers, they proliferate more slowly than these cell types in normal brain. The GBM-associated ECs are resistant to cytotoxic drugs, and they undergo less apoptosis than control cells. Also, GBM-associated ECs migrate faster than controls and constitutively produce high levels of growth factors such as endothelin-1, interleukin-8, and vascular endothelial growth factor. An understanding of these unique characteristics of glioma-associated ECs is important for the development of novel antiangiogenic agents that specifically target tumor-associated ECs in gliomas.

Dynamic control of lymphocyte trafficking by fever-range thermal stress

Migration of blood-borne lymphocytes into tissues involves a tightly orchestrated sequence of adhesion events. Adhesion molecules and chemokine receptors on the surface of circulating lymphocytes initiate contact with specialized endothelial cells under hemodynamic shear prior to extravasation across the vascular barrier into tissues. Lymphocyte-endothelial adhesion occurs preferentially in high endothelial venules (HEV) of peripheral lymphoid organs. The continuous recirculation of naïve and central memory lymphocytes across lymph node and Peyer's patch HEV underlies immune surveillance and immune homeostasis. Lymphocyte-endothelial interactions are markedly enhanced in HEV-like vessels of extralymphoid organs during physiological responses associated with acute and chronic inflammation. Similar adhesive mechanisms must be invoked for efficient trafficking of immune effector cells to tumor sites in order for the immune system to have an impact on tumor progression. Here we discuss recent evidence for the role of fever-range thermal stress in promoting lymphocyte-endothelial adhesion and trafficking across HEV in peripheral lymphoid organs. Findings are also presented that support the hypothesis that lymphocyte-endothelial interactions are limited within tumor microenvironments. Further understanding of the molecular mechanisms that dynamically promote lymphocyte trafficking in HEV may provide the basis for novel approaches to improve recruitment of immune effector cells to tumor sites.

Association between serum carcinoembryonic antigen and endothelial cell adhesion molecules in colorectal cancer

OBJECTIVES

To analyse the behaviour of pre-surgical serum levels of soluble (s)E-selectin and vascular cell adhesion molecule (sVCAM) in patients with colorectal cancer, and to evaluate their possible correlation with carcinoembryonic antigen (CEA), pro-inflammatory cytokines and clinicopathological features with respect to their prognostic value in predicting metastatic disease.

METHODS

Pre-surgical serum levels of sE-selectin, sVCAM, interleukin-6 (IL-6), IL-1beta, tumour necrosis factor-alpha (TNF-alpha) and CEA were measured in 194 patients with colorectal adenocarcinoma, 40 patients with benign colorectal diseases and 59 healthy subjects.

RESULTS

sE-selectin, sVCAM, TNF-alpha and IL-6 levels were significantly higher in patients with colorectal cancer compared to either healthy subjects or patients with benign disease. Positive rates of sE-selectin, sVCAM and TNF-alpha levels were significantly associated with Dukes' stage D colorectal cancer, and all three variables were independently associated to the presence of distant metastases. Positive sE-selectin, sVCAM and TNF-alpha levels were significantly associated to CEA. TNF-alpha and CEA levels were independently related to the presence of positive levels of sE-selectin and/or sVCAM.

CONCLUSIONS

Our findings suggest that the host inflammatory response to cancer cells, and/or their released products (i.e. CEA), might be responsible (via cytokine release) for the elevation in circulating adhesion molecules in patients with colorectal cancer.

Clinical significance of serum levels of E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 in gastric cancer patients

OBJECTIVES

This study evaluated serum concentrations of soluble cell adhesion molecules in patients with gastric cancer and in healthy control subjects. Our objectives were to correlate these levels with clinicopathological features, established tumor markers, and patient survival, and to assess changes in serum levels of cell adhesion molecules after tumor surgery.

METHODS

The serum concentrations of the adhesion molecules E-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) were investigated by ELISA in 57 gastric cancer patients, both before and 7 days after surgery, and in 47 healthy control subjects.

RESULTS

Preoperative serum concentrations of ICAM-1 and VCAM-1 in gastric cancer patients were significantly higher when compared with those of healthy controls, whereas there were no differences regarding serum E-selectin levels. Serum levels of E-selectin, ICAM-1, and VCAM-1 correlated significantly with each other. There was a significant association between preoperative levels of all three adhesion molecules and disease stage, gastric wall invasion, lymph node involvement, and presence of distant metastases. Their concentrations decreased significantly after radical resection of the tumor, whereas they remained almost unchanged in patients with unresectable disease. Elevated preoperative serum levels of E-selectin, ICAM-1, and VCAM-1 levels were found in 24.6%, 33.3%, and 28.1% of patients, respectively. Elevated levels of all three molecules were significant prognostic factors for patient survival but not independent of disease stage.

CONCLUSIONS

These findings suggest that serum concentrations of E-selectin, ICAM-1, and VCAM-1 may reflect tumor progression and metastasis, and may be clinically useful.

Leukocyte recruitment in colon cancer: role of cell adhesion molecules, nitric oxide, and transforming growth factor beta1

BACKGROUND & AIMS

A deficient leukocyte recruitment has been suggested in tumor vasculature, but little is known about the underlying molecular mechanism. To characterize leukocyte-endothelium interaction in experimental colon cancer, quantify the main endothelial cell adhesion molecules (CAMs), and evaluate the effect of tumor-derived products.

METHODS

Leukocyte recruitment was assessed by intravital videomicroscopy in mice bearing HT29-derived tumors. Endothelial CAMs were measured using the dual-radiolabeled antibody technique. The role of molecules mediating leukocyte rolling (P-, E-, and L-selectin) or adhesion (intercellular adhesion molecule 1 [ICAM-1] and vascular cell adhesion molecule 1 [VCAM-1]) carcinoembryonic antigen (CEA), and transforming growth factor (TGF) beta1 was assessed through immunoblockade, whereas participation of nitric oxide (NO) and cyclooxygenase (COX) metabolites were evaluated by means of nonselective and selective inhibition.

RESULTS

Basal and lipopolysaccharide-stimulated leukocyte rolling and adhesion were markedly reduced in tumor vasculature. ICAM-1 immunoblockade prevented leukocyte adhesion in both tumor and nontumor microvessels. Neither baseline nor LPS-induced endothelial ICAM-1, P-, and E-selectin expression in tumors were reduced with respect to nontumor vasculature. Although VCAM-1 expression was reduced in tumor endothelium, immunoneutralization of VCAM-1 failed to reverse LPS-induced leukocyte recruitment in this setting. CEA immunoblockade and COX inhibition did not modify the deficient leukocyte rolling. Nonselective NO inhibition partially reversed the defective adhesion response in tumor microvessels. Finally, TGF-beta1 immunoblockade partially and selectively restored impaired leukocyte rolling and adhesion in tumor microvessels.

CONCLUSIONS

Impaired leukocyte recruitment in tumor vasculature cannot be attributed to a depressed expression of the main CAMs. Selective restoration after NO inhibition and TGF-beta1 immunoblockade suggests involvement of both molecules in this phenomenon.

Serum levels of E-selectin, ICAM-1 and VCAM-1 in colorectal cancer patients: correlations with clinicopathological features, patient survival and tumour surgery

The serum concentrations of the cell adhesion molecules E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were investigated in 63 patients with colorectal cancer and in 51 controls by an enzyme-linked immunosorbent assay (ELISA). Their relationship to clinicopathological variables and patient survival and changes in their levels after surgery were examined. Colorectal cancer patients showed significantly higher serum levels of E-selectin, ICAM-1 and VCAM-1 compared with healthy controls. There was a significant association between the serum levels of these molecules, disease stage and the presence of both lymph node and distant metastases. Both ICAM-1 and VCAM-1 levels correlated with serum E-selectin and carcinoembryonic antigen (CEA) levels. Serum levels of all three molecules decreased significantly after radical resection of the tumour. Elevated pre-operative E-selectin, ICAM-1 and VCAM-1 levels were significant prognostic factors, although not independent of stage, for patient survival. These findings suggest that serum concentrations of E-selectin, ICAM-1 and VCAM-1 may reflect tumour progression and metastasis. Since these markers are linked to CEA levels, it is uncertain whether their measurement will prove cost-effective in colorectal cancer management.

Relationship of vascular maturation in breast cancer blood vessels to vascular density and metastasis, assessed by expression of a novel basement membrane component, LH39

Angiogenesis, the formation of new vessels, has been demonstrated to be an indicator of prognosis in breast cancer patients. The extent of differentiation of the tumour vessels may affect access of peripheral white cells and egress or invasion of tumour cells. This has not been assessed in relation to tumour microvessel density or other variables and may be a marker of vascular remodelling. LH39 is a monoclonal antibody recognizing an epitope located at the lamina lucida of mature small veins and capillaries but not in newly formed vessels. To study vascular differentiation in breast tumours, we examined the vascular maturation index (VMI) in 12 normal and 50 breast carcinomas and this was correlated with different clinicopathological variables including angiogenesis. Mature vessels were defined by staining with antibodies to both LH39 and to CD31, using double immunohistochemistry, whereas immature vessels stained only for CD31. VMI was defined as the % fraction of mature vessels (LH39-positive) / total number of vessels (CD31-positive). The VMI was significantly higher in normal (54-68.5%; median 66.5%) than in tumours (0-47%; median 8.8%) (P = 0.0005). There was a significant inverse correlation between the tumour VMI and nodal status (Fisher's exact test, P = 0.01) and between high VMI and low thymidine phosphorylase (TP) expression (Mann-Whitney U-test, P= 0.01). No significant association between VMI and tumour size, oestrogen receptor, epidermal growth factor receptor, grade, angiogenesis, patient age, or E-selectin was seen. There was a significant reduction in relapse-free survival (P = 0.01) with high angiogenesis. These findings show that the VMI gives new information on the mechanism of tumour angiogenesis independently from microvessel quantitation, there is a wide variation in the differentiation of tumour vasculature but the degree of capillary differentiation is not associated with quantitative angiogenesis. The VMI identifies a subset of patients who have a high chance of regional node involvement.

Quantification of murine endothelial cell adhesion molecules in solid tumors

Coordinated adhesive interactions between lymphocyte receptors and endothelial cell adhesion molecules (CAMs) are a prerequisite for effector cell entry into tumor stroma. Whereas the diminished leukocyte-endothelial cell interactions observed in tumor microvessels have been attributed to a reduced expression of endothelial CAMs, there is no quantitative data bearing on this issue. The dual-radiolabeled monoclonal antibody technique was used to quantify constitutive and tumor necrosis factor (TNF)-alpha-induced expression of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), ICAM-2, P-selectin, E-selectin, and platelet-endothelial cell adhesion molecule 1 (PECAM-1) in different vascular beds of normal (C57Bl/6) and RM-1 tumor-bearing mice. When corrected for endothelial surface area, the constitutive expression of selectins in tumor vessels was higher than that observed in other vascular beds. Both constitutive and induced expression of endothelial CAMs in peripheral vascular beds did not differ between normal and tumor-bearing mice. Within the tumor, the magnitude of the upregulation of P-selectin, ICAM-1, and VCAM-1 after TNF-alpha was similar to that within other vascular beds. E-selectin expression in tumors was refractory to TNF-alpha, whereas PECAM-1 and ICAM-2 expression were significantly reduced. Our findings suggest that the presence of a solid tumor does not influence endothelial CAM expression in other vascular beds and that the higher density of selectins in nonstimulated tumor vessels may promote the recruitment of rolling leukocytes in this tissue.

Angiogenesis modulates the tumour immune response

Outgrowth of solid tumors and metastases is dependent on the process of angiogenesis. Tumors escape from the formation of an effective infiltrate by downregulation of endothelial adhesion molecules. This downregulation of adhesion receptors is governed by the exposure to angiogenic factors. In recent years proof for this has been provided by demonstrating that freshly isolated tumor endothelial cells exhibit a decreased expression of ICAM-1 and -2 as compared to endothelial cells in normal tissue. In addition, adhesion molecules are downregulated on normal tissue endothelial cells when cultured with angiogenesis stimulators such as basic fibroblast growth factor and vascular endothelial cell growth factor, while under these conditions endothelial cells become less responsive to cytokines such as tumor necrosis factor-alpha with respect to the upregulation of endothelial adhesion molecules. Very recently it has been demonstrated that this harmful endothelial cell anergy can be counteracted by inhibitors of angiogenesis.

Serum concentrations of soluble adhesion molecules in patients with colorectal cancer

The concentrations of the soluble adhesion molecules E-cadherin, E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were investigated in 48 patients with colorectal cancer before treatment, and their relation to clinical, histological and routine laboratory parameters was examined. Data were collected on tumour stage at presentation, presence and sites of metastatic disease, tumour pathology and results of routine laboratory tests. Serum concentrations of ICAM-1 and VCAM-1 were significantly elevated in the patients with colorectal cancer in comparison with a group of healthy subjects (P < 0.00001). Levels of circulating ICAM-1 and VCAM-1 were increased both in patients with local and those with metastatic disease. Although elevated in some patients soluble E-cadherin and E-selectin concentrations were not significantly elevated compared with the control group (P = 0.71 and P = 0.052 respectively). The levels of circulating ICAM-1 were significantly correlated with those of VCAM-1 and E-selectin. A correlation was also found between the serum concentrations of E-selectin and ICAM-1 and alkaline phosphatase, total white cell count and platelet count. VCAM-1 was positively correlated with age and negatively with degree of tumour differentiation and haemoglobin concentration. The biological implications and possible clinical relevance of these findings are discussed.

Angiogenesis as a biologic and prognostic indicator in human breast carcinoma

In this review we describe angiogenesis pathways involved in the development of breast carcinoma. Different assessment techniques for angiogenesis and their optimisation are discussed. Angiogenesis is an important factor for prognosis and will be increasingly important in therapeutic decisions.

Tumor vascular endothelium: barrier or target in tumor directed drug delivery and immunotherapy

The therapy of solid tumors with conventional chemotherapeutics, drug delivery preparations and immunomodulatory agents directed against the tumor cells is corrupted by a major barrier presented by the tumor vasculature. Permeability of the tumor blood vessels for transport of small molecules and macromolecular drug-carrier conjugates is only sufficient in the blood vessels at the tumor-host interface. Downregulation of the expression of adhesion molecules, required for the facilitation of immune cell recruitment, by the tumor vascular endothelium results in an escape of the tumor from host defence. New therapeutic approaches for the treatment of solid tumors are aimed at the tumor vasculature, either at the endothelial cells themselves or at basement membrane or tumor stroma components. Angiogenesis can be directly blocked with angiogenesis inhibitors, while angiogenesis related factors can serve as tumor vasculature specific epitopes for drug delivery strategies. Some glycoproteins expressed by tumor endothelial cells or present in the basement membrane and tumor stroma are also potential tumor selective targets. Therapeutic modalities that are suitable for site specific delivery are agents that increase tumor accumulation of (targeted) chemo/radiotherapeutics through increasing tumor vascular permeability. The observation that for tumor growth the blood supply is a limiting factor, led to the development of strategies to inhibit angiogenesis or block the tumor blood flow. Manipulation of the expression of endothelial cell adhesion molecules by selectively delivering modulatory agents at or in the tumor vascular endothelial cells may induce (bispecific antibody mediated) host defense activity directed against the tumor cells.

Leukocyte-endothelial adhesion and angiogenesis in tumors

Leukocyte-endothelial adhesion and angiogenesis, until recently considered as separate processes, have been shown to be linked by two recent findings: soluble cellular adhesion molecules (CAMs) involved in leukocyte-endothelial interactions are angiogenic and well known angiogenic molecules secreted by cancer or immune. cells can modulate the endothelial CAMs. This molecular link may partially explain why the overall leukocyte-endothelial interaction is often low and heterogeneous in angiogenic tumor vessels and why activated lymphocytes adhere nonuniformly to tumor vessels when injected into the tumor's blood supply.

The increased expression of adhesion molecules ICAM-3, E- and P-selectins on breast cancer endothelium

Sequential interaction of neoplastic cells with the endothelium of tumour neovasculature is believed to be a significant step in tumour metastasis. Increasing evidence suggests that inducible endothelial adhesion molecules are intimately involved in this process. An immunohistochemical approach was used to examine the expression of adhesion molecules in 14 normal controls and a series of 64 invasive breast carcinomas. Endothelium in normal breast showed constitutive expression of PECAM (100 per cent), ICAM-2 (100 per cent), and P-selectin (64 per cent); variable and focal expression of ICAM-1 (71 per cent); and only weak staining for E-selectin (21 per cent). No ICAM-3 or VCAM-1 expression was observed. Similarly to normal breast endothelium, widespread and intense immunoreactivity on the endothelium of tumour-associated vessels was seen for PECAM (100 per cent), ICAM-1 (69 per cent), and ICAM-2 (95 per cent). In contrast to normal tissues, E- and P-selectins showed increased intensity of staining (52 and 67 per cent of cases, respectively) and expression of E- and P-selectins was more prominent at the tumour periphery. ICAM-3 expression was increased on tumour endothelium (15 per cent of cases), but in common with VCAM-1 (10 per cent) expression was focal. A previously unreported finding was the immunoreactivity of the neoplastic epithelial cells for the non-epithelial lineage markers ICAM-1 (34 per cent), ICAM-3 (10.9 per cent), PECAM (1.6 per cent), and E- and P-selectins (7 and 37 per cent of cases, respectively). These findings show that tumour endothelium displays significant heterogeneity and can assume a pro-inflammatory phenotype, probably as a result of cytokine stimulation. Upregulation of adhesion molecules might contribute to changes in invasive phenotype by promoting endothelial cell adhesion and angiogenesis, as well as forming a substratum for tumour cells to assemble and attract macrophages.

Microvascular expression of MALA-2 correlates with in vivo lymphocyte trafficking and is preferentially enhanced in tumors by tumor necrosis factor-alpha and interleukin-1 alpha

The role of endothelial cell adhesion molecule expression in the immune response to tumors is unknown. We have investigated the expression of murine lymphocyte activation antigen (MALA-2), the murine equivalent of intercellular adhesion molecule-1 (ICAM-1), in blood vessels of normal murine tissues and in melanoma tumors and evaluated the relationship between MALA-2 expression and lymphocyte trafficking in vivo. C3H/HeN mice were injected both i.p. and s.c. with a clone of K-1735 syngeneic melanoma cells. Day 11 tumor-bearing mice were killed and vascular expression of MALA-2 was quantified using immunohistochemistry. MALA-2 expression was high in lung, liver and spleen and low in lymph node, small bowel, muscle and tumor. Systemic administration of either recombinant tumor necrosis factor alpha (rTNF alpha) or recombinant interleukin-1 alpha (rIL-1 alpha) over 2 days prior to organ harvest resulted in an increase in the number of tumor vessels expressing MALA-2, with no change in MALA-2 expression in other tissues. In vivo lymphocyte trafficking was evaluated using cultured, activated splenocytes radiolabeled with 111In. 111In-labeled splenocyte distribution correlated closely with MALA-2 expression, with high localization to spleen, liver and lung and poor localization to lymph node, small bowel, muscle and tumor. Systemic administration of rTNF alpha, but not rIL-1 alpha, resulted in a significant increase in 111In-labeled splenocyte distribution to tumor, but neither rTNF alpha nor IL-1 alpha altered 111In-labeled splenocyte distribution to normal organs. Our data demonstrate the in vivo pattern of vascular MALA-2 expression in normal murine tissues and tumors and suggest that the expression of MALA-2 can be preferentially enhanced in tumors by systemic administration of cytokines. Lymphocyte distribution in vivo correlates closely with the pattern of MALA-2 expression, and these data support the conclusion that MALA-2 plays an important role in the regulation of lymphocyte trafficking.