Adhesion molecules and tumor cell interaction with endothelium and subendothelial matrix

Mechanisms of bone metastasis in prostate cancer: clinical implications

Prostate cancer shows a strong predilection to spread to the bones. Once prostate tumour cells are engrafted in the skeleton, curative therapy is no longer possible and palliative treatment becomes the only option. Herein, we review the multifactorial mechanisms and complex cellular interactions that take place inside the bone metastatic microenvironment. Emphasis is given to the detection and treatment of the micrometastatic stage of prostate cancer, as well as our recent attempts to target the bone metastasis microenvironment-related survival factors using an anti-survival factor manipulation which can increase the efficacy of anticancer therapies such as androgen ablation therapy and chemotherapy in advanced prostate cancer.

Beyond angiogenesis: the role of endothelium in the bone marrow vascular niche

Specific tissue microenvironments, or niches, are critical for homing and maintenance of both stem cells and tumor cells in vivo. Little is known, however, about the molecular interactions between individual cells within these microenvironments. Recent studies that describe a newly identified hematopoietic stem and tumor cell vascular niche in the bone marrow (BM) suggest a critical role for vascular endothelial cell signaling and raise the possibility that bidirectional interactions of these cells with the vasculature regulate the niche dynamically. The mechanisms that govern hematopoietic stem cell (HSC)/tumor cell cross-talk with endothelial cells provide a promising new direction for future studies. Here we review recent advances that open new avenues of study in this field.

Adhesion molecules and chemokines: the navigation system for circulating tumor (stem) cells to metastasize in an organ-specific manner

To date, cancer is still the second most prevalent cause of death after cardiovascular diseases in the industrialized word, whereby the primary cause of cancer is not attributed to primary tumor formation, but rather to the growth of metastases at distant organ sites. For several years it was considered that the well-known phenomenon of organ-specific spreading of tumor cells is mostly a mechanical process either directed passively due to size constraints (mechanical trapping theory) or due to a fertile environment provided by the organ in which tumor cells can proliferate (seed and soil hypothesis). Both mechanisms strongly depend on the adhesive properties of tumor cells either to endothelial cells and/or cancer cells, which are facilitated by a variety of cell adhesion molecules including carbohydrates and integrins. Within the past years it became evident that the organ-specific metastatic spreading of tumor cells does not only rely on heterotypic and homotypic adhesive interactions, but also on the interplay of chemokines and their appropriate receptors. Moreover, the identification of cancer stem cells in various tumor tissues has opened new questions. Cancer stem cells possess self-renewal, differentiation, and tumor-initiating capacities. Thus these cells are ideal candidates to be the seed of a secondary tumor. In the present review we will give a brief overview about the complex process of organ-specific metastasis formation depending on the interplay of adhesion molecules, chemokines, and the putative role of cancer stem cells in metastasis formation.

Role of nitric oxide in the development of distant metastasis from squamous cell carcinoma

BACKGROUND

Metastasis, the dissemination of malignant cells to distant sites, remains one of the most significant factors responsible for death from cancer. Recent studies have shown some improvement in the rate of distant metastasis (DM) with the addition of chemotherapy to surgery and radiation for treatment of head and neck squamous cell carcinoma (HNSCC). However, diagnosis and treatment at an early stage ultimately leads to a better prognosis. The prediction of which patients will develop metastasis and the selection of treatment most effective at preventing and treating metastasis remains dependent on an incomplete understanding of prognostic factors and the biological and molecular basis for metastatic development. This study was undertaken using an in vivo model to investigate the possible role of nitric oxide (NO) in the development of metastasis from HNSCC. The findings will result in better understanding of the metastatic process for HNSCC, with the potential to develop and implement therapies that could prevent and treat metastasis in patients.

OBJECTIVES/HYPOTHESIS

1) To analyze whether in vivo videomicroscopy (IVVM) is useful for the study of DM from squamous cell carcinoma of the head and neck; 2) with use of IVVM, investigate the effect of the biological mediators NO and interleukin (IL)-1 on the adhesion of circulating human HNSCC cells in the hepatic microcirculation.

STUDY DESIGN

Prospective study using an animal model.

METHODS

Phase 1: athymic nude rats and mice were used for IVVM experiments. The cremaster muscle and liver, used as arterial and venous flow models, were tested to determine whether IVVM was useful for the study of human HNSCC interactions with the microcirculation. A human squamous cell carcinoma cell line (FaDu) labeled with the intracytoplasmic fluorescent marker BCECF-am. was used for all experiments. Videomicroscopic images of FaDu cells in the microcirculation were analyzed for cell adhesion, morphology, deformation, circulation, location of adhesion within the microcirculation, and alteration of microvascular circulation. Phase 2: the effect of IL-1, NO, and NO inhibitors on HNSCC cell adhesion in the hepatic microcirculation of nude mice was analyzed by IVVM. This was followed by histologic determination of the ratio of FaDu cells present for liver area analyzed. Nude mice were treated with 1) IL-1; 2) L-arginine (an NO substrate); or 3) L-N-monomethyl-L-arginine (an NO synthase inhibitor) alone or in combination. These data were analyzed statistically to determine the effect on cell adhesion in the liver.

RESULTS

IVVM provided a method for the study of circulating HNSCC with the microcirculation in both the cremaster and liver models. FaDu cells were arrested at the inflow side of the circulation, with maintenance of cell integrity. L-arginine and IL-1 both increased FaDu cell arrest in the liver above baseline (P = .00008 and P = .03), and the combination of these agents potentiated the effect (P = .000009).

CONCLUSIONS

IVVM allows direct assessment of circulating HNSCC with the microcirculation and is a powerful model for the study of DM. NO and IL-1 play a role in increasing the arrest of HNSCC in the liver and are important in the generation of DM in patients with HNSCC.

Consistent liver metastases in a rat model by portal injection of microencapsulated cancer cells

Consistent liver metastases in animal models is generally observed only with certain cancer cell lines. With the aim of improving on existing animal models of liver metastases, we hypothesized that cancer cells encased in 300 microm microcapsules, mimicking micrometastatic foci, might be effective seeds of liver metastases. A total of 3,000 microcapsules, containing 700 to 1,500 viable cells/capsule in logarithmic growth phase of three human pancreatic cancer cell lines (SUIT-2, AsPC-1, and BxPC-3), were transplanted in nude rats by portal injection. The rate of liver metastases was 100% (12 of 12), 100% (6 of 6), and 83% (5 of 6) for SUIT-2, AsPC-1, and BxPC-3 microcapsules, respectively. In contrast, the administration of an identical number of single cancer cells (2.1-4.5 x 10(6)) did not lead to liver metastases. Metastases was strictly limited to the liver, was quite stable, and could be proportionately tailored by varying the number of cancer microcapsules administered. Microscopic observation showed that two-thirds of the cancer microcapsules were lodged in the peripheral small (20-50 microm) portal veins, although one-third of the cancer microcapsules were trapped in the central wide (200-400 microm) portal vein. Capsules began to burst at day 3, with recognizable metastases produced at day 7, resulting in overt metastases production at days 28 to 42. The present cancer microcapsule method may be useful for obtaining liver metastases in animal models, especially for cell lines that will not form liver metastases with conventional single cell injection methods and/or for experiments requiring the consistent formation of liver metastases.

Intravascular cell-to-cell adhesive interactions and bone metastasis

Metastatic cancer spread to bones, causing intractable pain, pathological fractures, spinal cord compression, and ultimately death, represents massive clinical problem. Intravascular cell-to-cell heterotypic (between cancer and other types of cells) and homotypic (between cancer cells) adhesive interactions, leading to the establishment of metastatic deposits in bone marrow vasculature, represent important rate-limiting steps in bone metastasis. In this review, we discuss molecular and cellular mechanisms underpinning metastasis-associated intravascular cell-to-cell adhesive interactions, their role in a multi-step metastatic cascade, and a potential for therapeutic targeting of early metastasis-associated adhesive events.

The metastatic cascade in prostate cancer

Morbidity and mortality due to prostate cancer are mainly a result of prostate cancer metastases. After the initial neoplastic transformation of cells, the process of metastasis involves a series of sequential steps, which involve neoangiogenesis and lymphangiogenesis, loss of adhesion with migration away from the primary tumour and entry into the systemic vasculature or lymphatics. Metastatic growth in sites such as lymph nodes and bone marrow then involves the specific non-random homing of prostate cancer cells. An appreciation and understanding of this metastatic cascade in relation to prostate cancer is clinically important in order to stratify men with prostate cancer into prognostic groups. Moreover, it is crucial in the future development of therapies that can prevent metastases.

Inhibition of B16 Melanoma Metastases with the Ruthenium Complex Imidazoliumtrans-Imidazoledimethylsulfoxide-tetrachlororuthenate and Down-Regulation of Tumor Cell Invasion

The antimetastatic ruthenium complex imidazolium trans-imidazoledimethylsulfoxide-tetrachlorouthenate (NAMI-A) is tested in the B16 melanoma model in vitro and in vivo. Treatment of B6D2F1 mice carrying intra-footpad B16 melanoma with 35 mg/kg/day NAMI-A for 6 days reduces metastasis weight independently of whether NAMI-A is given before or after surgical removal of the primary tumor. Metastasis reduction is unrelated to NAMI-A concentration, which is 10-fold lower than on primary site (1 versus 0.1 mM), and is correlated to the reduction of plasma gelatinolitic activity and to the decrease of cells expressing CD44, CD54, and integrin-beta(3) adhesion molecules. Metastatic cells also show the reduction of the S-phase cells with accumulation in the G(0)/G(1) phase. In vitro, on the highly metastatic B16F10 cell line, NAMI-A reduces cell Matrigel invasion and its ability to cross a layer of endothelial cells after short exposure (1 h) to 1 to 100 microM concentrations. In these conditions, NAMI-A reduces the gelatinase activity of tumor cells, and it also increases cell adhesion to poly-L-lysine and, in particular, to fibronectin, and this effect is associated to the increase of F-actin condensation. This work shows the selective effectiveness of NAMI-A on the metastatic melanoma and suggests that metastasis inhibition is due to the negative modulation of tumor cell invasion processes, a mechanism in which the reduction of the gelatinolitic activity of tumor cells plays a crucial role.

Platelet-Mimicry of Cancer Cells: Epiphenomenon with Clinical Significance

Stem cell mimicry of cancer cells has been known for a long time and is considered to be responsible for ectopic gene expressions. The stem cell characteristics of tumor cells are shown to be involved in epithelial-mesenchymal transition and in the phenomenon of vascular mimicry. Certain cancer types acquire a geno-phenotype closely resembling the platelets and express several megakaryocytic genes (adhesion receptors alpha IIb beta 3, thrombin receptor and PECAM/CD 31 and/or platelet-type 12-LOX) able to activate the coagulation cascade or the platelets themselves. Here we define these potentials as platelet mimicry of cancer cells typical of pancreatic, breast, prostate, colorectal and urogenital cancers and melanoma. Data all support that platelet mimicry of certain cancer types is an important factor in their hematogenous dissemination and provides an attractive therapeutic target. Besides the long-available preclinical data, clinical trials have only recently provided evidence that targeting platelet mimicry of cancers is an efficient way to prevent tumor progression. The systematic discovery of the markers of platelet mimicry in various cancer types and their molecular targeting may provide new supportive therapeutic modalities for the management of the progressing disease.

GLB prevents tumor metastasis of Lewis lung carcinoma by inhibiting tumor adhesion actions

AIM

To investigate the inhibitory effect of a new compound of GLB on tumor metastasis in vivo and analyze its actions on tumor cell adhesion to clarify its mechanism.

METHODS

The effect of GLB on tumor metastasis was analyzed by Lewis lung carcinoma model. The pathological morphology of lung alveolar was evaluated by hematoxylin-eosin staining. The effect of GLB on the proliferation of human prostate cancer cell (PC-3M, with a high metastatic characteristic) was studied using the MTT method, and its actions on PC-3M cell adhesion to human umbilical vein endothelial cells (HUVEC) and laminin were analyzed in vitro.

RESULTS

GLB (100 mg/kg/d for 28 d, ig) reduced the number of lung colonies of Lewis lung carcinoma metastasis significantly (P<0.05). Simultaneously, GLB could mitigate the damage of lung alveolar caused by metastasic tumor deposits. In vitro, GLB inhibited dramatically the adhesion of PC-3M cells to HUVEC (P< 0.01) and laminin (P<0.05), without cytotoxic or anti-proliferative action on PC-3M cells.

CONCLUSION

GLB has anti-tumor metastatic activity, which partly depends on its inhibition of tumor adhesion.

In vivo imaging of specialized bone marrow endothelial microdomains for tumour engraftment

The organization of cellular niches is known to have a key role in regulating normal stem cell differentiation and regeneration, but relatively little is known about the architecture of microenvironments that support malignant metastasis. Using dynamic in vivo confocal imaging, here we show that murine bone marrow contains unique anatomic regions defined by specialized endothelium. This vasculature expresses the adhesion molecule E-selectin and the chemoattractant stromal-cell-derived factor 1 (SDF-1) in discrete, discontinuous areas that influence the homing of a variety of tumour cell lines. Disruption of the interactions between SDF-1 and its receptor CXCR4 inhibits the homing of Nalm-6 cells (an acute lymphoblastic leukaemia cell line) to these vessels. Further studies revealed that circulating leukaemic cells can engraft around these vessels, suggesting that this molecularly distinct vasculature demarcates a microenvironment for early metastatic tumour spread in bone marrow. Finally, purified haematopoietic stem/progenitor cells and lymphocytes also localize to the same microdomains, indicating that this vasculature might also function in benign states to demarcate specific portals for the entry of cells into the marrow space. Specialized vascular structures therefore appear to delineate a microenvironment with unique physiology that can be exploited by circulating malignant cells.

The “Emigration, Migration, and Immigration” of Prostate Cancer

In the vast majority of cases, cancer continues to be an incurable disease when it has spread beyond the primary organ. Most cancer research and therapy design to date has focused on chemotherapy directed at killing the replicating tumor cells. Little attention has been placed on targeting the microenvironments of the primary tumor site, the circulating tumor cells, or the metastatic or secondary (target) tumor site and how cancer cells move among them. To develop these targets, a better understanding of metastasis and the mechanisms underlying the spread of tumors is required. This review describes the steps of metastasis using a paradigm of emigration to migration to immigration, with prostate cancer as a model system.

Discovery of Inhibitors of MCF-7 Tumor Cell Adhesion to Endothelial Cells and Investigation on their Mode of Action

Metastasis, the main reason for high mortality of cancer, is a multistep process. One important step in this process is the adhesion of tumor cells to vascular endothelium at sites distant from primary tumors during hematogenous dissemination. In order to investigate and quantify the adhesion of tumor cells to endothelial cells we developed an in vitro model using MCF-7 breast cancer cells and monolayers of human umbilical vein endothelial cells (HUVEC). The tumor cells were specifically labeled with a fluorescent dye for quantification; for increasing the amount of adherent cells, HUVEC monolayers were stimulated with phorbol ester before the addition of the tumor cells. Due to previous reports that products of several P450 enzymes contribute to the progression of certain kinds of cancer, inhibitors of CYP5 (thromboxane A(2) synthase), CYP17 (17alpha-hydroxylase-C17, 20-lyase), and CYP19 (aromatase) were tested in this in vitro model for their potency to reduce cancer cell adhesion. Within each series of P450 inhibitors, compounds with high inhibitory activity on tumor cell adhesion were identified. At an initial concentration of 100 microM, BW26, a potent inhibitor of CYP5, reduced tumor cell adhesion of MCF-7 to HUVECs to 15%, BW40 (CYP17) to 29%, and SU5a (CYP19) to 11% of the corresponding controls (no inhibitor). Reduction of tumor cell adhesion was shown to occur in a concentration-dependent manner. In addition to these inhibitors of CYP5, CYP17, and CYP19, liarozole, known to be a potent inhibitor of CYP26 (retinoic acid-4-hydroxylase) and ATRA (all-trans-retinoic acid) metabolism, was able to reduce tumor cell adhesion to 51% of the initial rate. Experiments elucidating the mode of action of these compounds revealed that inhibition of the mentioned CYP enzymes is not responsible for their ability to reduce tumor cell adhesion.

Antimetastatic drugs in prostate cancer

Despite the benefits of local therapy with radical prostatectomy and radiation, many patients with prostate cancer require hormonal ablation. While chemotherapy has proven efficacy when the disease progresses to androgen-independent prostate cancer, patients ultimately succumb to the disease, thus the identification of other active therapies is needed. Future treatment modalities include molecular targeted therapies. Prostate cancer has been an ideal model to study the multiple steps required in the metastatic cascade. These steps have been utilized in the development of metastasis inhibitors. This review will present promising agents that have been tested preclinically or are undergoing clinical investigation for their abilities in preventing prostate cancer metastasis. Because prostate cancer metastasizes preferentially to the bone, special attention will be given to agents that interfere with this pattern of metastasis. Specifically, the efficacy of angiogenesis inhibitors, metalloproteinase inhibitors, inhibitors of prostate cancer cell- endothelial cell interactions, and bisphosphonates will be reported. In addition, the introduction of these novel agents has raised many questions as to the relevance and optimal utilization of current clinical trial designs. Issues regarding combination therapy with chemotherapy, optimal timing of treatment with metastatic inhibitors, and the need for surrogate endpoints for molecular targeted therapies will be discussed.

Dynamic process of prostate cancer metastasis to bone

Prostate cancer metastasis to the bone occurs at high frequency in patients with advanced disease, causing significant morbidity and mortality. Over a century ago, the "seed and soil" theory was proposed to explain organ-specific patterns of metastases. Today, this theory continues to be relevant as we continue to discover factors involved in the attraction and subsequent growth of prostate cancer cells to the bone. These include the accumulation of genetic changes within cancer cells, the preferential binding of cancer cells to bone marrow endothelial cells, and the release of cancer cell chemoattractants from bone elements. A key mediator throughout this metastatic process is the integrin family of proteins. Alterations in integrin expression and function promote dissociation of cancer cells from the primary tumor mass and migration into the blood stream. Once in circulation, integrins facilitate cancer cell survival through interactions between other cancer cells, platelets, and endothelial cells of the target bone. Furthermore, dynamic changes in integrins and in integrin-associated signal transduction aid in the extravasation of cancer cells into the bone and in expansion to a clinically relevant metastasis. Thus, we will review the critical roles of integrins in the process of prostate cancer bone metastasis, from the escape of cancer cells from the primary tumor, to their survival in the harsh "third microenvironment" of the circulation, and ultimately to their attachment and growth at distant bone sites.

GnT-V, macrophage and cancer metastasis: a common link

GnT-V generated, beta1,6-branched polylactosamines are a common feature shared by normal granulocytes, monocytes, and a variety of malignant cells. Furthermore, activation of GnT-V in oncogenic transformation induces invasiveness and metastatic potential in mice as well as in humans. In view of the common expression of lymphocytic/monocytic trait, motility, and GnT-V by metastatic cancer cells, macrophage fusion hybrids were generated in vitro with Cloudman S91 mouse melanoma cells to test whether the parental traits are co-expressed in hybrids and how those are related to altered phenotypes in relation to metastasis. In fact, the fusion hybrids are highly metastatic in vivo, motile in vitro, and express macrophage-associated traits of increased GnT-V activity, beta1,6 branching, and polylactosamine content. A Spontaneously formed lung melanoma metastases have been identified and characterized as host x tumor hybrid containing higher DNA content than parental cells and increased GnT-V activity. The results, taken together, could reflect prior fusion of tumor-associated macrophages with cells of the primary tumor, and therefore establish a possible common link between elevated expression of GnT-V and malignant transformation, a well-known report. Moreover, the fusion hybrids with metastatic potential ranging from high to low offer a genetically matched model system, for identification and characterization of differentially expressed genes in association with metastasis, since the fusion partners are derived from the same species of mouse (DBA/2J).

Light stimulates IFNgamma-mediated intercellular adhesion molecule-1 upregulation of cancer cells

Intercellular adhesion molecule-1 (ICAM-1) works as one of the ligands for activating the killing activity of natural killer (NK) cells and cancer specific cytotoxic T lymphocytes (CTL). Expression of ICAM-1 enhances lymphocyte adhesion to the cancer cells in vivo. Cancer cell lines express significantly lower level of ICAM-1 than that of normal epithelium or benign cells. Overexpression of LIGHT (LIGHT: homologous to lymphotoxins, indicating inducible expression, and competes with herpes simplex virus glycoprotein D for herpes virus entry mediator [HVEM/TR2]) in MDA-MB-231 human breast cancer cells was observed to suppress tumor growth in vivo. In order to elucidate the mechanisms how LIGHT overexpression could trigger tumor suppression, the expression level of a panel of cell surface makers CD54, CD56, CD95, and CD119 was investigated in a group of cancer cells. Flow cytometry analysis results demonstrate that LIGHT gene expression in cancer cells can greatly increase ICAM-1 expression level, IFNgamma alone can stimulate cancer cells to express ICAM-1, which can be highly augmented by LIGHT in a dose-dependent manner. This upregulation of ICAM-1 expression is not only at ICAM-1 protein trafficking level on cell surface as demonstrated by flow cytometry analysis, but also at ICAM-1 total protein level as confirmed by Western blot. There is no difference of expression level among these cancer cell lines for the other three cell surface markers: CD56, CD95 (Fas), and CD119. It was confirmed that LIGHT enhancement upregulation of ICAM-1 expression is at least STAT1 and JAK1 dependent by using STAT1-deficient U3A and JAK1-deficient E2A4 cells. These findings suggest that LIGHT-induced inhibition of tumor growth is highly correlated with its upregulation of ICAM-1 expression.

Stromal factors involved in prostate carcinoma metastasis to bone

BACKGROUND

Prostate carcinoma (PC) frequently metastasizes to bone, where it causes significant morbidity and mortality. Stromal elements in the primary and metastatic target organs are important mediators of tumor cell intravasation, chemoattraction, adhesion to target organ microvascular endothelium, extravasation, and growth at the metastatic site.

METHODS

The role of stromal factors in bone metastasis was determined with a cyclic DNA microarray comparison of a bone-derived cell PC cell line with a soft tissue-derived cell PC cell line and by evaluating the effects of selected stromal components on PC cell chemotaxis, cell adhesion to human bone marrow endothelium (HBME), and PC cell growth.

RESULTS

The authors demonstrate that PC cells express protease-activated receptor 1 (PAR1; thrombin receptor), and its expression is up-regulated in PC compared with normal prostate tissue. In addition, this overexpression was very pronounced in bone-derived PC cell lines (VCaP and PC-3) compared with soft tissue PC cell lines (DUCaP, DU145, and LNCaP). The authors report that bone stromal factors, including stromal cell-derived factor 1 (SDF-1) and collagen Type I peptides, are chemoattractants for PC cells, and they demonstrate that some of these factors (e.g., extracellular matrix components, transforming growth factor beta, bone morphogenic proteins [BMPs], and SDF-1) significantly alter PC-HBME interaction in vitro. Finally, stromal factors, such as BMPs, can regulate the proliferation of PC cells in vitro.

CONCLUSIONS

Soluble and insoluble elements of the stroma are involved in multiple steps of PC metastasis to bone. The authors hypothesize that PAR1 may play a central role in prostate tumorigenesis.

Involvement of tumor cell integrin alpha v beta 3 in hematogenous metastasis of human melanoma cells

Early metastasis is the primary cause of death in melanoma patients. The adhesion receptor integrin alpha v beta 3 contributes to tumor cell functions that are potentially involved in melanoma growth and metastasis. We tested whether integrin alpha v beta 3 supports metastasis of human melanoma cells when injected into the bloodstream of immune deficient mice. Comparing variants of the same melanoma cell type that expressed either alpha v beta 3, alpha IIb beta 3 or no beta 3 integrin, we found that only alpha v beta 3 strongly supported metastasis. Inhibition of tumor cell alpha v beta 3 function reduced melanoma metastasis significantly and prolonged animal survival. To understand mechanisms that allow alpha v beta 3, but not alpha IIb beta 3 to support melanoma metastasis, we analyzed proteolytic and migratory activities of the melanoma cell variants. Melanoma cells expressing alpha v beta 3, but not those expressing alpha IIb beta 3 or no beta 3 integrin, produced the active form of metalloproteinase MMP-2 and expressed elevated mRNA levels of MT1-MMP and TIMP-2. This indicates an association between alpha v beta 3 expression and protease processing. Furthermore, alpha v beta 3 expression was required for efficient melanoma cell migration toward the matrix proteins fibronectin and vitronectin. The results suggest that expression of integrin alpha v beta 3 promotes the metastatic phenotype in human melanoma by supporting specific adhesive, invasive and migratory properties of the tumor cells and that the related integrin alpha IIb beta 3 cannot substitute for alpha v beta 3 in this respect.

Loss of expression and altered localization of KAI1 and CD9 protein are associated with epithelial ovarian cancer progression

OBJECTIVE

Impairment of cell adhesion plays a vital role in tumor progression. E- and N-cadherin, CD9, and KAI1 are all adhesion molecules that have been implicated in the progression of several different tumor types. To help explain the potential role these adhesion molecules have in ovarian cancer, comparisons were made between expression patterns in normal ovary and various grades of primary and metastatic epithelial ovarian cancers.

METHODS

Thirty-two primary and 8 metastatic human ovarian epithelial carcinomas and 18 samples of normal ovarian tissue were examined for adhesion molecule expression using immunohistochemistry.

RESULTS

KAI1 and CD9 revealed an inverse relationship between tumor grade and expression levels, characterized by high expression in low-grade tumors and low expression in high-grade tumors and metastases. KAI1 and CD9 also demonstrated a shift in cellular localization from the membrane in grade 1 tumors to the cytoplasm in grade 3 tumors. N-cadherin expression showed a positive trend between expression levels and tumor grade. E-cadherin expression varied little between different tumor grades and metastases. Inclusion cysts (n = 6) and surface invaginations often strongly expressed KAI1, CD9, and E-cadherin. KAI1 expression was variable in ovarian follicles and corpora lutea depending on their stage of development.

CONCLUSIONS

Although sample size is limited, these findings suggest that progression of ovarian epithelial carcinomas is associated with down-regulation and altered cellular localization of KAI1 and CD9. In addition, variable KAI1 expression during follicular and luteal development suggests that it has a physiological function in the ovary. Further investigation will be needed to see if it is also regulated this way during progression of ovarian cancers.

Carp oil or oleic acid, but not linoleic acid or linolenic acid, inhibits tumor growth and metastasis in Lewis lung carcinoma-bearing mice

I examined the effects of carp oil, oleic acid, linoleic acid and linolenic acid on tumor growth and metastasis to the liver in mice implanted intrasplenically with highly metastatic Lewis lung carcinoma (LLC) tumors. Carp oil (0.1 or 0.2 mL per mouse) significantly reduced tumor growth and metastasis to the liver. Carp oil at 100 or 1000 mg/L inhibited the DNA synthesis in LLC cells, the capillary-like tube formation of human dermal microvascular endothelial cells (HMVEC) at 1000 mg/L and the adherence of LLC cells to HMVEC at 10 to 1000 mg/L (in vitro). Carp oil (0.2 mL per mouse) inhibited the angiogenesis induced by Matrigel supplemented with vascular endothelial growth factor (VEGF) and heparin (in vivo). Antitumor and antimetastatic actions of carp oil might be partly attributable to the inhibition of DNA synthesis in LLC cells and angiogenesis through the inhibition of the adherence of LLC cells to the microvascular endothelium. Oleic acid (0.1 or 0.2 mL per mouse) significantly inhibited the metastasis to the liver, but it had no effect on the primary solid-tumor growth. Oleic acid inhibited the angiogenesis in both in vitro and in vivo models. Oleic acid at 1000 micromol/L inhibited the DNA synthesis in LLC cells but did not affect the DNA synthesis in HMVEC. These inhibitory actions of oleic acid may be attributable to the inhibition of angiogenesis induced by the tumor. Linoleic acid and linolenic acid had no effect on tumor growth or metastasis to the liver.

The role of alpha(v)beta(3) in prostate cancer progression

Integrin alpha(v)beta(3) is involved in varied cell biological activities, including angiogenesis, cell adhesion, and migration on several extracellular matrix components. Although alpha(v)beta(3) is not typically expressed in epithelial cells, it is expressed in macrophages, activated leukocytes, cytokine-stimulated endothelial cells, osteoclasts, and certain invasive tumors. Interestingly, the adhesion and migration of breast cancer cells on bone matrix are mediated, in part, by alpha(v)beta(3). Similar to breast cancer cells, prostate cancer cells preferentially metastasize to the bone. The biological events that mediate this metastatic pattern of prostate cancer are not well defined. This review discusses the role alpha(v)beta(3) plays in prostate cancer progression, with specific emphasis on bone metastasis and on alpha(v)beta(3) signaling in prostate cancer cells. The data suggest that alpha(v)beta(3), in part, facilitates prostate cancer metastasis to bone by mediating prostate cancer cell adhesion to and migration on osteopontin and vitronectin, which are common proteins in the bone microenvironment. These biological events require the activation of focal adhesion kinase and the subsequent activation of PI-3 kinase/Akt signaling pathway.

The role of alpha(v)beta(3) in prostate cancer progression

Integrin alpha(v)beta(3) is involved in varied cell biological activities, including angiogenesis, cell adhesion, and migration on several extracellular matrix components. Although alpha(v)beta(3) is not typically expressed in epithelial cells, it is expressed in macrophages, activated leukocytes, cytokine-stimulated endothelial cells, osteoclasts, and certain invasive tumors. Interestingly, the adhesion and migration of breast cancer cells on bone matrix are mediated, in part, by alpha(v)beta(3). Similar to breast cancer cells, prostate cancer cells preferentially metastasize to the bone. The biological events that mediate this metastatic pattern of prostate cancer are not well defined. This review discusses the role alpha(v)beta(3) plays in prostate cancer progression, with specific emphasis on bone metastasis and on alpha(v)beta(3) signaling in prostate cancer cells. The data suggest that alpha(v)beta(3), in part, facilitates prostate cancer metastasis to bone by mediating prostate cancer cell adhesion to and migration on osteopontin and vitronectin, which are common proteins in the bone microenvironment. These biological events require the activation of focal adhesion kinase and the subsequent activation of PI-3 kinase/Akt signaling pathway.

Adhesion molecules

The exact mechanisms by which serous ovarian cancer cells invade through their underlying basement membrane or are released from the surface of the ovary have yet to be elucidated. This process undoubtedly has a complex molecular basis that most likely involves multiple cell surface receptors, basement membrane components, intercellular adhesion molecules, and signaling from the cell [137]. One possible mechanism by which ovarian carcinoma tumor cells may alter their basement membrane is by the synthesis and secretion of proteolytic enzymes that degrade their basement membranes [88-94, 138]. Alternatively, metastatic ovarian carcinoma cells may decrease their synthesis and/or secretion of ECM molecules. Additional studies are required to determine whether the more aggressive behavior of malignant ovarian carcinoma cells, compared to normal ovarian epithelial cells, is related to an altered cellular response towards ECM molecules, perhaps due to alterations in adhesion molecules/receptors. A further elucidation of the mechanisms by which serous ovarian carcinoma cells regulate their expression of ECM molecules and adhesion molecules/receptors will help in our understanding of the invasion and metastasis of tumor cells. Members of several families of adhesion molecules have been described that seem to be important in the progression of ovarian carcinoma, including CD44, integrins, and E-cadherin. Due to the complexity of this disease, it is likely that other adhesion molecules will also be implicated in the adhesion, migration, invasion, growth, proliferation, and apoptosis of ovarian carcinoma cells. Our group and others have shown that CD44 and the beta 1 integrin subunit play fundamental roles in the adhesion and migration of ovarian carcinoma cells to mesothelial cells and their associated pericellular matrix. Subsequent to the initial adhesion, the ovarian carcinoma cells may migrate through the layer of mesothelial cells, penetrate through the underlying basement membrane, invade into the tissue, and establish a secondary site of growth. Further studies will be required in order to fully understand the relationship of each adhesion molecule and their ligand(s) in the progression of this disease. Once the adhesion molecules and their ligand(s) for each step of the progression of this disease have been identified, it should be possible to develop reagents that can inhibit these interactions. Then, when ovarian carcinoma cells can no longer interact with mesothelial cells and their associated ECM, the dissemination of ovarian carcinoma cells in vivo may be prevented.

Selective activation of cervical microvascular endothelial cells by human papillomavirus 16-e7 oncoprotein

BACKGROUND

Human papillomavirus type 16 (HPV16) is strongly implicated in the etiology of cervical cancer, with the expression of HPV16-encoded E7 oncoprotein in infected epithelial cells contributing to their malignant transformation. Although nuclear E7 interacts with several nuclear targets, we have previously shown that extracellular E7 can cause suppression of immune cell function. Moreover, cervical microvascular endothelial (CrMVEn) cells treated with E7 increase their expression of adhesion molecules. High levels of some cytokines in serum and in cervicovaginal secretions are associated with the progression of cervical cancer. In this study, we investigated the effects of extracellular E7 on cytokine production and on cytoskeleton structure of CrMVEn cells and vascular endothelial cells from different organs.

METHODS

Immunocytochemical staining and flow cytometry techniques were used to detect E7 in endothelial cells incubated with purified E7 protein. Laser scanning confocal microscopy was used to study the E7-induced modification of the endothelial cytoskeleton. An enzyme-linked immunosorbent assay was performed to measure the production of two cytokines, interleukin 6 (IL-6) and interleukin 8 (IL-8), by E7-treated endothelial cells. All statistical tests were two-sided.

RESULTS

Extracellular E7 was taken up by CrMVEn cells and localized to the cytoplasm. CrMVEn cells showed a statistically significant (P<.02) increase in the production of IL-6 and IL-8 after treatment with E7 compared with the controls. CrMVEn cells also produced higher levels of these cytokines than did the other endothelial cells (P<.01). E7 also induced marked alterations in the endothelial cytoskeleton of CrMVEn cells as a result of actin fiber polymerization.

CONCLUSION

These findings suggest a novel mechanism by which E7, as an extracellular factor, can play a role in the progression and dissemination of cervical cancer via its selective effects on endothelial cells.

Sialosyl Le(a)-carrying gangliosides present on the surface of colon carcinoma cells are not directly involved in adhesion to E-selectin

We have shown previously that human colon cancer CX-1 cells contain lipid- and protein-bound sialosyl Lewis(a) structures that support the adhesion of these cells to E-selectin. Treatment of cancer cells with O-sialoglycoprotease did not decrease either the binding of anti-sialosyl Le(a) antibodies or binding to E-selectin-expressing CHO cells. This suggested that cleavage of sialomucins uncovered cryptic sialosyl Le(a) gangliosides that support such interactions. In the present study, inhibitors of glycolipid and O-glycan biosynthesis, d,l-threo-PPPP and GalNAc-alpha-O-benzyl, respectively, were used to study whether the binding of anti-sialosyl Le(a) antibody and adhesion of CX-1 cells to E-selectin can be mediated by sialosyl Le(a) gangliosides. Treatment of cancer cells with each of the inhibitors decreased the expression of the respective glycoconjugates as shown by TLC-binding assay and immunoblotting with anti-sialosyl Le(a) antibody. However, only slight differences in binding of antisialosyl Le(a) antibody to the surfaces of control and inhibitor-treated CX-1 cells were found by flow cytometry, as well no differences were observed in binding of control and inhibitor-treated CX-1 cells to E-selectin-expressing CHO cells, supporting the earlier hypothesis on the involvement of gangliosides in binding of anti-sialosyl Lewis(a) in the partial absence of mucin O-glycans. This hypothesis was further proven by electron microscopy data. Both native CX-1 and d,l-threo-PPPP-treated cells were labelled with anti-sialosyl Lewis(a) antibody mostly at a distance 70-90 nm from cell surface, suggesting interaction with protein-bound carbohydrate structures only. In contrast, the cancer cells treated with GalNAc-alpha-O-benzyl showed most of the staining around 20 nm distance from the plasmalemma, implying that the antibody interacts with lipid-bound sialosyl Lewis(a) instead. The electron microscopy data in conjunction with other results described in this report strongly support the hypothesis that sialosyl Lea gangliosides are not involved in the adhesion of CX-1 cells to E-selectin when mucins are present on the cell surface, but they may be involved in binding to E-selectin in their absence.

Interactions of human prostatic epithelial cells with bone marrow endothelium: binding and invasion

Prostate cancer shows a propensity to form secondary tumours within the bone marrow. Such tumours are the major cause of mortality in this disease. We have developed an in vitro system to study the binding of prostate epithelial cells to bone marrow endothelium (BME) and stroma (BMS). The metastatic prostate cancer cell line, PC3 (derived from a bone metastasis), was seeded onto confluent layers of BME and its binding characteristics compared to human umbilical vein endothelial cells (HUVEC), lung endothelium (Hs888Lu) and BMS. The PC3 cell line showed significantly increased binding to BME (P< 0.05) compared to endothelium derived from HUVEC and lung or BMS with maximal binding occurring at 1 h. Following pre-incubation with a β1 integrin antibody PC3 binding to BME was inhibited by 64% (P< 0.001). Antibodies directed against the integrins β4, α2, α4, α5 and the cellular adhesion molecules P-selectin, CD31, VCAM-1 and sialy Lewis X showed no effect on blocking PC3 binding. Primary prostatic epithelial cells from both malignant (n = 11) and non-malignant tissue (n = 11) also demonstrated equivalent levels of increased adhesion to BME and BMS compared to HUVEC, peaking at 24 h. Further studies examined the invasive ability of prostate epithelial cells in response to bone marrow endothelium using Matrigel invasion chamber assays. In contrast to the previous results, malignant cells showed an increase (1000 fold) in invasive ability, whilst non-malignant prostate epithelia did not respond. We have shown that both malignant and non-malignant prostate epithelial cells can bind at equivalent levels and preferentially to primary human bone marrow endothelium in comparison to controls. However, only malignant prostate epithelia show increased invasive ability in response to BME. © 2001 Cancer Research Campaign www.bjcancer.com

Resveratrol isolated from Polygonum cuspidatum root prevents tumor growth and metastasis to lung and tumor-induced neovascularization in Lewis lung carcinoma-bearing mice

Resveratrol is a naturally occurring phytoalexine found in medicinal plants. We found that resveratrol, at doses of 2.5 and 10 mg/kg, significantly reduced the tumor volume (42%), tumor weight (44%) and metastasis to the lung (56%) in mice bearing highly metastatic Lewis lung carcinoma (LLC) tumors, but not at a dose of 0.6 mg/kg. Resveratrol did not affect the number of CD4(+), CD8(+) and natural killer (NK)1.1.(+) T cells in the spleen. Therefore, the inhibitory effects of resveratrol on tumor growth and lung metastasis could not be explained by natural killer or cytotoxic T-lymphocyte activation. In addition, resveratrol inhibited DNA synthesis most strongly in LLC cells; its 50% inhibitory concentration (IC(50)) was 6.8 micromol/L. Resveratrol at 100 micromol/L increased apoptosis to 20.6 +/- 1.35% from 12.1 +/- 0.36% (P < 0.05) in LLC cells, and decreased the S phase population to 22.1 +/- 1.03% and 29.2 +/- 0.27% from 35.2 +/- 1.72% (P < 0.05) at concentrations of 50 and 100 micromol/L, respectively. Resveratrol inhibited tumor-induced neovascularization at doses of 2.5 and 10 mg/kg in an in vivo model. Moreover, resveratrol significantly inhibited the formation of capillary-like tube formation from human umbilical vein endothelial cells (HUVEC) at concentrations of 10-100 micromol/L; the degree of the inhibition of capillary-like tube formation by resveratrol was 45.5% at 10 micromol/L, 50.2% at 50 micromol/L and 52.6% at 100 micromol/L. Resveratrol inhibited the binding of vascular endothelial growth factor (VEGF) to HUVEC at concentrations of 10-100 micromol/L, but not at concentrations of 1 and 5 micromol/L. The degree of inhibition of VEGF binding to HUVEC by resveratrol was 16.9% at 10 micromol/L, 53.2% at 50 micromol/L and 47.8% at 100 micromol/L. We suggest that the antitumor and antimetastatic activities of resveratrol might be due to the inhibition of DNA synthesis in LLC cells and the inhibition of LLC-induced neovascularization and tube formation (angiogensis) of HUVEC by resveratrol

A cell-based drug delivery system for lung targeting: II. Therapeutic activities on B16-F10 melanoma in mouse lungs

The in vitro and in vivo anticancer activities of doxorubicin-loaded B16-F10 murine melanoma cells (DLTC) were evaluated. DLTC showed similar growth-inhibitory effects against live B16-F10 cells with doxorubicin solution in cell culture system, with the IC50 of 0.11 microM and 0.17 microM, respectively. However, DLTC demonstrated higher effectiveness than the free solution in treating mouse lung cancer caused by live B16-F10 cells. Syngeneic C57BL mice were inoculated intravenously with live B16-F10 cells first, and then received daily treatment of intravenous injections of doxorubicin in either DLTC or free solution form. Compared with the control group treated with phosphate-buffered saline, DLTC eradicated almost all the lung cancer colonies (>99%), while the free solution form reduced the colonies by 61%, when the treatment was given at an early stage. If the treatment started after the establishment of micrometastatic colonies in the mouse lungs, DLTC and free solution treatment resulted in 85% and 30% cancer reduction, respectively. Additional experiments demonstrated that the reduction of lung cancer colonies by DLTC was related to the initial treatment time: the earlier the treatment, the greater the effect. In conclusion, DLTC showed better therapeutic outcomes than free solution form in treating lung cancer of our animal model.

A cell-based drug delivery system for lung targeting: I. Preparation and pharmacokinetics

A drug-loaded tumor cell (DLTC) system has been developed for lung metastasis-targeting drug delivery. Doxorubicin was loaded into B16-F10 murine melanoma cells (96 microg/10(6) cells). The loading process led to the death of all the carrier cells. The diameter of DLTC was 15.03+/-2.36 microm (mean +/- SD). The amount and rate of doxorubicin being released from the DLTC mainly depended on the drug loading and carrier cell concentration. Over a 6-month storage in phosphate buffered saline (PBS) at 4 degrees C, the decrease in intracellular drug concentration and the carrier cell number were less than 25% and 5%, respectively. After a bolus injection of 30 microg doxorubicin in either DLTC form or free solution into the mice tail veins, drug deposit in the lung from DLTC was 3.6-fold of that achieved by free drug solution. The latter resulted in higher drug content in liver and spleen. Extensive trypsinization of DLTC reduced its lung targeting effect by 30%, and the density of surface adhesion molecule GM3 on DLTC surface by 25%. In conclusion, this DLTC system demonstrated a lung-targeting activity that may be partially attributed to its specific surface characteristics.

Allyl sulfides modify cell growth

Extensive evidence points to the ability of allyl sulfides from garlic to suppress tumor proliferation both in vitro and in vivo. This antineoplastic effect is generally greater for lipid-soluble than water-soluble allyl sulfides. Both concentration and duration of exposure can increase the antiproliferative effects of lipid- and water-soluble allyl sulfides. Part of their antiproliferative effects may relate to an increase in membrane fluidity and a suppression of integrin glycoprotein IIb-IIIa mediated adhesion. Alterations in cholesterol, arachidonic acid, phospholipids and/or thiols may account for these changes in membrane function. Allyl sulfides are also recognized for their ability to suppress cellular proliferation by blocking cells in the G2/M phase and by the induction of apoptosis. This increase in the G2/M and apoptotic cell populations correlates with depressed p34cdc2 kinase activity, increased histone acetylation, increased intracellular calcium and elevated cellular peroxide production. While impressive pre-clinical data exist about the antineoplastic effects of allyl sulfur compounds, considerably more attention needs to be given to their effects in humans. The composition of the entire diet and a host of genetic/epigenetic factors will likely determine the true benefits that might arise from allyl sulfur compounds from garlic and other Allium foods.

Pharmacological aspects of targeting cancer gene therapy to endothelial cells

Targeting cancer gene therapy to endothelial cells seems to be a rational approach, because (a) a clear correlation exists between proliferation of tumor vessels and tumor growth and malignancy, (b) differences of cell membrane structures between tumor endothelial cells and normal endothelial cells exist which could be used for targeting of vectors and (c) tumor endothelial cells are accessible to vector vehicles in spite of the peculiarities of the transvascular and interstitial blood flow in tumors. Based on the knowledge on the pharmacokinetics of macromolecules it can be concluded that vectors targeting tumor endothelial cells should own a long blood residence time after intravascular application. This precondition seems to be fulfilled best by vectors exhibiting a slight anionic charge. A long blood residence time would allow the formation of a high amount of complexes between tumor endothelial cells and vector particles. Such high amount of complexes should enable a high transfection rate of tumor endothelial cells. In view of their pharmacokinetic behavior nonviral vectors seem to be more suitable for in vivo targeting tumor endothelial cells than viral vectors. Specific binding of nonviral vectors to tumor endothelial cells should be enhanced by multifunctional ligands and the transduction efficiency should be improved by cationic carriers. Effector genes should encode proteins potent enough to induce reactions which eliminate the tumor tissue. To be effective to that degree such proteins should induce self-amplifying antitumor reactions. Examples for proteins which have the potential to induce such self-amplifying tumor reactions are proteins endowed with antiangiogenic and antiproliferative activity, enzymes which convert prodrugs into drugs and possibly also proteins which induce embolization of tumor vessels. The pharmacological data for such examples are discussed in detail.

The lymph node as a bridgehead in the metastatic dissemination of tumors

The metastatic spread of tumors is not a random process. Distinct patterns of metastasis can be discerned which vary from tumor type to tumor type. A common pattern, particularly for carcinomas, is that regional lymph nodes are often the first organs to develop metastases. This pattern of metastasis is central to the utility of the sentinel lymphonodectomy surgical technique. However, not all tumors and tumor types metastasize first to the regional lymph nodes. The mechanisms which determine whether regional lymph nodes or other sites first develop metastases remain poorly understood. In this article I review the anatomical, cellular and molecular factors which play a role in metastatic dissemination and determine patterns of metastasis. I then explore the importance of tumor heterogeneity and the selection of metastatically competent tumor cells during systemic dissemination, and suggest that some secondary sites are more readily colonised by metastasizing cells than others. Metastases at these sites act as bridgeheads, constituting a reservoir of tumor cells which, because they have already successfully metastasized, possess many of the properties required for metastasis to further sites. These tumor cells are therefore more likely than cells in the primary tumor to acquire all of the properties required for metastasis to less favourable secondary sites. To illustrate the bridgehead concept, I argue that features of the design and function of the lymphatic system make it highly amenable to the entry of metastasizing tumor cells and the formation of lymph node metastases, and suggest that lymph node metastases form a bridgehead for further metastatic spread.

Prostate Cancer - Old Problems and New Approaches. (Part II. Diagnostic and Prognostic Markers, Pathology and Biological Aspects)

Diagnostic and prognostic markers for prostatic cancer (PCa) include conventional protein markers (e.g., PAP, PSA, PSMA, PIP, OA-519, Ki-67, PCNA, TF, collagenase, and TIMP 1), angiogenesis indicator (e.g., factor VIII), neuroendocrine differentiation status, adhesion molecules (E-cadherin, integrin), bone matrix degrading products (e.g., ICPT), as well as molecular markers (e.g., PSA, PSMA, p53, 12-LOX, and MSI). Currently, only PSA is used clinically for early diagnosis and monitoring of PCa. The histological differential diagnosis of prostatic adenocarcinoma includes normal tissues such as Cowper's gland, paraganglion tissue and seminal vesicle or ejaculatory duct as well as pathological conditions such as atypical adenomatous hyperplasia, atrophy, basal cell hyperplasia and sclerosing adenosis. A common PCa is characterized by a remarkable heterogeneity in terms of its differentiation, microscopic growth patterns and biological aggressiveness. Most PCa are multifocal with signi ficant variations in tumor grade between anatomically separated tumor foci. The Gleason grading system which recognizes five major grades defined by patterns of neoplastic growth has gained almost uniform acceptance. In predicting the biologic behavior of PCa clinical and pathological stages are used as the major prognostic indicators. Among the cell proliferation and death regulators androgens are critical survival factors for normal prostate epithelial cells as well as for the androgen-dependent human prostatic cancer cells. The androgen ablation has been shown to increase the apoptotic index in prostatic cancer patients and castration also promotes apoptotic death of human prostate carcinoma grown in mice. The progression of PCa, similarly to other malignancies, is a multistep process, accompanied by genetic and epigenetic changes, involving phenomenons as adhesion, invasion and angiogenesis (without prostate specific features).

Tyrosine Phosphorylation of a ~30 kD Protein Precedes avb3 Integrin-signaled Endothelial Cell Spreading and Motility on Matrix Proteins

A microvascular endothelial cell line (CD clone 4) isolated from murine lung adheres to and spreads well on fibronectin, vitronectin, and fibrinogen, but poorly on collagen type IV and laminin. Ligating cell surface av, b3, a4, a5, or b1 integrin receptors with monospecific antibodies promoted a dramatic cell spreading and motility on vitronectin or collagen IV. Antibodies directed to other adhesion molecules, including aIIb, PECAM-1, and P-selectin were ineffective. Ligation with monoclonal anti-av or -b3, but not -a4, -a5, or -b1 antibodies, induced a rapid, and dose-dependent tyrosine phosphorylation of a ~30 kD protein, which preceded CD clone 4 endothelial cell spreading and motility and was partially inhibited by genistein and completely inhibited by BAPTA. All other antibodies tested did not induce the tyrosine phosphorylation of the 30 kD protein as well as cell spreading and motility. The present results suggest that b1 and b3 integrins employ different biochemical mechanisms in signaling endothelial cell spreading and motility and that the tyrosine phosphorylation of the 30 kD protein (and probably other proteins) may play an important role in signaling b3 integrin-mediated endothelial cell interaction with other cells (e.g., tumor cells) and extracellular matrix.

Effects of naturally occurring stilbene glucosides from medicinal plants and wine, on tumour growth and lung metastasis in Lewis lung carcinoma-bearing mice

Stilbene glucosides are naturally occurring phytoalexins, found in a variety of medicinal plants. Among the stilbene derivatives, resveratrol 3-O-D-glucoside (piceid) is found in grapes and wine. We studied the effects of stilbene glucosides isolated from medicinal plants and grapes on tumour growth and lung metastasis in mice bearing highly metastatic Lewis lung carcinoma (LLC) tumours. We also studied the inhibitory effects of stilbene glucosides on differentiation of human umbilical vein endothelial cells (HUVECs) to form a capillary network. Tumour growth in the right hind paw and lung metastasis were inhibited by oral administration of the stilbene glucosides, piceid and 2,3,5,4'-tetrahydroxystilbene-2-O-D-glucoside for 33 consecutive days, in LLC-bearing mice. As the number of CD8+ and NK1.1+ T cells in the spleen was not affected, the inhibitory effects of these stilbene glucosides on tumour growth and lung metastasis could not be explained by natural killer or cytotoxic T lymphocyte activation. Piceid inhibited the DNA synthesis in LLC cells at a concentration of 1000 microM, but not at lower concentrations (10-100 microM). 2,3,5,4'-Tetra-hydroxystilbene-2-O-D-glucoside also inhibited DNA synthesis in LLC cells (IC50 81 microM). In addition, both stilbene glucosides inhibited the formation of capillary-like tube networks (angiogenesis) of HUVECs at concentrations of 100 to 1000 microM. We suggest that the antitumour and antimetastatic activity of the stilbene glucosides, piceid and 2,3,5,4'-tetrahydroxystilbene-2-O-D-glucoside, might be due to the inhibition of DNA synthesis in LLC cells and angiogenesis of HUVECs.

Possible role of immune surveillance at the initial phase of metastasis produced by B16BL6 melanoma cells

The relationship among the real-time trafficking of lung metastatic B16BL6 cells, metastatic potential, and the injected number of the cells was examined, since the smaller the number of tumor cells injected, the more clearly the immune defense may be observed. When 1x10(6) or 1x10(5) B16BL6 cells were injected into mice via the tail vein, both numbers of cells accumulated in the lung at a similar rate: there was an approximately 10-fold difference in the number of accumulated cells between the two doses. Elimination from the lung was not dependent on the cell number but on the proportion of accumulated cells. However, the injection of 1x10(4) cells resulted in lung accumulation less than one-tenth of that obtained with 1x10(5) cell injection. Metastasis was observed when 1x10(5) or 1x10(6) B16BL6 cells were injected, but not after injection of 1x10(4) cells. To clarify the roles of the immune defense system at the initial phase of metastasis, we challenged macrophage-depleted mice with 1x10(4) tumor cells. Treatment of mice with 2-chloroadenosine prior to the tumor cell challenge cancelled the suppression of not only metastasis but also the lung accumulation. Furthermore, the administration of 2-chloroadenosine following the tumor cell challenge had little effect on the metastatic potential. These results suggest that the immune surveillance whose action was obvious at the low dose of challenged tumor cells functions strongly at the initial phase but not at the advanced stages of the metastatic process, and that macrophages play an important role in the suppression of metastasis.

E-selectin can mediate the arrest type of adhesion of colon cancer cells under physiological shear flow

The aim of this study was to determine whether colon cancer cells flowing in blood exhibit the same adhesion pattern to the vascular bed as leucocytes using a flow adhesion system. In shear flow conditions, five colon cancer cell lines showed less tethering to E-selectin substrates than polymorphonuclear cells (PMN). However, some of the Colo201 cells formed complete arrest on E-selectin in continuous shear flow which was never observed in PMN cells. Colo201 cells expressed both sialyl Le-x and sialyl Le-a at similar levels in flow cytometry. However, the staining pattern showed marked contrast under the fluorescein microscope. The cell membrane of Colo201 cells was uniformly stained with anti-sialyl Le-a MAb, whereas anti-sialyl Le-x MAb only stained in the patchy areas. Pretreatment of Colo201 cells with anti-sLe-a decreased tethering, while anti-sLe-x significantly inhibited the arrest formation. Our data suggest that E-selectin alone can mediate colon cancer cell lodgement and subsequent metastasis without the contribution of integrin molecules and that the different distribution of E-selectin ligands may affect the adhesion behaviour of colon cancer cells in flow conditions.

PTEN gene and integrin signaling in cancer

Integrins are major adhesion- and signaling-receptor proteins that mediate cell migration and invasion. They also trigger a variety of signal transduction pathways and regulate cytoskeletal organization, specific gene expression, growth control, and apoptosis (programmed cell death). Consequently, integrins are thought to play important roles in embryonic development and in the biology of cancers. The functions of integrins can be negatively regulated by the recently discovered tumor suppressor PTEN, a protein with homology to protein tyrosine phosphatases and tensin. The PTEN gene is mutated in a wide range of human cancers. PTEN inhibits cell migration and invasion by directly dephosphorylating two key tyrosine-phosphorylated proteins, thereby antagonizing interactions of integrins with the extracellular matrix and integrin-triggered signaling pathways. Other studies demonstrate important roles for PTEN in dephosphorylating a key signal transduction lipid. In the absence of PTEN, this lipid signal transduction pathway can protect tumor cells from apoptosis. Thus, PTEN appears to be a unique tumor suppressor-with both lipid phosphatase and protein tyrosine phosphatase activities-that negatively regulates cell interactions with the extracellular matrix and that maintains cell sensitivity to apoptosis, e.g., after loss of cell contact with the extracellular matrix. The complex signal transduction pathways regulated by PTEN are described in this review. PTEN and the signaling pathways it regulates may provide novel targets for potential therapy.

Prognostic importance of the expression of CD44 splice variants in oral squamous cell carcinomas

Considering squamous cell carcinomas (SCCs) of the oral cavity and oropharynx the molecular mechanisms underlying the infiltration and destruction of adjacent tissue as well as the metastatic spread are largely unknown. In this context, the detection of defective expression of cellular adhesion molecules in the tumour cells, e.g. CD44, might be important and correlated with prognosis. Paraffin-embedded tumour-tissue from 99 patients with primary oral and oropharyngeal SCC, additionally including corresponding lymph-node metastases in nine cases, was analysed for expression of the CD44 splice variants v4, v5, v6, v7, and v9 by means of immunohistochemistry. A diminution of at least one of the examined CD44 isoforms compared to the normal oral epithelium was observed in 39.4% of the squamous cell carcinomas. No correlations could be found between CD44 expression and pT- or pN-stage. However, decreased expression of v9 was correlated with higher histological grade (p < 0.001). Moreover, reduced CD44 expression was a statistically significant independent predictor for shorter survival time (p = 0.002) as well as shorter recurrence-free interval (p = 0.004) in addition to pT- and pN-stage. The separate analysis showed that particularly the decreased v7 (p = 0.04) and v9 (p < 0.02) expression in the tumour cells was associated negatively with survival.

Dietary factors in human colorectal cancer

Colorectal cancer is a significant cause of mortality in Western societies. The progression of the disease from normal colonic epithelium to the acquisition of the malignant phenotype is accompanied by numerous genetic and epigenetic alterations. Compelling experimental and epidemiological evidence indicates that diet and nutrition are key factors in the modulation of colorectal cancer. A salient case in point is the recent observation that a dietary regimen based on a Western-style diet provokes in the rodent colon the appearance of preneoplastic lesions in the absence of any genotoxic insult. This review mainly describes dietary factors that inhibit the development and progression of colorectal cancer. Much is unknown about the precise mechanisms of action of chemically disparate nutrients and how they interfere with the development and progression of this disease. Current knowledge about this important issue is summarized. We believe that continuing scrutiny and precise assessment of the benefits (and potential risks) of nutrients in the treatment and prevention of colorectal cancer will prove significant to controlling this devastating disease.

Laminin mediates tethering and spreading of colon cancer cells in physiological shear flow

Under the physiological shear condition, cultured colon cancer cells bound to laminin (LM), but not to fibronectin or vitronectin. Most of the tethered cells did not roll, but arrested immediately and spread within 10-30 min on LM under the continuous presence of shear flow. The tethering of Colo201 was partially inhibited by monoclonal antibodies (mAbs) to alpha6 integrin and a combination of mAbs to beta1 and beta4 integrins, but not by mAb to 67KD laminin receptor. Some Colo201 cells still tethered at 4 degrees C. This suggests that alpha6beta1 and alpha6beta4 integrins participate in Colo201 tethering on LM, although other non-integrin molecules play roles. In contrast, the spread of Colo201 was effectively inhibited by the mAbs to integrin alpha2, alpha6 and beta1 chains. The effect of anti-alpha2 plus anti-alpha6 mAbs was almost equal to anti-beta1, suggesting that Colo201 cells mainly use alpha2beta1 and alpha6beta1 integrins for spreading on LM. When the cells were perfused on subconfluent endothelial cells (HUVEC) cultured on LM, they did not tether on HUVEC but did on coated LM exposed at intercellular gap area. Immunohistochemistry revealed that LM abundantly existed in the cytosol of human portal and hepatic vein endothelial cells. These data suggest that LM can mediate from tethering to spreading of colon cancer cells under the blood flow and plays an essential role in haematogeneous metastasis.