Cancer cell interactions with injured or activated endothelium

Changes in dynamics of tumor/endothelial cell adhesive interactions depending on endothelial cell growth state and elastic properties

Cancer cell adhesion to the endothelium is a crucial process in hematogenous metastasis, but how the integrity of the endothelial barrier and endothelial cell (EC) mechanical properties influence the adhesion between metastatic cancer cells and the endothelium remain unclear. In the present study, we have measured the adhesion between single cancer cells and two types of ECs at various growth states and their mechanical properties (elasticity) using atomic force microscopy single cell force spectroscopy. We demonstrated that the EC stiffness increased and adhesion with cancer cells decreased, as ECs grew from a single cell to a confluent state and developed cell-cell contacts, but this was reversed when confluent cells returned to a single state in a scratch assay. Our results suggest that the integrity of the endothelial barrier is an important factor in reducing the ability of the metastatic tumor cells to adhere to the vascular endothelium, extravasate and lodge in the vasculature of a distant organ where secondary metastatic tumors would develop.

Does the mobilization of circulating tumour cells during cancer therapy cause metastasis?

Despite progressive improvements in the management of patients with locoregionally confined, advanced-stage solid tumours, distant metastasis remains a very common - and usually fatal - mode of failure after attempted curative treatment. Surgery and radiotherapy are the primary curative modalities for these patients, often combined with each other and/or with chemotherapy. Distant metastasis occurring after treatment can arise from previously undetected micrometastases or, alternatively, from persistent locoregional disease. Another possibility is that treatment itself might sometimes cause or promote metastasis. Surgical interventions in patients with cancer, including biopsies, are commonly associated with increased concentrations of circulating tumour cells (CTCs). High CTC numbers are associated with an unfavourable prognosis in many cancers. Radiotherapy and systemic antitumour therapies might also mobilize CTCs. We review the preclinical and clinical data concerning cancer treatments, CTC mobilization and other factors that might promote metastasis. Contemporary treatment regimens represent the best available curative options for patients who might otherwise die from locally confined, advanced-stage cancers; however, if such treatments can promote metastasis, this process must be understood and addressed therapeutically to improve patient survival.

The current role of circulating tumor cells in the diagnosis and management of bone metastases in advanced prostate cancer

Prostate-specific antigen (PSA) has been used for over two decades as a serum marker for adenocarcinoma of the prostate. Although PSA screening remains an important part of disease screening and monitoring in early prostate cancer (PC), its utility in monitoring disease progression in advanced PC is undetermined. Furthermore, the role of PSA monitoring in the management of patients with PC and bone metastases appears limited. The purpose of this review is to evaluate the role of circulating tumor cells (CTCs) as potential novel biomarkers in advanced PC. We present a review of CTC testing and the clinical data supporting the prognostic potential of CTCs in this setting. We propose that combination of CTCs and PSA velocity or doubling-time assessments may offer insights into the prognosis and management of advanced PC.

Insulin-like growth factor-I regulates the liver microenvironment in obese mice and promotes liver metastasis

Among the mechanisms implicated in the tumor-promoting effects of obesity, signaling by insulin-like growth factor-I (IGF-I) and insulin has received considerable attention. However, the emerging realization that obesity is associated with chronic inflammation has prompted other consideration of how the IGF-I axis may participate in cancer progression. In the present study, we used two mouse models of chronic (LID) and inducible (iLID) igf-1 gene deficiency in the liver to investigate the role of IGF-I in regulating the host microenvironment and colorectal carcinoma growth and metastasis in obese mice. Obese mice had a heightened inflammatory response in the liver, which was abolished in mice with chronic IGF-I deficiency (LID). In control animals changes to the hepatic microenvironment associated with obesity sustained the presence of tumor cells in the liver and increased the incidence of hepatic metastases after intrasplenic/portal inoculation of colon carcinoma cells. These changes did not occur in LID mice with chronic IGF-1 deficiency. In contrast, these changes occurred in iLID mice with acute IGF-1 deficiency, in the same manner as the control animals, revealing a fundamental difference in the nature of the requirement for IGF-1 on tumor growth and metastasis. In the setting of obesity, our findings imply that IGF-1 is critical to activate and sustain an inflammatory response in the liver that is needed for hepatic metastasis, not only through direct, paracrine effect on tumor cell growth, but also through indirect effects involving the tumor microenvironment.

Circulating tumor cells: evolving evidence and future challenges

Circulating tumor cells (CTCs) are rare malignant cells found in the peripheral blood that originate from the primary tumor or metastatic sites. New techniques have been developed to isolate and characterize these cells. CTC enumeration has been incorporated into different fields of oncology as a prognostic marker, a tool to monitor therapy response, and a method to understand basic tumor characteristics. This review covers the different techniques available for isolation of CTCs, the clinical utility of CTCs in breast, prostate, and colon cancer, and future directions in this field.

Glutathione in Cancer Biology and Therapy

The glutathione (GSH) content of cancer cells is particularly relevant in regulating mutagenic mechanisms, DNA synthesis, growth, and multidrug and radiation resistance. In malignant tumors, as compared with normal tissues, that resistance associates in most cases with higher GSH levels within these cancer cells. Thus, approaches to cancer treatment based on modulation of GSH should control possible growth-associated changes in GSH content and synthesis in these cells. Despite the potential benefits for cancer therapy of a selective GSH-depleting strategy, such a methodology has remained elusive up to now. Metastatic spread, not primary tumor burden, is the leading cause of cancer death. For patient prognosis to improve, new systemic therapies capable of effectively inhibiting the outgrowth of seeded tumor cells are needed. Interaction of metastatic cells with the vascular endothelium activates local release of proinflammatory cytokines, which act as signals promoting cancer cell adhesion, extravasation, and proliferation. Recent work shows that a high percentage of metastatic cells with high GSH levels survive the combined nitrosative and oxidative stresses elicited by the vascular endothelium and possibly by macrophages and granulocytes. ?-Glutamyl transpeptidase overexpression and an inter-organ flow of GSH (where the liver plays a central role), by increasing cysteine availability for tumor GSH synthesis, function in combination as a metastatic-growth promoting mechanism. The present review focuses on an analysis of links among GSH, adaptive responses to stress, molecular mechanisms of invasive cancer cell survival and death, and sensitization of metastatic cells to therapy. Experimental evidence shows that acceleration of GSH efflux facilitates selective GSH depletion in metastatic cells.

A "class action" against the microenvironment: do cancer cells cooperate in metastasis?

The authors review how cancer cells may cooperate in metastasis by means of microenvironmental changes. The main mechanisms underlying this cooperation are clustered migration of cancer cells, extracellular matrix degradation, paracrine loops of released signaling factors and/or induction of adhesion molecules on stromal cells. Another critical factor could be temporal cooperation: successive waves of cancer cells may induce progressive conditioning of the microenvironment. The "class action" of cancer cells against the microenvironment involves successive steps of the metastatic process: invasion of the primary tumor microenvironment, collective migration through the extracellular matrix, blood vessel disruption, vascular or lymphatic tumor emboli, establishment of a premetastatic niche by secreted factors and endothelial precursor recruitment, induction of cell adhesion molecule expression in endothelial cells, extravasation, micrometastasis dormancy and establishment of a new growth in distant sites. As a result, after completion of the metastatic process, the series of microenvironmental changes from the primary tumor to the metastatic site may promote colonization of metastases by nonmetastatic cancer cells of the primary tumor.

The clinical significance of circulating tumor cells in the peripheral blood

Tumors launch malignant cells into the circulation continuously. In early stages, the immune surveillance system eliminates these cells from the circulation, but at later times they may persist longer and be detected. The first recorded evidence of the presence of circulating tumor cells in the peripheral blood of cancer patients was documented in 1869. Now, modern molecular biologic and cell sorting techniques make their detection and characterization more practicable. This review will consider the methods currently available for their detection and characterization, and the clinical implications of their presence in various malignant conditions.

Influence of different dietary fat intake on liver metastasis and hepatic lipid peroxidation in BOP-induced pancreatic cancer in Syrian hamsters

OBJECTIVES

Effects of polyunsaturated fatty acids (PUFA) on carcinogenesis are discussed controversially. Thus, tumor growth seems to be influenced by type and composition of fat dietary; however, the pathomechanism is still unknown. Therefore, we investigated the impact of different PUFAs on liver metastasis and hepatic lipid peroxidation in a solid model of ductal pancreatic cancer in Syrian hamsters.

METHODS

90 male hamsters were randomized into 6 groups (n = 15). Accordingly groups 2, 4 and 6 received 10 mg N-nitrosobis-2-oxopropylamine (BOP)/kg body weight weekly by subcutaneous injection for 12 weeks in order to induce ductal pancreatic cancer, while groups 1, 3 and 5 were treated with 0.5 ml 0.9% sodium chloride. All hamsters received a standard fat diet (SFD) rich in n-6 PUFA for 16 weeks (2.9% fat). Afterwards, groups 1 and 2 had free access to SFD, while groups 3 and 4 were given a diet enriched with n-3, n-6 and n-9 PUFA (SMOF) and groups 5 and 6 were fed a diet high in n-3 PUFA (FISH-OIL). After 32 weeks all hamsters were sacrificed in order to determine incidence of pancreatic carcinoma and liver metastasis. Furthermore hepatic activities of glutathionperoxidase (GSH-Px) and superoxiddismutase (SOD) as well as levels of lipidperoxidation were analyzed intra- and extrametastatically.

RESULTS

The incidence of liver metastasis was decreased in the FISH-OIL tumor group compared to the SFD and SMOF groups. However, GSH-Px activity was not influenced by different diets. Extrametastatic hepatic SOD activity did not differ between all groups, while intrametastatic hepatic SOD activity in the SFD-BOP group was increased. In the FISH-OIL-BOP and the SMOF-BOP group intrametastatic SOD activity was lower than in non-metastatic hepatic tissue. Furthermore levels of hepatic lipid peroxidation were decreased in the tumor groups treated with fish oil and SMOF compared to the SFD group. Comparing intra- and extrametastatic TBARS concentration there was no difference in the SFD-BOP and the SMOF-BOP groups, while in the FISH-OIL-BOP group intrametastatic TBARS concentration was increased.

CONCLUSION

Conclusively, fish oil reduced the incidence of liver metastasis in experimental ductal pancreatic cancer. Maybe this effect is caused by an increase of intrametastatic hepatic lipid peroxidation.

In vitro age-related responses of endothelial cells to breast cancer cell addition

AIM

The purpose of this study was to determine if the in vitro age of endothelial cells alters endothelial response(s) to breast cancer cells.

METHOD

After characterizing lower passage ("young"; passages 10-16) and higher passage ("old"; passages 30-36) bovine pulmonary artery endothelial cells (BPAECs), fluorescently labeled MCF-7 breast cancer cells were added to confluent monolayers of young and old BPAECs.

RESULTS

Transient gaps that peaked in size by 12 h and closed by 48h occurred between the young BPAECs, while large persistent gaps formed between the old BPAECs. Gap formation did not occur when 184A1 cells, a non-malignant mammary epithelial cell line, were added in place of MCF-7 cells, suggesting that the age-related responses of the endothelial cells to MCF-7 cell addition were specific to the tumor cell addition. Additionally, more MCF-7 cells migrated through old BPAEC monolayers, than young BPAEC monolayers, grown on Matrigel-coated filters. Finally, DNA fragmentation and fluorescent annexin-V binding assays suggested increased MCF-7 cell-induced apoptosis in older BPAECs, though results from a caspase-3 activation assay were equivocal.

CONCLUSIONS

In sum, our findings support the notion that aged endothelial cells are more susceptible to breast cancer-induced injury, perhaps due to increased apoptosis.

Ajoene inhibits both primary tumor growth and metastasis of B16/BL6 melanoma cells in C57BL/6 mice

Ajoene is an organosulphur compound derived from garlic with important effects on several membrane-associated processes such as platelet aggregation, as well as being cytotoxic for tumor cell lines in vitro. In the present study, we investigated the effect of ajoene on different cell types in vitro, as well as its inhibitory effects on both primary tumors and metastasis in a mouse model. We found ajoene to inhibit tumor cell growth in vitro, but also to inhibit strongly metastasis to lung in the B16/BL6 melanoma tumor model in C57BL/6 mice. As far as we are aware, this is the first report of the anti-metastatic effect of ajoene. Ajoene also inhibited tumor-endothelial cell adhesion, as well as the in vivo TNF-alpha response to lipopolysaccharide. Possible mechanisms of its antitumoral activity are discussed in the light of these results.

Effects of the antioxidative vitamins A, C and E on liver metastasis and intrametastatic lipid peroxidation in BOP-induced pancreatic cancer in Syrian hamsters

BACKGROUND/AIMS

Antioxidative vitamins are known to inhibit metastasis. Therefore we evaluated the impact of vitamins A (retinol), C (ascorbic acid) and E (alpha-tocopherol) on liver metastasis in a model of ductal pancreatic adenocarcinoma in hamster.

METHODS

One hundred and twenty male Syrian hamsters were randomized into 8 groups (Gr.) (n = 15). Gr. 1-4 were given 0.5 ml normal saline subcutaneously (s.c.) weekly, whereas Gr. 5-8 received 10 mg N-nitrosobis(2-oxopropyl)amine (BOP)/kg body weight s.c. for 3 months for tumor induction. In the 13th week Gr. 2 and 6 were administered retinol, Gr. 3 and 7 received ascorbic acid and Gr. 4 and 8 were given alpha-tocopherol orally. No treatment was performed in Gr. 1 and 5. After 24 weeks animals were sacrificed, pancreas and liver were histologically determined. Activities of glutathione-peroxidase (GSH-Px), superoxide dismutase (SOD) and concentration of thiobarbituric-acid-reactive substances (TBARS) were analyzed in hepatic tissue.

RESULTS

Retinol and alpha-tocopherol decreased the incidence of liver metastases (44.4 vs. 86.7%, p < 0.05). The number and size of liver metastases were significantly reduced by retinol. Activities of GSH-Px and SOD were increased and concentration of TBARS was decreased in NML and LiMe by all vitamins.

CONCLUSION

Obviously, antioxidative vitamins prevent oxidative stress in hepatocytes. This may be one mechanism decreasing liver metastasis in pancreatic cancer in the present trial.

Acceleration of glutathione efflux and inhibition of gamma-glutamyltranspeptidase sensitize metastatic B16 melanoma cells to endothelium-induced cytotoxicity

Highly metastatic B16 melanoma (B16M)-F10 cells, as compared with the low metastatic B16M-F1 line, have higher GSH content and preferentially overexpress BCL-2. In addition to its anti-apoptotic properties, BCL-2 inhibits efflux of GSH from B16M-F10 cells and thereby may facilitate metastatic cell resistance against endothelium-induced oxidative/nitrosative stress. Thus, we investigated in B16M-F10 cells which molecular mechanisms channel GSH release and whether their modulation may influence metastatic activity. GSH efflux was abolished in multidrug resistance protein 1 knock-out (MRP-/-1) B16M-F10 transfected with the Bcl-2 gene or in MRP-/-1 B16M-F10 cells incubated with l-methionine, which indicates that GSH release from B16M-F10 cells is channeled through MRP1 and a BCL-2-dependent system (likely related to an l-methionine-sensitive GSH carrier previously detected in hepatocytes). The BCL-2-dependent system was identified as the cystic fibrosis transmembrane conductance regulator, since monoclonal antibodies against this ion channel or H-89 (a protein kinase A-selective inhibitor)-induced inhibition of cystic fibrosis transmembrane conductance regulator gene expression completely blocked the BCL-2-sensitive GSH release. By using a perifusion system that mimics in vivo conditions, we found that GSH depletion in metastatic cells can be achieved by using Bcl-2 antisense oligodeoxynucleotide- and verapamil (an MRP1 activator)-induced acceleration of GSH efflux, in combination with acivicin-induced inhibition of gamma-glutamyltranspeptidase (which limits GSH synthesis by preventing cysteine generation from extracellular GSH). When applied under in vivo conditions, this strategy increased tumor cytotoxicity (up to approximately 90%) during B16M-F10 cell adhesion to the hepatic sinusoidal endothelium.

VEGF regulates PCB 104-mediated stimulation of permeability and transmigration of breast cancer cells in human microvascular endothelial cells

Polychlorinated biphenyl (PCB) congeners, a group of worldwide, persistent environmental contaminants, are known to cause carcinogenesis and tumor promotion, and may also affect the development of cancer metastasis. Because vascular endothelial cells create a selective barrier to the passage of cancer cells, we hypothesize that specific PCB congeners can disrupt endothelial integrity and increase the transendothelial migration of tumor cells. To examine this hypothesis, we elucidated the effects of 2,2',4,6,6'-pentachlorobiphenyl (PCB 104), a representative of highly ortho-substituted non-coplanar PCB congeners, on the endothelial permeability and transendothelial migration of MDA-MB-231 breast cancer cells. Exposure of human microvascular endothelial cell 1 (HMEC-1) to PCB 104 induced endothelial hyperpermeability and markedly increased transendothelial migration of MDA-MB-231 cells. These effects were associated with overexpression of vascular endothelial growth factor (VEGF). PCB 104-mediated elevation of VEGF expression was induced by phosphatidylinositol 3-kinase (PI3K) but not affected by co-treatments with antioxidants or the NF-kappaB inhibitor SN50. In addition, the PI3K-dependent pathway was involved in PCB 104-induced activation of AP-1, a transcription factor implicated in the regulation of VEGF gene expression. The VEGF receptor (KDR/Flk-1) antagonist SU1498 and the PI3K inhibitor LY294002 inhibited PCB 104-induced hyperpermeability. These results indicate that PCB 104 may contribute to tumor metastasis by inducing VEGF overexpression that stimulates endothelial hyperpermeability and transendothelial migration of cancer cells.

Aging and the endothelium

One link between aging and endothelial function is the inflammatory response. On one hand, the latter shortens the biological engaged by activated leukocytes against invaders or stressing agents. On the other hand, the surveyed tissues become targets of the toxicity of reactive oxygen species, ROS. The ensuing regeneration is source of transcriptional infidelity, leading to the alteration of the repaired tissue. Hence, the toll of inflammatory stress consists in premature senescence of cell and tissues. This hypothesis is discussed in the present review, which focuses on the molecular targets relevant for cancer and degenerative diseases, both tributary to an inflammatory environment and taking advantage from the consequences of cell and tissue dysfunctions characteristic of aging. Eventually, adaptation to stress, whatever its origin -inflammatory and/or psychosocial-is discussed. Basal nitric oxide (NO) release, such as provided through moderate exercise, seems to be the most potent guardian against immune, nervous and cardiovascular over-stimulation. Tissue regeneration is also obtained by circulating endothelial progenitors able to recognize the damaged tissue. To avoid post-inflammatory alterations resulting in detrimental changes of tissues and organs, the pharmacological protection of endothelium by agents able to modulate its activation seems crucial to us.

2,2',4,6,6'-pentachlorobiphenyl (PCB 104) induces apoptosis of human microvascular endothelial cells through the caspase-dependent activation of CREB

It has been proposed that endothelial integrity can play an active regulatory role in the extravasation of tumor cells during cancer metastasis. Since polychlorinated biphenyls (PCBs) have been shown to cause endothelial cell activation or injury and to lead to various diseases that involve dysfunction of the vascular endothelium, the present study was designed to determine the cellular and molecular signaling mechanisms of PCB-induced apoptosis in human microvascular endothelial cells (HMEC-1). A significant and marked decrease in cell viability was observed in HMEC-1 treated with 2,2',4,6,6'-pentachlorobiphenyl (PCB 104) in a time- and dose-dependent manner. Exposure of HMEC-1 to PCB 104 also dramatically induced internucleosomal DNA fragmentation. However, the caspase inhibitor zVAD-fmk significantly reversed the PCB 104-induced DNA fragmentation in HMEC-1, suggesting that endothelial cell death induced by PCB 104 exposure is, at least in part, due to caspase-dependent apoptotic pathways. To elucidate the molecular signaling mechanisms of PCB 104-induced apoptotic cell death in human microvascular endothelial cells, the present study focused on the effects of acute exposure of PCB 104 on the activation of several transcription factors, such as cAMP responsive element-binding protein (CREB), activator protein-1 (AP-1), nuclear factor-kappaB (NF-kappaB), and signal transducers and activators of transcription (STAT1), which have been known to play a pivotal role in the molecular signaling cascades for the induction of apoptosis. A series of electrophoretic mobility shift assay showed that PCB 104 specifically increased only CREB DNA-binding activity in a dose-dependent manner. AP-1, NF-kappaB, and STAT1, however, were not activated. In addition, zVAD-fmk significantly and dose-dependently blocked the CREB activation enhanced by PCB 104 exposure. These results suggest that PCB-induced death of human microvascular endothelial cells is mediated, at least in part, via the caspase-dependent apoptotic pathways and that the selective activation of CREB is involved in this process.

Tumor cytotoxicity by endothelial cells. Impairment of the mitochondrial system for glutathione uptake in mouse B16 melanoma cells that survive after in vitro interaction with the hepatic sinusoidal endothelium

High GSH content associates with high metastatic activity in B16-F10 melanoma cells cultured to low density (LD B16M). GSH homeostasis was investigated in LD B16M cells that survive after adhesion to the hepatic sinusoidal endothelium (HSE). Invasive B16M (iB16M) cells were isolated using anti-Met-72 monoclonal antibodies and flow cytometry-coupled cell sorting. HSE-derived NO and H(2)O(2) caused GSH depletion and a decrease in gamma-glutamylcysteine synthetase activity in iB16M cells. Overexpression of gamma-glutamylcysteine synthetase heavy and light subunits led to a rapid recovery of cytosolic GSH, whereas mitochondrial GSH (mtGSH) further decreased during the first 18 h of culture. NO and H(2)O(2) damaged the mitochondrial system for GSH uptake (rates in iB16M were approximately 75% lower than in LD B16M cells). iB16M cells also showed a decreased activity of mitochondrial complexes II, III, and IV, less O(2) consumption, lower ATP levels, higher O(2) and H(2)O(2) production, and lower mitochondrial membrane potential. In vitro growing iB16M cells maintained high viability (>98%) and repaired HSE-induced mitochondrial damages within 48 h. However, iB16M cells with low mtGSH levels were highly susceptible to TNF-alpha-induced oxidative stress and death. Therefore depletion of mtGSH levels may represent a critical target to challenge survival of invasive cancer cells.

Influence of conjugated vs. conventional linoleic acid on liver metastasis and hepatic lipidperoxidation in BOP-induced pancreatic cancer in Syrian hamster

While conjugated linoleic acid (CLA) is regarded as an essential fatty acid with anticarcinogenic effects, conventional linoleic acid (LA) is reported to promote tumour growth in various experimental studies probably caused by high sensitivity to non-enzymatic lipid peroxidation. In order to evaluate the impact of dietary LA and CLA on liver metastasis and lipidperoxidation (LPO), 60 Syrian hamsters were injected with 10 mg N -nitrosobis-2-oxopropylamine (BOP)/kg body weight s.c. for 12 weeks. Animals were fed a special diet containing LA or CLA. The experiment was terminated after 24 weeks. Incidence, number and size of liver metastases were histologically determined. Furthermore, the activities of antioxidative enzymes and concentration of hepatic lipidperoxidation were measured intra- and extrametastatically. Incidence, number and size of liver metastases did not differ between the tumour groups. Otherwise, antioxidative enzyme activity of GSH-Px was higher in non-metastatic liver, while SOD activity and lipidperoxidation were increased in liver metastases. Conclusively there was no difference between the groups fed with LA and CLA according to the impact on liver metastasis in ductal pancreatic cancer.

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.

Regulatory role of tetraspanin CD9 in tumor-endothelial cell interaction during transendothelial invasion of melanoma cells

Heterotypic interaction among tumor cells (TCs) and endothelial cells (ECs) may play a critical role during the vascular dissemination of neoplastic cells and during pathologic angiogenesis in tumors. To identify molecules involved in these processes, the distribution of vascular junctional proteins was first studied by immunofluorescence at sites of heterologous intercellular contact using TC-EC mosaic monolayers grown on 2-dimensional collagen. Several members of the tetraspanin superfamily, including CD9, CD81, and CD151, were found to localize at the TC-EC contact area. The localization of tetraspanins to the TC-EC heterologous contact area was also observed during the active transmigration of TCs across EC monolayers grown onto 3-dimensional collagen matrices. Dynamic studies by time-lapse immunofluorescence confocal microscopy showed an active redistribution of endothelial CD9 to points of melanoma insertion. Anti-CD9 monoclonal antibodies were found to specifically inhibit the transendothelial migration of melanoma cells; the inhibitory effect was likely caused by a strengthening of CD9-mediated heterotypic interactions of TCs to the EC monolayer. These data support a novel mechanism of tetraspanin-mediated regulation of TC transcellular migration independent of TC motility and growth during metastasis and a role for these molecules in the formation of TC-EC mosaic monolayers during tumor angiogenesis.

Influence of octreotide on liver metastasis and hepatic lipid peroxidation in BOP-induced pancreatic cancer in Syrian hamsters

INTRODUCTION

In prospective clinical trials, octreotide improved quality of life and survival time in patients with pancreatic cancer.

AIMS

To analyze whether octreotide modulates the hepatic oxygen radical metabolism and thus might decrease liver metastasis in an animal model of pancreatic cancer.

METHODOLOGY

Syrian hamsters received 0.9% NaCl or N-nitrosobis(2-oxopropyl)amine (BOP) for 3 months. Therapy was performed for 12 weeks by 0.9% NaCl or octreotide. Hamsters received a standard diet (3.5% fat) or were fed a high-fat diet (21.4% fat). In the 25th week, the pancreas and liver were examined macroscopically and histologically. The level of lipid peroxidation and activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) were determined intrahepatically.

RESULTS

The number of liver metastases per animal and the size of liver metastases were increased by the high-fat diet, whereas they were decreased by octreotide. Octreotide increased activities of GSH-Px and SOD. The concentration of thiobarbituric acid reactive substances was increased by BOP and a high-fat diet and decreased by octreotide.

CONCLUSION

Octreotide decreases the number and size of liver metastases in chemically induced pancreatic cancer in Syrian hamsters. This is accompanied by high hepatic GSH-Px and SOD activity and a low level of lipid peroxidation.

Tumoricidal activity of endothelial cells. Inhibition of endothelial nitric oxide production abrogates tumor cytotoxicity induced by hepatic sinusoidal endothelium in response to B16 melanoma adhesion in vitro

The mechanism of NO- and H(2)O(2)-induced tumor cytotoxicity was examined during B16 melanoma (B16M) adhesion to the hepatic sinusoidal endothelium (HSE) in vitro. We used endothelial nitric-oxide synthetase gene disruption and N(G)-nitro-l-arginine methyl ester-induced inhibition of nitric-oxide synthetase activity to study the effect of HSE-derived NO on B16M cell viability. Extracellular H(2)O(2) was removed by exogenous catalase. H(2)O(2) was not cytotoxic in the absence of NO. However, NO-induced tumor cytotoxicity was increased by H(2)O(2) due to the formation of potent oxidants, likely ( small middle dot)OH and (-)OONO radicals, via a trace metal-dependent process. B16M cells cultured to low density (LD cells), with high GSH content, were more resistant to NO and H(2)O(2) than B16M cells cultured to high density (HD cells; with approximately 25% of the GSH content found in LD cells). Resistance of LD cells decreased using buthionine sulfoximine, a specific GSH synthesis inhibitor, whereas resistance increased in HD cells using GSH ester, which delivers free intracellular GSH. Because NO and H(2)O(2) were particularly cytotoxic in HD cells, we investigated the enzyme activities that degrade H(2)O(2). NO and H(2)O(2) caused an approximately 75% (LD cells) and a 60% (HD cells) decrease in catalase activity without affecting the GSH peroxidase/GSH reductase system. Therefore, B16M resistance to the HSE-induced cytotoxicity appears highly dependent on GSH and GSH peroxidase, which are both required to eliminate H(2)O(2). In agreement with this fact, ebselen, a GSH peroxidase mimic, abrogated the increase in NO toxicity induced by H(2)O(2).

Does alpha-linolenic acid in combination with linoleic acid influence liver metastasis and hepatic lipid peroxidation in BOP-induced pancreatic cancer in Syrian hamsters?

Some fatty acids are reported to inhibit tumor growth of pancreatic carcinoma. However, it is still unknown if alpha-linolenic acid (ALA) and linoleic acid (LA) inhibit liver metastasis of ductal pancreatic adenocarcinoma. Therefore we studied the effect of these fatty acids on liver metastasis in the animal model of N-nitrosobis(2-oxopropyl)amine (BOP)-induced pancreatic adenocarcinoma in Syrian hamsters. Since lipid peroxidation seems to be involved in carcinogenesis and metastasis, we further analyzed the intrahepatic concentration of thiobarbituric acid-reactive substances (TBARS) and activity of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). We observed an increase in the incidence and the number of liver metastases in response to the combination of ALA and LA. This was accompanied by a decrease in hepatic GSH-Px activity and an increase in hepatic SOD activity and TBARS concentration. The increase in hepatic lipid peroxidation seems to be one possible mechanism of increasing liver metastasis in this study.

Epitheliotropic T-cell gastrointestinal tract lymphosarcoma with metastases to lung and skeletal muscle in a cat

An Abyssinian cat examined because of hypoproteinemia and weight loss was found to have epitheliotropic T-cell lymphosarcoma of the gastrointestinal tract. Neoplastic lymphocytes infiltrated the epithelium and lamina propria of the stomach, small intestine, and large intestine. Metastatic foci were found in the lungs and the musculature of the right hind limb. Chemotherapy resulted in transient shrinkage of the lung and limb masses; however, these masses grew to approximately their original size within 2 weeks after initiation of treatment, and the cat was euthanatized.

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.

Interactions between cancer cells and the endothelium in metastasis

The haematogenous phase of cancer metastasis facilitates the transport of metastatic cells within the blood and incorporates a sequence of interactions between circulating intravascular cancer cells and the endothelium of blood vessels at the sites of tumour cell arrest. Initial interactions involve mechanical contact and transient adhesion, mediated by endothelial selectins and their ligands on the neoplastic cells. This contact initiates a sequence of activation pathways that involves cytokines, growth factors, bioactive lipids, and reactive oxygen species produced by either the cancer cell or the endothelium. These molecules elicit expression of integrin adhesion molecules in cancer cells and the endothelium, matrix metalloproteinases, and chemotactic factors that promote the attachment of tumour cells to the vessel wall and/or transvascular penetration. Induction of endothelial free radicals can be cytotoxic to cancer cells. Collectively, the sum of these interactions constitutes an interdependent relationship, the outcome of which determines the fate of the metastatic process.

Transforming growth factor-beta 1 increases the adhesion of MDA-MB-231 mammary adenocarcinoma cells to the microvascular subendothelium

The increase of tumor cell adhesion to the subendothelium in the presence of TGF-beta 1 is thought to be mediated by two major events: an enrichment of extracellular matrix proteins secreted by endothelial cells and an increase of the integrins on the surface of tumor cells. In this study, we analyzed the effect of TGF-beta 1 on the adhesion of a mammary adenocarcinoma cell line (MDA-MB-231) to the matrix of human microvascular endothelial cells (HMEC-1). The adhesion of TGF-beta 1-treated tumor cells to a non-treated matrix or to purified matrix proteins was enhanced, while no increase was observed when non-treated tumor cells were let to adhere to a matrix secreted by HMEC-1 in the presence of the cytokine. Thus, the increase of cell adhesion was due to the effect of TGF-beta 1 on tumor cells and not to the matrix enrichment induced by this cytokine. The hyper-adhesion was inhibited by the RGD peptide and EDTA indicating that integrins were involved. Integrin subunits concentrations (alpha 5, alpha v and beta 1) on the surface of TGF-beta 1-treated tumor cells were not modified, while confocal microscopy showed a reorganization of beta 1 integrin subunits on the cell surface and in the cytoplasm resulting in actin fibers reorganization in the cytoskeleton. This indicates that the enhanced adhesion of TGF-beta 1-treated MDA-MB-231 cells to the subendothelium is due to a qualitative change of integrins.

Role of sialylglycoconjugate(s) in the initial phase of metastasis of liver-metastatic RAW117 lymphoma cells

To elucidate the early events of blood-borne metastasis under actual blood flow, real-time trafficking of RAW117 large cell lymphoma cells, namely parental RAW117-P and liver-metastatic RAW117-H10 cells, was investigated using positron emission tomography (PET). Both types of cells accumulated in the liver immediately after injection via the portal vein, and were eliminated from the liver time-dependently. The elimination rate of RAW117-H10 cells, however, was slower than that of RAW117-P cells, suggesting that RAW117-H10 cells interact more strongly with hepatic sinusoidal endothelium than the parental cells. This result correlated with the metastatic potential of these cells: RAW117-H10 cells metastasized in the liver to a greater extent than RAW117-P cells after injection via this route. To investigate the role of sialylglycoconjugates in the interaction of RAW117-H10 cells with the hepatic endothelium after injection via the portal vein, the trafficking of RAW117-H10 cells was examined after the cells had been treated with sialidase. The elimination rate of RAW117-H10 cells from liver was observed to be greatly accelerated by sialidase treatment. To elucidate what kind of sialylglycoconjugates is related to this phenomenon, we analyzed the distribution of sialyl Lewis A and sialyl Lewis X antigens of both sublines of RAW117 by using flow cytometry. RAW117-H10 cells were found to express a much higher level of sialyl Lewis A than RAW117-P cells, whereas the amount of sialyl Lewis X did not differ significantly. These findings suggest that some sialylglycoconjugates, perhaps sialyl Lewis A in particular, play an important role in the initial interaction of RAW117-H10 cells with the hepatic endothelium, leading to metastasis.

Collagenase-1, stromelysin-1 and 92 kDa gelatinase are associated with tumor necrosis factor-alpha induced morphological change of human endothelial cells in vitro

Recently, we have shown that the tumor necrosis factor-alpha (TNF-alpha)-induced morphological change of EA.hy 926 human endothelial cells is associated with a decrease in the net synthesis of two proteoglycans (PGs), biglycan and syndecan-1, both of which have been suggested to play a role in cell adhesion. Here we have examined whether this phenotypic modulation of EA.hy 926 cells also involves altered expression of matrix metalloproteinases (MMPs) or their tissue inhibitors (TIMPs). We demonstrate that, when forming cobblestone-like monolayer cultures, these cells express and synthesize collagenase-1 (MMP-1), stromelysin-1 (MMP-3) and 72 kDa (MMP-2) and 92 kDa (MMP-9) gelatinases, all of which have previously been found in either normal or pathological human vascular wall. EA.hy 926 cells also express membrane-typel MMP (MT1-MMP), but not matrilysin (MMP-7) and collagenase-3 (MMP-13). As regards TIMPs, we show that these cells express TIMP-1 and TIMP-2, but not TIMP-3 or TIMP-4. Exposure of the cells to TNF-alpha changed the cell morphology from a polygonal shape into a spindle shape and also increased the mRNA levels of MMP-1, MMP-3 and MMP-9, but slightly decreased the MMP-2 mRNA level. No change at the mRNA level of MT1-MMP was observed. Similarly to unstimulated cultures, no mRNA for MMP-7 or MMP-13 was detected in the TNF-alpha treated cultures. TNF-alpha had no effect on the TIMP-1 and TIMP-2 mRNA levels and did not induce TIMP-3 or TIMP-4 expression. Gelatin zymography and Western blot analysis revealed that the increase observed at the mRNA level of MMP-3 and MMP-9 was similar to that of their net protein level; furthermore, the active form of MMP-1 was induced. Our results indicate that the TNF-alpha-induced morphological change of EA.hy 926 cells is associated not only with specific changes in the expression of PGs by the cells, but also with specific changes in the expression of MMPs.

Endothelial cell intracellular Ca2+ concentration is increased upon breast tumor cell contact and mediates tumor cell transendothelial migration

Tumor cell extravasation is a determinant step in the process of hematogenous metastasis. The signal transduction pathways involved in the interactions between tumor cells and the vascular endothelium during transendothelial migration are still undefined. In the present study, we have investigated the influence of human breast adenocarcinoma cells (MCF7) on human umbilical vein endothelial cell (HUVEC) intracellular Ca2+ concentration ([Ca2+]i). We show that the contact between MCF7 cells and a confluent HUVEC monolayer induces an immediate and transient increase in HUVEC [Ca2+]i. This [Ca2+]i rise could not be elicited by tumor cell-conditioned medium, isolated tumor cell membranes, inert beads or normal breast epithelial cells, demonstrating the involvement of specific recognition mechanisms between MCF7 cells and HUVEC. Depletion of HUVEC intracellular Ca2+ stores by the endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin as well as the selective depletion of inositol 1,4,5-triphosphate (IP3)-sensitive Ca2+ stores by prior activation of HUVEC using histamine resulted in a complete inhibition of tumor cell-induced [Ca2+]i elevation. Similar results were obtained when HUVEC monolayers were treated with the tyrosine kinase inhibitor herbimycin A, suggesting a role for tyrosine kinase-associated cell surface receptors in tumor cell-endothelial cell interactions. The depletion of HUVEC intracellular Ca2+ stores by thapsigargin was also shown to delay MCF7-induced endothelial cell disjunction, to prevent their spreading on the subendothelial extracellular matrix and transendothelial migration in vitro. These results suggest that transient changes in endothelial [Ca2+]i may govern multiple steps of tumor cell extravasation.

Alteration of interendothelial adherens junctions following tumor cell-endothelial cell interaction in vitro

The integrity of the vascular endothelium is mainly dependent upon the organization of interendothelial adherens junctions (AJ). These junctions are formed by the homotypic interaction of a transmembrane protein, vascular endothelial cadherin (VE-cadherin), which is complexed to an intracellular protein network including alpha-, beta-, and gamma-catenin. Additional proteins such as vinculin and alpha-actinin have been suggested to link the VE-cadherin/catenin complex to the actin-based cytoskeleton. During the process of hematogenous metastasis, circulating tumor cells must disrupt these intercellular junctions in order to extravasate. In the present study, we have investigated the influence of tumor cell-endothelial cell interaction upon interendothelial AJ. We show that human breast adenocarcinoma cells (MCF-7), but not normal human mammary epithelial cells, induce a rapid endothelial cell (EC) dissociation which correlates with the loss of VE-cadherin expression at the site of tumor cell-EC contact and with profound changes in vinculin distribution and organization. This process could not be inhibited by metalloproteinase nor serine protease inhibitors. Immunoprecipitations and Western blot analysis demonstrate that the overall expression of VE-cadherin and vinculin as well as the composition of the VE-cadherin/catenins complex are not affected by tumor cells while the tyrosine phosphorylation status of proteins within the complex is significantly altered. Our data suggest that tumor cells modulate AJ protein distribution and phosphorylation in EC and may, thereby, facilitate EC dissociation.

Cellular effects of hypercholesterolemia in modulation of cancer growth and metastasis: a review of the evidence

Hypercholesterolemia and increased cancer risk have been associated, particularly with the high fat diets characteristic of Western societies. We were interested in the possible association between preexisting hypercholesterolemia and the rapidity and extent of tumor metastases in these patients. To date there has been only a few studies that have suggested and explored this determinant of cancer metastases although it may play a role in a subset of patients who develop cancers. This article will review the literature on the effects of LDL-cholesterol on cell proliferation and differentiation and speculate on mechanisms of involvement of a hypercholesterolemic milieu on cancer progression and enhancement of metastatic potential.

Tumor cell motility and metastasis : Autocrine motility factor as an example of ecto/exoenzyme cytokines

Cellular locomotion plays a critical role in such normal processes as embryonic development, tissue segregation, as well as the infiltration of fibroblasts and vascular cells during wound repair and the inflammatory responses of the adult immune system. During tumor invasion and metastasis the processes of cell migration achieve dire significance. Disruption of normal homeostatic mechanisms to benefit the survival of the individual tumor cell is a common theme discovered during the characterization of factors once thought to be tumor-specific. One such molecule, tumor cell autocrine motility factor, was so described and has only recently been identified as a normal protein involved in intracellular glycolysis as well as implicated as an extracellular effector of normal cell functions including survival of certain populations of neurons. This molecule represents a member of the newly emerging family of intracellular enzymes whose disparate functions as extracellular mediators of cellular responses defines a new class of ecto/exoenzymes which play a role in normal cellular processes and are inappropriately utilized by tumor cells to elicit new survival strategies.

Increased endothelial cell retraction and tumor cell invasion by soluble factors derived from pancreatic cancer cells

BACKGROUND

Tumor cells induce endothelial cell retraction before invasion. In pancreatic cancer cells, the factors affecting endothelial cell retraction are not well-understood.

METHODS

The activities of the endothelial cell retraction in conditioned media (CM) derived from three human pancreatic cancer cell lines, PSN-1, MiaPaca-2, and Capan-1, were measured for the amount of intercellular junctional transport of FITC dextran through an endothelial cell monolayer in a transwell cell culture system.

RESULTS

The CM derived from the three pancreatic cancer cells induced endothelial cell retraction. The endothelial cell retraction activity in the CM from PSN-1 cells was significantly higher than those from MiaPaca-2 and Capan-1 cells. The CM from PSN-1 cells enhanced both the adhesion and the invasion of MiaPaca-2 and Capan-1 cells. The factors with endothelial cell retraction activity in the CM from PSN-1 cells were characterized as heat-stable, trypsin-sensitive glycoproteins ranging from 10,000 to 50,000 in molecular weight, and were found both in heparin-bound and unbound fractions.

CONCLUSIONS

PSN-1 cells produced and secreted at least two factors inducing the endothelial cell retraction. The factors could play an important role in the establishment of invasion and metastasis of PSN-1 cells.

Interleukin-1-mediated H2O2 production by hepatic sinusoidal endothelium in response to B16 melanoma cell adhesion

We have examined H2O2 production by in vitro enriched hepatic sinusoidal endothelium (HSE) during interleukin-1 beta (IL-1 beta) stimulation and B16 melanoma cell adhesion. Production of H2O2 was quantified by flow cytometry and multiwell plate-scanning fluorimetry of intracellular 2', 7'-dichlorofluorescein (DCFH) oxidation in HSE. Under IL-1 beta treatment there was a 6-fold increase in endothelial cells producing H2O2 (67%) and a 4-fold augmentation in the Kupffer cell population (86%). The average H2O2 content per cell size unit significantly (P < 0.01) increased in endothelial cells (2.6-fold) and Kupffer cells (1.7-fold). In contrast to the homogeneity of Kupffer cells, H2O2 production intensity was largely heterogeneous in IL-1 beta-activated HSE. Enhancement of H2O2 production by IL-beta-treated HSE started at the 4th h and peaked 2-3 h later. The addition of increasing concentration of IL-1 beta to HSE for 4 h caused the progressive activation of H2O2 production by treated cells. The addition of 80 M excess of IL-1 receptor antagonist (IL-1 Ra) 10 min before IL-1 beta treatment abrogated IL-1 beta-mediated enhancement of H2O2. From the 2nd h of B16 melanoma adhesion to HSE there was significantly (P < 0.05) enhancement of H2O2 content in HSE. This activation increased 2.25-fold by the 3rd h of coculture and had reduced again by the 5th h. IL-1 Ra (80 ng/ml) given to HSE 10 min before melanoma cells abrogated the HSE response to melanoma cells. The addition of 1% paraformaldehyde (PFA)-fixed B16 melanoma cells to HSE did not affect H2O2 production response, indicating that HSE-activating agents were on the melanoma cell surface. Preincubation of B16 melanoma cells in the presence of 5 micrograms/ml anti-mouse IL-1 beta neutralizing antibody reduced the melanoma cell-induced HSE production of H2O2 by 80%. On the contrary, B16 melanoma cell-conditioned medium did not vary HSE production of H2O2 compared to control HSE. Western blot analysis of cytosolic and membrane sediments from B16 melanoma cells confirmed the presence of IL-1 beta (17.4 kDa) in both cell compartments. Thus, HSE responded to melanoma cell contact with a rapid production of H2O2. HSE activation was IL-1-dependent. This cytokine was directly provided to HSE by the cell surface of adhered melanoma cells.

Enhancement of in vitro tumor-cell transcellular migration by tumor-cell-secreted endothelial-cell-retraction factor

To investigate the factors affecting endothelial-cell retraction, we have studied the interaction of tumor cells with endothelial cells in 2 human pancreatic cancer cell lines, PSN-1 and MiaPaca-2. The extent of endothelial-cell retraction measured by the amount of intercellular junctional transport of FITC-dextran through an endothelial monolayer was increased by the addition of a conditioned medium (CM) from both cell lines, while CM from PSN-1 cells was 2 to 3 times more potent than that from MiaPaca-2 cells. After the treatment of endothelial monolayer with CM of PSN-1 cells, the ability of both PSN-1 cells and MiaPaca cells to adhere to or invade the monolayer increased. The addition of CM from PSN-1 cells did not affect the growth rate of either the endothelial or the tumor cells. The activity in the CM was heat-stable and bound to heparin-Sepharose, but was inactivated when treated by 0.5% trypsin. Protease inhibitors did not influence the activity. Pre-treatment of PSN-1 cells by an inhibitor of protein synthesis, cycloheximide, or of protein processing, benzyl-N-acetyl-alpha-D-galactosaminide, reduced endothelial-cell-retraction activity in the CM. The active substance in the CM fractionated in the molecular-weight range of 10,000 to 50,000. These results suggest that PSN-1 cells produce and secrete (a) soluble factor(s) that can induce endothelial-cell retraction, thus facilitating tumor-cell invasion.

CD44: physiological expression of distinct isoforms as evidence for organ-specific metastasis formation

Continuous progress has been achieved during recent decades in the therapy of metastasizing malignancies by improving chemotherapeutic strategies and new approaches in radiation therapy. Genetic manipulation of tumor cells and of the tumor fighting immune system is hoped to add significant contributions to curative interventions in disseminated tumors. That we are still far from eradicating death by malignant growth is due ultimately to our limited understanding of the cascade of events resulting in metastasis formation, which until recently was believed to rely on multiple rounds of mutation and selection processes. This implies an individually specific history of each metastatic tumor, which would rule out uniform diagnostic and therapeutic concepts. When it was noted in a rat tumor model that the transfer of cDNA of a single gene, a CD44 variant isoform (CD44v) covering the exons v4-v7, sufficed to initiate metastasis formation of a locally growing tumor, hope was created that a "metastogene" may have been identified. Although the idea of CD44v expression as a unifying concept for tumor progression was not sustained, the discovery of CD44v-initiated metastatic spread allowed a conceptually new hypothesis on tumor progression as a consequence of the reactivation of genetic programs of ontogeny, stem cell differentiation, and/or lymphocyte activation. Since distinct CD44 isoforms play an important role in these processes, unraveling the functions of this family of molecules can indeed provide a cornerstone in the understanding of tumor progression. This article summarizes briefly the present knowledge on known functions of CD44 isoforms with particular focus on parallels between physiological programs and tumor progression.

A simple fluorometric assay for quantifying the adhesion of tumour cells to endothelial monolayers

A static adhesion assay employing 6-carboxy-3',6'-diacetylfluorescein (6-CFDA) as a fluorescent marker has been developed to study the interactions of tumour cell lines with endothelial monolayers. This assay allows simple, safe quantification of cell-cell adhesion using living cells. It has been used to demonstrate that the integrin adhesion molecule VLA-4 mediates the attachment of RPMI-7951 melanoma cells to human umbilical vein endothelial cells (HUVEC) which have been activated by TNF alpha. In addition, MDA-MB-231 breast adenocarcinoma cells display greater adhesion to microvessel endothelial cells than to large vessel endothelial cells.

Tobacco smoke tumor promoters, catechol and hydroquinone, induce oxidative regulation of protein kinase C and influence invasion and metastasis of lung carcinoma cells

Cigarette smoke polyphenolic agents (catechol and hydroquinone) that generate oxidants have been shown to be tumor promoters. Furthermore, oxidants can influence protein kinase C (PKC)-mediated signal transduction. Since terpenoid tumor promoters, phorbol esters, increase invasion and metastasis by activating PKC, we have determined whether polyphenolic agents present in the cigarette smoke condensate (CSC) could also influence these events. Hydroquinone (50 microM), catechol (500 microM), or CSC (50 micrograms/ml) induced an initial cytosol-to-membrane translocation of PKC in LL/2 lung carcinoma cells, followed by a later down-regulation of the enzyme. LL/2 cells treated with these CSC-related agents for a limited time (45 min) and exhibiting high membrane-associated PKC activity, when injected into mice through the tail vein, produced an increase in metastatic nodules in the lungs after 20 days. However, cells treated with CSC-related agents for a prolonged period did not exhibit an increase in metastasis. Agents that decrease the rate of production of reactive oxygen species, such as catalase either alone or in combination with superoxide dismutase, and a cell-permeable iron-chelator, o-phenanthroline, inhibited CSC-mediated membrane association of PKC and metastasis. Prior treatment of CSC with tyrosinase to modify polyphenols resulted in a partial loss of CSC stimulation of metastasis. Furthermore, a cell-permeable Ca2+ chelator and diverse PKC inhibitors, such as calphostin C, hypericin, chelerythrine, and bisindolylmaleimide, inhibited CSC-enhanced metastasis. CSC increased in vitro tumor cell adhesion to endothelial monolayers and to reconstituted basement membrane (Matrigel) and also enhanced the invasion through Matrigel coated on the polycarbonate filters in Transwells. All these CSC effects were found to be temporary and were blocked by the above mentioned antioxidant systems and PKC inhibitors. Thus, these results suggest that the oxidants generated by autooxidation of polyphenolic agents present in tobacco smoke increase tumor cell invasion and metastasis, at least in part by activation of Ca2+/PKC signal transduction. Conceivably, cigarette smoke constituents not only promote tumorigenesis but also may increase the spread of cancer in the body.

12-lipoxygenases and 12(S)-HETE: role in cancer metastasis

Arachidonic acid metabolites have been implicated in multiple steps of carcinogenesis. Their role in tumor cell metastasis, the ultimate challenge for the treatment of cancer patients, are however not well-documented. Arachidonic acid is primarily metabolized through three pathways, i.e., cyclooxygenase, lipoxygenase, and P450-dependent monooxygenase. In this review we focus our attention on one specific lipoxygenase, i.e., 12-lipoxygenase, and its potential role in modulating the metastatic process. In mammalian cells there exist three types of 12-lipoxygenases which differ in tissue distribution, preferential substrates, and profile of their metabolites. Most of these 12-lipoxygenases have been cloned and sequenced, and the molecular and biochemical determinants responsible for catalysis of specific substrates characterized. Solid tumor cells express 12-lipoxygenase mRNA, possess 12-lipoxygenase protein, and biosynthesize 12(S)-HETE [12(S)-hydroxyeicosatetraenoic acid], as revealed by numerous experimental approaches. The ability of tumor cells to generate 12(S)-HETE is positively correlated to their metastatic potential. A large collection of experimental data suggest that 12(S)-HETE is a crucial intracellular signaling molecule that activates protein kinase C and mediates the biological functions of many growth factors and cytokines such as bFGF, PDGF, EGF, and AMF. 12(S)-HETE plays a pivotal role in multiple steps of the metastatic 'cascade' encompassing tumor cell-vasculature interactions, tumor cell motility, proteolysis, invasion, and angiogenesis. The fact that 12-lipoxygenase is expressed in a wide diversity of tumor cell lines and 12(S)-HETE is a key modulatory molecule in metastasis provides the rationale for targeting these molecules in anti-cancer and anti-metastasis therapeutic protocols.

Lipoproteins in hypoxic tumor cells as traps of free radicals

We examined the role of main cell protective mechanisms in retaining the high resistance of ascitic cells (EAC, ZAH) to lipid peroxidation with respect to different stages of tumor-organism metabolic interactions. The following mechanisms were studied: (1) the activity of main EAC enzymatic antioxidants (GSH-Px, SOD); (2) changes in lipid metabolism, especially the content of the main PUFA (linoleic and arachidonic fatty acids) in EAC cells; (3) comparison of intracellular resistance between EAC/ZAH cytoplasmic sections (containing LP-granules or not) to lipid peroxidation (initialized directly by UV-light). We found that the high resistance to lipid peroxidation was typical for cytoplasma sections (without LP-granules) on all stages of tumor development in vivo. The intracellular LP-granules become the main sensitive targets for FR-action, but only in the chronic hypoxia state of EAC/ZAH tumor cells. The latter effect developed in close correlation with the following metabolic interactions: (1) increasing the proportion of PUFA (especially, arachidonic and linoleic acids) transported to EAC tumor cells from host organs and accumulated mainly in tumor LP-granules, and (2) decreasing the alpha-tocopherol content of these hypoxic EAC cells while no activation of the main cell antioxidative enzymes (GSH-Px, SOD) took place. The vitality and high resistance of EAC stationary cells were accompanied by the 'paradoxical' state with great differences between the resistance of the intracellular PUFA-rich granules and other cytoplasmic sections. A similar state was found in stationary ZAH cells. The cell state is in good agreement with the Dormandy's suggestion that PUFA-rich granules can trap reactive radical species preventing their interaction with 'critical' PUFA-membranes.

Expression of intercellular adhesion molecule-1 in hepatocellular carcinoma

The expression of intercellular adhesion molecule-1 (ICAM-1) was investigated in frozen sections obtained from 40 resected liver specimens of patients with hepatocellular carcinoma using immunoperoxidase techniques and immunoelectron microscopy. ICAM-1 was expressed in 80% of the HCC specimens on the membrane of cancer cells. In noncancerous regions characterized by cirrhosis in 28 cases and chronic hepatitis in 12 cases, ICAM-1 was rarely expressed on hepatocytes but was expressed mainly on the endothelium of portal vessels and sinusoidal lining cells. These results suggest that expression of ICAM-1 in hepatocellular carcinoma may be induced by malignant transformation of hepatocytes.