Factors promoting tumor angiogenesis

Angiogenesis and Multiple Sclerosis Pathogenesis: A Glance at New Pharmaceutical Approaches

Multiple sclerosis is a chronic disease of the central nervous system characterized by demyelination and destruction of axons. The most common form of the disease is the relapsing-remitting multiple sclerosis in which episodic attacks with typical neurological symptoms are followed by episodes of partial or complete recovery. One of the underestimated factors that contribute to the pathogenesis of multiple sclerosis is excessive angiogenesis. Here, we review the role of angiogenesis in the onset and in the development of the disease, the molecular mechanisms underlying angiogenesis, the current therapeutic approaches, and the potential therapeutic strategies with a look at natural compounds as multi-target drugs with both neuroprotective and anti-angiogenic properties.

Ruta graveolens water extract inhibits cell-cell network formation in human umbilical endothelial cells via MEK-ERK1/2 pathway

Angiogenesis is a process encompassing several steps such as endothelial cells proliferation, differentiation and migration to form a vascular network, involving different signal transduction pathways. Among these, ERK1/2 signaling mediates VEGF-dependent signaling pathway. Here we report that the water extract of Ruta graveolens (RGWE), widely known as a medicinal plant, is able to impair in a dose-dependent manner, cell network formation without affecting cell viability. Biochemical analysis showed that the major component of RGWE is rutin, unable to reproduce RGWE effect. We found that RGWE inhibits ERK1/2 phosphorylation and that this event is crucial in cell network formation since the transfection of HUVEC with a constitutively active MEK (caMEK), the ERK1/2 activator, induces a robust cell network formation as compared to untransfected and/or mock transfected cells and, more importantly, caMEK transfected cells became unresponsive to RGWE. Moreover, RGWE inhibits VEGF and nestin gene expression, necessary for vessel formation, and the caMEK transfection induces their higher expression. In conclusion, we report that RGWE is able to significantly impair vessels network formation without affecting cell viability, preventing ERK1/2 activation and, in turn, down-regulating VEGF and nestin expression. These findings point to RGWE as a potential therapeutic tool capable to interfere with pathologic angiogenesis.

Biological and Prognostic Significance of the Morphological Types and Vascular Patterns in Colorectal Liver Metastases (CRLM): Looking Beyond the Tumor Margin

Patients with encapsulated colorectal liver metastases (CRLM) have a better prognosis than those without a capsule. The reason for the encapsulation is unknown. Hypoxia inducible factor-1α (HIF-1α) increases tumor angiogenesis and tumor tissue expression is associated with reduced survival. Our aim was to determine whether the good prognosis of encapsulated CRLM is associated with reduced HIF-1α expression by the cancer.The study selected only patients who had not undergone neoadjuvant chemotherapy prior to a potentially curative hepatectomy for CRLM. From 30 selected patients, serial sections were cut from a single randomly selected metastasis. Morphology was assessed following H&E staining. Tumor hypoxia, vascular endothelial growth factor (VEGF), proliferation, and microvascular density (MVD) were assessed by immunostaining for HIF-1α and carbonic anhydrase-9 (CA-9), VEGF, Ki67, and cluster of differentiation-31, respectively. MVD was calculated in the vascular hot spots. Pathology was reported without clinical outcome information. Actual long-term survival was recorded.Thirteen (43%) of the cancers were encapsulated CRLM containing glands which were large, complex, and cribriform. Thirteen (43%) were infiltrative CRLM and their glands were small, closely packed, and rounded with vessels in the interglandular fibrous tissue with no capsule; 3 (10%) had a mixed picture. Encapsulated CRLM had a higher expression of HIF-1α (58% vs 8%, P = 0.03), CA-9 (42% vs 0%, P = 0.04), and VEGF (92% vs 25%, P = 0.02). MVD was lower in the encapsulated CRLM group (37 mm vs 143 mm, P < 0.001). The median follow-up was 115 months. The encapsulated CRLM group had a better overall and 5-year survival (relative hazard: 0.58, P = 0.057 and hazard ratio: 0.52, P = 0.044).There are 2 main morphological appearances of CRLM which have very different long-term survival following liver resection surgery. The morphology is associated with differences in expression of HIF-1α, CA-9, VEGF, and angiogenesis.

Comparison of (18)F-fluorodeoxyglucose PET/CT findings with vascular endothelial growth factors and receptors in colorectal cancer

The purpose of this study was to evaluate the association of (18)F-fluorodeoxyglucose (FDG)-PET/CT findings with the vascular endothelial growth factor (VEGF) family and its receptor (VEGFR) levels in metastatic and nonmetastatic colorectal cancer (CRC). Fluorine-18 FDG-PET/CT scans were performed for initial staging and restaging of patients with CRC. FDG-PET/CT findings of tumor (such as the presence of a primary tumor, the lymphatic or distance metastases, and the maximum standardized uptake value (SUVmax) of the primary tumor), serum VEGF A-C-D-E levels, and serum VEGF receptor 1-2-3 levels were analyzed. A total of 63 patients were included into the study (35 males, mean age 61.3 ± 11.9 years). Patients were divided into two groups, based on positive and negative PET/CT findings. Patients were also categorized according to the presence of metastasis. All evaluated parameters were significantly higher in the PET/CT-positive group than the PET/CT-negative group (p < 0.001). All those parameters were also positively correlated with each other. The highest correlation for SUVmax of primary tumor was found with VEGFR-3 (p < 0.001, r = 0.665). Patients with metastases had high levels of VEGF-D, VEGF-A, VEGF-C, VEGF-E, and VEGFR-3 than those without metastases. These parameters had better specificity and sensitivity values than the SUVmax of the primary tumor for detection of metastases. However, VEGF-D was the best indicator of metastasis in all of those parameters (VEGF-D vs SUVmax; sensitivity 100 vs 100 %; specificity 76 vs 76 %; AUC 0.903 vs 0.835; p < 0.001, respectively). Vascular endothelial growth factor family and its receptors were significantly higher in metastatic CRC patients. VEGF-D was the best indicator of metastasis than all VEGF family, VEGFR-3, and primary tumor SUVmax. VEGF family (A-C-D-E) and VEGFR-3 may help to determine the prognosis and management of CRC.

Antiangiogenic Activity of Acer tegmentosum Maxim Water Extract in Vitro and in Vivo

Angiogenesis, the formation of new blood vessels, is critical for tumor growth and metastasis. Notably, tumors themselves can lead to angiogenesis by inducing vascular endothelial growth factor (VEGF), which is one of the most potent angiogenic factors. Inhibition of angiogenesis is currently perceived as one of the most promising strategies for the blockage of tumor growth. In this study, we investigated the effects of Acer tegmentosum maxim water extract (ATME) on angiogenesis and its underlying signal mechanism. We studied the antiangiogenic activity of ATME by using human umbilical vein endothelial cells (HUVECs). ATME strongly inhibited VEGF-induced endothelial cell proliferation, migration, invasion, and tube formation, as well as vessel sprouting in a rat aortic ring sprouting assay. Moreover, we found that the p44/42 mitogen activated protein (MAP) kinase signaling pathway is involved in the inhibition of angiogenesis by ATME. Moreover, when we performed the in vivo matrigel plug assay, VEGF-induced angiogenesis was potently reduced when compared to that for the control group. Taken together, these results suggest that ATME exhibits potent antiangiogenic activity in vivo and in vitro and that these effects are regulated by the extracellular regulated kinase (ERK) pathway.

Inhibition of P38 MAPK Reduces Tumor Conditioned Medium-Induced Angiogenesis in Co-Cultured Human Umbilical Vein Endothelial Cells and Fibroblasts

Tumor conditioned medium (CM) has been widely used to stimulate endothelial cells to form capillary-like structures in in vitro angiogenesis models. We report herein the effect of HT1080 and A549 CM after they were mixed with microvascular endothelial cells medium-2 (EGM-2) on angiogenesis in human umbilical vein endothelial cells (HUVECs). Both HT1080 and A549 CM decreased HUVEC proliferation, to different extents. While A549 CM significantly increased capillary-like structure formation in a co-culture system, no effect of HT1080 was apparent. Inhibition of p38 mitogen-activated protein kinase (MAPK) blocked both basal and A549 CM induced capillary-like structure formation, but inhibition of extracellular signal-regulated kinases (ERK) and that of c-Jun N-terminal protein kinases (JNK) MAPK had no such effect. Activation of ERK MAPK was inhibited by both CMs, whereas p38 MAPK was inactivated by HT1080 and activated by A549 CM and a control. Neither CM had an effect on JNK MAPK. The results suggest that p38 MAPK played a critical role in capillary-like structure formation in the co-culture, partly via promotion of apoptosis in HUVECs.

Molecular neuro-oncology and development of targeted therapeutic strategies for brain tumors. Part 2: PI3K/Akt/PTEN, mTOR, SHH/PTCH and angiogenesis

Brain tumors are a diverse group of malignancies that remain refractory to conventional treatment approaches. Molecular neuro-oncology has now begun to clarify the transformed phenotype of brain tumors and identify oncogenic pathways that might be amenable to targeted therapy. Activity of the phosphoinositide 3; kinase (PI3K)/Akt pathway is often upregulated in brain tumors due to excessive stimulation by growth factor receptors and Ras. Loss of function of the tumor suppressor gene PTEN also frequently contributes to upregulation of PI3K/Akt. Several compounds, such as wortmannin and LY-294002, can target PI3K and inhibit activity of this pathway. The mammalian target of rapamycin (mTOR) is an important regulator of cell growth and metabolism and is often upregulated by Akt. Clinical trials of CCI-779, an inhibitor of mTOR, are ongoing in recurrent malignant glioma patients. The sonic hedgehog/PTCH pathway is involved in the tumorigenesis of some familial and sporadic medulloblastomas. This pathway can be targeted by cyclopamine, which is under evaluation in preclinical studies. Angiogenesis is a critical process for development and progression of brain tumors. Targeted approaches to inhibit angiogenesis include monoclonal antibodies, receptor tyrosine kinase inhibitors, antisense oligonucleotides and gene therapy. Clinical trials are ongoing for numerous angiogenesis inhibitors, including thalidomide, CC-5103 and PTK 787/ZK 222584. Further development of targeted therapies and evaluation of these new agents in clinical trials will be needed to improve survival and quality of life of patients with brain tumors.

Metastasis-associated factors facilitating the progression of colorectal cancer

Tumor metastasis remains the principal cause of treatment failure and poor prognosis in patients with colorectal cancer. It is a multistage process which includes proteolysis, motility and migration of cells, proliferation in a new site, and neoangiogenesis. A crucial step in the process of intra- and extra-vasation is the activation of proteolytic enzymes capable of degrading the extracellular matrix (ECM). In this stage, urokinase plasminogen activator receptor (uPAR) and matrix metalloproteinases (MMPs) are necessary. Micrometastases need the presence of growth factor and vascular growth factor so that they can form macrometastasis. In addition, cell adhesion molecules (CAMs) and guanine nucleotide exchange factors (GEFs) play important roles in the progression of colorectal cancer and metastatic migration. Further elucidation of the mechanisms of how these molecules contribute will aid in the identification of diagnostic and prognostic markers as well as therapeutic targets for patients with colorectal metastasis.

Clinicopathological and prognostic significance of HER-2/neu and VEGF expression in colon carcinomas

BACKGROUND

HER-2/neu and VEGF expression is correlated with disease behaviors in various cancers. However, evidence for their expression in colon cancer is rather contradictory both for the protein expression status and prognostic value. HER-2/neu is found to participate in VEGF regulation, and has known correlation with VEGF expression in some tumors. In this study, we investigated HER-2/neu and VEGF expression in Chinese colon patients and explored whether there was any correlation between their expression patterns.

METHODS

HER-2/neu and VEGF were investigated immunohistochemically using tumor samples obtained from 317 colon cancer patients with all tumor stages. Correlation of the degree of staining with clinicopathological parameters and survival was investigated.

RESULTS

Positive expression rates of HER-2/neu and VEGF in colon cancer were 15.5% and 55.5% respectively. HER-2/neu expression was significantly correlated with tumor size and distant metastases (P < 0.05), but was not an independent prognostic marker of survival (P > 0.05). Expression of VEGF was significantly correlated with tumor size, tumor stage, lymph node metastases, and distant metastases (P < 0.05). The 5-year survival rate in patients with negative and positive VEGF expression was 70.2% and 61.9% respectively; the difference was not statistically significant (P = 0.146). No correlation between HER-2/neu and VEGF expression was detected (P = 0.151).

CONCLUSIONS

HER-2/neu and VEGF are not important prognostic markers of colon cancer. The present results do not support any association between HER2/neu and VEGF expression in this setting.

Effects of ionizing radiation on three-dimensional human vessel models: differential effects according to radiation quality and cellular development

Little is known about the effects of space radiation on the human body. There are a number of potential chronic and acute effects, and one major target for noncarcinogenic effects is the human vasculature. Cellular stress, inflammatory response, and other radiation effects on endothelial cells may affect vascular function. This study was aimed at understanding the effects of space ionizing radiation on the formation and maintenance of capillary-like blood vessels. We used a 3D human vessel model created with human endothelial cells in a gel matrix to assess the effects of low-LET protons and high-LET iron ions. Iron ions were more damaging and caused significant reduction in the length of intact vessels in both developing and mature vessels at a dose of 80 cGy. Protons had no effect on mature vessels up to a dose of 3.2 Gy but did inhibit vessel formation at 80 cGy. Comparison with γ radiation showed that photons had even less effect, although, as with protons, developing vessels were more sensitive. Apoptosis assays showed that inhibition of vessel development or deterioration of mature vessels was not due to cell death by apoptosis even in the case of iron ions. These are the first data to show the effects of radiation with varying linear energy transfer on a human vessel model.

Prognostic significance of c-erbB-2 and vascular endothelial growth factor in colorectal liver metastases

BACKGROUND

The prognostic value of c-erbB-2 and vascular endothelial growth factor (VEGF) expression in colorectal liver metastases (CLM) is unclear. The purpose of this study was to clarify the relationship of c-erbB-2 and VEGF with the clinicopathological parameters and the survival results in CLM.

METHODS

For 44 patients who had undergone liver resection for CLM at Fudan University Cancer Hospital from 2000 to 2007, the expression of c-erbB-2 and VEGF in CLM and the corresponding primary cancer specimens were evaluated immunohistochemically. The correlations among c-erbB-2 and VEGF, clinicopathologic factors, and survival were then statistically analyzed.

RESULTS

Positive expression rates of c-erbB-2 and VEGF in CLM lesions were 38.64% and 52.72%, respectively. The expression of c-erbB-2 and VEGF in CLM were similar to that of corresponding primary tumor. c-erbB-2 expression correlated with number of metastatic lesions and the distribution of liver metastases. The expression of VEGF correlated with the size of liver metastatic lesion and distribution of liver metastases. A statistically significant association between the expression of c-erbB-2 and VEGF in both CLM and primary tumor was noted. Univariate analysis showed that VEGF was a prognostic factor. However, on multivariate analysis, expression of VEGF was not an independent prognostic marker. Patients with both negative expression of c-erbB-2 and VEGF expression had a better outcome than others.

CONCLUSIONS

VEGF might be a statistically significant prognostic factor. The combined analysis of c-erbB-2 and VEGF is of added prognostic value. An association exists between c-erbB-2 and VEGF. However, further studies are required to confirm this issue.

AIF-1 expression regulates endothelial cell activation, signal transduction, and vasculogenesis

Endothelial cell (EC) activation plays a key role in vascular inflammation, thrombosis, and angiogenesis. Allograft inflammatory factor-1 (AIF-1) is a cytoplasmic, calcium-binding, inflammation-responsive scaffold protein that has been implicated in the regulation of inflammation. The expression and function of AIF-1 in EC is uncharacterized, and the purpose of this study was to characterize AIF-1 expression and function in ECs. AIF-1 expression colocalized with CD31-positive ECs in neointima of inflamed human arteries but not normal arteries. AIF-1 is detected at low levels in unstimulated EC, but expression can be increased in response to serum and soluble factors. Stable transfection of AIF-1 small interfering RNA (siRNA) in ECs reduced AIF-1 protein expression by 73% and significantly reduced EC proliferation and migration (P < 0.05 and 0.001). Rescue of AIF-1 expression restored both proliferation and migration of siRNA-expressing ECs, and AIF-1 overexpression enhanced both of these activities, suggesting a strong association between AIF-1 expression and EC activation. Activation of mitogen-activated protein kinase p44/42 and PAK1 was significantly reduced in siRNA ECs challenged with inflammatory stimuli. Reduction of AIF-1 expression did not decrease EC tube-like structure or microvessel formation from aortic rings, but overexpression of AIF-1 did significantly increase the number and complexity of these structures. These data indicate that AIF-1 expression plays an important role in signal transduction and activation of ECs and may also participate in new vessel formation.

Angiogenesis and the tumour hypoxia response in prostate cancer: a review

The formation of new blood vessels, angiogenesis, is a highly-regulated active process that is critical for the development of the normal and malignant prostate. The vascular endothelial growth factor (VEGF) system assumes a critical role in the angiogenic process. Angiogenesis is a prerequisite for the expansion of solid tumours beyond 1-3 mm3 and is stimulated in response to a hypoxic environment. This review discusses the process of angiogenesis and the key angiogenic mediator, VEGF, and their role in tumour progression and metastasis. A better understanding of the mechanisms behind angiogenesis will ultimately lead to the development of new anti-angiogenic agents in the management of prostate cancer.

The human papillomavirus type 18 E6 oncoprotein induces Vascular Endothelial Growth Factor 121 (VEGF121) transcription from the promoter through a p53-independent mechanism

Altered angiogenic response is associated with high-grade cervical dysplasia and with invasive squamous carcinoma of the cervix. Vascular Endothelial Growth Factor (VEGF) is one of the most potent inducers of angiogenesis and is up-regulated in carcinoma of the cervix. Infection by high-risk human papillomavirus and persistent expression of viral oncogene E6 are etiologically linked to the development of cervical cancer. E6 is able to immortalize cells and induce malignant transformation by inactivating p53. In cervical cancer, regulation of VEGF expression is poorly described. Thus, we investigated whether E6 oncoprotein could regulate VEGF expression in HPV18-positive cervical cancer-derived HeLa cells harboring a wild-type p53. The alternative splicing of vegf mRNA renders three major isoforms of 121, 165 and 189 amino-acids in humans. We have designed isoform specific real time QRT-PCR assays to quantitate vegf transcripts and VEGF121 was the predominant isoform. Silencing HPV18 E6 mRNA with specific siRNA reduced VEGF121 expression by at least 50% whereas silencing of p53 did not alter its expression. Treatment with cycloheximide did not inhibit E6-induced VEGF121 expression. Collectively, these results suggest that HPV18 E6 oncoprotein contributes to tumor angiogenesis by inducing VEGF transcription from the promoter in a p53-independent manner.

Antiangiogenic activity of the endocannabinoid anandamide: correlation to its tumor-suppressor efficacy

Endocannabinoids are now emerging as suppressors of key cell-signaling pathways involved in cancer cell growth, invasion, and metastasis. We have previously observed that the metabolically stable anandamide analog, 2-methyl-2'-F-anandamide (Met-F-AEA) can inhibit the growth of thyroid cancer in vivo. Our hypothesis was that the anti-tumor effect observed could be at least in part ascribed to inhibition of neo-angiogenesis. Therefore, the aim of this study was to assess the anti-angiogenic activity of Met-F-AEA, to investigate the molecular mechanisms underlying this effect and whether Met-F-AEA could antagonize tumor-induced endothelial cell sprouting. We show that Met-F-AEA inhibited bFGF-stimulated endothelial cell proliferation, in a dose-dependent manner, and also induced apoptosis, both effects reliant on cannabinoid CB1 receptor stimulation. Analyzing the signaling pathways implicated in angiogenesis, we observed that the bFGF-induced ERK phosphorylation was antagonized by Met-F-AEA, and we found that p38 MAPK was involved in Met-F-AEA-induced apoptosis. Moreover, Met-F-AEA was able to inhibit bi-dimensional capillary-like tube formation and activity of matrix metalloprotease MMP-2, a major matrix degrading enzyme. Importantly, we demonstrated that Met-F-AEA is also functional in vivo since it inhibited angiogenesis in the chick chorioallantoic neovascularization model. Finally, Met-F-AEA inhibited tumor-induced angiogenesis in a three-dimensional model of endothelial and thyroid tumor cell (KiMol) spheroids co-cultures in different 3-D polymeric matrices that resemble tumor microenvironment and architecture. Thus, our results suggest that anandamide could be involved in the control of cancer growth targeting both tumor cell proliferation and the angiogenic stimulation of the vasculature.

The angiogenic effects ofAngelica sinensis extract on HUVEC in vitro and zebrafish in vivo

Angiogenesis plays an important role in a wide range of physiological processes such as wound healing and fetal development. Many diseases are associated with imbalances in regulation of angiogenesis, in which it is either excessive or there is insufficient blood vessel formation. Angelica sinensis (AS), commonly used in the prescriptions of Chinese medicine, is a potential candidate for curing such diseases. However, biological effects of AS on angiogenesis and underlying mechanisms are yet to be fully elucidated. This investigation describes the angiogenic effects of AS extract on human endothelial cells (HUVEC) in vitro and zebrafish in vivo. The extract was demonstrated, by XTT assay and microscopic cell counting, to stimulate the proliferation of HUVEC; in addition, flow cytometry analysis indicated that the extract increased the percentage of HUVEC in the S phase. The wound healing migration assay illustrated that a dramatic increase in migration could be measured in AS extract-treated HUVEC. Meanwhile, the number of invaded cells and the mean tube length were significantly increased in AS extract treatment groups. The extract was also demonstrated to promote changes in subintestinal vessels (SIVs) in zebrafish, one feature of angiogenesis. In addition, AS extract was found by real-time PCR to enhance vascular endothelial growth factor (VEGF) mRNA expression. In a bead-based immunoassay, higher levels of p38 and JNK 1/2 expression were also observed in effusions compared with control cells. All results suggest that Angelica sinensis extract can promote angiogenesis, and that the angiogenic effects involve p38 and JNK 1/2 phosphorylation.

Protein kinase C and downstream signaling pathways in a three-dimensional model of phorbol ester-induced angiogenesis

Angiogenesis, a critical process in both health and disease, is mediated by a number of signaling pathways. Although proangiogenic stimuli, including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and the phorbol ester phorbol-12 myristate-13 acetate (PMA) are known to promote blood vessel formation, their downstream targets are ill defined. We sought to investigate the signaling pathways required for vessel assembly by utilizing a three-dimensional collagen matrix in which human umbilical vein endothelial cells (HUVECs) form tubular structures. Our data show that PMA is sufficient for the induction of angiogenesis, and that protein kinase C (PKC) is necessary for this process. Evaluation of PKC isoforms alpha and sigma revealed that these proteins are uniquely regulated. Characterization of an additional PMA target, protein kinase D (PKD) demonstrated that this enzyme becomes phosphorylated in HUVECs, and may therefore be involved in proangiogenic signaling. Further examination of downstream effectors of PKC showed that extracellular signal-regulated kinase (ERK) is critical for angiogenesis, and is accordingly phosphorylated in response to PMA. Surprisingly however, phosphorylation of ERK is independent of PKC activity. In addition, we show that the PKC target sphingosine kinase (SPK) is required for vessel formation. These findings illustrate the complexities of blood vessel formation, and suggest that activators utilize multiple independent pathways to invoke a complete angiogenic response.

Molecular mechanisms of hepatic metastasis in colorectal cancer

BACKGROUND

Colorectal cancer currently accounts for 11% of all cancers in the United States and is the second leading cause of cancer-related death, with the majority of deaths attributable to hepatic metastases. Many new studies are elucidating the complex molecular factors involved in this event, which could be used to generate clinically applicable screening and therapeutic tools.

METHODS

An initial Pubmed and Medline literature search using keywords such as, molecular factor, colorectal cancer, hepatic metastasis/es, and main headings, such as angiogenesis, was reviewed. Since there are many molecular factors involved in this process not all could be included in this review. The list of discussed gene products was limited to the most studied factors, identified by the number of references in the literature search, and additional recently discovered gene products with in-vivo evidence of strong metastasis association.

RESULTS

Twenty molecular factors were identified and included in the discussion of this review article. The molecular factors were separated into four groups based on their function, they are: proteolysis, adhesion, angiogenesis, and cell survival. All factors have a promising role as a screening or therapeutic target.

CONCLUSION

This review has identified the many recent advances in elucidating the pathways involved in colorectal cancer hepatic metastasis. By better understanding the many complex molecular events involved in metastasis, novel screening and therapeutic tools may be developed with the ultimate goal of preventing metastasis and increasing patient survival.

Downregulation of angiogenic factors in Ewing tumor xenografts by the combination of human interferon-alpha or interferon-beta with ifosfamide

Ewing sarcoma is the second most common bone tumor in childhood. Despite aggressive chemotherapy and radiotherapy, the prognosis of metastatic disease remains poor. In a nude mouse model of Ewing tumor xenografts, we recently showed that human type I interferons (IFNs) inhibit the growth of established xenografts. Combined therapy with human IFNs and ifosfamide (IFO), an alkylating agent widely used in high-dose chemotherapy of Ewing tumors, results in a strong synergistic antitumor effect. We have investigated the effect of IFNs/IFO treatment on the expression of vascular endothelial growth factor (VEGF), matrix metalloproteinase 9 (MMP-9), and urokinase plasminogen activator receptor (uPAR), three key mediators of tumor growth and angiogenesis, in tumor xenografts generated either from a primary tumor (EW7) or from a metastatic tumor (COH). COH tumors expressed 5-fold higher levels of VEGF than EW7 tumors. IFNs/IFO treatment reduced by >70% the amount of VEGF in COH and EW7 tumors. We did not detect constitutive MMP-9 activity in EW7 tumors. In contrast, the metastasis-derived COH tumor expressed very high levels of active MMP-9. Although the total amount of MMP-9 remained unchanged, active MMP-9 was reduced by up to 75% in IFNs/IFO-treated COH tumors. IFNs/IFO treatment triggered in both COH and EW7 tumors the downregulation of uPAR expression, a molecule involved in vascularization and endothelial cell migration. Our results partly explain the mechanism of tumor growth inhibition by IFNs/IFO therapy and provide a rational foundation for the development of a new therapeutic approach to Ewing tumors resistant to conventional chemotherapy.

Two faces of high-molecular-weight kininogen (HK) in angiogenesis: bradykinin turns it on and cleaved HK (HKa) turns it off

High-molecular-weight kininogen (HK) is a plasma protein that possesses multiple physiological functions. Originally identified as a precursor of bradykinin, a bioactive peptide that regulates many cardiovascular processes, it is now recognized that HK plays important roles in fibrinolysis, thrombosis, and inflammation. HK binds to endothelial cells where it can be cleaved by plasma kallikrein to release bradykinin (BK). The remaining portion of the molecule, cleaved HK, is designated cleaved high-molecular-weight kininogen or HKa. While BK has been intensively studied, the physiological implication of the generation of HKa is not clear. Recent studies have revealed that HKa inhibits angiogenesis while BK promotes angiogenesis. These findings represent novel functions of the kallikrein-kinin system that have not yet been fully appreciated. In this review, we will briefly discuss the recent progress in the studies of the molecular mechanisms that mediate the antiangiogenic effect of HKa and the proangiogenic activity of BK.

Angiogenesis and its role in colorectal tumor and metastasis formation

Advances in our comprehension of cancer biology and metastasis formation have led to the development of new therapeutic approaches that target tumor biology. The survival and establishment of metastatic lesions depend on a shift in the normal balance of key regulatory factors in favor of angiogenesis. Although a number of these factors have been identified, the most potent regulator of angiogenesis is vascular endothelial growth factor (VEGF). In phase I trials, targeting VEGF with single-agent therapy did not produce clinical benefit for patients, despite promise in preclinical trials. However, the recent data showing that anti-VEGF therapy can enhance the effects of chemotherapy demonstrate the utility in targeting angiogenic factors as a component of antineoplastic regimens. A better understanding of the functions of VEGF allows the development of new hypotheses with regard to its mechanism of action. This article will highlight what is known about colorectal cancer angiogenesis, and will discuss how therapy targeting VEGF may enhance the effects of chemotherapy (and radiation therapy).

Loss of heterozygosity reveals non-VHL allelic loss in hemangioblastomas at 22q13

Hemangioblastomas (HBs) are low-grade (World Health Organization grade I/IV) central nervous system (CNS) tumors that frequently contain VHL (3p26) mutations. They occur sporadically and in von Hippel Lindau (VHL) disease. Encoded pVHL aids degradation of hypoxia-inducible factors (HIFs) in the presence of normal oxygen levels. HBs provide an in vivo view of HIF effects within a CNS tumor. Typically, HBs are cystic tumors containing a mural nodule formed by noninvasive, vacuolated stromal cells that are embedded in a network of capillaries. Nine HBs, consecutively resected from 8 patients at our institution during a recent 2-year time span, were evaluated for additional losses of tumor suppressor genes. Non-VHL microsatellites studied for loss of heterozygosity (LOH) are near tumor suppressor genes lost in gliomas, pituitary adenomas, several CNS tumors on 22q, neurofibromatosis 1, and colon carcinomas (13, 2, 2, 1, and 2 markers for each, respectively). LOH in the region of 3p21.3-3p26.3 occurred in 3 of 8 HBs informative for at least 1 marker (D3S1539, D3S2303, or D3S2373). By using 2 markers (D22S417 and D22S532) for 22q13.2, LOH was found in 5 of 8 informative HBs. All 3 HBs with allelic losses near VHL also showed LOH at 22q13.2. No consistent losses were found with markers for 1p34, LMYC, 5q21, 5q32, 9p21, 10q23, 17p13, and 19q13. LOH for the 22q13.2 region in HBs suggests that the loss of another tumor suppressor gene is involved in the pathogenesis of HBs in addition to VHL. Absence of LOH for glioma markers is consistent with the low-grade behavior of HBs.

β4 integrin is involved in statin-induced endothelial cell death

HMG-CoA reductase inhibitors (statins) have been shown to inhibit angiogenesis. The molecular mechanism mediating the anti-endothelial activities of statins remains unclear. The present study demonstrated that the antiangiogenic effect of atorvastatin (ATV) was associated with endothelial death. Molecular profiling data identified a 29-fold upregulation of beta4 integrin mRNA. Western blot and flow cytometry confirmed robust increases of total and cell-surface beta4 integrin. Blockage of beta4 integrin activity by antagonizing antibody abrogated ATV-induced endothelial death. The endothelial death and beta4 integrin upregulation by ATV could be reversed by intermediate metabilites of the HMG-CoA reductase pathway mevalonate or GGPP, but not by FPP, suggesting that these effects were results of specific inhibition of the pathway. These data indicate that the HMG-CoA reductase might represent an important survival pathway in angiogenic endothelial cells and thus, a potential target for antiangiogenic therapy.

Urokinase-type plasminogen activator receptor is involved in mediating the apoptotic effect of cleaved high molecular weight kininogen in human endothelial cells

Cleaved high molecular weight kininogen (HKa) has been shown to inhibit in vivo neovascularization and induce apoptosis of endothelial cells. We have shown that HKa-induced apoptosis correlated with its antiadhesive effect and was regulated by extracellular matrix (ECM) proteins. In this study, we identified the urokinase-type plasminogen activator receptor (uPAR) as a target of HKa activity at the endothelial cell surface. Anti-uPAR antibodies blocked the apoptotic effect of HKa. Further studies revealed that uPAR formed a signaling complex containing integrin alpha(v)beta3 or alpha5beta1, caveolin, and Src kinase Yes in endothelial cells. HKa physically disrupted the formation of this complex in a manner that paralleled its apoptotic effect. For the first time, our results provide a mechanistic explanation for the previous observation that HKa selectively induces apoptosis of endothelial cells grown on vitronectin, but not cells grown on fibronectin. These data also resolve the controversial role of uPAR in mediating the apoptotic and antiadhesive activities of HKa.

Cancer therapy with tetrathiomolybdate: antiangiogenesis by lowering body copper--a review

A new anticopper drug, tetrathiomolybdate (TM), developed for Wilson's disease, is a very promising antiangiogenic agent. Copper levels lowered into an antiangiogenic window by TM have shown efficacy against cancer in a variety of animal models as well as in patients. The only significant toxicity so far results from overtreatment and excessive bone marrow depletion of copper. The resulting anemia and/or leukopenia is easily treatable by dose reduction or drug holiday. The underlying concept for TM efficacy as an anticancer agent is that when the body's copper status is in the window, cellular copper needs are met and toxicity is avoided. Copper status is relatively easily monitored by following serum ceruloplasmin, a copper-containing protein secreted by the liver at a rate dependent upon the amount of copper in the liver available to incorporate into the protein. The authors speculate that the copper level is a primitive angiogenesis and growth-signaling regulator that has been retained throughout evolution.

Transmembrane proteases in cell growth and invasion: new contributors to angiogenesis?

Transmembrane proteases (TPs) are proteins anchored in the plasma membrane with their catalytic site exposed to the external surface of the membrane. TPs are widely expressed, and their dysregulated expression is associated with cancer, infection, inflammation, autoimmune and cardiovascular diseases, all diseases where angiogenesis is part of the pathology. TPs participate in extracellular proteolysis (degradation of extracellular matrix components, regulation of chemokine activity, release of membrane-anchored cytokines, cytokine receptors and adhesion molecules) and influence cell functions (growth, secretion of angiogenic molecules, motility). Recent attention has been focused on the ADAM-17 (a disintegrin and metalloprotease)/TACE/CD156q, the MT1-MMP (membrane-type-1 matrix metallo proteinase)/MMP-14, and the ectopeptidases aminopeptidase N (APN/CD13), dipeptidyl peptidase IV (DPPIV/CD26) and angiotensin-converting enzyme (ACE/CD143), that appear to have a critical role in angiogenesis. This article summarizes current knowledge on these TPs, and reviews recent investigations that document their participation during angiogenic-related events. Through their multiple roles, TPs may thereby provide critical links in angiogenesis.

Effects of adrenomedullin on endothelial cells in the multistep process of angiogenesis: Involvement of CRLR/RAMP2 and CRLR/RAMP3 receptors

Recently, we demonstrated that U87 glioblastoma xenograft tumors treated with anti-adrenomedullin (AM) antibody were less vascularized than control tumors, suggesting that AM might be involved in neovascularization and/or vessel stabilization. Angiogenesis, the sprouting of new capillaries from preexisting blood vessels, is a multistep process that involves migration and proliferation of endothelial cells, remodeling of the extracellular matrix and functional maturation of the newly assembled vessels. In our study, we analyzed the role of AM on human umbilical vein endothelial cell (HUVEC) phenotype related to different stages of angiogenesis. Here we report evidence that AM promoted HUVEC migration and invasion in a dose-dependent manner. The action of AM is specific and is mediated by the calcitonin receptor-like receptor/receptor activity-modifying protein-2 and -3 (CRLR/RAMP2; CRLR/RAMP3) receptors. Furthermore, AM was able to induce HUVEC differentiation into cord-like structures on Matrigel. Suboptimal concentrations of vascular endothelial growth factor (VEGF) and AM acted synergistically to induce angiogenic-related effects on endothelial cells in vitro. Blocking antibodies to VEGF did not significantly inhibit AM-induced capillary tube formation by human endothelial cells, indicating that AM does not function indirectly through upregulation of VEGF. These findings suggest that the proangiogenic action of AM on cultured endothelial cells via CRLR/RAMP2 and CRLR/RAMP3 receptors may translate in vivo into enhanced neovascularization and therefore identify AM and its receptors acting as potential new targets for antiangiogenic therapies.

Different roles of ERK and p38 MAP kinases during tube formation from endothelial cells cultured in 3-dimensional collagen matrices

In a two-dimensional (2D) culture dish, the major activity of endothelial cells is proliferation with limited morphological change. When cultured in a three-dimensional (3D) collagen gel matrix, endothelial cells undergo a series of morphological changes starting with development of intracellular vacuoles and followed by cell elongation. Adjacent cells then coalesce to form tube-like structures. This process mimics the steps of capillary formation during angiogenesis. Using this model, we investigated the roles of extracellular signal-regulated kinase (ERK) and p38 MAP kinase (p38) in the tube formation from human umbilical vein endothelial cells (HUVEC). Proliferating HUVEC gradually lost their ability to divide after being transferred to 3D collagen matrices, where differentiation became the dominant cellular activity. The transition from proliferation to the differentiation state was accompanied by a drastic reduction of cyclin-dependent kinases CDC2, CDK4, and retinoblastoma (Rb) protein, but the expression of cyclin-dependent kinase inhibitor, p27kip1, was increased. Inhibition of p38 by SB203580 partially prevented these changes and increased the proliferation rate of HUVEC. However, cells under this condition exhibited unusually elongated cell bodies, and they were unable to coalesce to form tube structures. Inhibition of ERK neither affected the cell proliferation rate nor the expression levels of cell cycle regulators, but it completely blocked tube formation by inducing apoptosis, a finding different from the best-known role of ERK in cell proliferation in the 2D cell culture systems. We conclude that the major function of ERK is to maintain cell viability while p38 plays multiple roles in controlling cell proliferation, viability, and morphogenesis during tube formation.

Angiogenesis in hypersensitivity pneumonitis

Angiogenesis is an essential process required for growth and tissue repair after injury, but it may also contribute to the pathology of a number of human disorders including neoplasias, atherosclerosis and inflammatory diseases. Vascular endothelial growth factor (VEGF) is a potent angiogenic peptide upregulated by many cytokines and endothelium shear stresses. Lung is a highly vascular tissue with finely organized and regulated microvascular beds, and its inflammation may lead to dysregulated angiogenesis. Hypersensitivity pneumonitis (HP) is a lung disorder characterized by chronic lymphocytic inflammation and endothelial damage. However, neovascularization has not been previously explored. In this study, we examined the expression and localization of VEGF in 38 patients with HP and 14 healthy control subjects (CS). VEGF levels in bronchoalveolar lavage fluid (BALF) were measured by ELISA, and cellular lung localization was determined by immunohistochemistry. In addition, VEGF expression was analyzed in lung tissue by RT-PCR. Our results showed sera levels significantly increased in HP patients compared with CS (209.3 +/- 189.3 vs. 55.3 +/- 31.4 pg/ml; p = 0.004). By contrast, BALF levels of VEGF were significantly decreased in HP patients compared with CS (35.3 +/- 51.5 pg/ml vs. 185.1 +/- 191.4 pg/ml; p < 0.001). VEGF was primary expressed by epithelial cells, smooth muscle cells, and interstitial macrophages in HP tissue. Flt-1 and Flk-1 receptors were highly expressed by endothelial cells from medium and small vessels in HP tissue. By RT-PCR the VEGF RNA was increased compared with those in normal lung. Our results suggest that abnormal expression of VEGF may contribute to impair the lung repair in HP.

Angiogenesis and antiangiogenic therapy of colon cancer liver metastasis

The fact that tumor growth and metastatic spread relies on angiogenesis has been widely proven and accepted. The understanding of cancer biology and metastasis formation has led to the development of new therapeutic approaches that target tumor biology. The survival and establishment of metastatic lesions depend on a shift in the normal balance of proangiogenic and antiangiogenic factors that favor angiogenesis. Colorectal cancer is one of the leading cancer deaths worldwide. Angiogenesis has been associated with colon cancer progression and metastatic spread, thereby significantly affecting patient survival. New experimental approaches that inhibit angiogenic processes have demonstrated promising antineoplastic effects on metastatic colorectal cancer and are partially being investigated in clinical trials. This review focuses on angiogenesis in colorectal cancer metastasis formation as a target for antiangiogenic therapy, describing the experience from experimental studies and current clinical trials.

Current status of thalidomide and its role in the treatment of metastatic prostate cancer

Following the discovery of its anti-angiogenic properties and despite its tragic history, thalidomide has re-surfaced in the field of oncology. Concurrent with its evaluation in various clinical trials for cancer, thalidomide's mechanism of action is sought and new analogues with improved efficacy and pharmacological profile are emerging. This review is a critical evaluation of thalidomide metabolism, molecular targets, anti-angiogenic activity and clinical efficacy with an emphasis on metastatic prostate cancer.

Upregulation of Cdc2 and cyclin A during apoptosis of endothelial cells induced by cleaved high-molecular-weight kininogen

We (8) reported that the cleaved high-molecular-weight kininogen (HKa) and its domain 5 (D5) inhibited angiogenesis. Further studies (15) revealed that D5 could inhibit cell proliferation and induce apoptosis of proliferating endothelial cells, which together may represent a critical part of antiangiogenic activity of HKa and D5. In the present study, we further examined the effect of HKa on cell cycle progression and cell viability. We report that HKa induced a significant upregulation of Cdc2 and cyclin A in proliferating endothelial cells, concurrent with a marked increase of Cdc2 activity. The increased expression of Cdc2 and cyclin A by HKa was not associated with an apparent change in cell cycle profiles of basic fibroblast growth factor-stimulated proliferating cells, but closely correlated with a marked increase of apoptosis, suggesting that the elevated Cdc2 activity is involved in HKa-induced apoptosis of proliferating endothelial cells. Our results support an emerging hypothesis that Cdc2 and cyclin A are important regulators for cell cycle as well as for apoptosis.

Apoptotic effect of cleaved high molecular weight kininogen is regulated by extracellular matrix proteins

We previously reported that cleaved high molecular weight kininogen (HKa) and its domain 5 (D5) inhibit critical steps required for angiogenesis and in vivo neovascularization (Colman et al. 2000: Blood 95:543-550). We have further shown that D5 is able to induce apoptosis of endothelial cells, which may represent a critical part of the anti-angiogenic activity of HKa and D5 (Guo et al. 2001: Arterioscler Thromb Vasc Biol 21:1427-1433). In this study, we demonstrate that HKa- and D5-induced apoptosis is closely correlated with their anti-adhesive effect. An important new finding is that the apoptotic activity of HKa and D5 is highly regulated by their interactions with different extracellular matrix (ECM) proteins. HKa inhibited cell adhesion to vitronectin (Vn, 90%) and gelatin (Gel) (40%), but it had no apparent effect on cell adhesion to fibronectin (Fn). D5 showed a similar pattern on cell adhesion but was less potent than HKa. HKa induced apoptosis of endothelial cells grown on Vn and Gel but not cells grown on Fn which closely parallels with its anti-adhesive potency. Further results revealed that the anti-adhesive effect and the apoptotic effect of HKa are associated with its ability to inhibit phosphorylation of focal adhesion kinase (FAK) and paxillin, two important signal molecules required for cell adhesion and cell viability. We conclude that the anti-adhesive activity of HKa and D5 is responsible for their apoptotic effect and that Vn is likely an ECM component that mediates the effect of HKa and D5.

Effect of p53 gene transfection on vascular endothelial growth factor expression in endometrial cancer cells

It has been reported that tumor suppressor gene p53 regulates vascular endothelial growth factor (VEGF) expression, but the relation between them in endometrial carcinoma remains unclear. We investigated VEGF expression in 11 endometrial carcinoma cell lines and the effect of p53 gene transfection on VEGF expression in the p53-mutated endometrial carcinoma cell line, HEC-50B. Immunoblotting for detecting VEGF, p53, and beta-actin was performed. Wild type p53 gene was transfected using the SuperFect method. The mean VEGF value of 0.8 +/- 0.3 (n = 6) in p53 wild-type group was significantly lower than the 1.6 +/- 0.8 (n = 5) that was found in the p53 mutant group (P < 0.05). Levels of VEGF in the culture medium were measured by enzyme immunoassay (EIA). VEGF levels in the p53 gene-transfected HEC-50B cells and the conditioned medium were decreased at 48 h after p53 gene transfection. VEGF expression was downregulated by p53 in endometrial carcinoma cells.

VEGF expression and its reguration by p53 gene transfection in endometrial carcinoma cells

Vascular endothelial growth factor (VEGF) that activates endothelial cell growth induces angiogenesis, which is indispensable to tumor igenesis and tumor progression. On the other hand, tumor suppressor gene p53 has been considered to regulate VEGF expression, but the detailed relationship between them remains unclear. In this study, we aimed to study VEGF expression in endometrial carcinoma cells and the effect of p53 gene transfection on VEGF expression using p53-mutated endometrial carcinoma cell line, HEC-50B. Immunoblotting for detecting VEGF protein, p53 protein and beta-actin was performed using 11 endometrial carcinoma cell lines. Levels of VEGF in the cultured media were measured by Enzyme immunoassay(EIA). Transfection of wild p53 gene was carried out by SuperFect method in HEC-50B cells, which had mutant p53 gene and did not express p53 protein. The results of immunoblotting were analyzed by NIH image and expressed as values. The results of EIA were expressed as the relative value. The VEGF value was 0.8 +/- 0.3 (n = 6) in p53-wild group, whereas in p53-mutant group it was 1.6 +/- 0.8 (n = 5). VEGF expression was correlated significantly with p53 status (P < 0.05). VEGF levels in p53 gene-transfected cells and the conditioned medium were decreased in 48 hours after p53 gene transfection. VEGF expression was down-regulated by p53 in endometrial carcinoma cells.

Immunohistochemical expression of angiogenic cytokines and their receptors in reactive benign lymph nodes and non-Hodgkin lymphoma

Angiogenic cytokines regulate B-cell lymphopoiesis and are related to prognosis in B-cell lymphoproliferative disorders. Transforming growth factor-beta (TGF-beta) inhibits mature B-cell proliferation and immunoglobulin production. Increased levels of serum vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) are associated with poor prognosis in non-Hodgkin lymphoma (NHL). To understand the expression of angiogenic cytokines at different stages of B-cell differentiation in lymph nodes, we examined the immunohistochemical expression of TGF-beta, VEGF, bFGF, and their receptors in five patients with reactive benign lymphadenopathy and 12 patients with B-cell NHL (mantle cell lymphoma, 4; small cleaved cell follicular lymphoma, 5; lymphoplasmacytic lymphoma, 3). In benign lymph nodes, TGF-beta1, TGF-beta2, and TGFbetaRII were positive in prefollicular mantle cells, follicular center cells, and postfollicular plasma cells. Basic FGF, FGF-R1, and FGF-R4 were positive in large follicular center cells and postfollicular plasma cells. Vascular endothelial growth factor was positive in large follicular center cells and postfollicular plasma cells. In NHL, TGF-beta and its receptors were weakly positive in small cleaved cell follicular lymphoma; VEGF was strongly positive in lymphoplasmacytic lymphoma and weakly positive in mantle cell lymphoma. Basic FGF and its receptors were negative in NHL; however, FGF-R4 was positive in some cases of small cleaved cell follicular lymphoma. Our findings suggest that TGF-beta, bFGF, and their receptors have opposite roles in B-cell differentiation and maturation in benign lymph nodes. Transforming growth factor-beta and its receptors have an important role in germinal center development; loss of their activity could be associated with abnormal clonal proliferation of NHL.

Biology of angiogenesis in tumors of the gastrointestinal tract

The realization that the growth and spread of tumors are dependent on angiogenesis has created new avenues of research designed to help us to better understand cancer biology and to facilitate the development of new therapeutic strategies. However, the process of angiogenesis consists of multiple, sequential, and interdependent steps with a myriad of positive and negative regulators of angiogenesis being involved. The survival of tumors and thus their metastases are dependent upon the balance of endogenous angiogenic and anti-angiogenic factors such that the outcome favors increased angiogenesis. Several growth factors have been identified that regulate angiogenesis in cancers of the gastrointestinal tract. These include pro-angiogenic factors like vascular endothelial growth factor (VEGF) and anti-angiogenic factors, i.e., thrombospondin. The following review provides a brief overview about the most important factors that are involved in the angiogenic process in tumors derived from colon, stomach, and pancreas. A thorough understanding of the role these factors play in the angiogenic process may lead to the development of novel therapeutic antineoplastic strategies.

Tetrathiomolybdate anticopper therapy for Wilson's disease inhibits angiogenesis, fibrosis and inflammation

The need for agents to lower body copper in Wilson's disease, a disease which results from copper toxicity has been the driving force for the development of the effective anticopper drugs penicillamine, trientine, zinc, and now tetrathiomolybdate (TM). Because of its rapid action, potency, and safety, TM is proving to be a very effective drug for initial treatment of acutely ill Wilson's disease patients. Beyond this, TM has antiangiogenic effects, because many proangiogenic cytokines require normal levels of copper. This has led to use of TM in cancer, where it is generally effective in animal tumor models, and has shown efficacy in preliminary clinical studies. Most recently, it has been found that TM has antifibrotic and antiinflammatory effects through inhibition of profibrotic and proinflammatory cytokines.

Kininostatin as an antiangiogenic inhibitor: what we know and what we do not know

High-molecular-weight kininogen (HK) is a plasma protein consisting of six domains (designated D1-D6). It was first characterized as a precursor of bradykinin, a bioactive peptide that regulates many cardiovascular processes. HK can bind to endothelial cells where it can be cleaved by plasma kallikrein to release bradykinin contained within domain 4. The remaining portion of the molecule, cleaved HK, is designated HKa. While bradykinin has been intensively studied, the physiological implication of the generation of HKa is not clear. HKa has recently been shown to inhibit the important steps required for angiogenesis such as proliferation and migration of endothelial cells. The antiangiogenic activity of HKa has further been demonstrated in animal models in which HKa inhibits neovascularization. Because domain 5 (D5) of HKa reproduces the antiangiogenic effect of HKa, D5 is named kininostatin for this novel function. In this review, we will briefly discuss the recent progress in the studies of the molecular mechanisms that mediate the antiangiogenic effect of HKa and D5.

Chemotherapy for the treatment of metastatic brain tumors

Metastatic brain tumors are the most common complication of systemic cancer and affect 20-40% of all adult cancer patients. Whole-brain radiotherapy and surgical resection of accessible, solitary lesions have been the mainstay of treatment. Recently, chemotherapy has become a more viable treatment option for metastatic brain tumors. Many different drugs and administrative approaches have been shown to be clinically active. Traditional chemotherapy given before or during irradiation can be effective with agents such as cyclophosphamide, cisplatin and etoposide. Nontraditional approaches, such as tempozolomide and intra-arterial administration of carboplatin, have demonstrated activity against recurrent metastatic disease. In early clinical trials of interstitial chemotherapy, biodegradable polymers have shown some clinical efficacy and have been well-tolerated. Molecular approaches are also under investigation in response to new information regarding the metastatic phenotype. Potential targets include growth factor receptors and other protein tyrosine kinases, internal signal transduction pathways, ras activation and matrix metalloprotease activity. New clinical trials will be needed to investigate these new molecular-based therapeutics, alone and in combination with currently available treatment options, to determine the optimal application of chemotherapy to metastatic brain tumors.

Extracellular angio-associated migratory cell protein plays a positive role in angiogenesis and is regulated by astrocytes in coculture

The extracellular form of angio-associated migratory cell protein (AAMP), a recently discovered protein, plays a positive role in angiogenesis and can be regulated by astrocytes. Angiogenic activities are inhibited by an affinity-purified, polyclonal antibody generated to recombinant AAMP. Inhibition of endothelial cell tube formation was previously shown and now endothelial cell migration assays using this antibody show dose-dependent inhibition (75%) of endothelial cell migration. Also, antisense inhibition has been used to determine the effects of reducing total AAMP (extracellular and intracellular forms). An AAMP-specific antisense oligonucleotide that targets a region near its amino terminus, anti-MES, inhibits (45%) total AAMP production by bovine aortic endothelial cells (BAECs), compared to a negative control oligonucleotide. Paradoxically, comparable use of antisense-MES results in a 27% increase in BAEC motility. Decreased cellular production of total AAMP (via antisense) that results in an increase of endothelial migration contrasts with antibody inhibition of extracellular AAMP that decreases migration. This indicates compartment-specific roles for AAMP in angiogenesis. Transwell cocultures of human astrocytes and BAECs increase (53%) the amount of extracellular AAMP found associated with endothelial cells. Therefore, regulation of extracellular AAMP by astrocytes is hypothesized to aid in angiogenesis of the nervous system. Extracellular AAMP's positive role may be either as a promoter or as a permissive protein in this process.

Differences of vascular endothelial growth factor (VEGF) expression between liver and abdominal metastases from colon cancer. Implications for the treatment with VEGF inhibitors

The vascular endothelial growth factor (VEGF) plays a central role in promoting angiogenesis, and it is the target of innovative anti-cancer therapies. In colorectal carcinomas, differences in the VEGF expression have been found between the primary tumor and its metastases. We postulated that differences in the VEGF expression may also exist between liver and abdominal metastases from colon cancer. Consecutive colon cancer patients with liver or abdominal metastases were considered eligible for the study. Biopsies had to be performed before chemotherapy and the VEGF analysis were conducted through immunohistochemistry. The staining results were correlated to the metastatic pattern. The study population consisted of 41 patients with a metastatic site in the liver in 19 patients and the abdomen in 22 patients. A positive VEGF staining was found in 19 of the 41 metastatic samples (46%). Cases with positive VEGF expression were found more frequently in abdominal (15 out of 22 patients; 68%) than in liver metastases (4 out of 19 patients; 21%). Also, the degree of VEGF immunoreactivity was significantly higher in abdominal than in liver metastases. Evidence is supported that the VEGF expression may be different between colon cancer metastatic sites. The efficacy of anti-VEGF treatments may depend on the VEGF expression status, and this finding deserves further investigation.