Angiogenesis, metastasis, and endogenous inhibition

TMEM60 Promotes the Proliferation and Migration and Inhibits the Apoptosis of Glioma through Modulating AKT Signaling

Glioma is a highly fatal malignancy with aggressive proliferation, migration, and invasion metastasis due to aberrant genetic regulation. This work aimed to determine the function of transmembrane protein 60 (TMEM60) during glioma development. The level of TMEM60 in glioma tissues and normal tissues and its correlation with glioma prognosis were checked in The Cancer Genome Atlas (TCGA) database. The levels of TMEM60 in glioma cell lines and normal astrocytes were determined by quantitative real-time PCR and western blotting assay. TMEM60 knockdown and overexpression were conducted, followed by detection of cell viability, migration, invasion, and apoptosis. CCK-8 and colony formation assay were adopted to detect cell viability proliferation. Transwell assay was performed to measure cell migration and invasion. Cell apoptosis was evaluated by flow cytometry. The alternation of key proteins in the PI3K/Akt signaling pathway was measured by western blotting. TMEM60 expression was significantly higher in glioma tissues than that in the healthy control and was correlated with poor overall survival of patients. The protein and mRNA levels of TMEM60 were both elevated in glioma cell lines in comparison with the normal cell lines. Elevated level of TMEM60 led to enhanced proliferation, migration, and invasion and suppressed cell apoptosis. TMEM60 promoted the activation of PI3K/Akt signaling. Our data suggested that TMEM60 plays an oncogenic role in glioma progression via activating the PI3K/Akt signaling pathway.

An E3 Ubiquitin Ligase RNF139 Serves as a Tumor-Suppressor in Glioma

Glioma is highly lethal because of its high malignancy. Ubiquitination, a type of ubiquitin-dependent protein modification, has been reported to play an oncogenic or tumor-suppressive role in glioma development, depending on the targets. Ring finger protein 139 (RNF139) is a membrane-bound E3 ubiquitin ligase serving as a tumor suppressor by ubiquitylation-dependently suppressing cell growth. Herein, we firstly confirmed the abnormal downregulation of RNF139 in glioma tissues and cell lines. In glioma cells, ectopic RNF139 overexpression could inhibit, whereas RNF139 knockdown could aggravate the aggressive behaviors of glioma cells, including hyperproliferation, migration, and invasion. Moreover, in two glioma cell lines, RNF139 overexpression inhibited, whereas RNF139 knockdown enhanced the phosphorylation of phosphatidylinositol 3-kinase (PI3K) and AKT serine/threonine kinase 1 (AKT). In a word, we demonstrate the aberration in RNF139 expression in glioma tissue samples and cell lines. RNF139 serves as a tumor-suppressor in glioma by inhibiting glioma cell proliferation, migration, and invasion and promoting glioma cell apoptosis through regulating PI3K/AKT signaling.

Potential Therapeutic Strategies for Lung and Breast Cancers through Understanding the Anti-Angiogenesis Resistance Mechanisms

Breast and lung cancers are among the top cancer types in terms of incidence and mortality burden worldwide. One of the challenges in the treatment of breast and lung cancers is their resistance to administered drugs, as observed with angiogenesis inhibitors. Based on clinical and pre-clinical findings, these two types of cancers have gained the ability to resist angiogenesis inhibitors through several mechanisms that rely on cellular and extracellular factors. This resistance is mediated through angiogenesis-independent vascularization, and it is related to cancer cells and their microenvironment. The mechanisms that cancer cells utilize include metabolic symbiosis and invasion, and they also take advantage of neighboring cells like macrophages, endothelial cells, myeloid and adipose cells. Overcoming resistance is of great interest, and researchers are investigating possible strategies to enhance sensitivity towards angiogenesis inhibitors. These strategies involved targeting multiple players in angiogenesis, epigenetics, hypoxia, cellular metabolism and the immune system. This review aims to discuss the mechanisms of resistance to angiogenesis inhibitors and to highlight recently developed approaches to overcome this resistance.

Anti-angiogenic agents for the treatment of solid tumors: Potential pathways, therapy and current strategies - A review

Recent strategies for the treatment of cancer, other than just tumor cell killing have been under intensive development, such as anti-angiogenic therapeutic approach. Angiogenesis inhibition is an important strategy for the treatment of solid tumors, which basically depends on cutting off the blood supply to tumor micro-regions, resulting in pan-hypoxia and pan-necrosis within solid tumor tissues. The differential activation of angiogenesis between normal and tumor tissues makes this process an attractive strategic target for anti-tumor drug discovery. The principles of anti-angiogenic treatment for solid tumors were originally proposed in 1972, and ever since, it has become a putative target for therapies directed against solid tumors. In the early twenty first century, the FDA approved anti-angiogenic drugs, such as bevacizumab and sorafenib for the treatment of several solid tumors. Over the past two decades, researches have continued to improve the performance of anti-angiogenic drugs, describe their drug interaction potential, and uncover possible reasons for potential treatment resistance. Herein, we present an update to the pre-clinical and clinical situations of anti-angiogenic agents and discuss the most recent trends in this field.

Pre-metastatic niches: organ-specific homes for metastases

It is well established that organs of future metastasis are not passive receivers of circulating tumour cells, but are instead selectively and actively modified by the primary tumour before metastatic spread has even occurred. Sowing the 'seeds' of metastasis requires the action of tumour-secreted factors and tumour-shed extracellular vesicles that enable the 'soil' at distant metastatic sites to encourage the outgrowth of incoming cancer cells. In this Review, we summarize the main processes and new mechanisms involved in the formation of the pre-metastatic niche.

Effects of cisplatin on the LSD1-mediated invasion and metastasis of prostate cancer cells

Prostate cancer poses a major public health problem in men. Metastatic prostate cancer is incurable, and ultimately threatens the life of patients. Lysine-specific demethylase 1 (LSD1) is an androgen receptor-interacting protein that exerts a key role in regulating gene expression and is involved in numerous biological processes associated with prostate cancer. Cisplatin, also known as cis-diamminedichloroplatinum or DDP, is a standard chemotherapeutic agent used to treat prostate cancer; however, it has the disadvantage of various serious side effects. The present study aimed to investigate the effects of LSD1 knockdown, and the interplay between LSD1 and DDP, on prostate cancer cell proliferation, apoptosis and invasion, and, therefore, the potential of LSD1 as a target for prostate cancer therapy. Flow cytometric analysis, Cell Counting kit 8 assay, Transwell assay and western blotting results revealed that LSD1 knockdown, in combination with DDP treatment, exerted antiproliferative, proapoptotic and anti–invasive effects on PC3 prostate cancer cells. In addition, knockdown of LSD1 acted synergistically with DDP, thereby enhancing the induction of apoptosis, and the inhibition of proliferation and invasion in prostate cancer cells. These results indicated that LSD1 may serve as a potential therapeutic target, and may enhance the sensitivity of PC3 cells to DDP.

MicroRNA‑566 modulates vascular endothelial growth factor by targeting Von Hippel‑Landau in human glioblastoma in vitro and in vivo

MicroRNAs (miRNAs) are able to function as either oncogenes or tumor suppressor genes in tumorigenesis, and have been proposed as novel targets for anticancer treatment. It has previously been suggested that miRNAs have important roles in the initiation and progression of glioblastoma; however, the effects of miR‑566 in glioblastoma are currently unclear. The present study aimed to demonstrate that miR-566 can modulate vascular endothelial growth factor (VEGF) by targeting Von Hippel‑Lindau (VHL) in glioblastoma in vitro and in vivo by inhibiting the expression of miR-566. Glioblastoma is a highly vascularized tumor, which exhibits increased expression of angiogenic factors, including VEGF, which are crucial in the process of glioblastoma angiogenesis. Existing research has demonstrated that VHL is a tumor suppressor gene that is associated with various tumors. In addition, VHL is able to regulate the expression of VEGF by promoting the degradation of hypoxia‑inducible factor‑1α via ubiquitination. It has been predicted, using bioinformatics, that the VHL gene is regulated by miR‑566. Therefore, the present study hypothesized that miR‑566 may regulate VEGF expression by targeting VHL during the angiogenic process of glioblastoma multiforme. The results of the present study demonstrated that inhibition of miR‑566 expression increases the expression levels of VHL, decreases the expression levels of VEGF, and inhibits the invasive and migratory abilities of glioblastoma. In addition, VHL was identified as a functional target of miR‑566.

Targeting vascular pericytes in hypoxic tumors increases lung metastasis via angiopoietin-2

Strategies to target angiogenesis include inhibition of the vessel-stabilizing properties of vascular pericytes. Pericyte depletion in early-stage non-hypoxic tumors suppressed nascent angiogenesis, tumor growth, and lung metastasis. In contrast, pericyte depletion in advanced-stage hypoxic tumors with pre-established vasculature resulted in enhanced intra-tumoral hypoxia, decreased tumor growth, and increased lung metastasis. Furthermore, depletion of pericytes in post-natal retinal blood vessels resulted in abnormal and leaky vasculature. Tumor transcriptome profiling and biological validation revealed that angiopoietin signaling is a key regulatory pathway associated with pericyte targeting. Indeed, pericyte targeting in established mouse tumors increased angiopoietin-2 (ANG2/Angpt2) expression. Depletion of pericytes, coupled with targeting of ANG2 signaling, restored vascular stability in multiple model systems and decreased tumor growth and metastasis. Importantly, ANGPT2 expression correlated with poor outcome in patients with breast cancer. These results emphasize the potential utility of therapeutic regimens that target pericytes and ANG2 signaling in metastatic breast cancer.

The dominant role of IL-8 as an angiogenic driver in a three-dimensional physiological tumor construct for drug testing

The induction of angiogenesis and the promotion of tumor growth and invasiveness are processes critical to metastasis, and are dependent on reciprocal interactions between tumor cells and their microenvironment. The formation of a clinically relevant tumor requires support from the surrounding stroma, and it is hypothesized that three-dimensional (3D) tumor coculture models offer a microenvironment that more closely resembles the physiological tumor microenvironment. In this study, we investigated the effects of tissue-engineered 3D architecture and tumor-stroma interaction on the angiogenic factor secretion profiles of U2OS osteosarcoma cells by coculturing the tumor cells with immortalized fibroblasts or human umbilical vein endothelial cells (HUVECs). We also carried out Transwell migration assays for U2OS cells grown in monoculture or fibroblast coculture systems to study the physiological effect of upregulated angiogenic factors on endothelial cell migration. Anti-IL-8 and anti-vascular endothelial growth factor (VEGF)-A therapies were tested out on these models to investigate the role of 3D culture and the coculture of tumor cells with immortalized fibroblasts on the efficacy of antiangiogenic treatments. The coculture of U2OS cells with immortalized fibroblasts led to the upregulation of IL-8 and VEGF-A, especially in 3D culture. Conversely, coculture with endothelial cells resulted in the downregulation of VEGF-A for cells seeded in 3D scaffolds. The migration of HUVECs through the Transwell polycarbonate inserts increased for the 3D and immortalized fibroblast coculture models, and the targeted inhibition of IL-8 greatly reduced HUVEC migration despite the presence of VEGF-A. A similar effect was not observed when anti-VEGF-A neutralizing antibody was used instead, suggesting that IL-8 plays a more critical role in endothelial cell migration than VEGF-A, with significant implications on the clinical utility of antiangiogenic therapy targeting VEGF-A.

An extremely rare, remote intracerebral metastasis of oral cavity cancer: a case report

Distant brain metastases from oral squamous cell carcinomas (OSCC) are extremely rare. Here we describe a case of a 53-year-old man with a primary OSCC who referred to the neurosurgical department because of epileptic seizures. MR imaging revealed an enhancing lesion in the right parietal lobe. A craniotomy with tumor removing was performed. Histopathological examination verified an invasive, minimally differentiated metastasis of the primary OSCC. The patient refused whole brain radiation therapy and died from pulmonary metastatic disease 10 months after the neurosurgical intervention without any cerebral recurrence. To the authors' knowledge, only two similar cases have been previously reported.

Blood oxygen level dependent angiography (BOLDangio) and its potential applications in cancer research

Clinically, development of anti-angiogenic drugs for cancer therapy is pivotal. Longitudinal monitoring of tumour angiogenesis can help clinicians determine the effectiveness of anti-angiogenic therapy. Blood oxygen level dependent (BOLD) effect has been widely used for functional imaging and tumour oxygenation assessment. In this study, the BOLD effect is investigated under different levels of oxygen inhalation for the development of a novel angiographic MRI technique, blood oxygen level dependent angiography (BOLDangio). Under short-term (<10 min) generalized hypoxia induced by inhalation of 8% oxygen, we measure BOLD contrast as high as 25% from vessels at 9.4T using a simple gradient echo (GRE) pulse sequence. This produces high-resolution 2D and 3D maps of normal and tumour brain vasculature in less than 10 minutes. Additionally, this technique reliably detects metastatic tumours and tumour-induced intracranial hemorrhage. BOLDangio provides a sensitive research tool for MRI of vasculature under normal and pathological conditions. Thus, it may be applied as a simple monitoring technique for measuring the effectiveness of anti-angiogenic drugs in a preclinical environment.

Different combination schedules of gemcitabine with endostar affect antitumor efficacy

PURPOSE

Antiangiogenic drugs inhibit tumor growth by decreasing blood supply and causing transient "normalization" of the tumor vasculature, thereby improving the delivery of systemic chemotherapy. A higher dose of antiangiogenic drugs may lead to a more marked decrease in intratumoral blood flow but may concomitantly cause a decrease in delivery of chemotherapeutic agents. The purpose of this study was to define an optimal schedule for the combination of gemcitabine with a recombinant endostatin, endostar.

METHODS

We evaluated the antitumor effects with different schedules of gemcitabine combined with or without endostar. The changes of vascular endothelial growth factor (VEGF) levels in tumor extracts and sera after gemcitabine treatment were examined. Endostar was also assessed for its abilities to inhibit the increase in VEGF levels. Apoptotic cells and microvessel density within tumor tissue were also examined.

RESULTS

Endostar administered simultaneously with or following gemcitabine improved the inhibition of tumor growth, compared with gemcitabine alone. VEGF levels decreased immediately after gemcitabine treatment, but increased in the following several days. Endostar administered simultaneously with or following gemcitabine could inhibit the increase in VEGF levels, thereby cause a decreased vessel density and an increased apoptosis in tumor tissue.

CONCLUSIONS

Our finding suggested that endostar given simultaneously with or following gemcitabine might be optimal to enhance the antitumor effect.

Endostatin gene therapy enhances the efficacy of IL-2 in suppressing metastatic renal cell carcinoma in mice

We investigated whether the administration of IL-2 combined with endostatin gene therapy was able to produce additive or even synergistic immunomodulatory activity in a mouse model of metastatic renal carcinoma. Renca cells were injected into the tail vein of BALB/c mice. After 24 h, the animals were randomly divided into four groups (5 mice/group). One group of mice was the control, the second group received treatment with 100,000 UI of Recombinant IL-2 (Proleukin, Chiron) twice a day, 1 day per week during 2 weeks (IL-2), the third group received treatment with a subcutaneous inoculation of 3.6 x 10(6) endostatin-producing cells, and the fourth group received both therapies (IL-2 + ES). Mice were treated for 2 weeks. In the survival studies, 10 mice/group daily, mice were monitored daily until they died. The presence of metastases led to a twofold increase in endostatin levels. Subcutaneous inoculation of NIH/3T3-LendSN cells resulted in a 2.75 and 2.78-fold increase in endostatin levels in the ES and IL-2 + ES group, respectively. At the end of the study, there was a significant decrease in lung wet weight, lung nodules area, and microvascular area (MVA) in all treated groups compared with the control group (P < 0.001). The significant difference in lung wet weight and lung nodules area between groups IL-2 and IL-2 + ES revealed a synergistic antitumor effect of the combined treatment (P < 0.05). The IL-2 + ES therapy Kaplan-Meier survival curves showed that the probability of survival was significantly higher for mice treated with the combined therapy (log-rank test, P = 0.0028). Conjugated therapy caused an increase in the infiltration of CD4, CD8 and CD49b lymphocytes. An increase in the amount of CD8 cells (P < 0.01) was observed when animals received both ES and IL-2, suggesting an additive effect of ES over IL-2 treatment. A synergistic effect of ES on the infiltration of CD4 (P < 0.001) and CD49b cells (P < 0.01) was also observed over the effect of IL-2. Here, we show that ES led to an increase in CD4 T helper cells as well as cytotoxic lymphocytes, such as NK cells and CD8 cells, within tumors of IL-2 treated mice. This means that ES plays a role in supporting the actions of T cells.

Dietary vitamin K intake in relation to cancer incidence and mortality: results from the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Heidelberg)

BACKGROUND

Anticarcinogenic activities of vitamin K have been observed in animal and cell studies.

OBJECTIVE

On the basis of the growth inhibitory effects of vitamin K as observed in a variety of cancer cell lines, we hypothesized that dietary intake of phylloquinone (vitamin K(1)) and menaquinones (vitamin K(2)) may be associated with overall cancer incidence and mortality.

DESIGN

In the prospective EPIC-Heidelberg (European Prospective Investigation into Cancer and Nutrition-Heidelberg) cohort study, 24,340 participants aged 35-64 y and free of cancer at enrollment (1994-1998) were actively followed up for cancer incidence and mortality through 2008. Dietary vitamin K intake was estimated from food-frequency questionnaires completed at baseline by using HPLC-based food-composition data. Multivariate-adjusted hazard ratios (HRs) and 95% CIs were estimated by using Cox proportional hazards models.

RESULTS

During a median follow-up time of >10 y, 1755 incident cancer cases occurred, of which 458 were fatal. Dietary intake of menaquinones was nonsignificantly inversely associated with overall cancer incidence (HR for the highest compared with the lowest quartile: 0.86; 95% CI: 0.73, 1.01; P for trend = 0.08), and the association was stronger for cancer mortality (HR: 0.72; 95% CI: 0.53, 0.98; P for trend = 0.03). Cancer risk reduction with increasing intake of menaquinones was more pronounced in men than in women, mainly driven by significant inverse associations with prostate (P for trend = 0.03) and lung (P for trend = 0.002) cancer. We found no association with phylloquinone intake.

CONCLUSION

These findings suggest that dietary intake of menaquinones, which is highly determined by the consumption of cheese, is associated with a reduced risk of incident and fatal cancer.

Targeting of VEGF-dependent transendothelial migration of cancer cells by bevacizumab

Cancer progression is often associated with the formation of malignant effusions. Vascular endothelial growth factor (VEGF) is a major regulator of vascular permeability and has been implicated as mediator of tumor progression. We examined the production and secretion of VEGF(165) in various primary cancer cells derived from malignant effusions, and the role of exogenous VEGF(165) as a mediator of effusion formation. VEGF(165) was constantly secreted by all cultured tumor cells in an mTOR-dependent manner, as it was inhibited by the mTOR inhibitor rapamycin. Secreted VEGF(165) showed functional activity by inducing endothelial leakiness and tumor cell-transendothelial migration in vitro, effects which could be reverted by the anti-VEGF antibody bevacizumab. Thus, mTOR inhibitors as well as bevacizumab should be considered as potential agents in cancer patients suffering from malignant effusions.

Angioarchitecture of squamous cell carcinoma from hamster buccal pouch: a scanning electron microscopy study

Tumoral angiogenesis has been widely studied by histochemical analysis but little has been done regarding morphology of these new vessels. The objective of this study was to perform a qualitative analysis of the angiogenic response to chemical induction with dimethylbenzanthracene (DMBA) and carbamide peroxide of squamous cell carcinoma in pouches of Syrian hamsters after different periods of treatment. Twenty-four Syrian golden hamsters, divided into three groups of eight animals each, had their right jugal pouches treated with a 5% DMBA solution three times a week and a 10% carbamide peroxide two times a week for 55, 70 and 90 days. The left pouch was considered the control. After tumor induction, five animals in each group had their pouches prepared for analysis under scanning electron microscopy and three animals for analysis under light microscopy. The control pouches showed a vascular system composed by few main vessels running parallel to the longest axis of the pouch with some branches. In the pouches submitted to tumor induction, a well-differentiated squamous cell carcinoma was present since 55 days induction in all samples. The new vascular system showed the presence of many tortuous vessels and the majority of them were veins and capillaries. Terminal loops were extremely sinuous adopting a glomerular or corkscrew shape. These tumor vessels are different from normal vessels, presenting irregular diameters, outpouchings and constrictions. Angiogenesis of sprouting and intussusceptive kind could be identified in the tumor pouches, and they were more frequent as the tumor developed.

Antiangiogenic drugs: current knowledge and new approaches to cancer therapy

Angiogenesis--process of new blood-vessel growth from existing vasculature--is an integral part of both normal developmental processes and numerous pathologies such as cancer, ischemic diseases and chronic inflammation. Angiogenesis plays a crucial role facilitating tumour growth and the metastatic process, and it is the result of a dynamic balance between proangiogenic and antiangiogenic factors. The potential to block tumour growth and metastases by angiogenesis inhibition represents an intriguing approach to the cancer treatment. Angiogenesis continues to be a topic of major scientific interest; and there are currently more antiangiogenic drugs in cancer clinical trials than those that fit into any other mechanistic category. Based on preclinical studies, researchers believe that targeting the blood vessels which support tumour growth could help treatment of a broad range of cancers. Angiogenic factors or their receptors, endothelial cell proliferation, matrix metalloproteinases or endothelial cell adhesion, are the main targets of an increasing number of clinical trials approved to test the tolerance and therapeutic efficacy of antiangiogenic agents. Unfortunately, contrary to initial expectations, it has been described that antiangiogenic treatment can cause different toxicities in cancer patients. The purpose of this article is to provide an overview of current attempts to inhibit tumour angiogenesis for cancer therapy.

Angiogenesis in gliomas

Angiogenesis, the sprouting of new blood vessels from preexisting blood vessels, is a hallmark of glioma progression. Malignant gliomas are among the most lethal tumors with a very dismal prognosis, despite advances in standard therapy, including surgery, radiation, and chemotherapy. The median survival of patients with malignant gliomas has changed little in the last few years and is still measured in months. In an attempt to develop new therapeutic strategies and identify the molecular mechanism involved in glioma growth and progression, there has been extraordinary scientific interest in the past 2 decades in angiogenic responses associated with gliomas. This chapter focuses on the molecular mechanism of glioma angiogenesis and summarizes some of the therapeutic approaches based on antiangiogenesis.

Successful inhibition of intracranial human glioblastoma multiforme xenograft growth via systemic adenoviral delivery of soluble endostatin and soluble vascular endothelial growth factor receptor-2: laboratory investigation

OBJECT

Glioblastoma multiforme (GBM) is characterized by neovascularization, raising the question of whether angiogenic blockade may be a useful therapeutic strategy for this disease. It has been suggested, however, that, to be useful, angiogenic blockade must be persistent and at levels sufficient to overcome proangiogenic signals from tumor cells. In this report, the authors tested the hypothesis that sustained high concentrations of 2 different antiangiogenic proteins, delivered using a systemic gene therapy strategy, could inhibit the growth of established intracranial U87 human GBM xenografts in nude mice.

METHODS

Mice harboring established U87 intracranial tumors received intravenous injections of adenoviral vectors encoding either the extracellular domain of vascular endothelial growth factor receptor-2-Fc fusion protein (Ad-VEGFR2-Fc) alone, soluble endostatin (Ad-ES) alone, a combination of Ad-VEGFR2-Fc and Ad-ES, or immunoglobulin 1-Fc (Ad-Fc) as a control.

RESULTS

Three weeks after treatment, magnetic resonance imaging-based determination of tumor volume showed that treatment with Ad-VEGFR2-Fc, Ad-ES, or Ad-VEGFR2-Fc in combination with Ad-ES, produced 69, 59, and 74% growth inhibition, respectively. Bioluminescent monitoring of tumor growth revealed growth inhibition in the same treatment groups to be 62, 74, and 72%, respectively. Staining with proliferating cell nuclear antigen and with terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling showed reduced tumor cell proliferation and increased apoptosis in all antiangiogenic treatment groups.

CONCLUSIONS

These results suggest that systemic delivery and sustained production of endostatin and soluble VEGFR2 can slow intracranial glial tumor growth by both reducing cell proliferation and increasing tumor apoptosis. This work adds further support to the concept of using antiangiogenesis therapy for intracranial GBM.

Increased permeability of the blood-brain barrier to chemotherapy in metastatic brain tumors: establishing a treatment paradigm

There is no accepted standard of care for the chemotherapy treatment of metastatic brain tumors, which has been generally limited to lipophilic alkylators, which may not have efficacy against the tumor that metastasized to the brain. More than 50% of chemotherapy agents are natural product drugs, which are rarely used in the treatment of metastatic brain tumors because they are thought to not cross the blood-brain barrier (BBB). A major protein constituent in the BBB is P-glycoprotein (P-gp), which pumps natural product chemotherapy drugs and toxins out of the CNS. However, P-gp expression in the neovasculature of metastatic brain tumors is similar to the P-gp expression in the neovasculature of the primary, extracranial tumor. In contrast, gliomas have higher P-gp expression in their neovasculature, similar to the greater intrinsic expression of P-gp in normal brain vasculature. This decreased immunohistochemical expression of P-gp in the neovasculature of metastatic tumors, as well as our recent pharmacologic demonstration of increased tissue concentrations of paclitaxel in metastatic brain tumors compared with gliomas, support the idea that the choice of chemotherapy agents should be based on the histologic origin of the metastatic brain tumor and not on the lipophilicity of the drug. Our hypothesis is that metastatic brain tumors from tumors with intrinsically low P-gp expression (eg, lung, melanoma, and untreated breast) may be more permeable to natural product chemotherapy drugs than gliomas. This information could lead to a paradigm shift in the use of natural product drugs for metastatic brain tumors.

Molecular events of brain metastasis

The brain is a privileged site of systemic cancer metastasis. The stages of the metastatic journey from the periphery to the brain are driven by molecular events that tie the original site of disease to the distant host tissue. This preference is not arbitrary but rather a directed phenomenon that includes such critical steps as angiogenesis and the preparation of the premetastatic niche. It appears that the connection between naive brain and cancer cells is made in advance of any metastatic breach of the blood-brain barrier. This contributes to the preferential homing of cancer cells to the brain. Delineation of the guidance mechanisms and elements that influence cancer cell motility and dormancy are important for the advancement of treatment modalities aimed at the remediation of this devastating disease.

A mathematical model for the regulation of tumor dormancy based on enzyme kinetics

In this paper we present a two-compartment model for tumor dormancy based on an idea of Zetter [1998, Ann. Rev. Med. 49, 407-422] to wit: The vascularization of a secondary (daughter) tumor can be suppressed by an inhibitor originating from a larger primary (mother) tumor. We apply this idea at the avascular level to develop a model for the remote suppression of secondary avascular tumors via the secretion of primary avascular tumor inhibitors. The model gives good agreement with the observations of [De Giorgi et al., 2003, Derm. Surgery 29, 664-667]. These authors reported on the emergence of a polypoid melanoma at a site remote from a primary polypoid melanoma after excision of the latter. The authors observed no recurrence of the melanoma at the primary site, but did observe secondary tumors at secondary sites 5-7 cm from the primary site within a period of 1 month after the excision of the primary site. We attempt to provide a reasonable biochemical/cell biological model for this phenomenon. We show that when the tumors are sufficiently remote, the primary tumor will not influence the secondary tumor while, if they are too close together, the primary tumor can effectively prevent the growth of the secondary tumor, even after it is removed. It should be possible to use the model as the basis for a testable hypothesis.

Morphological patterns of angiogenesis in ovarian follicle capillary networks. A scanning electron microscopy study of corrosion cast

To describe the morphological characteristics of the ovarian follicle (F) capillary neoformation and regression, the angiogenic figures were studied by means of scanning electron microscopy of corrosion casts in developing and mature F of rabbit, pig, and cow. Developing F showed gradual neoformation of thecal capillaries characterized by budding and then sprouting, likely from preexisting interstitial vessels. Postcapillary venules frequently showed vasoconstriction rings (sphincters). Vasodilation followed capillary elongation. Mature F, in addition to vessel elongation and dilation, also presented infolding of dilated capillary walls, followed by capillary duplication and sinusoidalization. Periovulatory F mainly showed functional changes, such as capillary dilation, signs of iperpermeabilization, and ischemia, the latter being limited to the apical follicular area. Vessel regression was characterized by thinning of capillaries and presence of avascular areas within the atretic F wall at any stage. This study showed two main types of angiogenic patterns. (a) longitudinal elongation (in series, sprouting angiogenesis) characterizing the initial phase of F development and (b) parallel duplication (in parallel, infolding or intussusceptive angiogenesis), ending in capillary lateral replication or splitting, secondary to functional microvascular changes. Indirect evidence of the establishment of postcapillary resistances contributing to capillary remodeling, was also shown. It is concluded that the sequence of capillary neoformation in mammalian ovarian F occurs in six steps: (1) budding, (2) sprouting (and elongation), (3) dilation, (4) infolding (intussusception), (5) duplication (splitting and elongation), and (6) sinusoidalization. Capillary regression hits F at any stage and characterizes F atresia.

Endostatin expression in pancreatic tissue is modulated by elastase

Pancreatic tumours are scirrhous, avascular tumours, suggesting that they may produce angiogenesis inhibitors that suppress the growth of the vasculature to the tumour and metastases. We have sought evidence for the angiogenesis inhibitor, endostatin, in normal and cancerous pancreatic tissue. Using Western blotting, we found mature 20 kDa endostatin in cancer tissue but not in normal tissue. Several endostatin-related peptides of higher mol wt were present in both tissues. Extracts from normal tissue were able to degrade exogenous endostatin, whereas extracts from cancer were without effect. Although the exocrine pancreas secretes inactive proenzymes of trypsin, chymotrypsin and elastase, their possible role in this degradation was examined. The trypsin/chymotrypsin inhibitor, Glycine max, did not prevent the degradation of endostatin by normal pancreatic extracts but elastatinal, a specific inhibitor of elastase, reduced the rate of degradation. Extracts of pancreatic tumours did not express any detectable elastase activity, but an elastase (Km 1.1 mM) was expressed by extracts of normal pancreas. We conclude that endostatin is present and stable in pancreatic cancer tissues, which may explain their avascular nature, but that normal pancreatic tissue expresses enzymes, including elastase, which rapidly degrade endostatin. The stability of endostatin may have implications for its therapeutic use.

Pathobiology of brain metastases

Brain metastasis is a major cause of systemic cancer morbidity and mortality. Many factors participate in the development and maintenance of brain metastases. The survival of the metastasis depends upon crucial interactions between tumour cells and the brain microenvironment during its development at the new site. This review focuses on the pathobiological mechanisms involved in the establishment and regulation of brain metastases. Developments in molecular biology have vastly expanded our knowledge about the mechanisms of invasion, proliferation, metastatic cell signalling, and angiogenesis in brain metastases. Advances in this understanding of the pathobiology of brain metastasis may lead to novel targeted treatment paradigms and a better prognosis for patients with brain metastatic disease.

The relationship between hypoxia and angiogenesis

Recent studies have generated a large amount of data supporting the hypothesis that hypoxia drives tumor angiogenesis. The relationship between the two is often considered a matter of supply and demand: ineffectively-vascularized tumor tissue becomes hypoxic, stimulating neoangiogenesis to improve the influx of oxygen, thereby diminishing the angiogenic drive. Although this paradigm is logically pleasing, much of what is known about tumor biology argues against such a straightforward relationship. In fact, some preclinical data convincingly shows that tumor hypoxia and angiogenesis do not always go hand in hand. It is important to begin to explore means of reconciling these discrepancies. Although poor oxygenation is a strong stimulus for tumor angiogenesis, (1) the pathogenesis of tumor hypoxia is much more complicated than the supply-demand paradigm lets on and (2) hypoxia is not necessarily sufficient or necessary for neovascularization to occur. These subtleties may help to explain why so much data disagrees with the current hypoxia-angiogenesis model and may begin to build a better understanding of the role hypoxia plays in tumor vascularization. This article will review what is known about hypoxia and angiogenesis in nononcological processes and will apply these lessons to tumor biology to more deeply describe their relationship.

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Molecular cloning of human canstatin gene

AIM: To clone human canstatin gene and to detect and analyze its coding sequence.

METHODS: The total RNA was extracted from human placenta. The canstatin gene fragment was synthesized and amplified from the total RNA by RT-PCR. pUCm-T vector was cloned into the RT-PCR product to obtain recombinant pUCm-T/ canstatin. The pUCm-T/canstatin was then transformed into E.coli DH 5a, and sequence of the gene was detected.

RESULTS: The extracted total RNA was separated into three clear bands indicating 28 S, 18 S, and 5 S after electrop-horesis. The values of A₂₆₀ and A₂₈₀ were 0.879 and 0.410 respectively (A₂₆₀:A₂₈₀ = 2.095). The concentration of total RNA was 1.8 g/L. The PCR product was the same as target gene canstatin. BamH I and Hind III digestion proved the final product positive. The sequence of the cloned gene (684 bp) completely matched with that of canstatin gene in Genbank.

CONCLUSION: Human canstatin gene is successfully cloned, which establishes the foundation for further study of its anti-tumor activity.

The role of fibrinogen and related fragments in tumour angiogenesis and metastasis

Angiogenesis, the development of new blood vessels from existing vasculature, involves the migration, proliferation and differentiation of endothelial cells and is crucial for the growth and mestastasis of tumours. A specific association between cancer and the haemostatic system has long been recognised. Haemostatic mechanisms regulate blood flow by controlling platelet adhesion and fibrin deposition, and a number of haemostatic proteins have been shown to regulate angiogenesis, either directly, by interacting with endothelial cells themselves, or indirectly, by interacting with other regulators of angiogenesis. The polypeptide fibrinogen is the central protein in the haemostasis pathway and is found deposited in the majority of human and experimental animal tumours. In this review, the evidence for the ability of fibrinogen and various protein/peptide fragment derivatives to modulate angiogenic mechanisms in vitro and to affect tumour growth and metastasis in vivo is discussed.

Prognostic factors in node-negative intrahepatic cholangiocarcinoma with special reference to angiogenesis

BACKGROUND

The aim of this study was to clarify prognostic factors and recurrence patterns in patients with node-negative intrahepatic cholangiocarcinoma (IHCC).

METHODS

A retrospective study was performed to review prognostic factors and recurrence patterns (1) in 22 patients with node-negative IHCC after curative hepatic resection and (2) in 49 patients who underwent resection and lymph node dissection for IHCC. In addition to determining the clinicopathologic factors, the investigators also performed immunohistochemical examination of microvessel counts using antihuman CD-31 and antibody.

RESULTS

The significant poor prognostic factors in node-negative IHCC were the presence of intrahepatic metastasis, portal vein invasion of cancer cells, and high microvessel counts. After multivariate analysis was conducted, the independent poor prognostic factors were the presence of intrahepatic metastases and high microvessel counts. Of 9 patients who had postoperative recurrence of their disease, intrahepatic recurrence was observed in 7 (78 %).

CONCLUSIONS

The factors linked to poor prognosis in IHCC were tumor angiogenesis and the presence of intrahepatic metastasis. Because intrahepatic recurrence was common, regional and adjuvant chemotherapy to the liver may improve the outcome of patients with these risk factors and node-negative IHCC.

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Mode of action of docetaxel - a basis for combination with novel anticancer agents

Different tumors have different aberrations in signaling and growth stimulation pathways that drive cancer growth. An understanding of these processes is key to the development of new anticancer agents and to identifying optimal treatment strategies and patient populations suitable for specific therapies. It is becoming clear that certain chemotherapeutic drugs such as docetaxel are not simply inhibitors of mitosis and may interact with these tumorigenic mechanisms at a number of levels. This review describes docetaxel's mechanism of action, and provides a basis for understanding how its antitumor activity can integrate with that of different novel agents. Against this background, key docetaxel-novel agent combinations that are currently under clinical investigation are reviewed. How these strategies can be targeted towards specific patient populations (e.g., HER-2 overexpressing metastatic breast cancer patients) to provide optimal therapy is highlighted.

Tumour-Induced Angiogenesis: A Review

Angiogenesis, the formation of new blood vessels, has become a broad subject and is a very active area for current research. This paper describes the main biological events involved in angiogenesis and their importance in cancer progression. In the first section, a fundamental overview of tumour biology is presented. In the second section, the biology of healthy blood vessels is described and, in the third section, the mechanisms of cell migration and proliferation, which are crucial to angiogenesis, are discussed. In the fourth section, a detailed account of tumour-induced angiogenesis is given, whilst the pro- and anti-angiogenic factors involved are reviewed in the fifth section. Finally, the processes of tumour invasion and metastasis are examined in the sixth section.

Adeno-associated virus type-2 expression of pigmented epithelium-derived factor or Kringles 1-3 of angiostatin reduce retinal neovascularization

Neovascular diseases of the retina include age-related macular degeneration and diabetic retinopathy, and together they comprise the leading causes of adult-onset blindness in developed countries. Current surgical, pharmaceutical, and laser therapies for age-related macular degeneration (AMD) rarely result in improved vision, do not significantly prevent neovascularization (NV), and often result in at least some vision loss. To address this therapeutic gap, we determined the efficacy of recombinant adeno-associated viral (rAAV) serotype-2-mediated expression of pigment epithelium-derived factor (PEDF) or Kringle domains 1-3 of angiostatin (K1K3) in reducing aberrant vessel formation in a mouse model of ischemia-induced retinal NV. Both PEDF and K1K3 are potent inhibitors of NV when injected directly, hence expression of these therapeutic factors from rAAV may provide long-term protection from neovascular eye disease. rAAV vectors expressing the therapeutic gene were injected into one eye of postnatal day 0 (P0) newborn mouse pups. Retinal NV was induced in P7 mice by exposure to elevated oxygen for 5 days followed by room air for another five days. Retinal NV was quantified by the number of vascular-endothelial-cell nuclei above the inner-limiting membrane in P17 eyes. The number of such vascular endothelial cell nuclei in eyes treated with rAAV-PEDF or rAAV-K1K3 was significantly reduced (both P < 0.0000002) compared with control eyes. Ocular protein levels detected by ELISA correlate well with the reduction in NV and confirm that expression of antineovascular agents from rAAV vectors may be a therapeutically useful treatment of retinal or choroidal neovascular disease.