Vascular endothelial growth factor overproduced by tumour cells acts predominantly as a potent angiogenic factor contributing to malignant progression

Promotor methylation in ocular surface squamous neoplasia development: epigenetics implications in molecular diagnosis

INTRODUCTION

Cancer is heavily influenced by epigenetic mechanisms that include DNA methylation, histone modifications, and non-coding RNA. A considerable proportion of human malignancies are believed to be associated with global DNA hypomethylation, with localized hypermethylation at promoters of certain genes.

AREA COVERED

The present review aims to emphasize on recent investigations on the epigenetic landscape of ocular surface squamous neoplasia, that could be targeted/explored using novel approaches such as personalized medicine.

EXPERT OPINION

While the former is thought to contribute to genomic instability, promoter-specific hypermethylation might facilitate tumorigenesis by silencing tumor suppressor genes. Ocular surface squamous neoplasia, the most prevalent type of ocular surface malignancy, is suggested to be affected by epigenetic mechanisms, as well. Although the exact role of epigenetics in ocular surface squamous neoplasia has mostly been unexplored, recent findings have greatly contributed to our understanding regarding this pathology of the eye.

Decellularized In Vitro Capillaries for Studies of Metastatic Tendency and Selection of Treatment

Vascularization plays an important role in the microenvironment of the tumor. Therefore, it should be a key element to be considered in the development of in vitro cancer assays. In this study, we decellularized in vitro capillaries to remove genetic material and optimized the medium used to increase the robustness and versatility of applications. The growth pattern and drug responses of cancer cell lines and patient-derived primary cells were studied on decellularized capillaries. Interestingly, two distinct growth patterns were seen when cancer cells were grown on decellularized capillaries: “network” and “cluster”. Network formation correlated with the metastatic properties of the cells and cluster formation was observed in non-metastatic cells. Drug responses of patient-derived cells correlated better with clinical findings when cells were cultured on decellularized capillaries compared with those cultured on plastic. Decellularized capillaries provide a novel method for cancer cell culture applications. It bridges the gap between complex 3D culture methods and traditional 2D culture methods by providing the ease and robustness of 2D culture as well as an in vivo-like microenvironment and scaffolding for 3D cultures.

Differential Angiogenic Responses of Human Endothelial Colony-Forming Cells to Different Molecular Subtypes of Breast Cancer Cells

Objective

Triple negative breast cancer (TNBC) is one subtype of breast cancer. It is characterized by lack of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Compared with non-TNBC, TNBC is more aggressive, of higher grade, and frequently metastatic with poor prognosis, which is correlated with upregulated microvascular density. Endothelial colony-forming cells (ECFCs) mediate neovascularization, which is the crucial contributor to cancer growth and metastasis. The present study aimed to determine whether angiogenic responses of ECFCs are regulated differently by TNBC compared with non-TNBC.

Methods

MDA-MB-231 and MCF7 cells were utilized for TNBC and non-TNBC, respectively. Bone-marrow-derived human ECFCs were treated with a conditioned medium (CM) of cancer cells to investigate the paracrine effect on angiogenesis. Also, ECFCs were co-cultured with cancer cells to evaluate the angiogenic effect of direct cell-to-cell interaction. Angiogenic responses of ECFCs were evaluated by proliferation, migration, and tube formation. Gene expression profiles of pro-angiogenic factors were also analyzed.

Results

Migration and tube formation of ECFCs were increased by treatment with CM of MDA-MB-231, which correlated with a higher gene expression profile of pro-angiogenic factors in MDA-MB-231 compared to MCF7. Interestingly, ECFCs co-cultured with MDA-MB-231 showed further increase of tube formation, suggesting synergic mechanisms between the paracrine effect and direct interaction between the cells.

Conclusion

The angiogenic potential of ECFCs was enhanced by TNBC through both direct and indirect mechanisms. Therefore, the investigation of signaling pathways to regulate ECFC-mediated angiogenesis will be important to the discovery of anti-angiogenic therapies to treat TNBC patients.

The MSC-MCF-7 Duet Playing Tumor Vasculogenesis and Angiogenesis onto the Chick Embryo Chorioallantoic Membrane

BACKGROUND/AIM

Human mesenchymal stem cells (hMSC) represent a versatile cell population, able to modulate the tumor microenvironment. Our aim was to recreate an open scene for the in vivo interaction between hMSC and the MCF-7 breast cancer cells (MCF-7), in order to enlighten the intimate involvement of hMSC in tumor vasculogenesis and angiogenesis.

MATERIALS AND METHODS

hMSC and MCF-7 were seeded onto the chick embryo chorioallantoic membrane (CAM) and incubated for 7 days. Consecutively, the morphology and the immunohistochemical profile of CAM were assessed.

RESULTS

Following this complex interaction, MCF-7 acquired a more aggressive phenotype, hMSC switched to a vascular precursor phenotype, while CAM underwent a major reset to an earlier stage, with hotspots of angiogenesis, vasculogenesis and hematopoiesis.

CONCLUSION

The hallmark of this study was the establishment of a veritable in vivo experimental model of MSC involvement in tumor vasculogenesis and angiogenesis, allowing further analysis in the field.

In Vitro Vascular Network Modified to Function as Culture Platform and Angiogenic Induction Potential Test for Cancer Cells

Drug treatments have been designed to inhibit tumor angiogenesis in hope of stopping tumor growth. However, not all tumor types respond to this type of treatment. A screening method which identifies angiogenesis inducing cancer types would help predict the efficacy of angiogenesis-inhibiting drugs for the patients. Our goal is to develop (1) a cell assay to assess the angiogenic induction potential of patient-derived tumor cells, and (2) a protocol for culturing cancer cells on a vascular platform. We optimized the media composition and seeding density of cells (hASC, HUVEC, and cancer cells) to 48-, 96-, and even 384-well plate sizes to allow vascular formation and cancer cell proliferation and subsequent analysis with high throughput. The angiogenic induction potential of patient-derived cancer cells was investigated by quantifying the formation of tubular structures and the drug response of cancer cells grown on a vascular platform was evaluated using gene expression and cell viability (WST-1) assay. Immunocytochemistry was performed with von Willebrand factor, collagen IV, CD44, cytokeratin 19 and ALDH1A1. The angiogenic induction potential test was shown to be responsive to the induction of angiogenesis by cancer cells. The responses of cancer cells were different when grown on a vascular platform or on plastic, seen in gene expression level and viability results. These two protocols are promising novel tools for aiding the selection of efficient cancer drugs for personalized medicine and as an alternative cancer cell culture platform.

VEGF as a potential target in lung cancer

Introduction The vascular endothelial growth factor A (VEGF) is the main mediator of angiogenesis. In addition, VEGF contributes to cancer growth and metastasis directly targeting tumor cells. VEGF overexpression and/or high VEGF serum levels have been reported in lung cancer. Areas covered We searched Pubmed for relevant preclinical studies with the terms 'lung cancer' 'VEGF' and 'in vivo'. We also searched the Clinicaltrials.gov database, the FDA and the EMA websites for the most recent updates on clinical development of anti-VEGF agents. Expert opinion VEGF plays an important role in sustaining the development and progression of lung cancer and it might represent an attractive target for therapeutic strategies. Nevertheless, clinical trials failed to attend the promising expectations deriving from preclinical studies with anti-VEGF agents. To improve the efficacy of anti-VEGF therapies in lung cancer, potential strategies might be the employment of combinatory therapies with immune checkpoint inhibitors or agents that inhibit signaling pathways and proangiogenic factors activated in response to VEGF blockade, and the identification of novel targets in the VEGF cascade. Finally, the identification of predictive markers might help to select patients who are more likely to respond to anti-angiogenic drugs.

Bevacizumab Modulation of the Interaction Between the MCF-7 Cell Line and the Chick Embryo Chorioallantoic Membrane

AIM

To evaluate the interaction between MCF-7 breast cancer cells and the chick embryo chorioallantoic membrane (CAM) and the ability of bevacizumab to modulate this process.

MATERIALS AND METHODS

We implanted MCF-7 cells onto CAM and repeatedly added bevacizumab to a subset of eggs. We then evaluated the morphological and immunohistochemical profiles of CAM and MCF-7.

RESULTS

MCF-7 cells entered the mesoderm and stimulated the mesenchymal cells to acquire vasculogenic and myofibroblastoid features. MCF-7 cells developed an estrogen receptor-, progesterone receptor-, p53- and Ki67-negative status and entered the epithelial-mesenchymal transition. Bevacizumab down-regulated the expression of B-cell lymphoma 2 protein (BCL-2), vascular endothelial growth factor (VEGF) and E-cadherin in MCF-7 and inhibited vasculogenesis.

CONCLUSION

MCF-7 cells turn the mesoderm of CAM into a surrogate tumor stroma. CAM induces a triple-negative, non-proliferative but still anti-apoptotic status in MCF-7 cells. Although antivasculogenic, bevacizumab stimulates MCF-7 cells to acquire a more aggressive status.

YBX1/YB-1 induces partial EMT and tumourigenicity through secretion of angiogenic factors into the extracellular microenvironment

Epithelial-mesenchymal transition (EMT) describes a morphogenetic program which confers mesenchymal cell properties, such as reduced cell-cell contact and increased cell migration and invasion, to epithelial cells. Here we investigate the role of the pleiotropic transcription/splicing factor and RNA-binding protein nuclease-sensitive element-binding protein 1 (YBX1/YB-1) in increasing the oncogenic potential of epithelial MDCK cells. Characterization of MDCK cells expressing YBX1 (MDCK^YBX1 cells) revealed a partial EMT phenotype, including cytosolic relocalization of E-cadherin, increased cell scattering, and anchorage-independent growth. Subcutaneous injection of parental MDCK cells into NOD/SCID mice did not form tumours. Critically, MDCK^YBX1 cells established viable tumour xenografts, and immuno-histochemical staining indicated murine vascularization by CD31+ endothelial cells. We analysed the total secretome (containing soluble and extracellular vesicles) of MDCK^YBX1 cells to investigate regulation of the tumour microenvironment. YBX1 expression elevated release of secreted factors known to enhance angiogenesis (TGF-β, CSF-1, NGF, VGF, ADAM9 and ADAM17), compared to MDCK cells. Importantly, treatment with MDCK^YBX1 cell-derived secretome increased recipient 2F-2B endothelial cell motility. This defines YBX1 as an oncogenic enhancer that can regulate tumour angiogenesis via release of secreted modulators into the extracellular microenvironment.

Bridging a 30 mm defect in the canine ulnar nerve using vessel-containing conduits with implantation of bone marrow stromal cells

Previously, we showed that undifferentiated bone marrow stromal cell (uBMSC) implantation and vessel insertion into a nerve conduit facilitated peripheral nerve regeneration in a rodent model. In this study, we investigated the efficacy of the uBMSC-laden vessel-containing conduit in repair of segmental nerve defects, using a canine model. Eight beagle dogs were used in this study. Thirty-millimeter ulnar nerve defects were repaired with the conduits (right forelimbs, n = 8) or autografts (left forelimbs, n = 7). In the conduit group, the ulnar artery was inserted into the l-lactide/ε-caprolactone tube, which was filled with autologous uBMSCs obtained from the ilium. In the autograft group, the reversed nerve segments were sutured in situ. At 8 weeks, one dog with only nerve repair with the conduit was sacrificed and the regenerated nerve in the conduit underwent immunohistochemistry for investigation of the differentiation capability of the implanted uBMSCs. In the remaining seven dogs, the repaired nerves underwent electrophysiological examination at 12 and 24 weeks and morphometric measurements at 24 weeks. The wet weight of hypothenar muscles was measured at 24 weeks. At 8 weeks, almost 35% of the implanted uBMSCs expressed glial markers. At 12 weeks, amplitude (0.4 ± 0.4mV) and conduction velocity (18.9 ± 14.3m/s) were significantly lower in the conduit group than in the autograft group (3.2 ± 2.5 mV, 34.9 ± 12.1 m/s, P < 0.05). Although the nerve regeneration in the conduit group was inferior when compared with the autograft group at 24 weeks, there were no significant differences between both groups, regarding amplitude (10.9 ± 7.3 vs. 25.3 ± 20.1 mV; P = 0.11), conduction velocity (23.5 ± 8.7 vs 31.6 ± 20.0m/s; P = 0.35), myelinated axon number (7032 ± 4188 vs 7165 ± 1814; P = 0.94), diameter (1.73 ± 0.31 vs 2.09 ± 0.39μm; P = 0.09), or muscle weight (1.02 ± 0.40 vs 1.19 ± 0.26g; P = 0.36). In conclusion, this study showed that vessel-containing tubes with uBMSC implantation may be an option for treatment of peripheral nerve injuries. However, further investigations are needed. © 2015 Wiley Periodicals, Inc. Microsurgery 36:316-324, 2016.

Pathophysiology of ocular surface squamous neoplasia

The incidence of ocular surface squamous neoplasia (OSSN) is strongly associated with solar ultraviolet (UV) radiation, HIV and human papilloma virus (HPV). Africa has the highest incidence rates in the world. Most lesions occur at the limbus within the interpalpebral fissure particularly the nasal sector. The nasal limbus receives the highest intensity of sunlight. Limbal epithelial crypts are concentrated nasally and contain niches of limbal epithelial stem cells in the basal layer. It is possible that these are the progenitor cells in OSSN. OSSN arises in the basal epithelial cells spreading towards the surface which resembles the movement of corneo-limbal stem cell progeny before it later invades through the basement membrane below. UV radiation damages DNA producing pyrimidine dimers in the DNA chain. Specific CC → TT base pair dimer transformations of the p53 tumour-suppressor gene occur in OSSN allowing cells with damaged DNA past the G1-S cell cycle checkpoint. UV radiation also causes local and systemic photoimmunosuppression and reactivates latent viruses such as HPV. The E7 proteins of HPV promote proliferation of infected epithelial cells via the retinoblastoma gene while E6 proteins prevent the p53 tumour suppressor gene from effecting cell-cycle arrest of DNA-damaged and infected cells. Immunosuppression from UV radiation, HIV and vitamin A deficiency impairs tumour immune surveillance allowing survival of aberrant cells. Tumour growth and metastases are enhanced by; telomerase reactivation which increases the number of cell divisions a cell can undergo; vascular endothelial growth factor for angiogenesis and matrix metalloproteinases (MMPs) that destroy the intercellular matrix between cells. Despite these potential triggers, the disease is usually unilateral. It is unclear how HPV reaches the conjunctiva.

Attenuation of lung cancer stem cell tumorigenesis and metastasis by cisplatin

PURPOSE

To investigate the effect of cisplatin on the growth and metastasis abilities of lung cancer stem cells (CSCs) via molecular imaging.

MATERIALS AND METHODS

The expression changes of lung CSCs cell marker in A549-Luc-C8 human non-small-cell lung cancer (NSCLC) cell line with or without cisplatin treatment were detected by flow cytometry. The tumorigenesis and metastasis abilities of A549-Luc-C8 cells were monitored both in vitro and in vivo, and the mechanism was assessed by gene sequencing.

RESULTS

About 1%-2% of CSCs were detected in A549-Luc-C8 cells and decreased CSCs percentage was observed after cisplatin treatment. Attenuated tumorigenesis and metastasis abilities of A549-Luc-C8 cells were found in cisplatin treated group.

CONCLUSIONS

Decreased percentage of CSCs in A549-Luc-C8 cells can be induced by cisplatin treatment, which may partly be attributed to the attenuated expression of growth factors.

RLIP76 regulates HIF-1 activity, VEGF expression and secretion in tumor cells, and secretome transactivation of endothelial cells

This study was undertaken to reveal the mechanisms by which RLIP76 regulates endothelial cell angiogenic responses. RLIP76 is an effector of the angiogenic modulator, R-Ras. RLIP76 is overexpressed in many tumors, required for tumor angiogenesis, and blockade of RLIP76 results in tumor regression in multiple models. We report here that RLIP76 was required for expression and secretion of vascular endothelial growth factor (VEGF) in carcinoma and melanoma cells. Conditioned medium derived from RLIP76-depleted tumor cells, but not control knockdown cells, could not stimulate proliferation, migration, or Matrigel cord formation in endothelial cell cultures, which indicates that RLIP76 regulates angiogenic components of the tumor cell secretome. Recombinant VEGF added to conditioned medium from RLIP76-knockdown tumor cells restored these endothelial cell functions. Transcriptional activity of hypoxia-inducible factor 1 (HIF-1), which drives VEGF expression, was blocked in RLIP76-depleted tumor cells. RLIP76 was required for PI3-kinase activation, known to regulate HIF-1, in these cells. However, HIF-1α expression and nuclear localization were unaffected by RLIP76 knockdown, which suggests that RLIP76 regulates HIF-1 at the functional level. Thus, RLIP76 regulates tumor cell transactivation of endothelial cells via control of VEGF expression and secretion, providing a new important link in the mechanism of tumor cell induction of angiogenesis.

Morphological appearance, content of extracellular matrix and vascular density of lung metastases predicts permissiveness to infiltration by adoptively transferred natural killer and T cells

We have recently shown that adoptively transferred, IL-2-activated natural killer (A-NK) cells are able to eliminate well-established B16-F10.P1 melanoma lung metastases. However, some B16-F10.P1 lung metastases were resistant to infiltration by the A-NK cells and also resistant to the A-NK cell treatment. The infiltration-resistant (I-R) B16-F10.P1 metastases had a unique "compact" morphology compared to the "loose" morphology of the infiltration-permissive (I-P) metastases. Here, we show that I-P loose tumors and I-R compact tumors are also found in lung metastases of mouse Lewis lung carcinoma (3LL), MCA-102 sarcoma, and MC38 colon carcinoma as well as rat MADB106 mammary carcinoma origin. Furthermore, the infiltration resistance of the compact tumors is not restricted to A-NK cells, since PHA and IL-2 stimulated CD8+ T-cells (T-LAK cells) also infiltrated the compact tumors poorly. Analyses of tumors for extracellular matrix (ECM) components and PECAM-1(+) vasculature, revealed that the I-R lesions are hypovascularized and contain very little laminin, collagen and fibronectin. In contrast, the I-P loose tumors are well-vascularized and they contain high amounts of ECM components. Interestingly, the distribution pattern of ECM components in the I-P loose tumors is almost identical to that of the normal lung tissue, indicating that these tumors develop around the alveolar walls which provide the loose tumors with both a supporting tissue and a rich blood supply. In conclusion, tumor infiltration by activated NK and T cells correlates with the presence of ECM components and PECAM-1(+) vasculature in the malignant tissue. Thus, analysis of the distribution of ECM and vasculature in tumor biopsies may help select patients most likely to benefit from cellular adoptive immunotherapy.

Angiogenic and antiangiogenic balance regulates concomitant antitumoral resistance

Concomitant antitumoral resistance (CAR), the phenomenon by which the growth of distant secondary tumor implants or metastases in some tumor-bearing hosts is inhibited by the presence of a primary tumor, has been previously ascribed to an antiangiogenic process. Here, we investigated vascular endothelial growth factor (VEGF) and endostatin serum levels in nude or BALB/c mice bearing human lung tumors (Calu-6 and H460) or murine mammary tumors (M3MC, M-234p and M-234m), respectively. In these experimental models we previously found an association between in vivo generation of CAR and in vitro conversion of plasminogen into angiostatin. Serum endostatin level in CAR+ Calu-6-bearing mice was significantly higher than in CAR- H460 counterpart. Sera from mammary tumor-bearing mice showed similar levels of endostatin, regardless of their ability to induce CAR. Conversely, serum VEGF levels in mice bearing CAR+ tumors were lower than those found in CAR- tumor-bearing hosts. Immunostaining with an anti-CD31 antibody revealed that secondary tumors subjected to CAR were significantly less vascularized than primary tumors, while this difference was not observed in CAR- tumors. In vitro studies showed an inhibitory effect of sera from CAR-inducing tumors on endothelial cell proliferation as compared to normal sera, whereas sera from non-CAR-inducing tumors did not alter endothelial proliferation and, in some instances, even caused stimulation of endothelial proliferation. These data suggest that the antiangiogenic mechanism operating in concomitant antitumoral resistance is the result of an increase in the ratio of antiangiogenic/proangiogenic regulators. The levels of the factors involved in this phenomenon can vary in the different tumor models, but the trend favoring the inhibition of angiogenesis is always conserved.

Correlation between VEGF and HIF-1alpha expression in human oral squamous cell carcinoma

Understanding the development and progression of oral cancer is critical in the quest for successful therapeutic intervention. The hypoxic microenvironment present in human oral tumor in vivo may actively influence tumor growth and neovascularization. This study correlates expression of both VEGF and HIF-1alpha in normal keratinocytes and oral cancer cell lines and determine whether hypoxia played a role in VEGF and HIF-1alpha regulation. Three human oral cancer cell lines and three normal keratinocytes were exposed to both normoxia and hypoxia culture conditions. Northern and Western blot analysis were used to assess VEGF and HIF-1alpha expression in the different culture conditions. ELISA assays were performed to measure VEGF production in the different cell lines tested. Hypoxia upregulated VEGF and HIF-1alpha expression on both normal and oral cancer cell lines, with a statistically significant difference between normal and oral cancer cell lines. Pattern of hypoxia-induced VEGF mRNA level tightly followed the HIF-1alpha mRNA expression in the cell lines tested. These results suggest that hypoxia regulates both VEGF and HIF-1alpha expression in head and neck carcinoma cell lines, thus establishing a biochemical pathway between tumor hypoxia and neoangiogenesis in these aggressive neoplasms.

Vascular endothelial growth factor and basic fibroblast growth factor expression in esophageal adenocarcinoma and Barrett esophagus

OBJECTIVE

This study was undertaken to investigate the role of the angiogenic factors vascular endothelial growth factor and basic fibroblast growth factor in the development and progression of Barrett esophagus and adenocarcinomas of the esophagus and gastroesophageal junction.

METHODS

Vascular endothelial growth factor and basic fibroblast growth factor messenger RNA expression levels, relative to the control gene encoding beta-actin, were measured by using a quantitative reverse transcription-polymerase chain reaction method (ABI 7700 Sequence Detector system) in specimens of Barrett intestinal metaplasia (n = 16), dysplasia (n = 11), adenocarcinoma (n = l 5), and matching normal squamous esophageal tissues (n = 35). Vascular endothelial growth factor and basic fibroblast growth factor protein expression and CD31(+) microvessel density were assessed by means of immunohistochemistry in 25 tissue sections that included representative areas for each of these Barrett stages.

RESULTS

Expression levels were significantly increased in adenocarcinoma compared with in either normal squamous mucosa (P <.0001 for both genes) or intestinal metaplasia (vascular endothelial growth factor, P =.002; basic fibroblast growth factor, P <.0001). Vascular endothelial growth factor levels were also significantly higher in cancer tissues compared with dysplasia tissues (P =.024, Mann-Whitney U test). Basic fibroblast growth factor expression was also significantly increased in Barrett dysplastic mucosa compared with in intestinal metaplasia or normal esophageal mucosa. Microvessel density was generally higher in adenocarcinoma compared with in preneoplastic Barrett tissues. The pattern of vascular endothelial growth factor and basic fibroblast growth factor protein expression was similar to the messenger RNA expression pattern, with the exception that mucin-containing goblet cells stained intensely for vascular endothelial growth factor and only weak vascular endothelial growth factor staining was present in some adenocarcinomas.

CONCLUSIONS

Vascular endothelial growth factor and basic fibroblast growth factor messenger RNA expression levels are significantly upregulated in esophageal and gastroesophageal junction adenocarcinomas, suggesting a role for these angiogenic factors in the development of these cancers. Vascular endothelial growth factor and basic fibroblast growth factor messenger RNA expression levels are also increased in some Barrett esophagus tissues, with this increase occurring at an earlier stage for basic fibroblast growth factor than for vascular endothelial growth factor. Basic fibroblast growth factor protein expression pattern is similar to the messenger RNA expression pattern, but unlike the messenger RNA findings, vascular endothelial growth factor protein expression is strongest in goblet cells.

Antiangiogenic activity of selenium in cancer chemoprevention: metabolite-specific effects

We review recent data that support a potential antiangiogenic effect of selenium (Se) in the chemoprevention of cancer and data that contrast two pools of Se metabolites, namely, methylselenol vs. hydrogen selenide, that differentially affect proteins and cellular processes crucial to tumor angiogenesis regulation. With regard to tumor angiogenesis, the chemopreventive effect of increased Se intake on chemically induced mammary carcinogenesis has been associated with reduced intratumoral microvessel density and an inhibition of the expression of vascular endothelial growth factor. The in vitro data show that monomethyl Se potently inhibits cell cycle progression of vascular endothelial cells to the S phase, endothelial expression of matrix metalloproteinase-2, and cancer epithelial expression of vascular endothelial growth factor with concentrations giving half-maximal inhibition that are within the plasma range of Se in US adults. The methyl Se-specific activities may therefore be physiologically pertinent for angiogenic switch regulation in early lesions in vivo in the context of cancer chemoprevention, which aims at retarding and blocking the growth and progression of early lesions. We argue for the antiangiogenic action of Se, especially the methyl Se pool of metabolites, as a primary mechanism for preventing avascular lesion growth. Contrary to the currently held paradigm, we speculate that there is a potential role for selenoproteins in regulating the growth and fate of transformed epithelial cells.

Regulation of activator protein-1 activity in the mediastinal lymph node metastasis of lung cancer

Orthotopic implantation of a metastatic cell line of Lewis lung carcinoma (LLC-MLN), which was isolated by an in vivo selection method, resulted in greater metastatic growth in mediastinal lymph nodes as compared with that of the original LLC cells. LLC-MLN cells also had increased invasive ability and activator protein-1 (AP-1) transcriptional activity as compared with the original LLC cells. This is well consistent with the previously reported finding that overexpression of AP-1 is associated with lymphatic metastasis in lung cancer patients. Oral administration of curcumin, which downregulates AP-1 transcription, significantly inhibited the mediastinal lymph node metastasis of orthotopically implanted LLC cells in a dose-dependent manner, but did not affect the tumor growth at the implantation site. Combined treatment with curcumin and an anti-cancer drug, cis-diamine-dichloroplatinum (CDDP), resulted in a marked inhibition of tumor growth at the implanted site and of lymphatic metastasis, and a significant prolongation of the survival time. The downregulation of transcriptional AP-1 activity by curcumin as seen in the dual luciferase assay caused inhibition of LLC cell invasion through the repression of expression of the mRNAs for urokinase-type plasminogen activator (u-PA) and its receptor (u-PAR). Inhibition of AP-1 transcriptional activity may offer improved therapeutic efficacy for lung cancer patients with lymphatic metastasis.

Pharmacological aspects of targeting cancer gene therapy to endothelial cells

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