Angiogenesis in human cancer: implications in cancer therapy

Biological aspects in controlling angiogenesis: current progress

All living beings continue their life by receiving energy and by excreting waste products. In animals, the arteries are the pathways of these transfers to the cells. Angiogenesis, the formation of the arteries by the development of pre-existed parental blood vessels, is a phenomenon that occurs naturally during puberty due to certain physiological processes such as menstruation, wound healing, or the adaptation of athletes' bodies during exercise. Nonetheless, the same life-giving process also occurs frequently in some patients and, conversely, occurs slowly in some physiological problems, such as cancer and diabetes, so inhibiting angiogenesis has been considered to be one of the important strategies to fight these diseases. Accordingly, in tissue engineering and regenerative medicine, the highly controlled process of angiogenesis is very important in tissue repairing. Excessive angiogenesis can promote tumor progression and lack of enough angiogensis can hinder tissue repair. Thereby, both excessive and deficient angiogenesis can be problematic, this review article introduces and describes the types of factors involved in controlling angiogenesis. Considering all of the existing strategies, we will try to lay out the latest knowledge that deals with stimulating/inhibiting the angiogenesis. At the end of the article, owing to the early-reviewed mechanical aspects that overshadow angiogenesis, the strategies of angiogenesis in tissue engineering will be discussed.

RNAi-mediated inhibition of Lgr5 leads to decreased angiogenesis in gastric cancer

Leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) is a novel gastric cancer marker. However, it is unclear whether it can play roles in tumor angiogenesis. In this study, we aim to investigate the role of Lgr5 on gastric cancer angiogenesis. Lgr5, VEGF expression levels and microvessel density (MVD) were detected in tumor tissue. Then, Lgr5 mRNA was downregulated by small interference RNA technique. Western blotting and real-time quantitative PCR (qRT-PCR) were performed to detect the expression of Lgr5 and VEGF protein and mRNA in Lgr5 siRNA-transfected gastric cancer cells. The effect of silencing Lgr5 on angiogenesis was examined by assessing human umbilical vein endothelia cell (HUVEC) capillary tube formation. The results indicated that Lgr5 expression was upregulated in gastric cancer and positively correlated with VEGF (r=0.305, P=0.001) and MVD (r=0.312, P=0.001). Silencing of Lgr5 expression resulted in suppression of VEGF mRNA and protein (all P=0.001). Moreover, when HUVECs were stimulated with conditioned medium from Lgr5 siRNA-transfected gastric cancer cells, tube formation was significantly decreased (2.51 ± 0.19 mm/mm2) compared with the treatment with regular cell culture medium (DMEM) (7.34 ± 0.30 mm/mm2) or medium from control siRNA-transfected cells (7.18 ± 0.33 mm/mm2) (all P=0.001). In conclusion, Lgr5 plays important roles in angiogenesis. Lgr5-specific siRNA could be designed into an effective therapeutic agent to inhibit gastric cancer angiogenesis.

Procyanidin B2 3,3″-di-O-gallate inhibits endothelial cells growth and motility by targeting VEGFR2 and integrin signaling pathways

Targeting angiogenesis, one of the hallmarks of carcinogenesis, using non-toxic phytochemicals has emerged as a translational opportunity for angioprevention and to control advanced stages of malignancy. Herein, we investigated the inhibitory effects and associated mechanism/s of action of Procyanidin B2-3,3″-di- O-gallate (B2G2), a major component of grape seed extract, on human umbilical vein endothelial cells (HUVECs) and human prostate microvascular endothelial cells (HPMECs). Our results showed that B2G2 (10-40 μM) inhibits growth and induces death in both HUVECs and HPMECs. Additional studies revealed that B2G2 causes a G1 arrest in cell cycle progression of HUVECs by down-regulating cyclins (D1 and A), CDKs (Cdk2 and Cdc2) and Cdc25c phosphatase and up-regulating CDK inhibitors (p21 and p27) expression. B2G2 also induced strong apoptotic death in HUVECs through increasing p53, Bax and Smac/Diablo expression while decreasing Bcl-2 and survivin levels. Additionally, B2G2 inhibited the growth factors-induced capillary tube formation in HUVECs and HPMECs. Interestingly, conditioned media (CCM) from prostate cancer (PCA) cells (LNCaP and PC3) grown under normoxic (~21% O2) and hypoxic (1% O2) conditions significantly enhanced the tube formation in HUVECs, which was compromised in presence of conditioned media from B2G2-treated PCA cells. B2G2 also inhibited the motility and invasiveness of both HUVECs and HPMECs. Mechanistic studies showed that B2G2 targets VEGFR2/PI3K/Akt and integrin signaling molecules which are important for endothelial cells survival, proliferation, tube formation and motility. Overall, we report that B2G2 inhibits several attributes of angiogenesis in cell culture; therefore, it warrants further investigation for efficacy for angioprevention and cancer control.

High and low frequency subharmonic imaging of angiogenesis in a murine breast cancer model

This project compared quantifiable measures of tumor vascularity obtained from contrast-enhanced high frequency (HF) and low frequency (LF) subharmonic ultrasound imaging (SHI) to 3 immunohistochemical markers of angiogenesis in a murine breast cancer model (since angiogenesis is an important marker of malignancy and the target of many novel cancer treatments). Nineteen athymic, nude, female rats were implanted with 5×10(6) breast cancer cells (MDA-MB-231) in the mammary fat pad. The contrast agent Definity (Lantheus Medical Imaging, N Billerica, MA) was injected in a tail vein (dose: 180μl/kg) and LF pulse-inversion SHI was performed with a modified Sonix RP scanner (Analogic Ultrasound, Richmond, BC, Canada) using a L9-4 linear array (transmitting/receiving at 8/4MHz in SHI mode) followed by HF imaging with a Vevo 2100 scanner (Visualsonics, Toronto, ON, Canada) using a MS250 linear array transmitting and receiving at 24MHz. The radiofrequency data was filtered using a 4th order IIR Butterworth bandpass filter (11-13MHz) to isolate the subharmonic signal. After the experiments, specimens were stained for endothelial cells (CD31), vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2). Fractional tumor vascularity was calculated as contrast-enhanced pixels over all tumor pixels for SHI, while the relative area stained over total tumor area was calculated from specimens. Results were compared using linear regression analysis. Out of 19 rats, 16 showed tumor growth (84%) and 11 of them were successfully imaged. HF SHI demonstrated better resolution, but weaker signals than LF SHI (0.06±0.017 vs. 0.39±0.059; p<0.001). The strongest overall correlation in this breast cancer model was between HF SHI and VEGF (r=-0.38; p=0.03). In conclusion, quantifiable measures of tumor neovascularity derived from contrast-enhanced HF SHI appear to be a better method than LF SHI for monitoring angiogenesis in a murine xenograft model of breast cancer (corresponding in particular to the expression of VEGF); albeit based on a limited sample size.

HIFs, angiogenesis, and cancer

Tumor hypoxia was first described in the 1950s by radiation oncologists as a frequent cause of failure to radiotherapy in solid tumors. Today, it is evident that tumor hypoxia is a common feature of many cancers and the master regulator of hypoxia, hypoxia-inducible factor-1 (HIF-1), regulates multiple aspects of tumorigenesis, including angiogenesis, proliferation, metabolism, metastasis, differentiation, and response to radiation therapy. Although the tumor hypoxia response mechanism leads to a multitude of downstream effects, it is angiogenesis that is most crucial and also most susceptible to molecular manipulation. The delineation of molecular mechanisms of angiogenesis has revealed a critical role for HIF-1 in the regulation of angiogenic growth factors. In this article, we review what has been described about HIF-1: its structure, its regulation, and its implication for cancer therapy and we focus on its role in angiogenesis and cancer.

The Amazing Power of Cancer Cells to Recapitulate Extraembryonic Functions: The Cuckoo's Tricks

Inflammation is implicated in tumor development, invasion, and metastasis. Hence, it has been suggested that common cellular and molecular mechanisms are activated in wound repair and in cancer development. In addition, it has been previously proposed that the inflammatory response, which is associated with the wound healing process, could recapitulate ontogeny through the reexpression of the extraembryonic, that is, amniotic and vitelline, functions in the interstitial space of the injured tissue. If so, the use of inflammation by the cancer-initiating cell can also be supported in the ability to reacquire extraembryonic functional axes for tumor development, invasion, and metastasis. Thus, the diverse components of the tumor microenvironment could represent the overlapping reexpression of amniotic and vitelline functions. These functions would favor a gastrulation-like process, that is, the creation of a reactive stroma in which fibrogenesis and angiogenesis stand out.

Construction of a DNA vaccine encoding Flk-1 extracellular domain and C3d fusion gene and investigation of its suppressing effect on tumor growth

Although the critical role of complement component C3d as a molecular adjuvant in preventing virus infection is well established, its role in cancer prophylaxis and treatment is unclear. In this study, we constructed a recombinant plasmid encoding Flk-1 and C3d3 fusion proteins and investigated its transient expression in vitro in transfected eukaryotic cells and its antibody response in immunized mice. Subsequently, we investigated the vaccine's ability to elicit an immune response leading to suppression of angiogenesis and tumor growth in mice bearing bladder transitional cell carcinoma. Using Western blotting, immunocytochemistry, and flow cytometry, we detected the expression of Flk-1 and C3d3 fusion proteins in COS-7 cells transfected with these recombinant plasmids. Further binding experiment using CR2 (C3d receptor) positive Raji cells that were incubated with transfected COS-7 supernatant indicated that C3d was successfully fused to Flk-1. Although both vaccines elicited peak antibody levels at 5 weeks, Flk-1-specific antibody titer in pSG.SS.Flk-1(ECD).C3d3.YL-immunized mice was significantly higher when compared to pSG.SS.Flk-1(ECD).YL-immunized mice. The results of experiments with bladder tumor-bearing mice showed that the vaccine inhibited tumor growth significantly. These results suggest that C3d plays a critical role in tumor immunotherapy by promoting antibody response in Flk-1-based DNA vaccines. This approach may provide a new strategy for the rational design of anti-angiogenic therapies for the treatment of solid tumors and provide a basis for the further exploitation and application of the anti-angiogenesis DNA vaccines.

Vascularization in primary breast carcinomas: its prognostic significance and relationship with tumor cell dissemination

PURPOSE

The interaction between tumor cells, stroma, and endothelial cells is important for the dissemination of tumor cells. The aim of the present study is to examine vascularity in primary breast carcinomas and its prognostic significance and relationship with tumor cell dissemination.

EXPERIMENTAL DESIGN

A total of 498 invasive breast carcinomas were analyzed. Representative tumor sections were stained for CD34 and CD105, and vascularity was quantified by the Chalkley method. The relationship between Chalkley counts, vascular invasion, disseminated tumor cells (DTC) in the bone marrow, other clinicopathologic variables, and clinical outcome was evaluated.

RESULTS

High vascular grades determined by Chalkley counts were significantly associated with shorter distant disease-free survival and breast cancer-specific survival in all patients (P < 0.001, log-rank) and in node-negative patients not receiving adjuvant systemic therapy (P < 0.05). In multivariate analysis, both CD34 and CD105 Chalkley counts showed prognostic significance for distant disease-free survival (P = 0.014 and P = 0.026), whereas CD34 also showed prognostic significance for breast cancer-specific survival (P = 0.007). Vascular invasion and DTCs in the bone marrow showed independent prognostic significance. DTC did not discriminate survival for CD34 low Chalkley counts, whereas a very poor prognosis was observed for DTC-positive patients with high CD34 counts. In node-negative patients not receiving systemic chemotherapy, high CD34 and high CD105 counts in combination identified patients with unfavorable outcome, as opposed to all other CD34/CD105 combinations.

CONCLUSIONS

Improved identification of risk groups could be obtained by adding CD34 and CD105 vascular analysis to DTC, vascular invasion, and other primary tumor factors. This may facilitate the selection of candidates for adjuvant systemic therapy.

Acute ethanol exposure disrupts VEGF receptor cell signaling in endothelial cells

Physiological angiogenesis is regulated by various factors, including signaling through vascular endothelial growth factor (VEGF) receptors. We previously reported that a single dose of ethanol (1.4 g/kg), yielding a blood alcohol concentration of 100 mg/dl, significantly impairs angiogenesis in murine wounds, despite adequate levels of VEGF, suggesting direct effects of ethanol on endothelial cell signaling (40). To examine the mechanism by which ethanol influences angiogenesis in wounds, we employed two different in vitro angiogenesis assays to determine whether acute ethanol exposure (100 mg/dl) would have long-lasting effects on VEGF-induced capillary network formation. Ethanol exposure resulted in reduced VEGF-induced cord formation on collagen and reduced capillary network structure on Matrigel in vitro. In addition, ethanol exposure decreased expression of endothelial VEGF receptor-2, as well as VEGF receptor-2 phosphorylation in vitro. Inhibition of ethanol metabolism by 4-methylpyrazole partially abrogated the effect of ethanol on endothelial cell cord formation. However, mice treated with t-butanol, an alcohol not metabolized by alcohol dehydrogenase, exhibited no change in wound vascularity. These results suggest that products of ethanol metabolism are important factors in the development of ethanol-induced changes in endothelial cell responsiveness to VEGF. In vivo, ethanol exposure caused both decreased angiogenesis and increased hypoxia in wounds. Moreover, in vitro experiments demonstrated a direct effect of ethanol on the response to hypoxia in endothelial cells, as ethanol diminished nuclear hypoxia-inducible factor-1alpha protein levels. Together, the data establish that acute ethanol exposure significantly impairs angiogenesis and suggest that this effect is mediated by changes in endothelial cell responsiveness to both VEGF and hypoxia.

Inhibition of tumor angiogenesis by cell-permeable dominant negative SOX18 mutants

Angiogenesis play a key roles in tumor growth, invasion and metastasis, and has become an attractive target for anticancer drug development. Though a number of anti-angiogenic agents had entered clinical trials, few of them could reproduce the spectacular results in cancer patients as that had been seen in pre-clinical tumor models. Therefore, exploring novel anti-angiogenic agents is highly deserved. SOX18, a member of the Sry-related HMG box-containing family of transcription factors, is expressed transiently in endothelial cells during the development of blood vessels. And mutations resulting in expression of dominant negative SOX18 have been shown to severely impair the vascular development. Recent research demonstrated that SOX18 is expressed during the initial steps of tumor vascularization and involved in regulation of the expression of the VEGF receptor Flk-1 and the vascular cell adhesion molecule-1 (VCAM-1). Moreover, allograft tumor growth in mice heterozygous for Ra(Op) (RaOp mice) which express a dominant negative mutant form of SOX18 (SOX18RaOp) that does not interact effectively with the endothelial partner protein MEF2C, was dramatically slower than that of wild-type mice. In this article, we postulate that recombinant cell-permeable dominant negative SOX18 mutants, prepared by fusion with protein transduction domains, would inhibit tumor angiogenesis with high efficiency by impairing endothelial tube formation. If the hypothesis was proved to be practical, the fusion proteins would show promise as single anti-angiogenic agents in cancer therapy.

Reading the tea leaves: anticarcinogenic properties of (-)-epigallocatechin-3-gallate

Green tea is an extremely popular beverage worldwide. Derivatives of green tea, particularly (-)-epigallocatechin-3-gallate (EGCG), have been proposed to have anticarcinogenic properties based on preclinical, observational, and clinical trial data. To summarize, clarify, and extend current knowledge, we conducted a comprehensive search of the PubMed database and other secondary data sources, as appropriate, regarding the chemopreventive potential of EGCG. Apparently, EGCG functions as an antioxidant, preventing oxidative damage in healthy cells, but also as an antiangiogenic agent, preventing tumors from developing a blood supply needed to grow larger. Furthermore, EGCG may stimulate apoptosis in cancerous cells by negatively regulating the cell cycle to prevent continued division. Finally, EGCG exhibits antibacterial activity, which may be implicated in the prevention of gastric cancer. Although in vitro research of the anticarcinogenic properties of EGCG seems promising, many diverse and unknown factors may influence its in vivo activity in animal and human models. Some epidemiological studies suggest that green tea compounds could protect against cancer, but existing data are inconsistent, and limitations in study design hinder full interpretation and generalizability of the published observational findings. Several clinical trials with green tea derivatives are ongoing, and further research should help to clarify the clinical potential of EGCG for chemoprevention and/or chemotherapy applications.

Cancer cell: using inflammation to invade the host

Background

Inflammation is increasingly recognized as an important component of tumorigenesis, although the mechanisms involved are not fully characterized. The invasive capacity of cancers is reflected in the classic metastatic cascade: tumor (T), node (N) and metastasis (M). However, this staging system for cancer would also have a tumoral biological significance.

Presentation of the hypothesis

To integrate the mechanisms that control the inflammatory response in the actual staging system of cancer. It is considered that in both processes of inflammation and cancer, three successive phenotypes are presented that represent the expression of trophic functional systems of increasing metabolic complexity for using oxygen.

Testing the hypothesis

While a malignant tumor develops it express phenotypes that also share the inflammatory response such as: an ischemic phenotype (anoxic-hypoxic), a leukocytic phenotype with anaerobic glycolysis and migration, and an angiogenic phenotype with hyperactivity of glycolytic enzymes, tumor proliferation and metastasis, and cachexia of the host. The increasing metabolic complexity of the tumor cell to use oxygen allows for it to be released, migrate and proliferate, thus creating structures of growing complexity.

Implication of the hypothesis

One aim of cancer gene therapy could be the induction of oxidative phosphorylation, the last metabolic step required by inflammation in order to differentiate the tissue that it produces.

Inflammation and cancer: is trophism the link?

The pathophysiological mechanisms of the inflammatory response can be common to wound repair and tumor development. We propose that this response evolves in three phases, the nervous or immediate phase, the immune or intermediate phase, and the endocrine or late phase. In wound repair and in these phases, the interstitial space successively presents edema due to ischemia-revascularization and nutrition by diffusion (nervous phase), infiltration by leukocytes, which would mediate the nutrition of damaged neighbor cells (immune phase) and by angiogenesis, nutrition mediated by the capillaries that favor regeneration or scarring (endocrine phase). At the same time, in tumor development, it is considered that the cancerous cell successively occupies the interstitial space, expressing three different phenotypes: the hypoxia-reperfusion phenotype, with anaerobic glycolisis, oxidative stress and edema (dormant stage); the immune phenotype that expresses the functions corresponding to leukocytes, including the hyperproduction of pro-inflammatory mediators, lymphangiogenesis, the invasion of lymph nodes (N stage) and systemic inflammatory response syndrome; and lastly, the endocrine phenotype, in which the appearance of both local (tumor or T stage) and systemic (metastasis or M stage) angiogenesis induce a growing disease.

Does three-dimensional power Doppler ultrasound help in discrimination between benign and malignant ovarian masses?

OBJECTIVES

To determine if tumor vascularity as assessed by three-dimensional (3D) power Doppler ultrasound can be used to discriminate between benign and malignant ovarian tumors, if adding 3D power Doppler ultrasound to gray-scale imaging improves differentiation between benignity and malignancy, and if 3D power Doppler ultrasound adds more to gray-scale ultrasound than does two-dimensional (2D) power Doppler ultrasound.

METHODS

One hundred and six women scheduled for surgery because of an ovarian mass were examined with transvaginal gray-scale ultrasound and 2D and 3D power Doppler ultrasound. The color content of the tumor scan was rated subjectively by the ultrasound examiner on a visual analog scale. Vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were calculated in the whole tumor and in a 5-cm(3) sample taken from the most vascularized area of the tumor. Logistic regression analysis was used to build models to predict malignancy.

RESULTS

There were 79 benign tumors, six borderline tumors and 21 invasive malignancies. A logistic regression model including only gray-scale ultrasound variables (the size of the largest solid component, wall irregularity, and lesion size) was built to predict malignancy. It had an area under the receiver-operating characteristics (ROC) curve of 0.98, sensitivity of 100%, false positive rate of 10%, and positive likelihood ratio (LR) of 10 when using the mathematically best cut-off value for risk of malignancy (0.12). The diagnostic performance of the 3D flow index with the best diagnostic performance, i.e. VI in a 5-cm(3) sample, was superior to that of the color content of the tumor scan (area under ROC curve 0.92 vs. 0.80, sensitivity 93% vs. 78%, false positive rate 16% vs. 27% using the mathematically best cut-off value). Adding the color content of the tumor scan or FI in a 5-cm(3) sample to the logistic regression model including the three gray-scale variables described above improved diagnostic performance only marginally, an additional two tumors being correctly classified.

CONCLUSIONS

Even though 2D and 3D power Doppler ultrasound can be used to discriminate between benign and malignant ovarian tumors, their use adds little to a correct diagnosis of malignancy in an ordinary population of ovarian tumors. Objective quantitation of the color content of the tumor scan using 3D power Doppler ultrasound does not seem to add more to gray-scale imaging than does subjective quantitation by the ultrasound examiner using 2D power Doppler ultrasound.

Interest of RGD-containing linear or cyclic peptide targeted tetraphenylchlorin as novel photosensitizers for selective photodynamic activity

Destruction of the neovasculature is essential for tumor eradication by photodynamic therapy. Since the over-expression of integrins is correlated with tumor angiogenesis, we conjugated a photosensitizer (5-(4-carboxyphenyl)-10,15,20-triphenylchlorin or porphyrin) to the alpha(v)beta(3) integrin specific peptide RGD (H-Arg-Gly-Asp-OH) motif as a common sequence. We reported an efficient solid-phase synthesis of a new family of peptidic photosensitizers with linear or cyclic[RGDfK] RGD motif and compared conjugates in vitro selectivity and photodynamic activity. The conjugates were characterized by (1)H NMR, MALDI, UV-visible spectroscopy and singlet oxygen formation was performed. Chlorins containing linear and constrained RGD motif were incorporated up to 98- and 80-fold more, respectively, than the unconjugated photosensitizer over a 24-h exposure in human umbilical vein endothelial cells (HUVEC) over-expressing alpha(v)beta(3) integrin. Peptidic moiety also led to a non-specific increased cellular uptake by murine mammary carcinoma cells (EMT-6), lacking RGD binding receptors. Survival measurements demonstrated that HUVEC were greatly sensitive to conjugates-mediated photodynamic therapy.

Alphastatin downregulates vascular endothelial cells sphingosine kinase activity and suppresses tumor growth in nude mice bearing human gastric cancer xenografts

AIM: To investigate whether alphastatin could inhibit human gastric cancer growth and furthermore whether sphingosine kinase (SPK) activity is involved in this process.

METHODS: Using migration assay, MTT assay and Matrigel assay, the effect of alphastatin on vascular endothelial cells (ECs) was evaluated in vitro. SPK and endothelial differentiation gene (EDG)-1, -3, -5 mRNAs were detected by reverse transcription-polymerase chain reaction (RT-PCR). SPK activity assay was used to evaluate the effect of alphastatin on ECs. Matrigel plug assay in nude mice was used to investigate the effect of alphastatin on angiogenesis in vivo. Female nude mice were subcutaneously implanted with human gastric cancer cells (BGC823) for the tumor xenografts studies. Micro vessel density was analyzed in Factor VIII-stained tumor sections by the immunohistochemical SP method.

RESULTS: In vitro, alphastatin inhibited the migration and tube formation of ECs, but had no effect on proliferation of ECs. RT-PCR analysis demonstrated that ECs expressed SPK and EDG-1, -3, -5 mRNAs. In vivo, alphastatin sufficiently suppressed neovascularization of the tumor in the nude mice. Daily administration of alphastatin produced significant tumor growth suppression. Immunohistochemical studies of tumor tissues revealed decreased micro vessel density in alphastatin-treated animals as compared with controls.

CONCLUSION: Downregulating ECs SPK activity may be one of the mechanisms that alphastatin inhibits gastric cancer angiogenesis. Alphastatin might be a useful and relatively nontoxic adjuvant therapy in the treatment of gastric cancer.

Angiostatin generating capacity and anti-tumour effects of D-penicillamine and plasminogen activators

Background

Upregulation of endogenous angiostatin levels may constitute a novel anti-angiogenic, and therefore anti-tumor therapy. In vitro, angiostatin generation is a two-step process, starting with the conversion of plasminogen to plasmin by plasminogen activators (PAs). Next, plasmin excises angiostatin from other plasmin molecules, a process requiring a donor of a free sulfhydryl group. In previous studies, it has been demonstrated that administration of PA in combination with the free sulfhydryl donor (FSD) agents captopril or N-acetyl cysteine, resulted in angiostatin generation, and anti-angiogenic and anti-tumour activity in murine models.

Methods

In this study we have investigated the angiostatin generating capacities of several FSDs. D-penicillamine proved to be most efficient in supporting the conversion of plasminogen to angiostatin in vitro. Next, from the optimal concentrations of tPA and D-penicillamine in vitro, equivalent dosages were administered to healthy Balb/c mice to explore upregulation of circulating angiostatin levels. Finally, anti-tumor effects of treatment with tPA and D-penicillamine were determined in a human melanoma xenograft model.

Results

Surprisingly, we found that despite the superior angiostatin generating capacity of D-penicillamine in vitro, both in vivo angiostatin generation and anti-tumour effects of tPA/D-penicillamine treatment were impaired compared to our previous studies with tPA and captopril.

Conclusion

Our results indicate that selecting the most appropriate free sulfhydryl donor for anti-angiogenic therapy in a (pre)clinical setting should be performed by in vivo rather than by in vitro studies. We conclude that D-penicillamine is not suitable for this type of therapy.

The role of immune cells in the tumor microenvironment

Interactions between tumor infiltrating leukocytes and tumor cells have been of great interest because of the possibility that immune cells either interfere with tumor progression or actively promote tumor growth. The tumor microenvironment is shaped by cells entering it, and their functions reflect the local conditions. Successive changes occurring at the tumor site during tumor progression resemble chronic inflammation. This chronic inflammatory reaction seems to be largely orchestrated by the tumor, and it seems to promote tumor survival. Molecular and cellular mechanisms linking the inflammatory reaction and cancer are emerging, and this review summarizes the current understanding of interactions between inflammatory and cancer cells in the tumor microenvironment.

Synthesis and evaluation of 4-[18F]fluorothalidomide for the in vivo studies of angiogenesis

In this study, we prepared 2-(2,6-dioxopiperidin-3-yl)-4-[(18)F]fluoroisoindole-1,3-dione (4-[(18)F]fluorothalidomide; [(18)F]1) for the in vivo studies of angiogenesis. Radiochemical synthesis of [(18)F]1 was carried out by labeling 4-trimethylammoniumthalidomide trifluoromethanesulfonate with nBu(4)N[(18)F]F in dimethyl sulfoxide (DMSO), followed by reverse-phase HPLC purification. Decay-corrected radiochemical yield of [(18)F]1 was 50-60%, with an effective specific activity of 42-120 GBq/micromol (end of synthesis). Incubation of the radioligand with human umbilical vein endothelial cells (HUVEC-C; American Type Culture Collection) showed a time-dependent increase in the uptake of the radioligand, and the uptake was inhibited by 8-11% in the presence of 10 microM thalidomide, indicating nonspecific binding of the radioligand. Positron emission tomography (PET) images of mice implanted with tumors in their right flanks revealed a marked accumulation of radioactivity in the livers, kidneys and bladders of the mice, and brain uptake appeared at approximately 40 min after injection. However, no radioactivity uptake was detected in the implanted tumor. Thin-layer chromatography (TLC), HPLC and LC-MS analyses of mouse liver microsomal metabolites of [(18)F]1 and 1 with or without nicotinamide adenine dinucleotide phosphate (NADPH) clearly revealed that the radioligand did not go through metabolic activation but underwent nonenzymatic hydrolysis at physiological pH. Therefore, these results would appear to indicate that [(18)F]1 may not be suitable for the in vivo studies of angiogenesis at least in mice, although it was reported that thalidomide and/or its hydrolysis products may be responsible for its activity in humans.

Breast cancer biomarkers

Substantial progress has been made over the past three decades in our understanding of the epidemiology, clinical course and basic biology of breast cancer. This chapter considers the existing ancillary tests and emerging molecular markers in breast cancer prognosis assessment and the prediction of response of breast cancer to treatment of the disease.

Immunoplacental therapy, a potential multi-epitope cancer vaccine

The field of tumor immunology has made great advancements in recent years. A retrospective analysis of previous vaccine strategies combined with present knowledge may provide additional insight in this treatment modality. This article provides a review of immunoplacental therapy (IPT), a cancer vaccine consisting of chorionic villi extractions from the human placenta after a live full-term delivery. This therapy was first introduced in the 1970s by Valentin I. Govallo, M.D., Ph.D., who noted the immunological similarities between pregnancy and cancer. The goal of cancer immunotherapy, according to Govallo, is to view the fetal allograft as an "impregnating tumor" and create an immunological state in the oncological patient analogous to a spontaneous abortion in a pregnant women. The placenta shares identical growth mechanisms, antigenic determinants, and immune-escape properties with cancer cells; this includes numerous tumor-associated antigens, angiogenic growth factors, complement regulatory proteins, and defective apoptotic mechanisms which aid in their survival. Placental vaccination may function as a multi-epitope vaccine; the body recognizes the placental antigens of this vaccine as foreign, and thus stimulates a cross reactive humoral and cell-mediated immune response targeting cancer tumor-associated antigens as well as proteins that aid in cancer angiogenesis, complement regulation, and apoptotic resistance. With recent advancements in molecular and cellular cancer immunology, the model introduced by Govallo may provide an important strategic approach to cancer immunotherapy.

Phosphatidylinositide 3-Kinase Is Important in Late-Stage Fibroblast Growth Factor-1-Mediated Angiogenesis in vivo

We previously reported that overexpression of a secreted version of fibroblast growth factor-1 (sp-FGF-1) has the ability to induce angiogenesis in the chicken chorioallantoic membrane (CAM). In our current study, we examine the effects of sp-FGF-1 through a time course analysis of angiogenesis in the chicken CAM on days 3, 4, and 5 after gene transfection. Significant angiogenesis was observed on days 4 and 5 after gene transfection in the CAM assay. To evaluate the role of phosphatidylinositide 3-kinase (PI3K) signaling in sp-FGF-1-induced angiogenesis, we analyzed mRNA expression levels of PI3K and protein activity through its immediate downstream target, AKT-1. We found upregulation of both PI3K and AKT mRNA expression levels in day 5 sp-FGF-1 versus day 5 vector control-transfected CAMs. Furthermore, by blocking PI3K phosphorylation using the specific inhibitor, LY294002, we found that downstream phosphorylation of AKT-1 was inhibited. More importantly, the blockade of the PI3K pathway via LY294002 in sp-FGF-1-transfected CAMs significantly inhibited angiogenesis. These results further elucidate the molecular mechanisms of the sp-FGF-1 signaling pathway and it underscores the importance of PI3K signaling in FGF-1-stimulated angiogenesis in vivo. It also provides a basis for the role of sp-FGF-1 in the development of therapeutic treatments to combat vascular insufficiencies and angiogenesis-dependent cancers.

Thalidomide inhibits the growth and progression of hepatic epithelioid hemangioendothelioma

Hepatic epithelioid hemangioendothelioma (HEH) is a rare vascular tumor of the liver with an unpredictable malignant potential. Its growth can lead to hepatic failure, extrahepatic metastasis and death. Surgical resection or liver transplantation is the treatment of choice if metastasis is not identified. Several antineoplastic agents have been proposed for cases of nonresectable HEH. We report the case of a 52-year-old patient with HEH metastatic to the lungs who was successfully treated with oral thalidomide therapy.