Angiogenesis inhibitor TNP-470 reduces human pancreatic cancer growth

Investigating underlying molecular mechanisms, signaling pathways, emerging therapeutic approaches in pancreatic cancer

Pancreatic adenocarcinoma, a clinically challenging malignancy constitutes a significant contributor to cancer-related mortality, characterized by an inherently poor prognosis. This review aims to provide a comprehensive understanding of pancreatic adenocarcinoma by examining its multifaceted etiologies, including genetic mutations and environmental factors. The review explains the complex molecular mechanisms underlying its pathogenesis and summarizes current therapeutic strategies, including surgery, chemotherapy, and emerging modalities such as immunotherapy. Critical molecular pathways driving pancreatic cancer development, including KRAS, Notch, and Hedgehog, are discussed. Current therapeutic strategies, including surgery, chemotherapy, and radiation, are discussed, with an emphasis on their limitations, particularly in terms of postoperative relapse. Promising research areas, including liquid biopsies, personalized medicine, and gene editing, are explored, demonstrating the significant potential for enhancing diagnosis and treatment. While immunotherapy presents promising prospects, it faces challenges related to immune evasion mechanisms. Emerging research directions, encompassing liquid biopsies, personalized medicine, CRISPR/Cas9 genome editing, and computational intelligence applications, hold promise for refining diagnostic approaches and therapeutic interventions. By integrating insights from genetic, molecular, and clinical research, innovative strategies that improve patient outcomes can be developed. Ongoing research in these emerging fields holds significant promise for advancing the diagnosis and treatment of this formidable malignancy.

The Heterogeneity of the Tumor Microenvironment as Essential Determinant of Development, Progression and Therapy Response of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is commonly diagnosed at advanced stages and most anti-cancer therapies have failed to substantially improve prognosis of PDAC patients. As a result, PDAC is still one of the deadliest tumors. Tumor heterogeneity, manifesting at multiple levels, provides a conclusive explanation for divergent survival times and therapy responses of PDAC patients. Besides tumor cell heterogeneity, PDAC is characterized by a pronounced inflammatory stroma comprising various non-neoplastic cells such as myofibroblasts, endothelial cells and different leukocyte populations which enrich in the tumor microenvironment (TME) during pancreatic tumorigenesis. Thus, the stromal compartment also displays a high temporal and spatial heterogeneity accounting for diverse effects on the development, progression and therapy responses of PDAC. Adding to this heterogeneity and the impact of the TME, the microbiome of PDAC patients is considerably altered. Understanding this multi-level heterogeneity and considering it for the development of novel therapeutic concepts might finally improve the dismal situation of PDAC patients. Here, we outline the current knowledge on PDAC cell heterogeneity focusing on different stromal cell populations and outline their impact on PDAC progression and therapy resistance. Based on this information, we propose some novel concepts for treatment of PDAC patients.

Pancreatic Cancer Signaling Pathways, Genetic Alterations, and Tumor Microenvironment: The Barriers Affecting the Method of Treatment

Genetic alterations, especially the K-Ras mutation, carry the heaviest burden in the progression of pancreatic precursor lesions into pancreatic ductal adenocarcinoma (PDAC). The tumor microenvironment is one of the challenges that hinder the therapeutic approaches from functioning sufficiently and leads to the immune evasion of pancreatic malignant cells. Mastering the mechanisms of these two hallmarks of PDAC can help us in dealing with the obstacles in the way of treatment. In this review, we have analyzed the signaling pathways involved in PDAC development and the immune system's role in pancreatic cancer and immune checkpoint inhibition as next-generation therapeutic strategy. The direct targeting of the involved signaling molecules and the immune checkpoint molecules, along with a combination with conventional therapies, have reached the most promising results in pancreatic cancer treatment.

Fumagillin, a Mycotoxin of Aspergillus fumigatus: Biosynthesis, Biological Activities, Detection, and Applications

Fumagillin is a mycotoxin produced, above all, by the saprophytic filamentous fungus Aspergillus fumigatus. This mold is an opportunistic pathogen that can cause invasive aspergillosis, a disease that has high mortality rates linked to it. Its ability to adapt to environmental stresses through the production of secondary metabolites, including several mycotoxins (gliotoxin, fumagillin, pseurotin A, etc.) also seem to play an important role in causing these infections. Since the discovery of the A. fumigatus fumagillin in 1949, many studies have focused on this toxin and in this review we gather all the information currently available. First of all, the structural characteristics of this mycotoxin and the different methods developed for its determination are given in detail. Then, the biosynthetic gene cluster and the metabolic pathway involved in its production and regulation are explained. The activity of fumagillin on its target, the methionine aminopeptidase type 2 (MetAP2) enzyme, and the effects of blocking this enzyme in the host are also described. Finally, the applications that this toxin and its derivatives have in different fields, such as the treatment of cancer and its microsporicidal activity in the treatment of honeybee hive infections with Nosema spp., are reviewed. Therefore, this work offers a complete review of all the information currently related to the fumagillin mycotoxin secreted by A. fumigatus, important because of its role in the fungal infection process but also because it has many other applications, notably in beekeeping, the treatment of infectious diseases, and in oncology.

Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) and its receptor PROKR2 are associated to human colorectal cancer progression and peritoneal carcinomatosis

BACKGROUND

The highest risk factor for mortality among malignant tumors is metastasis. Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is an angiogenic factor which biological activity is mediated via two G protein-coupled receptors, prokineticin receptor1 (PROKR1) and PROKR2. Recent studies suggested that EG-VEGF expression is deregulated in multiple cancers including colorectal cancer (CRC).

METHODS

Using distinctive CRC and peritoneal carcinomatosis (PC) cohorts and a corresponding control cohort, we determined the circulating levels of EG-VEGF and its in situ expression, and that of its related receptors.

RESULTS

Circulating EG-VEGF levels were significantly increased in patients with metastatic PC compared to CRC and control patients (p< 0.05). Furthermore, according to clinicopathologic examinations, local EG-VEGF expression correlated with higher tumor and nodal stages (p< 0.001) of CRC. EG-VEGF and PROKR2 were highly expressed in colorectal primary lesions compared to positive controls. PROKR1 expression was lower and did not change in tumor specimens. Also, EG-VEGF and its receptor PROKR2 were differentially expressed in the colorectal primary lesions and in the control groups.

CONCLUSION

Altogether these findings suggest that EG-VEGF/receptors system might be an important actor in the CRC progression into PC and might be involved in the ability of tumor cells to invade other organs. Circulating EG-VEGF could be proposed as a prognostic marker in human CRC and its progression into PC.

Endothelial loss of Fzd5 stimulates PKC/Ets1-mediated transcription of Angpt2 and Flt1

Aims

Formation of a functional vascular system is essential and its formation is a highly regulated process initiated during embryogenesis, which continues to play important roles throughout life in both health and disease. In previous studies, Fzd5 was shown to be critically involved in this process and here we investigated the molecular mechanism by which endothelial loss of this receptor attenuates angiogenesis.

Methods and results

Using short interference RNA-mediated loss-of-function assays, the function and mechanism of signaling via Fzd5 was studied in human endothelial cells (ECs). Our findings indicate that Fzd5 signaling promotes neovessel formation in vitro in a collagen matrix-based 3D co-culture of primary vascular cells. Silencing of Fzd5 reduced EC proliferation, as a result of G₀/G₁ cell cycle arrest, and decreased cell migration. Furthermore, Fzd5 knockdown resulted in enhanced expression of the factors Angpt2 and Flt1, which are mainly known for their destabilizing effects on the vasculature. In Fzd5-silenced ECs, Angpt2 and Flt1 upregulation was induced by enhanced PKC signaling, without the involvement of canonical Wnt signaling, non-canonical Wnt/Ca²⁺-mediated activation of NFAT, and non-canonical Wnt/PCP-mediated activation of JNK. We demonstrated that PKC-induced transcription of Angpt2 and Flt1 involved the transcription factor Ets1.

Conclusions

The current study demonstrates a pro-angiogenic role of Fzd5, which was shown to be involved in endothelial tubule formation, cell cycle progression and migration, and partly does so by repression of PKC/Ets1-mediated transcription of Flt1 and Angpt2.

Electronic supplementary material

The online version of this article (10.1007/s10456-018-9625-6) contains supplementary material, which is available to authorized users.

Targeting stroma in pancreatic cancer: Promises and failures of targeted therapies

Desmoplasia or abundant fibrotic stroma is a typical property of most malignancies, which has a great effect on tumorigenesis, angiogenesis, and resistance to therapy. The activated stroma cells comprises several cell types including endothelial cells, nerve cells, inflammatory/macrophages cells, stellate cells, and extracellular matrix. In other word, the interactions of cancer-stroma modulate tumorigenesis, therapy resistance, and poor delivery of drugs. Therefore, targeting the tumor stroma in combination with conventional chemotherapeutic agents could provide a promising approach in the treatment of pancreatic cancer. This review summarizes the current knowledge about pancreatic stellate cells, targeting stroma compartments with particular emphasis on preclinical, and clinical trials on targeting of stroma as an option in pancreatic cancer treatment.

Cancer of the Pancreas: Molecular Pathways and Current Advancement in Treatment

Pancreatic cancer is one of the most lethal cancers among all malignances, with a median overall survival of <1 year and a 5-year survival of ~5%. The dismal survival rate and prognosis are likely due to lack of early diagnosis, fulminant disease course, high metastasis rate, and disappointing treatment outcome. Pancreatic cancers harbor a variety of genetic alternations that render it difficult to treat even with targeted therapy. Recent studies revealed that pancreatic cancers are highly enriched with a cancer stem cell (CSC) population, which is resistant to chemotherapeutic drugs, and therefore escapes chemotherapy and promotes tumor recurrence. Cancer cell epithelial to mesenchymal transition (EMT) is highly associated with metastasis, generation of CSCs, and treatment resistance in pancreatic cancer. Reviewed here are the molecular biology of pancreatic cancer, the major signaling pathways regulating pancreatic cancer EMT and CSCs, and the advancement in current clinical and experimental treatments for pancreatic cancer.

Key players in pancreatic cancer-stroma interaction: Cancer-associated fibroblasts, endothelial and inflammatory cells

Pancreatic cancer (PC) is the most aggressive type of common cancers, and in 2014, nearly 40000 patients died from the disease in the United States. Pancreatic ductal adenocarcinoma, which accounts for the majority of PC cases, is characterized by an intense stromal desmoplastic reaction surrounding the cancer cells. Cancer-associated fibroblasts (CAFs) are the main effector cells in the desmoplastic reaction, and pancreatic stellate cells are the most important source of CAFs. However, other important components of the PC stroma are inflammatory cells and endothelial cells. The aim of this review is to describe the complex interplay between PC cells and the cellular and non-cellular components of the tumour stroma. Published data have indicated that the desmoplastic stroma protects PC cells against chemotherapy and radiation therapy and that it might promote the proliferation and migration of PC cells. However, in animal studies, experimental depletion of the desmoplastic stroma and CAFs has led to more aggressive cancers. Hence, the precise role of the tumour stroma in PC remains to be elucidated. However, it is likely that a context-dependent therapeutic modification, rather than pure depletion, of the PC stroma holds potential for the development of new treatment strategies for PC patients.

TCGA data and patient-derived orthotopic xenografts highlight pancreatic cancer-associated angiogenesis

Pancreatic ductal adenocarcinomas (PDACs) overexpress pro-angiogenic factors but are not viewed as vascular. Using data from The Cancer Genome Atlas we demonstrate that a subset of PDACs exhibits a strong pro-angiogenic signature that includes 37 genes, such as HDAC9, that are overexpressed in PDAC arising in KRC mice, which express mutated Kras and lack RB. Moreover, patient-derived orthotopic xenografts can exhibit tumor angiogenesis, whereas conditioned media (CM) from KRC-derived pancreatic cancer cells (PCCs) enhance endothelial cell (EC) growth and migration, and activate canonical TGF-β signaling and STAT3. Inhibition of the type I TGF-β receptor with SB505124 does not alter endothelial activation in vitro, but decreases pro-angiogenic gene expression and suppresses angiogenesis in vivo. Conversely, STAT3 silencing or JAK1-2 inhibition with ruxolitinib blocks CM-enhanced EC proliferation. STAT3 disruption also suppresses endothelial HDAC9 and blocks CM-induced HDAC9 expression, whereas HDAC9 re-expression restores CM-enhanced endothelial proliferation. Moreover, ruxolitinib blocks mitogenic EC/PCC cross-talk, and suppresses endothelial p-STAT3 and HDAC9, and PDAC progression and angiogenesis in vivo, while markedly prolonging survival of KRC mice. Thus, targeting JAK1-2 with ruxolitinib blocks a final pathway that is common to multiple pro-angiogenic factors, suppresses EC-mediated PCC proliferation, and may be useful in PDACs with a strong pro-angiogenic signature.

Compound K inhibits basic fibroblast growth factor-induced angiogenesis via regulation of p38 mitogen activated protein kinase and AKT in human umbilical vein endothelial cells

Compound K (CK; 20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol), an active ginseng saponin metabolite, exerts anticancer activity via apoptosis induction in various cancers. In the present study, we investigated the anti-angiogenic activity of CK and its molecular mechanisms in human umbilical vein endothelial cells (HUVECs). Angiogenesis was induced in HUVECS by basic fibroblast growth factor (bFGF), a potent angiogenic growth factor. CK significantly inhibited the proliferation and also attenuated the expression of a proliferating protein cyclin D1 in bFGF treated HUVECs. Also, CK significantly inhibited the migration and tube formation of bFGF treated HUVECs at non-cytotoxic concentrations, reduced secreted level of vascular endothelial growth factor (VEGF) and increased the secreted level of pigment epithelium-derived factor (PEDF) in HUVECs. In addition, CK effectively disrupted bFGF-induced neo-vascularization in the Matrigel plugs excised from mice in vivo. Notably, we have found that CK downregulated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and AKT in bFGF treated HUVECs. Taken together, our findings for the first time indicate that CK exerts anti-angiogenic activity via inhibition of p38 MAPK and AKT in HUVECs with the potential of a cancer chemopreventive agent.

Inhibition of NFkappaB and pancreatic cancer cell and tumor growth by curcumin is dependent on specificity protein down-regulation

Curcumin activates diverse anticancer activities that lead to inhibition of cancer cell and tumor growth, induction of apoptosis, and antiangiogenic responses. In this study, we observed that curcumin inhibits Panc28 and L3.6pL pancreatic cancer cell and tumor growth in nude mice bearing L3.6pL cells as xenografts. In addition, curcumin decreased expression of p50 and p65 proteins and NFkappaB-dependent transactivation and also decreased Sp1, Sp3, and Sp4 transcription factors that are overexpressed in pancreatic cancer cells. Because both Sp transcription factors and NFkappaB regulate several common genes such as cyclin D1, survivin, and vascular endothelial growth factor that contribute to the cancer phenotype, we also investigated interactions between Sp and NFkappaB transcription factors. Results of Sp1, Sp3, and Sp4 knockdown by RNA interference demonstrate that both p50 and p65 are Sp-regulated genes and that inhibition of constitutive or tumor necrosis factor-induced NFkappaB by curcumin is dependent on down-regulation of Sp1, Sp3, and Sp4 proteins by this compound. Curcumin also decreased mitochondrial membrane potential and induced reactive oxygen species in pancreatic cancer cells, and this pathway is required for down-regulation of Sp proteins in these cells, demonstrating that the mitochondriotoxic effects of curcumin are important for its anticancer activities.

Assessment of vessel size by MRI in an orthotopic model of human pancreatic cancer

Pancreatic cancer is a devastating disease with no cure. Therapies that target the tumor vasculature are promising new treatment strategies. Magnetic resonance imaging (MRI) can non-invasively determine a vessel size index and a blood volume fraction to characterize the vascular compartment in a tumor. The changes in the T2 and T2* relaxation rate constants after the administration of superparamagnetic iron oxide (SPIO) particles are dependent on the size and morphology of tissue blood vessels. In this study, MRI was used to investigate changes in the tumor vasculature in an orthotopic primary human pancreatic cancer xenograft model during tumor progression. The SPIO contrast agent Feridex I.V. was first validated as an intravascular contrast agent over the course of the imaging session, and shown to remain in the blood for at least 1.5 h. The average vessel size index was not correlated to the tumor area within an image slice, but the average blood volume fraction was significantly and negatively correlated to the tumor area (p<0.05). Blood volume fraction may serve as a non-invasive biomarker for changes in the tumor vasculature due to tumor growth Further investigation is needed to evaluate this promising technique as a tool to monitor tumor vascular changes in response to antiangiogenic therapies in pancreatic cancer.

In vitro models of pancreatic cancer for translational oncology research

BACKGROUND: Pancreatic cancer is a disease of near uniform fatality and the overwhelming majority of patients succumb to their advanced malignancy within a few months of diagnosis. Despite considerable advances in our understanding of molecular mechanisms underlying pancreatic carcinogenesis, this knowledge has not yet been fully translated into clinically available treatment strategies that yield significant improvements in disease free or overall survival. OBJECTIVE: Cell line-based in vitro model systems provide powerful tools to identify potential molecular targets for therapeutic intervention as well as for initial pre-clinical evaluation of novel drug candidates. Here we provide a brief overview of recent literature on cell line-based model systems of pancreatic cancer and their application in the search for novel therapeutics against this vicious disease. CONCLUSION: While in vitro models of pancreatic cancer are of tremendous value for genetic studies and initial functional screenings in drug discovery, they carry several imanent drawbacks and are often poor in predicting therapeutic response in humans. Therefore, in most instances they are successfully exploited to generate hypothesis and identify molecular targets for novel therapeutics, which are subsequently subject to further in-depth characterization using more advanced in vivo model systems and clinical trials.

Structure-dependent activation of endoplasmic reticulum stress-mediated apoptosis in pancreatic cancer by 1,1-bis(3'-indoly)-1-(p-substituted phenyl)methanes

1,1-Bis(3'-indoly)-1-(p-substituted phenyl)methanes (C-DIM) exhibit structure-dependent activation of peroxisome proliferator-activated receptor gamma and nerve growth factor-induced Balpha (Nur77) and induce receptor-dependent and receptor-independent apoptosis in cancer cells and tumors. In this study, we investigated the activation of apoptosis in pancreatic cancer cells by p-bromo (DIM-C-pPhBr) and p-fluoro (DIM-C-pPhF) and structurally related analogues that do not activate either peroxisome proliferator-activated receptor gamma or Nur77. The ortho, meta, and para-bromo and -fluoro isomers all activated endoplasmic reticulum (ER) stress-dependent apoptosis in pancreatic cancer cells; however, methylation of the indole N group significantly decreased activity, suggesting that a free N was important for activation of ER stress. Both DIM-C-pPhBr and DIM-C-pPhF resembled the classic ER stress inducer thapsigargin in pancreatic cancer cells and activated ER stress markers, such as glucose-related protein 78 and the c-Jun NH(2) kinase pathway, resulting in the induction of CCAAT/enhancer-binding protein homologous protein, death receptor 5, and the extrinsic apoptotic pathway. Moreover, DIM-C-pPhBr also inhibited tumor growth in an orthotopic model for pancreatic cancer, demonstrating the clinical potential for this C-DIM compound in pancreatic cancer chemotherapy.

Pancreatic cancer: from molecular pathogenesis to targeted therapy

Pancreatic cancer is a deadly malignancy with still high mortality and poor survival despite the significant advances in understanding, diagnosis, and access to conventional and novel treatments. Though cytotoxic chemotherapy based on the purine analogue gemcitabine remains the standard approach in adjuvant and palliative setting the need for novel agents aiming at the main pathophysiological abnormalities and molecular pathways involved remains soaring. So far, evidence of clinical benefit, though small, exists only from the addition of the targeted agent erlotinib on the standard gemcitabine chemotherapy. Apart from the popular monoclonal antibodies and small molecules tyrosine kinase inhibitors, other novel compounds being tested in preclinical and clinical studies target mTOR, NF-kappaB, proteasome and histone deacetylase. These new drugs along with gene therapy and immunotherapy, which are also under clinical evaluation, may alter the unfavorable natural course of this disease. In this review we present the main pathophysiological alterations met in pancreatic cancer and the results of the florid preclinical and clinical research with regards to the targeted therapy associated to these abnormalities.

Biological approaches to therapy of pancreatic cancer

Pancreatic cancer is a lethal disease and notoriously difficult to treat. Only a small proportion is curative by surgical resection, whilst standard chemotherapy for patients with advanced disease has only modest effect with substantial toxicity. Clearly there is a need for the continual development of novel therapeutic agents to improve the current situation. Improvement of our understanding of the disease has generated a large number of studies on biological approaches targeting the molecular abnormalities of pancreatic cancer, including gene therapy and signal transduction inhibition, antiangiogenic and matrix metalloproteinase inhibition, oncolytic viral therapy and immunotherapy. This article provides a review of these approaches, both investigated in the laboratories and in subsequent clinical trials.

A phase II study evaluating bevacizumab in combination with fixed-dose rate gemcitabine and low-dose cisplatin for metastatic pancreatic cancer: is an anti-VEGF strategy still applicable?

BACKGROUND

The role of bevacizumab, a recombinant humanized monoclonal antibody directed against vascular endothelial growth factor, in the treatment of pancreatic cancer remains unclear. The objectives of this study were to determine safety and efficacy in chemotherapy-naive patients with metastatic pancreatic cancer receiving bevacizumab in combination with fixed-dose rate (FDR) gemcitabine and low-dose cisplatin.

METHODS

Eligible patients received gemcitabine 1,000 mg/m2 at FDR infusion (10 mg/m(2) per minute), cisplatin 20 mg/m(2), and bevacizumab 10 mg/kg, on days 1 and 15 of a 28-day cycle. Patients were monitored by computed tomography scans every two cycles and monthly serum CA19-9 measurements.

RESULTS

Of 52 patients eligible for analysis, ten (19.2%) had an unconfirmed response and 30 (57.7%) had stable disease. Of 35 patients with elevated baseline CA19-9 levels, 20 (57.1%) had > or = 50% biomarker decline during treatment. Median time to tumor progression was 6.6 months and median survival was 8.2 months (estimated 1-year survival, 36%). Grade 3/4 toxicities possibly related to bevacizumab included thromboembolic events (15.1%), hypertension (13.2%), gastrointestinal bleeding (9.4%), cardiac events (7.5%), and bowel perforation (5.7%). Plasma vascular endothelial growth factor and basic fibroblast growth factor levels and circulating tumor cell concentration did not correlate with overall survival, either at baseline or after 2 months of therapy.

CONCLUSIONS

This bevacizumab-containing study regimen is modestly effective in patients with metastatic pancreatic cancer, although occasional serious complications may occur. Given the negative results of CALGB 80303, future efforts should be focused on identifying those specific patients who are most likely to benefit from bevacizumab-based therapy.

Angiotensin II induces vascular endothelial growth factor in pancreatic cancer cells through an angiotensin II type 1 receptor and ERK1/2 signaling

Vascular endothelial growth factor (VEGF) is a crucial pro-angiogenic component in pancreatic ductal adenocarcinoma (PDA), and its high expression levels have been correlated with poor prognosis and early postoperative recurrence. We have recently shown that high levels of angiotensin II (AngII) type 1 receptor (AT1R) correlate and colocalize with VEGF in invasive PDA and that AngII induces VEGF expression in PDA cell lines. In this study, we explored the signaling mechanisms involved in the AngII-mediated VEGF induction and correlated AT1R and VEGF expression in noninvasive precursor lesions. An AT1R antagonist significantly (p<0.05) inhibited the AngII-mediated induction of VEGF messenger RNA and protein in all PDA cell lines. AngII-VEGF induction was inhibited by the tyrosine kinase inhibitor genistein, suggesting a mitogen-activated protein kinase signaling mechanism. AngII activated the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), but not p38 or c-Jun NH2-terminal MAP kinases. Inhibition of ERK1/2 activation reduced the AngII-induced VEGF synthesis. Immunohistochemical analysis of precursor lesions showed increased expression of AT1R in most ductal cells undergoing metaplasia. Pancreatic intraepithelial neoplasms showed more intense AT1R staining when compared to intraductal papillary mucinous neoplasms, which showed heterogeneous immunoreactivity. VEGF followed the same distribution pattern of AT1R in both lesions. AT1R expression in the premalignant pancreatic lesions suggests its involvement in tumor progression and angiogenesis. Our mechanistic findings provide the first insight into an AngII-initiated signaling pathway that regulates PDA angiogenesis. An AT1R-mediated VEGF induction suggests the possibility of AT1R blockade as a novel therapeutic strategy to control angiogenesis in PDA.

Future strategies for targeted therapies and tailored patient management in pancreatic cancer

Pancreatic cancer represents the fourth leading cause of cancer-related mortality in the United States. The vast majority of patients are diagnosed at advanced stages of the disease, at which time gemcitabine-based chemotherapy is typically offered as the standard of care. However, as investigators have arrived at a greater understanding of pancreatic tumor biology, newer therapeutic agents that "target" specific pathways or molecules governing the growth, spread, and maintenance of tumor cells have gained considerable interest. Erlotinib, an orally bioavailable small molecule inhibitor of the epidermal growth factor receptor, is the first of these targeted compounds to be approved for use in combination with gemcitabine for patients with advanced pancreatic cancer. Other targeted agents, including monoclonal antibodies and small molecule inhibitors aimed at a variety of targets, also have been extensively evaluated, with limited success to date. A newer strategy worth pursuing involves tailoring an individual patient's therapy according to the molecular characteristics of both host and tumor, as has shown promise in other solid tumor types.

Antihypertensives as novel antineoplastics: angiotensin-I-converting enzyme inhibitors and angiotensin II type 1 receptor blockers in pancreatic ductal adenocarcinoma

BACKGROUND

Vascular endothelial growth factor (VEGF) is a crucial proangiogenic component in pancreatic ductal adenocarcinoma (PDA), and its high expression levels have been correlated with poor prognosis and early postoperative recurrence. Angiotensin II (AngII), which has been shown to increase VEGF production in a variety of cancers, is actively generated in the pancreas. We hypothesized that AngII plays a crucial role in PDA-associated angiogenesis.

STUDY DESIGN

We analyzed the expression and localization of AngI converting enzyme (ACE) and AngII type 1 receptor (AT1R) in relation to VEGF in matched invasive human PDA (n=25) and surrounding nonmalignant tissues using real-time polymerase chain reaction, Western immunoblotting, and immunohistochemistry. VEGF levels in conditioned media of HS766T and PK9 PDA cells treated with or without AngII (10(-7) mol/L) were measured by ELISA. The effects of an AT1R blocker (losartan) and an ACE inhibitor (captopril) on VEGF production and cellular proliferation were also examined.

RESULTS

ACE and AT1R mRNA and protein levels were significantly upregulated in 19 of the 25 neoplastic tissues examined (approximately 75%), when compared with matching controls. VEGF expression was significantly higher in tissues that expressed high levels of AT1R and ACE (n=19), compared with low levels (n=4) or negative (n=2) cases. ACE protein collocalized with AT1R and VEGF in the malignant ducts and in the stromal cells. Addition of AngII significantly enhanced VEGF mRNA production and protein secretion, an effect that was prevented when cells were preincubated with captopril or losartan. Blocking endogenous AngII by captopril or losartan significantly suppressed cell proliferation.

CONCLUSIONS

Both ACE and AT1R are functionally expressed in PDA and may be involved in tumor angiogenesis. Because AT1R blockers and ACE inhibitors are already widely used clinically, they may represent a potential novel and promising strategy for controlling angiogenesis, prevention of metastasis, and prolongation of survival in patients with primary or metastatic PDA.

Tumor cytotoxicity and endothelial Rac inhibition induced by TNP-470 in anaplastic thyroid cancer

Anaplastic thyroid carcinoma is an aggressive form of cancer with no treatment. Angiogenesis inhibitors, such as TNP-470, a synthetic derivative of fumagillin, have been shown to reduce tumor size and increase survival in heterotopic animal models of thyroid cancer. Our goals were to determine the effect of TNP-470 on anaplastic thyroid cancer using an orthotopic murine model, to identify the molecular pathways of TNP-470 actions on endothelial cells, and to determine the non-endothelial tumor effects of TNP-470. We injected human anaplastic thyroid carcinoma cells (DRO'90) into the thyroid glands of nude mice. Mice received TNP-470 (30 mg/kg) s.c. for 6 weeks. TNP-470 prolonged survival and reduced liver metastases. TNP-470 had direct cytotoxic effects on anaplastic thyroid carcinoma cells in vitro and in vivo. Paradoxically, TNP-470 increased vascular endothelial growth factor secretion from tumor cells in vitro and in vivo. However, there was no associated increase in tumor microvessel density. In endothelial cells, TNP-470 prevented vascular endothelial growth factor-induced endothelial permeability, intercellular gap formation, and ruffle formation by preventing Rac1 activation.

Hypoxia and angiogenesis in pancreatic cancer

BACKGROUND

Pancreatic cancer remains one of the most lethal of all solid tumours of the gastrointestinal tract. It is characterized by late diagnosis, aggressive local invasion, early metastasis and resistance to chemoradiotherapy. Increasing knowledge regarding the molecular events behind the growth and invasion of pancreatic cancer may lead to new targets for intervention.

METHODS

A search of Pubmed and Medline databases was undertaken using the keywords pancreatic cancer, gastrointestinal cancer, hypoxia, angiogenesis and anti-angiogenesis therapy.

RESULTS

Hypoxia is the driving force behind angiogenesis in pancreatic cancers. Research into angiogenesis has shown many different sites that can be targeted by agents such as tyrosine kinase inhibitors.

CONCLUSION

Anti-angiogenic therapy could be an important adjunct to conventional chemotherapy treatment of gastrointestinal neoplasia.

Suramin inhibits not only tumor growth and metastasis but also angiogenesis in experimental pancreatic cancer

Suramin inhibits the proliferation of several human tumors in vivo and in vitro. In this study, the effects of Suramin on proliferation and angiogenesis were investigated in human pancreatic cancer cell lines and in an orthotopic nude mouse model of human pancreatic cancer. The effects of Suramin on proliferation, viability, cell cycle, and apoptosis were studied in five human pancreatic cancer cell lines. Suramin inhibited the proliferation of pancreatic cancer cells in a dose-dependent manner and reduced viability at high concentrations. Cell cycle analysis revealed a decreased S-phase fraction in most cell lines, whereas the apoptotic fraction was not notably different. In vivo treatment with Suramin significantly reduced pancreatic tumor size (MiaPaCa-2, -74%; AsPC-1, -41%; and Capan-1, -49%) and metastatic spread (MiaPaCa-2, -79%; AsPC-1, -34%; and Capan, -38%). As a parameter for angiogenic activity, vascular endothelial growth factor (VEGF) secretion was measured, revealing reduced VEGF concentrations under Suramin treatment in both cell culture medium and ascites. Also, microvessel density quantified in primary tumors was reduced in animals treated with Suramin. Therefore, Suramin inhibits the proliferation of human pancreatic cancer in vitro and in vivo. The therapeutic effects seem to involve cell cycle kinetics and may be in part related to the antiangiogenic action of the drug.

Exploring Unique Structures: Flexibility is a Significant Factor in Biological Activity

The effect of molecular flexibility on biological activity was described for soft (e.g. hGH peptides) and hard molecules (e.g. biscoclaurine-type alkaloids). These molecules had a macrocyclic structure during molecular mechanics analysis, and the minimum essential unit, which affects insulin-involved fatty acid synthesis, was observed. The flexibility of the molecular center is concerning with biological activity through the diversification of structural feature, and compared with two types of molecules which have a rigid (haloacetylcarbamoyl-2-nitroimidazole analogs: chiral-TXs) or flexible (bis-quaternary ammonium compounds: bis-QACs) molecular center. Center flexibility reflected the conformation occurrence in TXs and bis-QACs. A parameter (solvation-free energy: dGW), which reflects structural hydrophobicity, was shown, and applied to the molecular design of brefeldin A analog. This hydrophobic index was very useful, and was used for conformational analysis of chiral-TXs and bis-QACs. In molecular dynamics analysis of cholesterol-dependent cytolysin (e.g. streptolysin O) and -independent cytolysin (e.g. intermedilysin), whole molecules moved like a bow and different conformations were shown in every moment. In such situations, the membrane-associated 11mer region in these cytolysins were flexible and could always interact with extramolecular factors (e.g. membrane constitution).

TNP-470 fails to block the onset of angiogenesis and early tumor establishment in an intravital minimal disease model

BACKGROUND AND AIMS

The angiogenesis inhibitor TNP-470 (AGM-1470) has shown encouraging results in animal models of established tumors. However, results of recent clinical trials using TNP-470 have been disappointing. Since little is known about the effects of TNP-470 at the minimal disease stage, we analyzed the effects of TNP-470 on the early stages of tumor establishment.

METHODS

Twenty thousand green fluorescent protein (GFP)-transfected murine CT-26 (colonic carcinoma) or Panc-02-H0 (pancreatic adenocarcinoma) cells were inoculated in dorsal skin-fold chambers in BALB/c or C57BL6 mice. Tumor area and microvessel density (MVD) were quantified by intravital microscopy (IVM). Body weight was also monitored. Effects were compared with those in a conventional model involving subcutaneous (s.c.) inoculation of 10(6) tumor cells, followed by measurement of tumor volume, endogenous plasma VEGF/endostatin (ELISA) and proliferation/apoptosis/microvessel density (Ki-67/TUNEL/CD-34). TNP-470 was injected s.c. over the 10-day experimental period (30 mg/kg every 2 days [n=6] to 100 mg/kg/day [n=5 dorsal skin-fold chamber model, n=4 s.c. tumor model]).

RESULTS

At 30 mg/kg/every second day neither CT-26 nor PANC-02-H0 tumors were inhibited in neither of the two models. TNP-470 dosage was escalated in CT-26-bearing animals until an antiangiogenic effect could be observed. In the IVM model, only TNP-470 100 mg/kg/day reduced MVD (P=0.006), but failed to block the onset of angiogenesis and tumor area increase. Body weight decreased by 25% (P<0.05). In the subcutaneous tumor model, tumor growth was reduced (P=0.045) but not blocked, while vascular endothelial growth factor (VEGF)/endostatin synthesis and Ki67/TUNEL/CD-34 were not significantly affected.

CONCLUSION

While capable of reducing tumor growth in a conventional model, treatment with TNP-470 does not block the onset of angiogenesis and tumor establishment in a model of minimal disease. When used as a single agent TNP-470 does not control minimal tumor disease in experimental colonic carcinoma.

A xenograft nude mouse model for perineural invasion and recurrence in pancreatic cancer

OBJECTIVE

Pancreatic cancer recurrence after initially "curative" resection is an unresolved clinical problem in the management of patients with this disease. Perineural invasion correlates with and might be partially responsible for tumor recurrence and poor survival. However, no adequate preclinical animal model is yet available to study this aspect of pancreatic cancer biology.

METHODS

We modified our orthotopic xenograft model of pancreatic cancer in nude mice to develop a model for pancreatic cancer perineural invasion and recurrence.

RESULTS

After initial orthotopic transplantation, complete surgical resection of MIA PaCa-2 (undifferentiated) and Capan-2 (well-differentiated) tumors at 4, 6, and 8 weeks was attempted. All animals that had undergone tumor resection survived the operation. Animals that had the MIA PaCa-2 tumor resected after 6 weeks developed recurrent pancreatic cancer with local invasion and distant metastasis. Histological evaluation revealed extensive invasion of retroperitoneal nerves by the cancer cells.

CONCLUSION

Complete resection of orthotopically transplanted pancreatic cancer in nude mice leads to local tumor recurrence. This model may eventually prove valuable for studying the mechanisms of pancreatic cancer perineural invasion and recurrence.

VEGF antisense therapy inhibits tumor growth and improves survival in experimental pancreatic cancer

BACKGROUND

Vascular endothelial growth factor (VEGF), a key mediator of angiogenesis, is overexpressed in pancreatic cancer. This study evaluated VEGF production in pancreatic cancer cells and the effect of VEGF antisense on growth and angiogenesis of human pancreatic cancer in a nude mouse model.

METHODS

In vitro: VEGF in cell culture supernatant of pancreatic cancer cells (AsPC-1, poorly differentiated; HPAF-2, moderately differentiated) was assessed by enzyme-linked immunosorbent assay. In vivo: A VEGF antisense oligonucleotide (AS-3) was synthesized. One-mm(3) fragments of subcutaneous pancreatic cancer donor tumors were implanted into the pancreas of nude mice also receiving AS-3 (10 mg/kg/day) or vehicle intraperitoneally for 14 weeks. Primary tumor volume, metastasis, and VEGF in plasma and ascites were determined at autopsy. Microvessel density was analyzed in CD31-stained tumors.

RESULTS

In vitro: Both pancreatic cancer cell lines secreted VEGF protein (AsPC-1, 4200 +/- 40 pg/10(6) cells; HPAF-2, 8120 +/- 60 pg/10(6) cells). In vivo: AS-3 reduced tumor volume in the HPAF-2 group (860 +/- 140 vs 3830 +/- 590 mm(3)) and metastatic spread in both groups (AsPC-1, 6.5 +/- 0.8 vs 16.7 +/- 0.9 points; HPAF-2, 2.5 +/- 0.2 vs 8.3 +/- 1.5 points). Tumor volume was not different in the AsPC-1 group (1050 +/- 80 vs 1400 +/- 150 mm(3)). Survival was increased in the AsPC-1 group. Plasma levels of VEGF and microvessel density in tumors were significantly reduced in treated animals. Only control animals (50%) developed ascites with high VEGF concentrations.

CONCLUSIONS

Human pancreatic cancer cells secrete VEGF at biologically relevant high levels. AS-3 therapy normalizes plasma VEGF and decreases neoangiogenesis, thereby reducing tumor growth and metastasis and improving survival. AS-3-treated animals developed no ascites, suggesting decreased vascular permeability by reducing VEGF expression in pancreatic cancer cells.

Antiangiogenic therapy for human pancreatic carcinoma xenografts in nude mice

AIM: To investigate the anti-tumor effects of antiangiogenic therapy (a combination of TNP-470, an antiangiogenic compound, with gemcitabine, an antimetabolite) on human pancreatic carcinoma xenografts and its mechanism.

METHODS: A surgical orthotopic implantation (SOI) model was established by suturing small pieces of SW1990 pancreatic carcinoma into the tail of pancreas in nude male mice. Mice then received either single therapy (n = 24) or combined therapy (n = 32). Mice receiving single therapy were randomly divided into control group, G100 group receiving 100 mg/kg gemcitabine IP on d 0, 3, 6 and 9 after transplantation, and T30 group receiving 30 mg/kg TNP-470 s.c on alternate days for 8 wk. Mice receiving combined therapy were randomly divided into control group, T15 group, G50 group and combination group (TNP-470 30 mg/kg and gemcitabine 50 mg/kg). Animals were killed 8 wk after transplantation. Transplanted tumors, liver, lymph node and peritoneum were removed. Weight of transplanted tumors, the T/C rate (the rate of mean treated tumor weight to mean control tumor weight), change of body weight, metastasis rate, and 9-wk survival rate were investigated. Tumor samples were taken from the control group, T30 group, G100 group and combination group. PCNA index (PI) and microvessel density (MVD) were investigated by immunohistochemical staining for PCNA and factor VIII, respectively.

RESULTS: There was a significant inhibitory effect on primary tumor growth of pancreatic carcinoma in G100 group, compared to T30 group, whereas tumor metastasis was significantly inhibited in T30 group compared to G100 group. There was no significant improvement in survival rate in these two groups. No significant inhibitory effect on tumor growth and metastasis in T15 group and G50 group. However, significant anti-tumor and anti-metastatic effects were observed in the combination group with a significant improvement in survival rate. The inhibitory effect on tumor growth in combination group enhanced 2 times in comparison with G50 group and 5 times in comparison with T15 group. Moreover, 25% of the animals bearing tumors were cured by the combination therapy. The levels of MVD and PI were 14.50±5.93 and 0.41±0.02, 12.38±1.60 and 0.30±0.07, 7.13±2.99 and 0.37±0.03, and 5.21±1.23 and 0.23±0.02 respectively in the control group, G100 group, T30 group and combination group. A significant inhibitory effect on PI level and MVD level was observed in G100 group and T30 group respectively whereas both MVD and PI levels were significantly inhibited in the combination group (P<0.05).

CONCLUSION: Antiangiogenic therapy shows significant anti-tumor and anti-metastatic effects, and is helpful to reduce the dosage of cytotoxic drugs and the side effects. These effects are related to the antiangiogenic effect of TNP-470 and cytotoxic effect of gemcitabine.

Angiogenesis inhibitor TX-1898: syntheses of the enantiomers of sterically diverse haloacetylcarbamoyl-2-nitroimidazole hypoxic cell radiosensitizers

(R)- and (S)-Epichlorohydrins were used to prepare the enantiomers of sterically diverse haloacetylcarbamoyl-2-nitroimidazoles that function as hypoxic cell radiosensitizers. The synthetic design allowed for introduction of a side chain of varying bulk that permitted an examination of the steric effects on enantio-discrimination in biological assay systems. The single stereocenter also connected the two pharmacophores--a 2-nitroimidazole moiety critical to hypoxic cell radiosensitization, and a haloacetylcarbamoyl group to function as an anti-angiogenesis pharmacophore. In the chick embryo chorioallantoic membrane (CAM) assay, the R-enantiomers possessing the bulky p-tert-butylphenyl group showed higher anti-angiogenic activity than the corresponding S-enantiomers, while there were no differences in the activity between the enantiomers containing the less bulky methyl and tert-butyl groups. Among the compounds we report, R-p-tert-butylphenyl-bromoacetylcarbamoyl-2-nitroimidazole, TX-1898, was found to be the most promising candidate for further development of as anti-angiogenic hypoxic cell radiosensitizer.

Vascular endothelial growth factor-trap suppresses tumorigenicity of multiple pancreatic cancer cell lines

PURPOSE

Vascular endothelial growth factor A (VEGF-A) is a potent angiogenic agent that binds to two high affinity VEGF receptors (VEGFRs), a process facilitated by the low affinity neuropilin receptors. Although VEGF-A is overexpressed in pancreatic ductal adenocarcinoma, it is not known whether the in vivo growth of multiple pancreatic cancer cells can be efficiently blocked by VEGF-A sequestration.

EXPERIMENTAL DESIGN

Four human pancreatic cancer cell lines were grown s.c. in athymic nude mice. One cell line also was used to generate an orthotopic model of metastatic pancreatic cancer. The consequences of VEGF-A sequestration on tumor growth and metastasis were examined by injecting the mice with a soluble VEGFR chimer (VEGF-Trap) that binds VEGF-A with high affinity.

RESULTS

VEGF-Trap, initiated 2 days after tumor cell inoculation, suppressed the s.c. growth of four pancreatic cancer cell lines and markedly decreased tumor microvessel density. Analysis of RNA from tumors generated with T3M4 cells revealed that VEGF-Trap decreased the expression of VEGFR-1 and neuropilin-1 and -2. VEGF-Trap, initiated 3 weeks after tumor implantation, also attenuated intrapancreatic tumor growth and metastasis in an orthotopic model using PANC-1 cells.

CONCLUSIONS

VEGF-Trap is a potent suppressor of pancreatic tumor growth and metastasis and also may act to attenuate neuropilin-1 and -2 and VEGFR-1 expression. Therefore, VEGF-Trap may represent an exceedingly useful therapeutic modality for pancreatic ductal adenocarcinoma.

Angiogenesis and tumor proliferation/metastasis of human colorectal cancer cell line SW620 transfected with endocrine glands-derived-vascular endothelial growth factor, as a new angiogenic factor

Endocrine glands-derived-vascular endothelial growth factor (EG-VEGF) was recently cloned as a new angiogenic factor that selectively acts on the endothelium of endocrine gland cells. We evaluated the involvement of EG-VEGF in colorectal cancer. The expression of EG-VEGF was confirmed in all of the colorectal cancer cell lines. (On the other hand, the expression of EG-VEGF mRNA was not detected in colorectal normal mucosae.) Stable EG-VEGF infectors of colorectal cancer cell line SW620 were produced, EG-VEGF transfectants were implanted into cecum and s.c., and cell proliferation was evaluated. Angiogenesis was evaluated by dorsal air sac method. Liver metastasis was evaluated after the implantation of EG-VEGF transfectants into the mouse spleen. Tumor proliferation (cecum, s.c.) was significantly higher in the EG-VEGF transfectants than in the control cells. The small vessels were significantly increased in EG-VEGF transfectants as compared with those in control cells. Also, liver metastatic ratio was higher in the EG-VEGF transfectants than in the control cells. In this study, EG-VEGF, a new angiogenic factor, may lead to angiogenesis, promoting cell proliferation and liver metastasis in colorectal cancers. When the EG-VEGF gene-overexpressing colorectal cancer cell line that had been treated with phosphorothioate antisense EG-VEGF oligonucleotides was injected s.c. into mice, angiogenesis and tumor growth were inhibited. Although the novel angiogenesis factor EG-VEGF was not expressed in the normal colorectal mucosa, it was expressed in colorectal cancer cells, which indicates that it is a cancer-specific and possibly tissue-specific angiogenesis factor in the large intestine, and which suggests that it can be targeted by a novel antiangiogenesis therapy.

The medical management of pancreatic cancer: a review

Pancreatic carcinoma is a commonly occurring cancer that tends to present late in its course when potentially curative surgical treatment is not possible. The majority of patients are, therefore, candidates for systemic therapy. We review the patient and disease-related factors that contribute to the difficulties in the medical management of this condition and discuss new methods of assessing response to treatment, including the introduction of more clinically relevant novel end points such as clinical benefit response. We review the current trial literature examining the use of conventional cytotoxic agents in this disease, both as single agents and in combination. We also review the use of more novel targeted agents and examine their potential utility in this disease. The use of the farnesyl transferase inhibitors, matrix metalloproteinase inhibitors, epidermal growth factor receptor antagonists, and angiogenesis inhibitors is discussed.

Correlation of CT enhancement, tumor angiogenesis and pathologic grading of pancreatic carcinoma

AIM: To study the correlation between pancreatic phase CT enhancement, intratumor microvessel density (MVD) and pathologic grading of pancreatic carcinoma and to evaluate the relationship between the degrees of CT enhancement and malignancy of pancreatic carcinoma.

METHODS: Thirty four patients with pancreatic carcinoma underwent CT scanning before resection. The enhancement degrees and forms of tumor were observed in pancreatic phase. The operative sample was stained with HE and CD34 marked by immunohistochemistry. MVD and histopathological grades of pancreatic carcinoma were examined. CT enhancement of the tumor, MVD counting in hot spot areas of neoplastic parenchymal cells and pathological grades of pancreatic carcinoma were comparatively analyzed.

RESULTS: Highly differentiated pancreatic adenocarcinoma was identified in 16 patients, moderately-differentiated tumor in 7 and poorly-differentiated in 11. Isodensity CT enhancement was demonstrated in 13 cases, slightly low density enhancement in 9, slightly low density enhancement with small cystic lesions in 9 and slightly low density enhancement with large cystic lesions in 3. The counting of MVD with CD34 marked by immunohistochemistry in hot spot areas of neoplastic parenchyma cells was small in 10 cases, medium in 16 and large in 8. The pathological grades correlated well with CT enhancement of the tumor (r = 0.7857, P < 0.001) and with MVD counting of tumor (r = 0.3613, P < 0.05). The CT enhancement of tumor correlated with MVD(r = 0.6768, P < 0.001).

CONCLUSION: There is an obvious and significant correlation between CT enhancement, pathological grades and MVD number in the hot spot areas of tumor. The extent of CT enhancement is inversely proportional to the malignant degree of pancreatic carcinoma, and to the MVD number in the hot spot areas of neoplastic parenchyma. The MVD in the hot spot areas of neoplastic parenchyma cells can also reflect the prognosis of the patients, and is directly proportional to the malignant degree of pancreatic carcinoma.

Clinical significance of angiogenesis in gastrointestinal cancers: a target for novel prognostic and therapeutic approaches

OBJECTIVE

To review the current data on the prognostic and therapeutic implications of tumor angiogenesis in gastrointestinal cancers.

SUMMARY BACKGROUND DATA

Numerous studies have evaluated the prognostic value of tumor angiogenesis and the potential role of antiangiogenic therapy in various gastrointestinal cancers.

METHODS

A Medline literature search was conducted using "angiogenesis" or the names of various angiogenic factors in combination with the names of gastrointestinal cancers as the key words.

RESULTS

Several studies have demonstrated a significant prognostic impact of tumor microvessel density and tumor expression of angiogenic factors, in particular vascular endothelial growth factor (VEGF), in various gastrointestinal cancers. A few studies have suggested that circulating VEGF might be a useful prognostic marker. However, results were not consistent across all studies and were limited by the retrospective nature of most studies. Antiangiogenic therapy has been shown to be effective against all common gastrointestinal cancers in preclinical studies, but currently there are few clinical data with regard to antiangiogenic therapy in gastrointestinal cancers.

CONCLUSIONS

There is mounting evidence to suggest that assessment of tumor angiogenesis might provide a novel approach of prognostication in patients with gastrointestinal cancers. However, current results from retrospective studies need to be validated by prospective studies. Antiangiogenic therapy is a promising strategy of cancer treatment that might be particularly useful in combination therapy for unresectable cancers or as an adjuvant therapy for resectable tumors.

Clinical significance of angiogenesis in gastrointestinal cancers: a target for novel prognostic and therapeutic approaches

OBJECTIVE

To review the current data on the prognostic and therapeutic implications of tumor angiogenesis in gastrointestinal cancers.

SUMMARY BACKGROUND DATA

Numerous studies have evaluated the prognostic value of tumor angiogenesis and the potential role of antiangiogenic therapy in various gastrointestinal cancers.

METHODS

A Medline literature search was conducted using "angiogenesis" or the names of various angiogenic factors in combination with the names of gastrointestinal cancers as the key words.

RESULTS

Several studies have demonstrated a significant prognostic impact of tumor microvessel density and tumor expression of angiogenic factors, in particular vascular endothelial growth factor (VEGF), in various gastrointestinal cancers. A few studies have suggested that circulating VEGF might be a useful prognostic marker. However, results were not consistent across all studies and were limited by the retrospective nature of most studies. Antiangiogenic therapy has been shown to be effective against all common gastrointestinal cancers in preclinical studies, but currently there are few clinical data with regard to antiangiogenic therapy in gastrointestinal cancers.

CONCLUSIONS

There is mounting evidence to suggest that assessment of tumor angiogenesis might provide a novel approach of prognostication in patients with gastrointestinal cancers. However, current results from retrospective studies need to be validated by prospective studies. Antiangiogenic therapy is a promising strategy of cancer treatment that might be particularly useful in combination therapy for unresectable cancers or as an adjuvant therapy for resectable tumors.

Serum vascular endothelial growth factor levels in pancreatic cancer patients correlate with advanced and metastatic disease and poor prognosis

The serum concentrations of vascular endothelial growth factor (VEGF) were measured by an enzyme linked immunosorbent assay in 51 healthy controls and in 58 patients with pancreatic cancer before and 30 days after surgery. Pancreatic cancer patients had significantly higher serum VEGF levels compared with healthy controls with a significant association between serum VEGF levels, disease stage and the presence of both lymph node and distant metastases. Serum levels of VEGF decreased significantly after radical resection of the tumor. Elevated preoperative serum VEGF level was a significant prognostic factor, although not independent of stage, for patient survival. These findings suggest that serum VEGF concentrations may reflect pancreatic cancer progression and that their determination may be clinically useful.

Angiogenesis inhibition with TNP-470, 2-methoxyestradiol, and paclitaxel in experimental pancreatic carcinoma

INTRODUCTION

Inhibition of tumor angiogenesis is a novel therapeutic modality for various malignancies.

AIM

To investigate the effect of different antiangiogenic agents (TNP-470, 2-methoxyestradiol, and paclitaxel) on growth and neovascularization of experimental pancreatic cancer.

METHODOLOGY

In 25 male Lewis rats, tumor induction was achieved by orthotopic and subcutaneous tumor fragment implantation of ductlike pancreatic cancer DSL6A. Four weeks after tumor implantation, the animals were randomly treated with TNP-470, 2-methoxyestradiol, or paclitaxel. After 2 weeks of antiangiogenic therapy, total tumor volume, vital tumor surface, vascular density, and apoptosis were measured.

RESULTS

Total tumor volume and vital tumor surface were not significantly different in any of the treatment groups. Similarly, vascular density and apoptosis were not altered by treatment with the various angiogenesis inhibitors at the specific doses used.

CONCLUSION

We conclude that in contrast to many earlier studies, angiogenesis inhibition by a single-drug application and by the doses used in the present model did not reveal a favorable therapeutic effect on pancreatic cancer DSL6A. The combination of different angiogenesis inhibitors or higher doses might be more effective.

Evaluation of vascular endothelial growth factor blockade and matrix metalloproteinase inhibition as a combination therapy for experimental human pancreatic cancer

Blockade of vascular endothelial growth factor (VEGF) and inhibition of matrix metalloproteinases (MMP) are promising therapies for cancer. This study assessed the effects of a neutralizing anti-VEGF antibody (A4.6.1) and an MMP inhibitor (BB-94) on pancreatic cancer (PaCa) in vivo. Five million cells of two human PaCa cell lines (AsPC-1 and HPAF-2) were injected subcutaneously into nude mice; 1 mm(3) fragments of the resulting tumors were implanted into the pancreas of other mice. Animals were randomized into a control group and three treatment groups: A4.6.1 (100 microg intraperitoneally twice weekly); BB-94 (50 mg/kg every other day); and combination (A4.6.1 plus BB-94). Treatment was started after 3 days and continued for 14 weeks. Tumor volume, local and distant spread (score), and ascites were determined at autopsy. Microvessel density as a parameter of neoangiogenesis was analyzed in CD31-stained tumor sections. Both monotherapies reduced tumor volume (HPAF-2: -89% by A4.6.1 and -75% by BB-94; AsPC-1: -48% by A4.6.1 and -72% by BB-94), spread (HPAF-2: -76% by A4.6.1 and -58% by BB-94; AsPC-1: -32% by A4.6.1 and -54% by BB-94), and microvessel density (HPAF-2: -75% by A4.6.1 and -30% by BB-94; AsPC-1: -59% by A4.6.1 and -30% by BB-94), resulting in a tendency toward increased survival (HPAF-2: 8 of 8 animals by A4.6.1 or BB-94 vs. 4 of 8; AsPC-1: 3 of 8 by A4.6.1, 4 of 8 by BB-94 vs. 1 of 8). Combination therapy yielded additional effects in the HPAF-2 group with regard to tumor volume (-95%) and development of ascites (0 of 8 vs. 2 of 8 by A4.6.1 or BB-94 vs. 5 of 8 control mice). Both VEGF blockade and MMP inhibition reduce primary tumor size, metastasis, and angiogenesis, thereby increasing survival in experimental pancreatic cancer. Combination treatment results in additive effects in moderately differentiated HPAF-2 tumors.

Antitumor activity of the angiogenesis inhibitor TNP-470 on murine lymphoma/leukemia cells in vivo and in vitro

OBJECTIVE

The aim of this study was to evaluate the effects of an angiogenesis inhibitor in a non-immunocompromised setting in which transplanted tumor cells home and expand in a manner mimicking the original tumor in the donor. We used a novel animal model for T-cell lymphoma/leukemia (TLL) to test the antitumor effect of TNP-470, a well-established angiogenesis inhibitor.

MATERIALS AND METHODS

Cells from spontaneously arisen TLL tumors were transferred to syngenic recipients. The mice were treated with TNP-470 (30 mg/kg) or vehicle every other day for 2 weeks. Mice were sacrificed on day 15 after transfer, and body and organ weights were measured. Cell cycle and morphologic analysis was performed on cells and/or sections from selected organs. The cytotoxic effect of TNP-470 was assayed in vitro using the TLL-M and HL-60 cell lines.

RESULTS

TNP-470 treatment significantly reduced total tumor load and tumor mass in specific organs infiltrated with lymphoma/leukemia. This was associated with an increased apoptosis in these organs. We also observed side effects of TNP-470 not previously reported, such as diminished extramedullary erythropoiesis and disrupted liver morphology. In vitro TLL-M cells were resistant to cytotoxic effects of moderate doses of TNP-470.

CONCLUSIONS

TNP-470 treatment has a beneficial effect on tumor load in the TLL transfer model, most likely caused by the antiangiogenic effect of TNP-470. This is supported by the observation of increased apoptosis in infiltrated organs. The TLL transfer model is well suited for further studies of combinations with TNP-470 or other angiogenesis inhibitors and cytotoxic drugs.

Influence of hypoxia and neoangiogenesis on the growth of pancreatic cancer

As with other solid tumors, the growth and metastasis of pancreatic cancer is critically dependent on tumor angiogenesis. A major stimulus for a tumor's recruitment of additional blood vessels is cellular hypoxia, a condition which is especially pronounced in this neoplasm. Hypoxia induces transcriptional activation of genes that alter cellular metabolism and promote neoangiogenesis. Pancreatic cancer cells have demonstrated activation of such adaptive pathways even in the absence of hypoxia. A highly-angiogenic response in this neoplasm correlates with increased tumor growth, increased metastasis, and decreased survival. Pancreatic cancers expressing high levels of vascular endothelial growth factor, a potent pro-angiogenic cytokine, also have a higher incidence of metastasis and poorer prognosis. Pancreatic cancer cells uniquely express receptors for vascular endothelial growth factor, indicating a role for an autocrine loop in tumor proliferation and invasion. Multiple experimental anti-angiogenic strategies, many of which target vascular endothelial growth factor, reduce pancreatic cancer growth, spread, and angiogenesis. Anti-angiogenic treatments for pancreatic cancer will likely be most effective when used as an integral part of a combination chemotherapeutic regimen.

Pathways for aberrant angiogenesis in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease. Although the specific mechanisms that dictate its biological aggressiveness are not clearly established, it is characterized by a variety of molecular alterations as well as by the overexpression of mitogenic and angiogenic growth factors and their receptors. PDACs also express high levels of vascular endothelial growth factor (VEGF). Recent studies indicate that suppression of VEGF expression attenuates pancreatic cancer cell tumorigenicity in a nude mouse model, and that VEGF can exert direct mitogenic effects on some pancreatic cancer cells. These findings suggest that cancer cell derived VEGF promotes pancreatic cancer growth in vivo via a paracrine angiogenic pathway and an autocrine mitogenic pathway, and provide novel opportunities for therapeutic intervention in this deadly disease.

Effect of the vascular endothelial growth factor receptor-2 antibody DC101 plus gemcitabine on growth, metastasis and angiogenesis of human pancreatic cancer growing orthotopically in nude mice

Vascular endothelial growth factor (VEGF) is the major pro-angiogenic factor for most tumors. VEGF expression has been shown to be associated with a poor prognosis in human pancreatic cancer. The purpose of our study was to determine the effect of blockade of VEGF receptor-2 activity with or without gemcitabine on tumor growth and metastasis in an orthotopic model of human pancreatic cancer in nude mice. Therapy with gemcitabine or DC101, a VEGF receptor-2 antibody, resulted in a significant reduction of primary pancreatic tumor growth compared to untreated controls. The combination of DC101 and gemcitabine inhibited primary pancreatic tumor growth and lymphatic metastasis to a greater degree than either agent alone. Treatment with DC101 decreased vessel counts and increased the area of hypoxic tumor tissue compared to controls. Immunofluorescent double staining for apoptotic endothelial cells demonstrated a significant increase in the number apoptotic endothelial cells 24 days after initiation of therapy with DC101 plus gemcitabine. DC101 plus gemcitabine also increased tumor cell death and decreased tumor cell proliferation in pancreatic tumors. These findings indicate that blockade of VEGF receptor activation interferes with the survival of tumor endothelial cells, resulting in a reduction of primary pancreatic tumor growth in nude mice. Furthermore, the data demonstrate that anti-VEGF receptor-2 therapy potentiates the tumoricidal effect of gemcitabine in this model. Anti-VEGF receptor-2 therapy in combination with gemcitabine may be a novel therapeutic approach for advanced pancreatic cancer.

Angiogenesis inhibitor TNP-470 suppresses growth of peritoneal disseminating foci of human colon cancer line Lovo

AIM: To study the effect of angiogenesis inhibitor TNP-470 on peritoneal dissemination of colon cancer in nude mice.

METHODS: The MTT assay was used to evaluate the inhibitory effect of TNP-470 on human colon cancer cell line Lovo. Lovo cells were injected into the peritoneal cavity of BABL/C nu/nu mice and the models of peritoneal dissemination were developed. Thirty nude mice were randomly divided into control and TNP-470-treated group. In TNP-470-treated group, TNP-470 was injected subcutaneously every other day from day 1 until sacrifice or death (30 mg•kg⁻¹). The control group received a sham injection of the same volume saline solution.

RESULTS: In vitro, TNP-470 inhibited the growth of Lovo cells, with its IC₅₀ at 2.14 × 10²μg•L^-1. In vivo, TNP-470 demonstrated growth inhibition of tumors. Mice body weight and abdominal circumferences were significantly different between TNP-470-treated group (24.5 ± 3.2 g, 7.0 ± 1.1 cm) and control group (29.5 ± 2.1 g, 10.3 ± 1.5 cm), P = 0.005 and P = 0.001. The number of disseminated foci was significantly different between the control group (92.1 ± 20.6) and the TNP-470-treated group (40.3 ± 12.3), P < 0.001. The maximal size of foci was significantly smaller in TNP-470-treated group (3.3 ± 0.7 mm) than that of control (7.3 ± 2.3 mm), P = 0.004. Mean survival time was significantly longer in TNP-470-treated group (98.00 ± 12.06 d) than that in control group (41.86 ± 9.51 d), P < 0.001.

CONCLUSION: Angiogenesis inhibitor TNP-470 might be effective in treating peritoneal dissemination of colon cancer and improve the survival rate of nude mice.

Angiogenesis as a target for cancer therapy

Antiangiogenic drugs are unique for having highly specific targets while carrying the potential to be effective against a wide variety of tumors. Moreover, some of the major limitations of cytotoxic therapies likely will be avoided by this entirely new class of anticancer weapons. After the realization of the potential advantages of antiangiogenic therapy, the field of angiogenesis research is growing exponentially. Still, there is much to learn about the machinery that tumors use to recruit new blood vessels, and the results of the clinical trials will show the best way to apply that knowledge for cancer therapy.

Specific targeting of tumor vasculature by diphtheria toxin-vascular endothelial growth factor fusion protein reduces angiogenesis and growth of pancreatic cancer

Tumor vessels abundantly express receptors for vascular endothelial growth factor (VEGF), a mediator of neoangiogenesis. The aim of this study was to specifically target and damage the vasculature of pancreatic cancer (PaCa) by fusing VEGF to diphtheria toxin (DT), which inhibits protein synthesis of target cells. DT-VEGF fusion protein was produced in vector pGEX-KG and expressed in E. coli SG12036. Human PaCa cell lines (HPAF-2 and AsPC-1) and human endothelial cells (HUVEC) were exposed to DT-VEGF (10 ng/ml - 10,000 ng/ml). Proliferation was assessed after 3 days. One mm(3) fragments of subcutaneous PaCa donor tumors were implanted into the pancreas of nude mice that received either DT-VEGF (200 microg/kg, every other day) or phosphate-buffered saline intraperitoneally for 14 weeks. Tumor volume, metastatic spread, and animal weight were determined at autopsy. Microvessel density was analyzed in CD31-stained tumor sections. Proliferation of PaCa cells was inhibited at high concentrations of DT-VEGF (>1000 ng/ml). DT-VEGF decreased the growth of HUVEC at 10 ng/ml. In vivo, DT-VEGF reduced tumor volume (HPAF-2, 76%; AsPC-1, 53%), microvessel density (HPAF-2, 54%; AsPC-1, 62%), and tumor spread (HPAF-2, 89%; AsPC-1, 50%). Survival was increased (HPAF-2, 7/8 vs. 4/8 animals; AsPC-1, 6/8 vs. 1/8 animals). Weight was not influenced by DT-VEGF. The DT-VEGF effect is due to its toxic action on the tumor vasculature rather than to direct inhibition of PaCa cell growth. DT-VEGF therapy was not associated with systemic side effects.