The role of angiogenesis in the tumor growth of Syrian hamster pancreatic cancer cell line HPD-NR

The molecular targets for the diagnosis and treatment of pancreatic cancer

Pancreatic cancer is considered an aggressive malignancy that responds poorly to current treatments and therefore has a dismal survival rate. This disease is usually not diagnosed until a late stage, at which point palliative chemotherapy with the purine analogue gemcitabine and/or a fluoropyrimidine or a platinum agent is the standard approach. There are some new data on the molecular and genetic changes that take place in pancreatic cancer, which may facilitate the accuracy of diagnosis and efficacy of treatments. However, translational efforts in clinical practice have increased clinicians' options with a targeted agent, erlotinib, in combination with the standard gemcitabine chemotherapy. Many other novel drugs currently being tested in the field of pharmaco-oncology target various altered biological pathways and molecules. Nevertheless, the lack of clinically significant improvements in treatments is rendering efforts to develop methods of early diagnosis both more urgent and promising. The aim of this review was to summarize the molecular basis of pancreatic carcinogenesis and the latest developments in diagnosis by molecular means, focusing on the results of clinical research into targeted and personalized treatments.

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.

Combination therapy with tumor-lysate pulsed dendritic cells and antiangiogenic drug TNP-470 for mouse pancreatic cancer

Most cases of pancreatic cancer are inoperable when diagnosed. Since immunotherapy and antiangiogenic therapy have been reported to be promising for pancreatic cancer, we examined whether the combination of immunotherapy with dendritic cells (DCs) and the antiangiogenic drug TNP-470 induces tumor regression. Syngeneic mouse pancreatic adenocarcinoma cells were orthotopically inoculated into C57/BL6 mice. DCs with or without tumor lysate (TL) were administered i.p. at 4 and 5 weeks. TNP-470 was injected s.c. into tumor-bearing mice every other day from 4 weeks to 6 weeks. We compared anticancer effects in 6 groups: NT (no treatment), DC/TL- (DCs without TL), DC/TL+ (DCs pulsed with TL), TNP (TNP-470 alone), DC/TL-TNP (DC/TL- plus TNP-470) and DC/TL+TNP (DC/TL+ plus TNP-470). We measured tumor volume, mean vascular density (MVD) and vessel diameter by FITC-dextran using an intravital microscope; degrees of proliferation and apoptosis of cancer cells by PCNA and TUNEL; infiltrating lymphocytes and expression levels of VEGF and MMP-9 by immunohistochemistry and immunoblotting. Tumor volume and MVD were significantly suppressed in the treatment groups with prolonged survival rate, especially in the DC/TL+TNP group. There were no significant differences in apoptosis among the 6 groups except DC/TL+. The number of infiltrating CD4+ cells in the DC/TL+ group was higher than that in the NT group. VEGF expression was significantly suppressed in the treatment groups containing TNP-470, and MMP-9 was also suppressed in the groups containing DC/TL+. Our data suggested that TL-pulsed DCs combined with TNP-470 induced regression of mouse pancreatic cancer, possibly through induction of immune responses and suppression of angiogenesis.

Pancreatic carcinogenesis: apoptosis and angiogenesis

Apoptosis and angiogenesis are critical biologic processes that are altered during carcinogenesis. Both apoptosis and angiogenesis may play an important role in pancreatic carcinogenesis. Despite numerous advances in the diagnosis and treatment of pancreatic cancer, its prognosis remains dismal and a new therapeutic approach is much needed. Recent research has revealed that apoptosis and angiogenesis are closely interrelated. Several reports show that a tumor suppresser gene that is expressed in pancreatic carcinoma and related to malignant potential can induce apoptosis and also inhibit angiogenesis. At present, it is generally accepted that tumor growth in cancers, including pancreatic cancer, depends on angiogenesis. We have identified 2 new angiogenesis inhibitors from a conditioned medium of human pancreatic carcinoma cell line (BxPC-3): antiangiogenic antithrombin III (aaAT-III) and vitamin D binding protein-macrophage activating factor (DBP-maf). These molecules were able to regress tumors in severe combined immunodeficiency disease (SCID) mice, demonstrating potent inhibition of endothelial cell proliferation. Moreover, the angiogenesis inhibitors induced tumor dormancy in the animal model. These results suggest that antiangiogenic therapy using angiogenesis inhibitors may become a new strategy for treatment of pancreatic cancer in the near future.

Expressions of angiogenic factors in pancreatic ductal carcinoma: a correlative study with clinicopathologic parameters and patient survival

INTRODUCTION

It has been reported that angiogenic factors play an important role in proliferation and metastasis in various cancers.AIMTo investigate the expression of angiogenic factors and microvessel density (MVD) in pancreatic ductal carcinoma and to examine the correlations among expression of angiogenic factors, clinicopathologic parameters, and clinical prognosis.

METHODOLOGY

Paraffin-embedded specimens from 55 patients with pancreatic ductal carcinoma were immunostained for vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2), platelet-derived endothelial cell growth factor (PD-ECGF), and CD34. The correlations among the expression of individual angiogenic factors and MVD, the clinicopathologic features, and the clinical prognoses were analyzed statistically.

RESULTS

Immunostaining demonstrated that 70.8% of pancreatic ductal carcinomas were positive for VEGF, 60.9% for FGF-2, and 57.2% for PD-ECGF. A significant correlation was observed between VEGF expression and MVD (p < 0.05) but not between FGF-2 or PD-ECGF and MVD. Although the expression of each angiogenic factor had no correlation with clinicopathologic features, the patients with tumors that showed high expression of VEGF and FGF-2 had significantly shorter survival times than those with low or no such expression (p < 0.05).

CONCLUSIONS

These observations suggest that the expression of VEGF closely correlates with MVD and with a poor prognosis in pancreatic ductal carcinoma.

Significance of vascular endothelial cell growth factor up-regulation mediated via a chymase-angiotensin-dependent pathway during angiogenesis in hamster sponge granulomas

Chymase is a serine protease responsible for local production of angiotensin (Ang) II from its precursor Ang I in several species, including humans, dogs, and hamsters. We have previously reported that chymase facilitates angiogenesis in sponge granulation tissues via local production of Ang II. Herein, we report the significance of vascular endothelial growth factor (VEGF) up-regulation mediated by Ang II during angiogenesis in hamster sponge granulomas. Treatment of granulation tissues with an anti-VEGF neutralizing antibody or antisense oligomers against VEGF mRNA significantly reduced Ang II-induced angiogenesis, supporting a significant role for VEGF during angiogenesis. In cultured fibroblasts prepared from granulation tissues, VEGF mRNA was up-regulated in response to Ang II within 2 h and this enhanced expression was abolished in the presence of an Ang II type 1 receptor-selective antagonist, an inhibitor of nuclear factor-kappaB activation, or an activator protein-1 inhibitor. To study the significance of local production of Ang II by chymase, we examined the effects of chymostatin on in vivo angiogenesis. We found that chymostatin markedly inhibited both up-regulation of VEGF mRNA and angiogenesis in granulation tissues treated by compound 48/80 or basic fibroblast growth factor. Our results suggest that Ang II directly acts on fibroblasts in granulation tissue to up-regulate VEGF mRNA and thereby induce angiogenesis. Furthermore, a chymase-Ang II-VEGF pathway may operate in granulation tissue as the primary mediator of angiogenesis.

Gene therapy for pancreatic cancer using an adenovirus vector encoding soluble flt-1 vascular endothelial growth factor receptor

INTRODUCTION

Vascular endothelial growth factor (VEGF) plays an important role in tumor angiogenesis. The soluble form of flt-1 VEGF receptor inhibits VEGF activity in a dominant-negative manner.

AIM

This study demonstrated the regional tumor suppression effect of adenovirus-mediated soluble flt-1 in human pancreatic cancer cells.

METHODOLOGY

The VEGF expression level was examined in nine cell lines. Panc-1 and PK-8 were used as lower- and higher-VEGF-producing cell lines, respectively. The in vitro proliferation of cancer cells infected with adenovirus vectors encoding soluble flt-1 (Adsflt) and control vectors (AdLacZ) was not different. To assess the in vivo tumor growth suppression, cancer cells were inoculated subcutaneously in SCID mice. Adsflt, AdLacZ, or vehicle was injected directly into the tumors. The early process of tumor angiogenesis in a dorsal skinfold chamber was monitored by intravital microscopy.

RESULTS

In both Panc-1 cells and PK-8 cells, the tumor growth of the Adsflt-treated group was significantly suppressed. The microvessel density, revealed by CD31 immunostaining, was also significantly lower in the Adsflt-treated group. Apoptosis index was higher in the Adsflt group. Immunofluorescence staining revealed the expression of VEGF not only in cancer cells but also in tumor stromal cells. Wild-type cells and AdLacZ-infected cells prompted strong tumor angiogenesis, whereas Adsflt-infected cells failed to exert such an effect.

CONCLUSION

These results indicate that antiangiogenic gene therapy using soluble flt-1 might be an effective approach for pancreatic cancer treatment.

Pancreatic cell lines: a review

Pancreatic cancer has an extremely poor prognosis and lacks early diagnostic and therapeutic possibilities, mainly because of its silent course and explosive fatal outcome. The histogenesis of the disease and early biochemical and genetic alterations surrounding carcinogenesis are still controversial. In vitro studies offer a useful tool to study physiologic, pathophysiologic, differentiation, and transformation processes of cells and to understand some of these shortcomings. The extreme difficulties in isolating individual pancreatic cells and their purification by maintaining their native characteristics have limited research in this area. This review is intended to present and discuss the current availability of rodent and pancreatic cell lines, their differences as well as the difficulties, limitations, and characteristics of these cultured cells. Discussed are in vitro models; ductal, islet, and acinar cell culture; cell differentiation; cell transformation, including genetic and chromosomal alterations; as well as tumor cell markers. Also addressed are the advantages and problems associated with the cell culture in humans and rodents. Advancements in tissue culture technique and molecular biology offer steady progress in this important line of research. The improved methods not only promise the establishment of beta-cell cultures for the treatment of diabetes, but also for studying sequential genetic alterations during pancreatic carcinogenesis and in understanding the tumor cell origin.

De novo expression of vascular endothelial growth factor in human pancreatic cancer: evidence for an autocrine mitogenic loop

BACKGROUND & AIMS

The role of vascular endothelial growth factor (VEGF) and its receptors in tumor angiogenesis has been well established. We analyzed the expression pattern and biologic significance of VEGF and its receptors in human pancreatic cancer.

METHODS

VEGF, KDR/flk-1, and flt-1 expression were examined by immunohistochemistry, in situ hybridization, reverse-transcription polymerase chain reaction, enzyme-linked immunosorbent assay, and receptor phosphorylation. VEGF-stimulated mitogenesis was investigated by mitogen-activated protein kinase (MAPK) phosphorylation, transactivation of a c-fos promoter reporter construct, DNA synthesis assays, and stable transfection of a dominant-negative flk-1 complementary DNA (cDNA) construct.

RESULTS

Compared with normal pancreas and chronic pancreatitis, VEGF and its receptors were overexpressed in pancreatic cancer. KDR and flt-1 were detected not only in endothelial cells but also in tumor cells. VEGF expression was observed in all human pancreatic tumor cell lines examined, and the KDR/flk-1 and flt-1 receptor was detected in 2 cell lines. VEGF treatment results in phosphorylation of MAPKs, transactivation of a c-fos promoter construct, and growth stimulation in KDR/flk-1-expressing cell lines, which could be blocked by VEGF antagonists. Furthermore, stable transfection of a dominant-negative flk-1 cDNA significantly inhibited tumor cell growth.

CONCLUSIONS

These results not only support the important role of the VEGF/VEGF receptor system in pancreatic tumor biology but also suggest the existence of an autocrine/paracrine mitogenic loop for pancreatic cancer cells.

Overexpression of midkine in pancreatic duct adenocarcinomas induced by N-Nitrosobis(2-oxopropyl)amine in hamsters and their cell lines

The expression of midkine (MK) was investigated in pancreatic ductal hyperplasias, atypical hyperplasias and adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine (BOP) in hamsters, and in hamster ductal adenocarcinoma cell lines (HPD-1NR, -2NR and -3NR). MK mRNA was clearly overexpressed in invasive pancreatic duct adenocarcinomas (PCs) and the three cell lines as assessed by northern blot analysis, and MK protein expression increased from ductal hyperplasia through atypical hyperplasias, intraductal carcinomas and invasive PCs by immunohistochemistry. The extent of overexpression of MK mRNA in PCs was almost the same as in hamster whole embryonic tissue. MK is reported to be a retinoid-responsive gene, but MK mRNA expression was not affected by treatment with all-trans retinoic acid (tRA) or N-(4-hydroxyphenyl)retinamide (4-HPR) in HPD-1NR cells. The results thus suggest that MK expression is involved in the development and progression of pancreatic ductal adenocarcinomas induced by BOP in hamsters, with loss of upregulation by retinoic acid.

High expression of vascular endothelial growth factor is associated with liver metastasis and a poor prognosis for patients with ductal pancreatic adenocarcinoma

BACKGROUND

Vascular endothelial growth factor (VEGF), a recently identified growth factor with significant angiogenic properties, is a multifunctional angiogenic cytokine that is expressed in many tumors. High VEGF expression has been shown to correlate with the incidence of metastasis and poor prognosis in various cancers. In this study, the authors investigated VEGF expression and microvessel density (MVD) in ductal pancreatic adenocarcinoma and examined the correlations among VEGF expression, clinicopathologic factors, and clinical outcome. The authors especially focused on the correlation between VEGF expression and liver metastasis.

METHODS

Paraffin embedded tumor specimens of 142 surgically resected pancreas carcinoma were immunohistochemically stained for VEGF and MVD. The correlations among VEGF expression and MVD, clinicopathologic factors, and clinical outcome were then statistically analyzed.

RESULTS

One hundred thirty-two (93%) of 142 ductal pancreatic adenocarcinomas were positive for VEGF protein by immunohistochemistry. A significant correlation was observed between VEGF positivity and MVD (P < 0.0001). Multivariate logistic regression analysis indicated a significant association between high VEGF expression and liver metastasis (P = 0.010) but no other factors, such as age, tumor size, histologic type, lymph node metastasis, venous invasion, neural invasion, peritoneal metastasis, or local recurrence. Patients with tumors that showed moderate or high VEGF expression had significantly shorter survival than patients with low VEGF expression or none at all in their tumors (P < 0.05).

CONCLUSIONS

These results indicate that VEGF expression is closely correlated with MVD and seems to be an important predictor for both liver metastasis and poor prognosis in ductal pancreatic adenocarcinoma.

Molecular biology of pancreatic cancer; oncogenes, tumour suppressor genes, growth factors, and their receptors from a clinical perspective

Pancreatic cancer represents the fourth leading cause of cancer death in men and the fifth in women. Prognosis remains dismal, mainly because the diagnosis is made late in the clinical course of the disease. The need to improve the diagnosis, detection, and treatment of pancreatic cancer is great. It is in this type of cancer, in which the mortality is so great and the clinical detection so difficult that the recent advances of molecular biology may have a significant impact. Genetic alterations can be detected at different levels. These alterations include oncogene mutations (most commonly, K-ras mutations, which occur in 75% to more than 95% of pancreatic cancer tissues), tumour suppressor genes alterations (mainly, p53, p16, DCC, etc.), overexpression of growth factors (such as EGF, TGF alpha, TGF beta 1-3, aFGF, bTGF, etc.) and their receptors (i.e., EGF receptor, TGF beta receptor I-III, etc.). Insights into the molecular genetics of pancreatic carcinogenesis are beginning to form a genetic model for pancreatic cancer and its precursors. These improvements in our understanding of the molecular biology of pancreatic cancer are not simply of research interest, but may have clinical implications, such as risk assessment, early diagnosis, treatment, and prognosis evaluation.

Expression of two angiogenic factors, vascular endothelial growth factor and platelet-derived endothelial cell growth factor in human pancreatic cancer, and its relationship to angiogenesis

Tumour angiogenesis, as assayed by microvessel density (MVD), and the expression of vascular endothelial growth factor (VEGF) and platelet-derived endothelial cell growth factor (PD-ECGF) have become established as important prognostic indicators for many tumour types. In this study, MVD and the expression of VEGF and PD-ECGF were examined by immunohistochemical staining of 50 pancreatic cancer tissues, and the relationships between either MVD or the expression of these two angiogenic factors and the clinicopathological features, including survival, were analysed. The expression of VEGF and PD-ECGF proteins were confirmed by Western blot analysis and VEGF mRNA isoforms were determined by reverse transcriptase-polymerase chain reaction (RT-PCR) in five pancreatic cancer cell lines. Twenty-eight (56%) of 50 pancreatic cancers were positive for VEGF protein in cancer cells, and 16 (32%) showed strong PD-ECGF staining in cancer and infiltrating cells. VEGF121 and VEGF165 were identified as the predominant species produced in pancreatic cancer cells. The overexpression of VEGF and PD-ECGF protein significantly correlated with high MVD (P = 0.002, 0.044, respectively). Advanced stage of disease was significantly more frequent in patients with high MVD (P = 0.025). No significant association was found between the expression of VEGF or PD-ECGF and clinicopathological features, except for tumour histology. The expression of PD-ECGF correlated with poor survival (P = 0.011), but MVD and VEGF expression were not found to be useful for the prediction of overall survival. This study suggests that VEGF and PD-ECGF may play an important role in tumour angiogenesis, and that PD-ECGF expression seems to be useful for establishing prognoses for pancreatic cancer.

Significance of angiogenesis in cancer therapy

BACKGROUND

For most solid tumours, surgery remains the most effective primary treatment. Despite apparently curative resection, significant numbers of patients develop secondary disease due to growth of undetected micrometastases. The ability of a tumour to metastasize is related to the degree of angiogenesis it induces. In addition, micrometastases rely on new vessel formation to provide the nutrients necessary for growth. A better understanding of how tumours acquire their blood supply may lead to more effective adjuvant therapies and improve survival following surgery.

METHODS

A systematic review of the literature on angiogenesis between 1971 and 1997 was performed using the Medline database to ascertain current thinking on angiogenesis and its relevance in oncological surgery.

RESULTS

Angiogenesis is a physiological process subject to autocrine and paracrine regulation which has the potential to become abnormal and play a part in a number of pathological states, including cancer. Increased angiogenic stimuli in the perioperative period, associated with concomitant reduction in tumour-derived antiangiogenic factors following resection of a primary tumour, result in a permissive environment which allows micrometastases to grow.

CONCLUSION

Recognition of the role of angiogenesis in metastatic tumour growth represents a significant development in our understanding of tumour biology. The development of antiangiogenic agents offers new promise in the treatment of malignancy. Such agents may prevent or control the development and growth of primary and metastatic tumours.

Shortened telomere length and increased telomerase activity in hamster pancreatic duct adenocarcinomas and cell lines

Recently, shortened telomere length and increased telomerase activity have been demonstrated in various human cancers. In the study reported here, we ascertained whether gene changes are characteristic of pancreatic cancers. Hamster duct carcinomas and cell lines were investigated by Southern blot analysis for telomere restriction fragment (TRF) length and by the telomeric repeat amplification protocol (TRAP) assay for telomerase activity. Comparison with normal pancreas and spleen revealed shortened TRF length and markedly increased telomerase activity in primary pancreatic duct carcinomas induced by the rapid-production model as well as in a transplantable carcinoma and the cell lines. The enzyme level was 86.0-215.7 times the low levels found in control pancreas and spleen tissues. Late-passage Syrian hamster embryo cells, known to be immortalized and tumorigenic, had shorter TRFs than the original cells in primary culture did. These results indicate that hamster pancreatic duct carcinoma cells are immortalized, with the potential for proliferation ad infinitum, and provide a model for basic therapeutic research into the substances targeting telomerase.

Inhibitory effect of the angiogenesis inhibitor TNP-470 on tumor growth and metastasis in nude mice bearing human hepatocellular carcinoma

The antitumor and anti-metastatic effects of a potent angiogenesis inhibitor, O-(chloroacetyl-carbamoyl)fumagillol (TNP-470), was investigated in a highly metastatic model of human hepatocellular carcinoma-LCI-D20. Small pieces of LCI-D20 tumor tissue were implanted subcutaneously into the right axillary region of 24 nude mice; the mice were then randomized into two groups. To one group, TNP-470 30 mg/kg was given as a subcutaneous injection every other day from day 1 to day 15 and the mice were sacrificed on day 26. An antitumor effect of TNP-470 was clearly demonstrated by tumor weight (0.97 +/- 0.34 g compared to 2.04 +/- 0.34 g, P < 0.001) and alpha-Fetoprotein value (93 +/- 59 micrograms/L compared to 769 +/- 282 micrograms/L, P < 0.001). There was also an anti-metastatic effect of TNP-470. Lung metastases developed in only 1 of 12 mice in the treated group, while they developed in 6 of mice of the control group. No severe side-effect of TNP-470 was found in this study. In vitro study revealed that the purified hepatoma cells were insensitive to TNP-470 (the 50% inhibitory concentration was 43 micrograms/ml). These results suggest that the angiogenesis inhibitor TNP-470 has both strong antitumor and anti-metastatic effects on a human hepatocellular carcinoma model in nude mice.