The angiogenic switch for vascular endothelial growth factor (VEGF)-A, VEGF-B, VEGF-C, and VEGF-D in the adenoma-carcinoma sequence during colorectal cancer progression

K-ras mutation status correlates with the expression of VEGFR1, VEGFR2, and PDGFRalpha in colorectal cancer

AIM

We initiated this study in order to analyze whether the expression level of targeted receptor tyrosine kinases (RTK) is associated with the K-ras mutation status.

METHODS

The expression pattern of VEGFR1, VEGFR2, VEGFR3, PDGFRalpha, PDGFRbeta, and EGFR1 was analyzed in 93 samples of human colorectal carcinoma samples and correlated with the K-ras mutation status as identified by PCR-RFLP.

RESULTS

VEGFR1, VEGFR2, VEGFR3, PDGFRalpha, PDGFRbeta, and EGFR1 were expressed at relevant levels in 95%, 46%, 46%, 85%, 62%, and 82%, respectively. K-ras mutations were present in 53% (codon 12, 47%; codon 13, 6%). Expression of VEGFR1 (P = 0.0263), VEGFR2 (P = 0.0466), and PDGFRalpha (P = 0.0063) was significantly linked to K-ras codon 12 or 13 mutation. In addition, co-expression of VEGFR2 and PDGFRalpha was significantly associated with K-ras mutation (P = 0.0145).

CONCLUSION

Our data reveal that specific RTKs are over-expressed in K-ras mutated cancers. It needs to be addressed in prospective studies whether these patients will benefit from tyrosine kinase inhibitors more than K-ras wild-type.

The prognostic significance of tryptophanyl-tRNA synthetase in colorectal cancer

BACKGROUND

Tryptophanyl-tRNA synthetase (TrpRS) is an aminoacyl-tRNA synthetase involved in protein synthesis and regulation of RNA transcription and translation and is an inhibitor of angiogenesis. TrpRS has been shown to be differentially expressed in colorectal cancer (CRC) and has thus been identified as a potential prognostic marker. The aim of this study was to analyze the correlation of TrpRS to the prognosis of patients diagnosed and treated for CRC within a defined population.

METHODS

With a polyclonal, monospecific IgG antibody, TrpRS expression was assessed by immunohistochemistry on tissue microarrays with tumors from a population-based CRC cohort (n = 320). Staining intensity and fraction of positive tumor cells were recorded. A Cox multivariate model including TrpRS expression, carcinoembryonic antigen, age, stage, tumor differentiation, and lymphatic and vascular vessel invasion was used to calculate the hazard ratio and 95% confidence interval (95% CI) for time to recurrence, disease-free survival, and overall survival.

RESULTS

Low expression of TrpRS correlated to increased risk for lymph node metastasis (P = 0.025) and a more advanced tumor stage (P = 0.001). Patients with tumors and increased levels of TrpRS expression had better survival than patients with low expression levels. Multivariate analyses revealed significantly better disease-free survival (relative risk, 0.59; 95% CI, 0.38-0.95) for patients with high expression than for patients with low expression of TrpRS. For colon cancer patients, a reduced risk for recurrence was seen in patients with increased TrpRS expression (relative risk, 0.23; 95% CI, 0.07-0.80).

CONCLUSION

Low expression of TrpRS in tumor tissue correlates with increased risk for recurrence and worse survival in patients with CRC. This can be related to its antiangiogenic properties and could aid in the future selection of new drugs in the treatment of CRC.

Lymphangiogenesis and lymphatic metastasis in breast cancer

Lymphatic metastasis is the main prognostic factor for survival of patients with breast cancer and other epithelial malignancies. Mounting clinical and experimental data suggest that migration of tumor cells into the lymph nodes is greatly facilitated by lymphangiogenesis, a process that generates new lymphatic vessels from pre-existing lymphatics with the aid of circulating lymphatic endothelial progenitor cells. The key protein that induces lymphangiogenesis is vascular endothelial growth factor receptor-3 (VEGFR-3), which is activated by vascular endothelial growth factor-C and -D (VEGF-C and VEGF-D). These lymphangiogenic factors are commonly expressed in malignant, tumor-infiltrating and stromal cells, creating a favorable environment for generation of new lymphatic vessels. Clinical evidence demonstrates that increased lymphatic vessel density in and around tumors is associated with lymphatic metastasis and reduced patient survival. Recent evidence shows that breast cancers induce remodeling of the local lymphatic vessels and the regional lymphatic network in the sentinel and distal lymph nodes. These changes include an increase in number and diameter of tumor-draining lymphatic vessels. Consequently, lymph flow away from the tumor is increased, which significantly increases tumor cell metastasis to draining lymph nodes and may contribute to systemic spread. Collectively, recent advances in the biology of tumor-induced lymphangiogenesis suggest that chemical inhibitors of this process may be an attractive target for inhibiting tumor metastasis and cancer-related death. Nevertheless, this is a relatively new field of study and much remains to be established before the concept of tumor-induced lymphangiogenesis is accepted as a viable anti-metastatic target. This review summarizes the current concepts related to breast cancer lymphangiogenesis and lymphatic metastasis while highlighting controversies and unanswered questions.

Dynamic changes of interleukin-8 network along the colorectal adenoma-carcinoma sequence

The interleukin-8 (IL-8) network is involved in the colorectal cancer (CRC) progression. However, its role during the adenoma-carcinoma transition to date has not been fully investigated. To evaluate the dynamic changes of IL-8 network along the colorectal adenoma-carcinoma sequence, we examined the tissue IL-8 mRNA level in colorectal biopsies from 53 colorectal adenomas, 44 CRCs and 18 controls by quantitative real-time PCR (Q-PCR), and the expressions of IL-8 and its receptors (IL-8RA and IL-8RB) in the tumor microenvironment by immunohistochemistry (IHC) and double IHCs. The results showed that the tissue IL-8 mRNA level began to increase in the precancerous lesions (adenomas) as compared with the controls and became even higher in the CRCs. Significantly, the increase of IL-8 mRNA levels was associated with the increase of dysplastic grades in the adenomas, and also paralleled to the increase of Duke's stages in the CRCs. IHC results revealed that IL-8 and its receptors, IL-8RA and IL-8RB, were observed both in the stroma and in the adenomatous/cancerous cells. By double IHCs, the IL-8 expression was characterized in macrophages, lymphocytes and myofibroblasts in the tumor stroma. Further double IHC identified the co-expression of IL-8 receptors (IL-8RA and IL-8RB) with CD34 positive tumor-associated microvessels in both the adenomas and CRCs. We, therefore, conclude that activated IL-8 network in the tumor microenvironment may function as a significant regulatory factor for the adenoma progression and the adenoma-carcinoma transition.

Expression of delta-like ligand 4 (Dll4) and markers of hypoxia in colon cancer

Background:

Delta-like ligand 4 (Dll4) is a Notch ligand that is upregulated by hypoxia and vascular endothelial growth factor-A (VEGF-A) and is reported to have a role in tumor angiogenesis. Evidence from xenograft studies suggests that inhibiting Dll4–Notch signalling may overcome resistance to anti-VEGF therapy. The aim of this study was to characterise the expression of Dll4 in colon cancer and to assess whether it is associated with markers of hypoxia and prognosis.

Method:

In all, 177 colon cancers were represented in tissue microarrays. Immunohistochemistry was performed using validated antibodies against Dll4, VEGF, hypoxia-inducible factor (HIF)-1α, HIF-2α, prolyl hydroxylase (PHD)1, PHD2, PHD3 and carbonic anhydrase 9 (CA9).

Results:

The expression of Dll4 was observed preferentially in the endothelium of 71% (125 out of 175) of colon cancers, but not in the endothelium adjacent to normal mucosa (none out of 107, P<0.0001). The expression of VEGF was significantly associated with HIF-2α (P<0.0001) and Dll4 (P=0.010). Only HIF-2α had a significant multivariate prognostic effect (hazard ratio 1.61, 95% confidence interval 1.01–2.57). Delta-like ligand 4 was also expressed by neoplastic cells, particularly neoplastic goblet cells.

Conclusion:

Endothelial expression of Dll4 is not a prognostic factor, but is significantly associated with VEGF. Assessing endothelial Dll4 expression may be critical in predicting response to anti-VEGF therapies.

Irinotecan therapy and molecular targets in colorectal cancer: a systemic review

Irinotecan is the second line chemotherapy for advanced stage colorectal cancer (CRC) after failure of first line chemotherapy with oxaliplatin and 5-fluorouracil. The aim of this review is to analyse the data on irinotecan as second line chemotherapy for advanced CRC and the potential roles of the molecular markers, p53 and vascular endothelial growth factor (VEGF) in the management of advanced CRC. Thus, the English literature from 1980 to 2008 concerning irinotecan, p53, VEGF and CRC was reviewed. On review, Phase II and III clinical trials showed that irinotecan improves pain-free survival, quality of life, 1-year survival, progression-free survival and overall survival in advanced CRC. p53 and VEGF were expressed in CRC and had a predictive power of aggressive clinical behaviour in CRC. Irinotecan sensitizes p53 wild type, mutant and null cells to Fas-mediated cell apoptosis in CRC cells. Wild type p53 cells were more sensitive to irinotecan than mutated p53. Irinotecan has an anti-VEGF effect inhibiting endothelial cell proliferation, increasing apoptosis and reducing microvascular density which is only limited by irinotecan toxicity levels. To conclude, irinotecan improves the patient's quality of life and the survival rates of patients with advanced CRC. p53 and VEGF status of the patients' tumour is likely to affect the responsiveness of CRC to irinotecan. It is recommended that studies of the expression of these molecular markers in relation to chemo-responsiveness of irinotecan should be carried out for better management of patients with advanced CRC.

Progressive cellular response in the lamina propria of the colorectal adenoma-carcinoma sequence

AIMS

The lamina propria is inevitably involved in epithelial transformation. The aim was to evaluate the dynamic cellular changes in the tumour lamina propria throughout the colorectal adenoma-carcinoma sequence.

METHODS AND RESULTS

Using immunohistochemistry and double immunohistochemistry, we examined lamina propria cellular changes in 41 colorectal adenomas, 25 colorectal cancers and 15 control tissues. The results showed that the proliferation labelling index in lamina propria cells began to increase in the precancerous lesions (adenomas) and became even higher in the colorectal cancers; these proliferative cells were primarily identified as myofibroblasts and lymphocytes. Phenotypic analysis revealed gradually increasing lymphocytic infiltration in both the lamina propria and adenomatous epithelium, as well as myofibroblasts in the lamina propria. However, the intraepithelial macrophage density also showed a tendency to increase gradually. Furthermore, cyclooxygenase-2-expressing cell density and microvessel density gradually increased in the tumour lamina propria throughout the adenoma-carcinoma sequence.

CONCLUSIONS

Progressive cellular responses in the lamina propria could be involved in the adenoma-carcinoma transition.

Mechanisms of lymphatic metastasis in human colorectal adenocarcinoma

The invasion of lymphatic vessels by colorectal cancer (CRC) and its subsequent spread to draining lymph nodes is a key determinant of prognosis in this common and frequently fatal malignancy. Although tumoural lymphangiogenesis is assumed to contribute to this process, review of the current literature fails to support any notion of a simple correlation between lymphatic vessel density and CRC metastasis. Furthermore, attempts to correlate the expression of various lymphangiogenic growth factors, most notably VEGF-C and VEGF-D, with the lymphatic metastasis of CRC have provided contradictory results. Recent evidence from animal and human models of tumour metastasis suggests that complex functional and biochemical interactions between the microvasculature of tumours and other cell types within the tumour microenvironment may play a pivotal role in the behaviour of commonly metastasizing tumours. Indeed, previous insights into tumoural blood vessels have provided candidate markers of tumoural angiogenesis that are currently the subject of intense investigation as future therapeutic targets. In this review article we survey the current evidence relating lymphangiogenesis and lymphangiogenic growth factor production to metastasis by CRC, and attempt to provide some insight into the apparent discrepancies within the literature. In particular, we also discuss some new and provocative insights into the properties of tumoural lymphatics suggesting that they have specific expression profiles distinct from those of normal lymphatic vessels and that appear to promote metastasis. These findings raise the exciting prospect of future biomarkers of lymphatic metastasis and identify potential targets for new generation anti-tumour therapies.

Comparison of blood neoangiogenesis and lymphatic vascularization in colorectal adenomas from patients with and without concomitant colorectal cancer

Blood and lymphatic vessel proliferation is essential for tumor growth and progression. Most colorectal carcinomas develop from adenomas (adenoma-carcinoma sequence) in a process due to accumulation of molecular genetic alterations. About 5% of adenomatous polyps are expected to become malignant, but data on the differential angiogenic patterns of these lesions in patients with and without concomitant cancer are missing. The aim of the present study is to compare the angiogenic and lymphatic patterns of adenomatous polyps from patients with and without sporadic cancer. Thirty adenomatous polyps (15 from patients with another principal malignant lesion, and 15 from patients without cancer) were submitted to immunohistochemical staining for CD105 (marker for neoangiogenesis) and D2-40 (marker for lymphatic endothelium). Microvessel density and total vascular area were determined by computer image analysis to quantify the immunostained and total areas, and to assess the number of microvessels. Adenomas from patients with carcinoma showed significantly higher values of total vascular area determined by immunostaining for CD105 (cutoff value = 4386 microm(2); P = 0.019) and of lymphatic microvessel density determined by immunostaining with D2-40 (cutoff value = 11.5; P = 0.041) when compared with those from patients without cancer. The present data indicate a significant increase in blood microvascular area and in lymphatic microvascular counts in adenomas removed from patients with cancer.

Increased lymphatic vascular density is seen before colorectal cancers reach stage II and growth factor FGF-2 is downregulated in tumor tissue compared with normal mucosa

Lymphangiogenesis is an important event in progression of colorectal cancer (CRC), and the estimated lymphatic vascular density (LVD) probably indicates facilitated lymphatic tumor cell invasion and metastasis. However, at what time point during tumor progression this process is triggered, is unclear. The aim of this study was twofold. Firstly, to examine LVD in paired samples of CRC tissue and normal mucosa with specific emphasis on possible difference in LVD between tumors stages II and III, and secondly, the expression of the lymphangiogenic growth factor fibroblast growth factor-2 (FGF-2). Eighteen patients were studied. Immunostaining for podoplanin was performed to highlight lymphatic vessels. FGF-2 mRNA expression was determined by quantitative real-time RT-PCR, whereas protein expression was quantitatively assessed by densitometric analysis of Western blot signal intensity. The immunoblots were further validated by FGF-2 immunostaining of histological sections. LVD was significantly increased in tumor tissue compared with the normal mucosa but no changes in LVD between stages II and III CRC was observed. FGF-2 was found to be downregulated both at the mRNA and protein level in tumor tissues compared with normal mucosa. Lymphangiogenesis was triggered early in tumor development. An increased LVD was established before the tumor reached stage II. FGF-2 was downregulated in tumor tissue. The importance of this finding remains unclear.

FLT1 and its ligands VEGFB and PlGF: drug targets for anti-angiogenic therapy?

Less than 5 years ago, it was still not clear whether anti-angiogenic drugs would prove successful in the clinic. After numerous patients with cancer or age-related macular degeneration have been treated with these drugs, they have now become part of the standard range of therapeutic tools. Despite this milestone, anti-angiogenic therapy still faces a number of clinical hurdles, such as improving efficacy, avoiding escape and resistance, and minimizing toxicity. Hopefully, other agents with complementary mechanisms, such as those that target placental growth factor, will offer novel opportunities for improved treatment.

A pilot trial of the anti-angiogenic copper lowering agent tetrathiomolybdate in combination with irinotecan, 5-flurouracil, and leucovorin for metastatic colorectal cancer

Tetrathiomolybdate (TM) is an oral copper chelator under development as an anti-angiogenic agent. We evaluated TM in combination with irinotecan, 5-fluorouracil, and leucovorin (IFL). Serum vascular endothelial growth factor (VEGF), basic fibroblast growth factor, interleukin 6 (IL-6), and IL-8 were measured to evaluate the anti-angiogenic effect. Twenty-four patients with metastatic colorectal cancer were treated. The combination with IFL was well tolerated and dose intensity of IFL was maintained during combination therapy with TM. By intention to treat analysis, the overall response rate (RR) was 25% (95% CI 9.8-46.7) and the median time to progression (TTP) was 5.6 months (95% CI 2.7-7.7). VEGF levels were correlated with TTP, as were changes in VEGF, IL-8, and IL-6. TM can be safely added to IFL without compromising dose intensity or diminishing the expected RR. Changes in serum VEGF, IL-8, and IL-6 after treatment may directly reflect changes in CRC tissue angiogenesis.

Expression of vascular endothelial growth factor expression and its relation with growth, invasion and metastasis of human colorectal cancer

AIM: To explore the relations of vascular endothelial growth factor (VEGF) expression with the growth, invasion and metastasis of colorectal cancer.

METHODS: We collected 23 fresh colorectal cancerous, distal cancerous tissues resected during operation, 16 colon polyps and 45 serum samples from colon cancer patients. The expression of VEGF in colorectal tissues and serum samples was detected by nested reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. The relationship was also analyzed between VEGF expression and Duke's staging.

RESULTS: The expression of VEGF mRNA was significantly higher in the colorectal cancer tissues than that in the distal cancerous tissues or colon polyps (65.22% vs 21.74%, 18.75%, both P < 0.01). VEGF mRNA expression was positive in 3 patients (37.5%) with Duke's stage A or B, and it was positive in 12 patients with (80.0%) stage C or D; there was significant difference between them (P < 0.05). The level of serum VEGF was markedly higher in patients with stage C or D than that in patients with stage A or B (716.71 + 229.39 ng/L vs 312.30 + 103.61 ng/L, P < 0. 01).

CONCLUSION: VEGF can serve as an index in predicting the growth, invasion and metastasis of colorectal cancer.

Tumor lymphangiogenesis and melanoma metastasis

Malignant melanomas of the skin primarily metastasize to lymph nodes, and the detection of sentinel lymph node metastases serves as an important prognostic parameter. There is now compelling evidence that melanomas can induce lymphangiogenesis (growth of lymphatic vessels), mainly at the tumor-stroma interface, and that the level of tumor lymphangiogenesis is correlated with the incidence of sentinel lymph node metastases and with disease-free survival. Thus, tumor lymphangiogenesis can serve as a novel prognostic predictor in melanoma. Vascular endothelial growth factor (VEGF)-C, released by melanoma cells and by tumor-associated macrophages, likely represents the major lymphangiogenic factor in melanoma, although other members of the VEGF family might also be involved. The recent discovery that tumors can induce a premetastatic niche, by inducing lymphatic vessel growth in sentinel lymph nodes even before metastasis, and that lymph node lymphangiogenesis enhances metastatic spread, indicates that activated lymphatic vessels represent novel targets for the detection and/or therapy of melanoma metastases.

Dual inhibition of VEGFR and EGFR signaling reduces the incidence and size of intestinal adenomas in Apc(Min/+) mice

Both the epidermal growth factor (EGF) and the vascular endothelial growth factor (VEGF) pathways are associated with intestinal cancer, and therapeutic approaches targeting either EGF receptor (EGFR) or VEGF receptor (VEGFR) signaling have recently been approved for patients with advanced colorectal cancer. The Apc(Min/+) mouse is a well-characterized in vivo model of intestinal tumorigenesis, and animals with this genetic mutation develop macroscopically detectable adenomas from approximately 6 weeks of age. Previous work in the Apc(Min/+) mouse has shown that therapeutic approaches targeting either VEGFR or EGFR signaling affect predominantly the size or number of adenomas, respectively. In this study, we have assessed the effect of inhibiting both these key pathways simultaneously using ZD6474 (Vandetanib, ZACTIMA), a selective inhibitor of VEGFR and EGFR tyrosine kinases. To assess the effects of ZD6474 on early- and later-stage disease, treatment was initiated in 6- and 10-week-old Apc(Min/+) mice for 28 days. ZD6474 markedly reduced both the number and the size of polyps when administered at either an early or a later stage of polyp development. This reduction in both adenoma number and size resulted in a total reduction in tumor burden in the small intestine of nearly 75% in both studies (P < 0.01). The current data build on the concept that EGFR-dependent tumor cell proliferation and VEGF/VEGFR2-dependent angiogenesis and survival are distinct key mechanisms in polyp development. Pharmacologic inhibition of both signaling pathways has significant antitumor effects at both early and late stages of polyp development. Therefore, targeting both VEGFR- and EGFR-dependent signaling may be a beneficial strategy in early intestinal cancer.

Osteopontin: regulation in tumor metastasis

Osteopontin is a secreted phosphoprotein that has been implicated as an important mediator of tumor metastasis and has been investigated for use as a biomarker for advanced disease and as a potential therapeutic target in the regulation of cancer metastasis. The OPN DNA sequence is highly conserved and the protein contains several important functional domains including alpha(v)beta integrin and CD44 binding sites. High levels of OPN expression correlate with tumor invasion, progression or metastasis in multiple cancer. Studies demonstrate that osteopontin mediates the molecular mechanisms which determine metastatic spread, such as prevention of apoptosis, extracellular matrix proteolysis and remodeling, cell migration, evasion of host-immune cells and neovascularization. Transcriptional regulation of OPN is complex and involves multiple pathways, including AP-1, Myc, v-Src, Runx/CBF, TGF-B/BMPs/Smad/Hox, and Wnt/ss-catenin/APC/GSK-3ss/Tcf-4. The current state of knowledge of OPN biology suggests that it is an attractive target for therapeutic modulation of metastatic disease.

Review: monoclonal antibodies to the vascular endothelial growth factor receptor-2 in cancer therapy

Angiogenesis is a fundamental mechanism of cancer growth and invasion. Current translational approaches are using both small-molecule inhibitors and antibodies that modulate various steps of these processes, and several such compounds have already received regulatory approval for the therapy of specific indications in cancer. Among the many molecular targets involved in the control of angiogenesis, the vascular endothelial growth factor receptor-2 (VEGFR-2; or kinase insert domain-containing receptor) is attractive as shown in part by the efficacy of small-molecule inhibitors directed to this receptor. Two small-molecule inhibitors that target VEGFR-2 have recently been granted approval for the treatment of renal cell cancer and gastrointestinal stromal tumors. The development of antibodies that can selectively block VEGFR-2 could potentially result in improved potency or tolerability. Here, we discuss the role of VEGFR-2 in cancer and ongoing efforts to develop highly specific monoclonal antibodies for cancer therapy.

Lymphangiogenesis in colorectal cancer--prognostic and therapeutic aspects

Colorectal cancer (CRC) represents the second most common cause of cancer mortality in the western world. The tumors frequently show metastatic spread which affects different organs such as lymph nodes, liver and lungs. Although the pattern of spread may vary, the initial step usually involves dissemination to regional lymph nodes. At present it is clear that neovessel formation, including lymphangiogenesis, represents key events in tumor progression. However, to what extent lymphangiogenesis contributes in the progression of CRC is unclear. This work focuses on recent progress within the field of tumor lymphangiogenesis with special reference to CRC, and on novel therapeutic strategies for anti-lymphangiogenic therapies. Inhibition of metastatic spread may be achieved by restriction of lymphatic vessel growth by using targeted therapeutic strategies towards molecules involved in lymphangiogenic signalling. Such adjuvant therapeutic approaches in addition to existing therapeutic strategies may represent a favourable treatment for CRCs with higher than average risk of disease recurrence and progression.

Lymphatic vessel density, microvessel density and lymphangiogenic growth factor expression in colorectal cancer

OBJECTIVE

Microvessel density (MVD) has been studied as a prognostic marker in human cancers. Quantification of lymphatic vessel density (LVD) is now possible by using new antibodies. Expression of the lymphangiogenic growth factors, VEGF-C and VEGF-D, is associated with poorer clinicopathological outcomes in various tumours. The aim of this study was to quantify LVD and MVD in colorectal cancer, determine the relationship between LVD, MVD and clinicopathological variables and examine the relationship between LVD and tumour expression of VEGF-C and VEGF-D.

METHOD

Thirty primary colorectal cancers were immunostained for CD34, lymph vessel endothelial hyaluronan receptor-1 (LYVE-1), VEGF-A and VEGF-D using standard techniques. LVD and MVD were determined by Chalkley grid counting. Tumours were assessed for the presence or absence of LYVE-1 positive lymphatics at different areas within the tumour and the tumour was scored for VEGF-C and VEGF-D immunostaining intensity at the invading tumour edge. Non-parametric tests were used for statistical analysis and a P-value of <0.05 was taken as significant.

RESULTS

Lymph vessel endothelial hyaluronan receptor-1 was an excellent lymphatic vessel marker. Within normal bowel wall, lymphatic vessels were found rarely in the superficial colonic mucosa, but were numerous in the submucosa and muscularis propria. In the majority of tumours, lymphatic vessels were located in the peri-tumoural area, intra-tumoural vessels were sparse and tended to be narrow with closed lumina. At the invading tumour edge, VEGF-C expression was higher (P = 0.028) and VEGF-D expression lower (P = 0.011), in tumours in which lymphatic vessels were present. No significant differences between LVD and any clinicopathological variable or route of metastasis were identified.

CONCLUSION

Lymphatic vessel density and MVD can be quantified in colorectal carcinoma using immunohistochemical techniques. The balance between expression of VEGF-C and VEGF-D at the invading tumour edge may enhance lymphatic metastasis, by promoting tumour lymphangiogenesis or by activation of pre-existing lymphatic vessels. No relationship was identified between LVD and clinicopathological variables.

Underexpression of mineralocorticoid receptor in colorectal carcinomas and association with VEGFR-2 overexpression

BACKGROUND

The human mineralocorticoid receptor (MR) is a steroid receptor widely expressed in colorectal mucosa. A significant role for the MR in the reduction of vascular endothelial growth factor receptor-2 (VEGFR-2) mRNA levels has been demonstrated in vitro. To evaluate a potential contribution of MR to colorectal carcinoma progression, we analyzed the expression of MR in relation to VEGFR-2.

METHODS

Fresh human colorectal cancer tissue and adjacent normal mucosa were harvested from 48 consecutive patients. MR and VEGFR-2 mRNA expression levels were determined by real-time reverse transcriptase-polymerase chain reaction and correlated with clinicopathological parameters.

RESULTS

A decline of MR expression was observed in all carcinomas compared to normal mucosa. Expression of MR was a median of 11-fold lower in carcinoma compared to the normal mucosa, irrespective of the location, size, stage, and differentiation. MR was a median of 20-fold underexpressed in carcinomas with VEGFR-2 overexpression vs only 9-fold in carcinomas with VEGFR-2 underexpression (p = 0.035, Mann-Whitney test).

CONCLUSIONS

These findings support the hypothesis that reduction of MR expression may be one of the early events involved in colorectal carcinoma progression. The inverse association between MR and VEGFR-2 expression in carcinoma suggests a potential tumor-suppressive function for MR.

Pathophysiological mechanisms of angiogenesis

The growth of new blood vessels may be either beneficial or harmful. The angiogenic process may be measured by a variety of techniques, although it may often be the quality rather than quantity of resulting blood vessels that determines function. Endothelial cells play a key role in the initiation of angiogenesis, and vascular endothelial growth factor (VEGF) may be viewed as a prototypical direct-acting angiogenic factor. VEGF acts through multiple cell surface receptors and signaling pathways to stimulate endothelial cell proliferation, survival, and migration. By inducing other growth factor expression, VEGF stimulates a cascade of angiogenic activity. Different tissues may utilize various angiogenic pathways that are modulated by diverse host tissue responses. Furthermore, a single tissue may progress through a sequence of angiogenic pathways, for example, as acute injury progresses to chronic inflammation. The phenotype of the resulting neovasculature is critically dependent on the context in which it is formed. Biomarkers of angiogenesis are being developed as an aid to assessing human disease. Histological assessment of vascular density and angiogenic factor expression, in vivo imaging, Doppler ultrasound, and biofluid assays each may have clinical utility. Therapeutic targeting of angiogenesis will depend both on the generation of acceptable pharmacological agents and on the identification of patients who may and do gain benefit from such treatments.

Prognostic value of carcinoembryonic antigen and vascular endothelial growth factor tumor tissue content in colorectal cancer

AIM

This study was designed to assess the prognostic significance of the combined measurement of vascular endothelial growth factor (VEGF) and carcinoembryonic antigen (CEA) tissue content with respect to relapse-free and overall survival of patients with colorectal cancer (CRC).

METHODS

Quantitative evaluation of VEGF and CEA content was performed on protein extracts obtained from tissue biopsies from 69 CRC patients and 15 healthy donors.

RESULTS

VEGF significantly correlated with CEA content of either tumor tissues (rho = 0.55, p < 0.0001) or corresponding normal mucosa (rho = 0.34, p < 0.005). General regression analyses demonstrated that CEA was an independent predictor of VEGF tissue content either in CRC biopsies (regression coefficient = 0.57, p < 0.0001) or normal mucosa (regression coefficient = 0.25, p < 0.05). Cox proportional hazards survival analysis showed that tumor tissue content of both VEGF and CEA had an independent prognostic value in predicting both relapse-free (hazards ratio = 5.98, p = 0.002) and overall (hazards ratio = 4.73, p = 0.007) survival, irrespective of Dukes' stage. Kaplan-Meier analysis demonstrated that an elevated tumor content of both CEA and VEGF had a negative prognostic value in respect to either relapse-free (log-rank test: 10.4, p = 0.001) or overall survival (log-rank test: 7.33, p = 0.007).

CONCLUSION

Tumor tissue VEGF and CEA content determination might add useful prognostic information in the management of patients with CRC.

Tumour-associated angiogenesis in human colorectal cancer

Tumour angiogenesis is a critical step in the growth, metastatic spread and regrowth of colorectal cancer. Angiogenesis specific to tumour is a complicated process, the mechanisms of which remain unclear. Metastasis of colorectal cancer may result from passive entry into the circulation secondary to the effect of angiogenic factors. The survival and growth of colorectal tumour and thus their metastases are dependent on the balance of endogenous angiogenic and anti-angiogenic factors such that the outcome favours increased angiogenesis. Angiogenesis has become an attractive target for anticancer drug development, based on its important roles in tumour growth, invasion and metastasis. Several growth factors have been identified that regulate angiogenesis in colorectal cancer; the most important of these are vascular endothelial growth factors (VEGF), and of the several angiogenic factors, VEGF expression at the deepest invasive site of tumour is the most statistically significant prognostic indicator in advanced colorectal carcinoma. In this review article, we provide an overview on angiogenic factors and their receptors, and discuss the role of newly identified tumour endothelial markers (TEMs) that are involved in tumour-associated angiogenesis in colorectal cancer.

The role of the VEGF-C/VEGFR-3 axis in cancer progression

Vascular endothelial growth factor (VEGF) receptor 3 (VEGFR-3) (also called VEGFR-3) is activated by its specific ligand, VEGF-C, which promotes cancer progression. The VEGF-C/VEGFR-3 axis is expressed not only by lymphatic endothelial cells but also by a variety of human tumour cells. Activation of the VEGF-C/VEGFR-3 axis in lymphatic endothelial cells can facilitate metastasis by increasing the formation of lymphatic vessels (lymphangiogenesis) within and around tumours. The VEGF-C/VEGFR-3 axis plays a critical role in leukaemic cell proliferation, survival, and resistance to chemotherapy. Moreover, activation of the VEGF-C/VEGFR-3 axis in several types of solid tumours enhances cancer cell mobility and invasion capabilities, promoting cancer cell metastasis. In this review, we discuss the novel function and molecular mechanism of the VEGF-C/VEGFR-3 axis in cancer progression.

Clinicopathological significance of stromal variables: angiogenesis, lymphangiogenesis, inflammatory infiltration, MMP and PINCH in colorectal carcinomas

Cancer research has mainly focused on alterations of genes and proteins in cancer cells themselves that result in either gain-of-function in oncogenes or loss-of-function in tumour-suppressor genes. However, stromal variables within or around tumours, including blood and lymph vessels, stromal cells and various proteins, have also important impacts on tumour development and progression. It has been shown that disruption of stromal-epithelial interactions influences cellular proliferation, differentiation, death, motility, genomic integrity, angiogenesis, and other phenotypes in various tissues. Moreover, stromal variables are also critical to therapy in cancer patients. In this review, we mainly focus on the clinicopathological significance of stromal variables including angiogenesis, lymphangiogenesis, inflammatory infiltration, matrix metalloproteinase (MMP), and the particularly interesting new cysteine-histidine rich protein (PINCH) in colorectal cancer (CRC).

Links between Biology, Prognosis and Prediction of Response to Chemotherapy in Colorectal Cancer

Compared with the progress achieved in breast cancer, the use of prognostic and predictive parameters in colorectal cancer is lagging behind. One of the reasons is the limited information provided by 'classic' mutations as markers for response to therapy. To bridge this gap, prospective clinical trials need to be conducted to evaluate the usefulness of gene expression profiling and candidate markers, such as DNA repair proteins, onset of the methylator phenotype, neo-angiogenetic pathways related to inflammation, matrix metalloproteinases, tumor suppressors and cell signaling pathways (e.g. Akt). In parallel, the unrivalled sensitivity of molecular techniques may be applied to diagnostic parameters, such as cytokeratin 20 mRNA, for the detection of lymph node metastases. This article reviews the current knowledge on prognostic and predictive parameters in order to highlight the close link between tumor biology and tumor pharmacology. The increasing number of candidate markers together with recently introduced therapeutic options offer novel opportunities for a stepwise approach to the ambitious goal of individualized therapy in colorectal cancer.

Crystal structure of human vascular endothelial growth factor-B: identification of amino acids important for receptor binding

The development of blood vessels (angiogenesis) is critical throughout embryogenesis and in some normal postnatal physiological processes. Pathological angiogenesis has a pivotal role in sustaining tumour growth and chronic inflammation. Vascular endothelial growth factor-B (VEGF-B) is a member of the VEGF family of growth factors that regulate blood vessel and lymphatic angiogenesis. VEGF-B is closely related to VEGF-A and placenta growth factor (PlGF), but unlike VEGF-A, which binds to two receptor tyrosine kinases VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR), VEGF-B and PlGF bind to VEGFR-1 and not VEGFR-2. There is growing evidence of a role for VEGF-B in physiological and pathological blood vessel angiogenesis. VEGF-B may provide novel therapeutic strategies for the treatment of vascular disease and be a potential therapeutic target in aberrant vessel formation. To help understand at the molecular level the differential receptor binding profile of the VEGF family of growth factors we have determined the crystal structure of human VEGF-B(10-108) at 2.48 Angstroms resolution. The overall structure is very similar to that of the previously determined cysteine-knot motif growth factors: VEGF-A, PlGF and platelet-derived growth factor-B (PDGF-B). We also present a predicted model for the association of VEGF-B with the second domain of its receptor, VEGFR-1. Based on this interaction and the present structural data of the native protein, we have identified several putative residues that could play an important role in receptor recognition and specificity.

Increased VEGF levels induced by anti-VEGF treatment are independent of tumor burden in colorectal carcinomas in mice

Inhibition of vascular endothelial growth factor (VEGF) by gene transfer techniques was effectively applied to control experimental tumor growth, whereas effects on systemic VEGF levels had not been investigated. Therefore, we evaluated the effect of VEGF inhibition by adenoviral-mediated gene delivery of a dominant-negative soluble fragment of FLK-1 (sFlk-1) on systemic VEGF levels, organ-specific VEGF-RNA expression and antitumor efficacy in a murine colorectal cancer (CRC) tumor model. Vector function of AdsFlk-1 was shown by Western blot analysis and transgene expression was documented over a time period of 42 days in the serum of treated mice. Although cell supernatant of CT26 cells contained considerable levels of VEGF, systemic VEGF levels in the serum of tumor-bearing mice remained unaffected. Interestingly, mice that were systemically treated with AdsFlk-1 showed a strong upraise of circulating VEGF, whereas VEGF remained at background levels in the control. Vascular endothelial growth factor was increased not only in tumor bearing but also in healthy, tumor-free mice. Vascular endothelial growth factor determination in liver tissue homogenates showed a 16.5-fold upraise in AdsFlk-1-treated animals as compared to the AdLacZ control. Consecutively, systemic small interfering RNA injection targeted against VEGF reverted elevated VEGF levels almost back to normal levels. In spite of elevated VEGF levels, AdsFlk-1 administration showed significant antitumor effects in a subcutaneous metastatic CRC tumor model. There was no significant correlation between antitumour treatment response and VEGF levels in this model. Collectively, we conclude that the systemic administration of AdsFlk-1 had significant inhibitory effects on metastatic CRC tumor growth in spite of elevated systemic VEGF levels and that VEGF serum concentrations did not correlate to tumor burden and antitumor treatment response in this model.

Tumor-induced lymphangiogenesis: a target for cancer therapy?

Recent advances in understanding the biology of lymphangiogenesis, the new growth of lymphatic vessels, have cast new light on the molecular basis of metastasis to regional lymph nodes. The receptor tyrosine kinase VEGFR-3 is virtually exclusively expressed on lymphatic but not blood endothelium in the adult, and activation of VEGFR-3 by its ligands VEGF-C and VEGF-D is sufficient to induce lymphangiogenesis. Correlative studies with human tumors and functional studies using animal tumor models show that increased levels of VEGF-C or VEGF-D in tumors lead to enhanced numbers of lymphatic vessels in the vicinity of tumors, which in turn promotes metastasis to regional lymph nodes by providing a greater number of entry sites into the lymphatic system for invading tumor cells. These findings have prompted studies to investigate whether inhibitors of VEGFR-3 activation might represent novel therapeutic agents for the suppression of metastasis. However, a number of points regarding the therapeutic potential of anti-lymphangiogenic treatments in the context of cancer remain to be addressed. The spectrum and relative importance of molecules that induce lymphangiogenesis and the regulation of their expression during tumor progression, the reversibility of tumor-induced lymphangiogenesis, and possible side-effects of anti-lymphangiogenesis-based therapies all need to be investigated. Most importantly, the extent to which lymph node metastases contribute to the formation of metastases in other organs remains to be elucidated. These aspects are the focus of this review, and their investigation should serve as a roadmap to possible translational application.

The biology of vascular endothelial growth factor-B (VEGF-B)

The formation of new blood vessels (angiogenesis) is critical for both embryonic development and a variety of normal postnatal physiological processes. Various pathological processes, most notably tumour growth and chronic inflammation, are also known to be dependent on the new vessel formation. Amongst the variety of factors that contribute to the regulation of this complex process, vascular endothelial growth factor (VEGF or VEGF-A) is arguably the most well characterised. The VEGF family of growth factors is now known to comprise of VEGF-A plus four additional members, including VEGF-B. In contrast to VEGF-A, surprisingly little is known about the precise biological role of VEGF-B. Unlike VEGF-A, which binds to the two receptor tyrosine kinases VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR), VEGF-B binds only to VEGFR-1 and the functional significance of VEGFR-1 signalling has remained problematic. More recently, however, evidence has emerged suggesting a key role for VEGFR-1 signalling in pathological angiogenesis and this has raised the possibility that, like VEGF-A, VEGFR-1 specific ligands such as VEGF-B may provide for novel therapeutic strategies and/or represent new therapeutic targets. Here we review current knowledge of the biology of VEGF-B. We note that although analysis to date, including expression profiling and the generation of gene targetted mice, has provided only limited insights, future studies using recently generated recombinant proteins and antagonist monoclonal antibodies should provide for a more comprehensive understanding.

Role of VEGF-C and VEGF-D in lymphangiogenesis in gastric cancer

BACKGROUND

The molecular mechanisms of lymphangiogenesis induced by vascular endothelial growth factor (VEGF)-C and VEGF-D in gastric cancer were studied.

METHODS

VEGF-C and VEGF-D gene expression vectors were transfected into the gastric cancer cell line KKLS, which did not originally express VEGF-C and VEGF-D, and stable transfectants (KKLS/VEGF-C and KKLS/VEGF-D) were established. The cell lines were inoculated into the subserosal layer of the stomach and subcutaneous tissue of nude mice.

RESULTS

VEGF-C and VEGF-D expression in KKLS/VEGF-C and KKLS/VEGF-D cells was found by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. Expression of mouse VEGF receptor (VEGFR)-2 and mouse VEGFR-3 mRNA was detected in the KKLS/VEGF-C and KKLS/VEGF-D gastric tumors. Newly formed lymphatic vessels were detected not only in the periphery but also in the center of the tumors. The intratumor lymphatic vessels connected with the preexisting lymphatic vessels in the muscularis mucosa. The average numbers of lymphatic vessels in KKLS/VEGF-C (52.0 +/- 9.5) and KKLS/VEGF-D (16.4 +/- 0.6) gastric tumors were significantly higher than that in the KKLS/control vector tumors (4.0 +/- 1.4).

CONCLUSION

VEGF-C and VEGF-D may induce neoformation of lymphatic vessels in experimental gastric tumors by the induction of VEGFR-3 expression.

Expression of vascular endothelial growth factors A and C in human pancreatic cancer

AIM: To study the expression of vascular endothelial growth factor A (VEGF - A) and VEGF - C and to determine whether the presence of VEGF - A and VEGF - C was associated with the clinicopathologic characteristics of pancreatic cancer.

METHODS: VEGF - A and VEGF - C mRNA transcripts were examined by Northern blot in 6 human pancreatic cancer cell lines and 8 normal pancreatic tissues and 8 pancreatic carcinoma specimens. The expression of VEGF - A and VEGF - C proteins was examined by Western blot in the tested cell lines and by immunohistochemical stain in 50 pancreatic carcinoma samples.

RESULTS: VEGF - A and VEGF - C mRNA transcripts were present in all the 6 human pancreatic cancer cell lines. Immunoblotting revealed the presence of VEGF - A and VEGF - C proteins in all the cell lines. Northern blot analysis of total RNA revealed 3.0-fold and 3.6 - fold increase in VEGF - A and VEGF - C mRNA transcript in the cancer samples, respectively. Immunohistochemical analysis confirmed the expression of VEGF - A and VEGF - C in cancer cells within the tumor mass. Immunohistochemical analysis of 50 pancreatic cancer tissue samples revealed the presence of VEGF-A and VEGF - C immunoreactivity in 50% and 80% of the cancer tissue samples, respectively. The presence of VEGF-A in these cells was associated with larger tumor size and enhanced local spread (χ²= 6.690, P = 0.035<0.05) but was not associated with decreased patient survival. However, the presence of VEGF-C in the cancer cells was associated with increased lymph node metastasis (χ²= 5.710, P  = 0.017<0.05), but was not associated with decreased patient survival. There was no correlation between the expression of VEGF - A and VEGF - C in the same cancer cells.

CONCLUSION: VEGF - A and VEGF-C are commonly overexpressed in human pancreatic cancer and may contribute to tumor growth and lymph node metastasis. There is no relationship between the expression of VEGF - A and VEGF - C in pancreatic cancer.

Expression of angiogenic VEGF-A (soluble isoforms 121, 165) and lymphangiogenic VEGF-C in colorectal cancers with micro-satellite instability

BACKGROUND AND OBJECTIVES

Colorectal cancers (CRC) with high-level micro-satellite instability (MSI-H) show reduced metastatic potential and better prognosis compared to stage-matched stable (MSS) cancers. Angiogenesis/lymphangiogenesis, central to tumour growth and spread, is mediated by vascular endothelial growth factor (VEGF) cytokines, but little is known of their relationship to MSI.

METHODS

In this study, 67 sporadic CRC with identified MSI status, and 8 samples of normal colon were analysed for VEGF-A soluble isoforms (VEGF-121/VEGF-165) and VEGF-C gene transcription (by RT-PCR and scanning densitometry), and blood vessel density (BVD; measuring angiogenesis) and VEGF-C protein expression (measuring lymphangiogenesis).

RESULTS

Compared to normal colon, VEGF-165 transcription was reduced (P < 0.05), but VEGF-121 transcription was higher in MSS (P < 0.06) and MSI-L (P < 0.01) cancers (but similar in MSI-H). VEGF-165 transcription was unrelated to MSI, but VEGF-121 transcription was elevated in MSI-L (P < 0.06). There was a weak inverse correlation with VEGF-121 transcription and Dukes stage (P < 0.09), and with BVD and MSI (P < 0.09). With a singular di-nucleotide loci mutation (MSI-L), VEGF-121 (P < 0.03) and VEGF-C (P < 0.04) transcription was elevated.

CONCLUSIONS

MSI-H cancers have reduced angiogenic/lymphangiogenic potential, and transcription of VEGF-121 may be important in early growth and spread of CRC. Elevated VEGF-121 and VEGF-C transcription with singular di-nucleotide mutations may aid in the identification of distinct MSI-L cancers.

Vascular endothelial growth factors and receptors in colorectal cancer: Implications for anti-angiogenic therapy

There are conflicting associations between growth factor expression and clinicopathological variables in colorectal cancer. This study aimed to define the expression of members of the VEGF family and the receptor, VEGFR2, in primary and metastatic sites of colorectal cancer and their relationship to metastatic potential. Thirty colorectal cancers, 12 lymph node metastases and 9 liver metastases were immunostained for VEGF-A, VEGF-C, VEGF-D and VEGFR2. VEGFR2 was expressed by endothelial cells and by the malignant epithelium. VEGF-C and VEGFR2 were co-expressed in the same territory and correlated throughout the primary tumour and in metastatic lymph nodes, but not in liver metastases. Their expression at the invasive tumour edge correlated with expression in metastatic nodes. The benefit of anti-VEGF antibodies might be increased by directing additional therapies against VEGF-C or against the kinase receptors to target redundancy in the system. A component of the therapeutic benefit might be due to a direct anti-tumour effect as well as an anti-angiogenic effect.

Expression of vascular endothelial growth factor-C in human hepatocellular carcinoma

BACKGROUND/AIMS

Vascular endothelial growth factor-C (VEGF-C) is thought to be an important factor in tumor angiogenesis/lymphangiogenesis, but its role in hepatocellular carcinoma (HCC) has not yet been fully investigated.

METHODS

We immunohistochemically examined VEGF-C expression in surgically resected tissues of 90 HCC.

RESULTS

In the 78 HCC with a single histological grade, VEGF-C expression was significantly stronger in poorly differentiated HCC than in well- (P=0.003) or moderately differentiated HCC (P=0.0002). A 'nodule-in-nodule' case presented VEGF-A expression in the well-differentiated component and VEGF-C expression in the moderately-poorly differentiated component. According to nodular diameter, VEGF-C expression was significantly higher in nodules of 3.0 cm or larger (P=0.0263). Extrahepatic metastases seen in seven cases expressed VEGF-C. In 20 of the 28 cases who were able to be followed up, the frequency of intrahepatic recurrence tended to be higher and extrahepatic metastasis was significantly higher in the cases who had VEGF-C expression in the tumor casts of the intrahepatic portal/hepatic vein branches than other cases without the expression (P=0.0139). Disease-free survival time tended to be shorter in cases with VEGF-C expression in tumor casts of the portal/hepatic vein than in those without VEGF-C expression (P=0.053; log-rank test).

CONCLUSIONS

VEGF-C expression is related to the progression of HCC, and VEGF-C expression in tumor casts of the intrahepatic portal/hepatic vein is considered to be a factor indicating recurrence/metastasis sites.

Lymphatic spread of ductal pancreatic adenocarcinoma is independent of lymphangiogenesis

Early lymph node metastasis is common in pancreatic ductal adenocarcinoma (PDAC). The present study has examined the relationship of lymphatic spread to lymph vessel development and the expression of lymphangiogenic cytokines in a series of well-characterized PDACs. The hot spot method revealed the intratumoural and peritumoural lymphatic vessel density (LVD) to be slightly higher in PDACs than in the normal pancreas. The average intratumoural LVD, however, was strikingly decreased. There was no overexpression of vascular endothelial growth factor (VEGF)-C and VEGF-D in PDACs compared with the normal pancreas. LVD and expression of lymphangiogenic cytokines were not related to any of the biological tumour features or to patient survival. Three orthotopic nude mouse PDAC models did not reveal any increase in tumour-associated LVD, despite a high rate of lymph node metastasis. Lymph vessel proliferation was comparable in PDAC and chronic pancreatitis, in both humans and mice. In conclusion, increased lymphangiogenic activity is not required for and does not significantly affect the lymphatic spread of PDAC. The reduced number of human and murine intratumoural lymph vessels indicates that lymphatic metastasis takes place predominantly via peritumoural lymphatic vessels. The weak expression of lymphangiogenic cytokines in neoplastic cells and lymphatic vessel proliferation in peritumoural regions and chronic pancreatitis indicate that inflammation may be the reason for the low rate of lymphangiogenesis.

Vascular endothelial growth factor (VEGF) in physiological and pathological conditions

Vascular endothelial growth factor (VEGF) is the major endothelial-cell specific stimulatory factor regarded as the most important positive regulator of angiogenesis and vascular permeability. Due to its powerful angiogenic and mitogenic properties, VEGF takes part in a variety of crucial biological processes, including wound repair and tumorigenesis. The elevated expression of VEGF and its receptors has been found in malignancies of various origin as being associated with metastasis formation and poor prognosis. Recently, some possibilities appeared to block the VEGF action when it is undesirable or promote its activity when it can be useful. These new therapeutic strategies based upon the knowledge of VEGF biological role, are being tried and up till now they proved to be successful, especially in anticancer therapy and the coronary heart disease treatment.

Defective DNA mismatch repair determines a characteristic transcriptional profile in proximal colon cancers

BACKGROUND & AIMS

Colon cancers with defective DNA mismatch repair (MMR) have peculiar molecular, pathologic, and clinical features, including high-level microsatellite instability, conspicuous lymphocytic infiltration, preferential location in the proximal colon, and better prognosis. Our aim was to characterize the transcriptional profile of this colon cancer subset.

METHODS

An oligonucleotide microarray containing 12,625 probes was used to evaluate gene expression in 25 proximal colon cancers, 10 samples of normal colon mucosa, and 14 colon cancer cell lines. Transcriptional profiles of MMR-deficient cancers and cell lines were compared with those of their MMR-proficient counterparts.

RESULTS

Unsupervised analysis of microarray data showed that MMR status exerts a predominant influence on the gene expression profile of proximal colon cancers. Hierarchical clustering divided the cancers into 2 groups corresponding almost perfectly with their MMR status. Supervised analysis identified numerous gene expression changes that represent a genetic signature of MMR-deficient colon cancers. Changes in genes involved in apoptosis and the immune response were consistent with the better prognosis of MMR-deficient cancers. In MMR-deficient cancers and cell lines, 4-1BBL, a crucial gene in the anti-tumor immune response, was, respectively, 2.4 and 6.0 times more expressed than in their MMR-proficient counterparts. This difference was confirmed by quantitative reverse-transcription polymerase chain reaction and flow cytometric assessment of 4-1BBL protein expression in colon cancer cell lines. Our analysis also showed novel possible gene targets of microsatellite instability.

CONCLUSIONS

MMR inactivation produces distinct changes in the cellular messenger RNA pool, which is consistent with a unique tumorigenesis pathway.

Pre-operative Plasma Levels of Vascular Endothelial Growth Factor A, C and D in Patients with Colorectal Cancer

AIMS

Vascular endothelial growth factor (VEGF)-C and VEGF-D are angiogenic and lymphangiogenic members of the VEGF family of growth factors. Increased VEGF-C or VEGF-D expression in human tumours may be associated with lymph-node metastasis and lymphatic invasion. Circulating plasma levels of VEGF-A, VEGF-C and VEGF-D were measured in patients with colorectal cancer, and assessed for their usefulness as a diagnostic tool for determining lymph-node metastasis.

MATERIALS AND METHODS

One hundred and twenty patients with colorectal cancer and 50 healthy control patients were included in the study. Plasma growth-factor levels were assessed by enzyme-linked immunosorbent assays.

RESULTS

No significant differences in plasma VEGF-C or VEGF-D levels were seen between patients subgrouped by clinicopathological variables. In particular, there were no differences in median plasma VEGF-C or VEGF-D level in patients with and without lymph-node involvement (VEGF-C: 11.2 U/ml [range, 4.9-51.9] vs 9.9 U/ml [4.4-93.4 U/ml]; P = 0.90; VEGF-D: 335 pg/ml [113-1102] vs 316.5 pg/ml [0-1343]; P = 0.68).

CONCLUSIONS

Circulating plasma levels of VEGF-C and VEGF-D do not allow pre-operative identification of lymph-node status in patients with colorectal cancer.

Treatment of metastatic colorectal carcinomas by systemic inhibition of vascular endothelial growth factor signaling in mice

AIM: Tumor angiogenesis has been shown to be promoted by vascular endothelial growth factor (VEGF) via stimulating endothelial cell proliferation, migration, and survival. Blockade of VEGF signaling by different means has been demonstrated to result in reduced tumor growth and suppression of tumor angiogenesis in distinct tumor entities. Here, we tested a recombinant adenovirus, AdsFlt1-3, that encodes an antagonistically acting fragment of the VEGF receptor 1 (Flt-1), for systemic antitumor effects in pre-established subcutaneous CRC tumors in mice.

METHODS: Murine colorectal carcinoma cells (CT26) were inoculated subcutaneously into Balb/c mice for in vivo studies. Tumor size and survival were determined. 293 cell line was used for propagation of the adenoviral vectors. Human lung cancer line A₅₄₉ and human umbilical vein endothelial cells were transfected for in vitro experiments.

RESULTS: Infection of tumor cells with AdsFlt1-3 resulted in protein secretion into cell supernatant, demonstrating correct vector function. As expected, the secreted sFlt1-3 protein had no direct effect on CT26 tumor cell proliferation in vitro, but endothelial cell function was inhibited by about 46% as compared to the AdLacZ control in a tube formation assay. When AdsFlt1-3 (5×10⁹ PFU/animal) was applied to tumor bearing mice, we found a tumor inhibition by 72% at d 12 after treatment initiation. In spite of these antitumoral effects, the survival time was not improved. According to reduced intratumoral microvessel density in AdsFlt1-3-treated mice, the antitumor mechanism can be attributed to angiostatic vector effects. We did not detect increased systemic VEGF levels after AdsFlt1-3 treatment and liver toxicity was low as judged by serum alanine aminotransferase determination.

CONCLUSION: In this study we confirmed the value of a systemic administration of AdsFlt1-3 to block VEGF signaling as antitumor therapy in an experimental metastatic colorectal carcinoma model in mice.

Expression of vascular endothelial growth factor (VEGF)-C in preoperative biopsy specimens and metastatic foci of regional lymph nodes in submucosal gastric carcinoma

BACKGROUND: Vascular endothelial growth factor (VEGF)-C is implicated in lymphangiogenesis, however the exact role of VEGF-C in promoting lymphatic spread of cancer cells remains largely unknown. METHODS: The expression of VEGF-C was immunohistochemically determined in 97 endoscopic biopsy specimens from 46 patients with submucosal gastric carcinoma (SGC). Nodal metastases including micrometastasis and isolated tumor cells (ITC) were evaluated by immunohistochemical staining for cytokeratin in 1650 lymph nodes, and tumor cells in these metastatic nodes were also examined for VEGF-C expression. RESULTS: In biopsy samples, VEGF-C was positively detected in 21 (47%) patients. Metastases were identified in 46 (2.8%) nodes from 15 (33%) patients. Metastases were detected in 39 nodes by hematoxylin-eosin (H&E) staining and in additional 7 nodes as ITC by immunohistochemical staining. The rate of lymph node metastases was significantly correlated with VEGF-C expression in biopsy samples (p < 0.05). The positive and negative predictive values of VEGF-C in biopsy specimens for nodal metastasis were 44 %(10/21) and 80% (20/25), respectively. Among the 46 metastatic nodes, tumor cells in 29 (63%) nodes positive patients expressed VEGF-C, whereas those in 17 (37%) nodes did not. VEGF-C expression was high in macronodular foci in medullary areas, whereas more than half of ITC or micrometastasis located in peripheral sinus lacked the expression of VEGF-C. CONCLUSIONS: Despite the significant correlation, immunodetcetion of VEGF-C in endoscopic biopsy specimens could not accurately predict the nodal status, and thus cannot be applied for the decision of the treatment for SGC. VEGF-C may not be essential for lymphatic transport, but rather important to develop the macronodular lesion in metastatic nodes.

The AKT/IκB kinase pathway promotes angiogenic/metastatic gene expression in colorectal cancer by activating nuclear factor-κB and β-catenin

Our laboratory has delineated that the phosphatidylinositol 3' kinase (PI3K)/AKT/I kappa B kinase (IKK) pathway positively regulates NF kappa B and beta-catenin, both important transcriptional regulators in colorectal cancer (CRC). Therefore, we investigated the effect of inhibiting the PI3K/AKT/IKK alpha pathway in regulating the inappropriate constitutive activation of NF kappa B and beta-catenin in CRC cell lines. SW480 and RKO CRC cell lines demonstrate constitutive activation of AKT as well as both NF kappa B- and beta-catenin-dependent transcription. The constitutive activation of NF kappa B- and beta-catenin-dependent transcription is inhibited by transiently transfecting either kinase dead (KD) IKK alpha, which blocks IKK alpha kinase activity, KD AKT, which blocks AKT activity, or wildtype (WT) PTEN, which inhibits PI3K and AKT activity. The ability of KD IKK alpha, KD AKT or WT PTEN to decrease beta-catenin-dependent transcription is independent of their effects on NF kappa B. Inducible expression of either KD IKK alpha or WT PTEN strongly inhibits both the constitutive NF kappa B- and beta-catenin-dependent promoter and endogenous gene activation. Targeted array-based gene expression analysis of this inducible system reveals that many of the genes downregulated upon inhibition of this pathway are involved in tumor angiogenesis and metastasis. The activation of this pathway and the expression of the three most repressed genes was further analysed in samples of CRC. These results indicate a role of this pathway in controlling gene expression important in tumor progression and metastasis.

The role of Osteopontin in tumor metastasis

Osteopontin (OPN) is a glyco-phosphoprotein that is expressed and secreted by numerous human cancers. OPN functions in cell adhesion, chemotaxis, macrophage-directed interleukin-10 (IL-10) suppression, stress-dependent angiogenesis, prevention of apoptosis, and anchorage-independent growth of tumor cells by regulating cell-matrix interactions and cellular signaling through binding with integrin and CD44 receptors. While constitutive expression of OPN exists in several cell types, induced expression has been detected in T-lymphocytes, epidermal cells, bone cells, macrophages, and tumor cells in remodeling processes such as inflammation, ischemia-reperfusion, bone resorption, and tumor progression. Recently, substantial evidence has linked OPN with the regulation of metastatic spread by tumor cells. However, the molecular mechanisms that define the role of OPN in tumor metastasis are incompletely understood. Transcriptional regulators that contribute to the induction of OPN expression have received significant attention as potential modulators of the OPN-mediated metastatic phenotype. The following review will discuss the molecular structure of OPN, the evidence for its functional role in tumor cell metastasis, the downstream signals that activate invasive mechanisms, and the recent reports concerning regulation of OPN transcription.