Overexpression of vascular endothelial growth factor is responsible for the hematogenous recurrence of early-stage gastric carcinoma

Clinical progress of anti-angiogenic targeted therapy and combination therapy for gastric cancer

The incidence of gastric cancer is increasing year by year. Most gastric cancers are already in the advanced stage with poor prognosis when diagnosed, which means the current treatment is not satisfactory. Angiogenesis is an important link in the occurrence and development of tumors, and there are multiple anti-angiogenesis targeted therapies. To comprehensively evaluate the efficacy and safety of anti-angiogenic targeted drugs alone and in combination against gastric cancer, we systematically searched and sorted out relevant literature. In this review, we summarized the efficacy and safety of Ramucirumab, Bevacizumab, Apatinib, Fruquintinib, Sorafenib, Sunitinib, Pazopanib on gastric cancer when used alone or in combination based on prospective clinical trials reported in the literature, and sorted response biomarkers. We also summarized the challenges faced by anti-angiogenesis therapy for gastric cancer and available solutions. Finally, the characteristics of the current clinical research are summarized and suggestions and prospects are raised. This review will serve as a good reference for the clinical research of anti-angiogenic targeted drugs in the treatment of gastric cancer.

Lentivirus-Mediated VEGF Knockdown Suppresses Gastric Cancer Cell Proliferation and Tumor Growth in vitro and in vivo

Purpose

Gastric cancer has a high mortality rate worldwide. Although treatments, such as molecular-targeted therapy, have been introduced, the resulting long-term survival and prognosis remain unsatisfactory. Downregulation of the target genes using lentivirus-mediated short hairpin RNA (shRNA) can be an effective therapeutic strategy for patients with gastric cancer. Overexpressed vascular endothelial growth factor A (VEGF) in human gastric cancer cells can be an effective novel therapeutic target for human gastric cancer. Thus, this study aimed to evaluate the therapeutic effects of lentivirus-mediated knockdown of VEGF gene expression in human gastric cancer growth.

Materials and Methods

Specific shRNA sequences targeting VEGF were designed to construct a lentiviral expression vector. After human gastric carcinoma cells (cell line NCI-N87) were infected with the lentiviral vector, the therapeutic effects of the lentivirus-mediated shRNA targeting VEGF were analyzed both in vitro and in vivo.

Results

Stable suppression of VEGF gene expression in NCI-N87 cells using shRNA (ShVEGF) showed significant inhibition of cell proliferation, clonogenicity, and cell motility. ShVEGF also showed increased G0/G1 cell cycle arrest and apoptosis. In addition, in vivo results from nude mice xenografted ShVEGF showed significant inhibition of tumor growth. Assessing the therapeutic effects of intratumoral injection of lentivirus-targeting VEGF (Virus_VEGF) revealed that it significantly inhibited tumor growth compared to that in the Virus_Scramble or saline injection control groups.

Conclusion

The constructed ShVEGF showed significant inhibition of NCI-N87 gastric cancer cell growth both in vitro and in vivo. These experimental results suggest a novel therapeutic strategy for patients with gastric cancer using lentivirus-mediated shRNA targeting VEGF.

Role of bevacizumab in colorectal cancer growth and its adverse effects: A review

Angiogenesis affects both wound healing and malignant cell growth through nutrients and oxygen. Vascular endothelial growth factor (VEGF) is the most important element involved in this complex process. Inhibition of VEGF influences angiogenesis and may restrict tumor growth and metastatic ability. Modern anti-angiogenic therapy is based on this theory. Bevacizumab is a recombinant humanized monoclonal antibody (immunoglobulin G1) which binds with VEGF-A forming a large molecule. It can not be bound with VEGF tyrosine kinase receptors preventing VEGF-A incorporation; thus its activity is inhibited inducing blockage of VEGF-mediated angiogenesis. Bevacizumab, in combination with chemotherapy or other novel targeted therapeutic agents, is currently used more frequently in clinical practice, mainly for managing advanced colorectal cancer. It is also used for managing other malignancies, such as breast cancer, pancreatic cancer, prostate cancer, non small-cell lung cancer, metastatic renal carcinoma and ovarian tumors. Although it is generally considered a safe treatment, there are reports of some rare side effects which should be taken into account. Recent experiments in rats and mice show promising results with a wider therapeutic range.

Effect of arsenic trioxide on vascular endothelial cell proliferation and expression of vascular endothelial growth factor receptors Flt-1 and KDR in gastric cancer in nude mice

AIM

To investigate the effect of arsenic trioxide (As2O3) on expression of vascular endothelial growth factor receptor-1 (VEGFR-1, Flt-1) and VEGFR-2 (KDR) in human gastric tumor cells and proliferation of vascular endothelial cells.

METHODS

The solid tumor model was formed in nude mice with the gastric cancer cell line SGC-7901. The animals were treated with As2O3. Microvessel density (MVD) and expression of Flt-1 and KDR were detected by immunofluorescence laser confocal microscopy. SGC-7901 cells were treated respectively by exogenous recombinant human VEGF165 or VEGF165 + As2O3. Cell viability was measured by MTT assay. Cell viability of ECV304 cells was measured by MTT assay, and cell cycle and apoptosis were analyzed using flow cytometry.

RESULTS

The tumor growth inhibition was 30.33% and 50.85%, respectively, in mice treated with As2O3 2.5 and 5 mg/kg. MVD was significantly lower in arsenic-treated mice than in the control group. The fluorescence intensity levels of Flt-1 and KDR were significantly less in the arsenic-treated mice than in the control group. VEGF165 may accelerate growth of SGC7901 cells, but As2O3 may disturb the stimulating effect of VEGF165. ECV304 cell growth was suppressed by 76.51%, 71.09% and 61.49% after 48 h treatment with As2O3 at 0.5, 2.5 and 5 micromol/L, respectively. Early apoptosis in the As2O3-treated mice was 2.88-5.1 times higher than that in the controls, and late apoptosis was 1.17-1.67 times higher than that in the controls.

CONCLUSION

Our results showed that As2O3 delays tumor growth, inhibits MVD, down-regulates Flt-1 and KDR expression, and disturbs the stimulating effect of VEGF165 on the growth of SGC7901 cells. These results suggest that As2O3 might delay growth of gastric tumors through inhibiting the paracrine and autocrine pathways of VEGF/VEGFRs.

Effect of arsenic trioxide on vascular endothelial cell proliferation and expression of vascular endothelial growth factor receptors Flt-1 and KDR in gastric cancer in nude mice

AIM: To investigate the effect of arsenic trioxide (As₂O₃) on expression of vascular endothelial growth factor receptor-1 (VEGFR-1, Flt-1) and VEGFR-2 (KDR) in human gastric tumor cells and proliferation of vascular endothelial cells.

METHODS: The solid tumor model was formed in nude mice with the gastric cancer cell line SGC-7901. The animals were treated with As₂O₃. Microvessel density (MVD) and expression of Flt-1 and KDR were detected by immunofluorescence laser confocal microscopy. SGC-7901 cells were treated respectively by exogenous recombinant human VEGF₁₆₅ or VEGF₁₆₅ + As₂O₃. Cell viability was measured by MTT assay. Cell viability of ECV304 cells was measured by MTT assay, and cell cycle and apoptosis were analyzed using flow cytometry.

RESULTS: The tumor growth inhibition was 30.33% and 50.85%, respectively, in mice treated with As₂O₃ 2.5 and 5 mg/kg. MVD was significantly lower in arsenic-treated mice than in the control group. The fluorescence intensity levels of Flt-1 and KDR were significantly less in the arsenic-treated mice than in the control group. VEGF₁₆₅ may accelerate growth of SGC7901 cells, but As₂O₃ may disturb the stimulating effect of VEGF₁₆₅. ECV304 cell growth was suppressed by 76.51%, 71.09% and 61.49% after 48 h treatment with As₂O₃ at 0.5, 2.5 and 5 μmol/L, respectively. Early apoptosis in the As₂O₃-treated mice was 2.88-5.1 times higher than that in the controls, and late apoptosis was 1.17-1.67 times higher than that in the controls.

CONCLUSION: Our results showed that As₂O₃ delays tumor growth, inhibits MVD, down-regulates Flt-1 and KDR expression, and disturbs the stimulating effect of VEGF₁₆₅ on the growth of SGC7901 cells. These results suggest that As₂O₃ might delay growth of gastric tumors through inhibiting the paracrine and autocrine pathways of VEGF/VEGFRs.

Vascular endothelial growth factor, hypoxia-inducible factor 1 alpha and CD34 expressions in early-stage gastric tumors: relationship with pathological factors and prognostic impact on survival

BACKGROUND

Angiogenesis is one of the key steps in solid tumor growth and metastasis. We planned to investigate the prognostic significance of vascular endothelial growth factor (VEGF), hypoxia-inducible factor 1alpha (HIF-1alpha) and CD34 expressions as markers of angiogenesis in gastric cancer.

PATIENTS AND METHODS

We retrospectively reviewed the medical records of 51 gastric cancer patients who had total or subtotal gastrectomy at Marmara University Hospital from 1990 to 2004 and evaluated the expression of VEGF, HIF-1alpha and CD34 by immunohistochemistry in their archival tumor tissues. We recorded the clinical and pathological characteristics of these patients and analyzed their survival outcome.

RESULTS

Thirty out of 51 patients were males. The median age was 63 years (range 34-81). The median follow-up was 17 months. Thirty-six patients had node-positive disease. The majority of patients (n = 43) had T2 and T3 disease. Vascular and lymphatic invasions were present in 57 and 77% of tumors, respectively. VEGF and HIF-1alpha were positive in 65 and 71% of tumors. The median CD34 staining score was 19 (3-68). VEGF, HIF-1alpha and CD34 expressions were more frequent in tumors without serosal invasion (p = 0.01, p = 0.01 and p = 0.003, respectively). CD34 expression was significantly more frequent in tumors with VEGF and HIF-1alpha expression (p = 0.00, p = 0.00). HIF-1alpha expression was more frequent in tumors with VEGF expression (p = 0.00). The 5-year overall survival was 45%. VEGF, HIF-1alpha, CD34 expressions and other pathological characteristics were found to have no impact on survival.

CONCLUSION

VEGF, HIF-1alpha and CD34 expressions were more common in tumors without serosal invasion. As a future perspective, biological agents targeting VEGF and HIF-1alpha might be more effective at earlier stages of gastric cancer.

Effects of shRNA targeting VEGF on VEGF mRNA expression in gastric cancer cells

In order to investigate the inhibitory effect of plasmid-mediated short hairpin RNA targeting vascular endothelial growth factor (VEGF) on the expression of VEGF mRNA in human gastric cancer cells, a plasmid vector for transcribing specific short hairpin RNA targeting VEGF (pU6-VEGF) was constructed, and then transfected into human gastric cancer cells using Lipofectamine2000. The VEGF mRNA expression level was detected by RT-PCR. RPMI1640 was used for blank control, and pSilencer 1.0-U6 empty plasmid for the negative control. Results showed the clone and sequence analysis revealed that the recombinant plasmid vector of pU6-VEGF was successfully constructed. The VEGF mRNA expression levels in blank control group, experimental group (pU6-VEGF) and negative control group (pSilencer1.0-U6) were 100%, 49% and 94%, respectively, indicating VEGF mRNA expression in the cells transfected with pU-VEGF vector was inhibited significantly as compared with blank control group and negative control group. It was concluded that the short hairpin RNA could significantly inhibit the expression of VEGF mRNA, which provided an experimental basis for treating human cancer with anti-angiogenesis.

Effect of Weikangning on gastric cancer cell growth and expression of vascular endothelial growth factor and its receptors KDR and Flt-1

AIM: To observe the effect of Chinese traditional herbal decoction Weikang-ning (WKN) on cell growth and expression of VEGF and its receptors KDR and Flt-1 in gastric cancer cell line MGC-803.

METHODS: A total of 120 male Wistar rats were divided into control group, high dose, medium dose and low dose groups fed with natural saline, 20, 10, and 5 g/kg of WKN, respectively. The experimental animals were finally killed for the preparation of drug-containing serum. The gastric cancer cell MGC-803 was cultured with the drug-containing serum drawn from the rats in different groups. We observed the growth condition of the cancer cells with light microscope and flow cytometer. The expression of mRNA of VEGF and its receptors KDR and Flt-1 was detected with RT-PCR.

RESULTS: The proportion of cells in G₀-G₁ phase was (65.40±0.41)%, (56.92±0.62)%, (55.89±0.69)% in high, medium and low dose groups respectively vs (41.35±0.55)% in control group (P<0.01), while the cells in G₂-S and S phases were (11.62±0.62)% and (22.99±0.69)%, (17.08±0.80)% and (26.00±0.71)%, (19.37±0.57)% and (24.74±0.64)% in high, medium and low dose groups, respectively, vs (23.65±0.56)% and (35.00±0.60)% in control group (P<0.01). The expression of mRNA of VEGF and its receptors was significantly decreased, the area of electrophoresis bands (AREA), the absorptivity of mean optical density (A) and the product of AREA and A were significantly lower in WKN-administered groups than that in control group (P<0.01).

CONCLUSION: The decoction of WKN suppresses the growth of gastric cancer cell MGC-803 and decreases the expression of mRNA of both VEGF and its receptors KDR and Flt-1.

Association between expression of transcription factor Sp1 and increased vascular endothelial growth factor expression, advanced stage, and poor survival in patients with resected gastric cancer

The biological and clinical behaviors of cancer are affected by multiple molecular pathways that are under the control of transcription factors. Improved understanding of how transcription factors affect cancer biology may lead to improved ability to predict clinical outcome and discovery of novel therapeutic strategies. We evaluated the relationship between Sp1 and vascular endothelial growth factor (VEGF) expression, as well as their effect on survival in 86 cases of resected human gastric cancer. The degree of VEGF expression correlated highly with Sp1 expression (P < 0.01). Patients with high Sp1 expression were 98 times more likely to have high VEGF expression compared with those with negative Sp1 expression. Clinically, negative or weak Sp1 expression was associated with early stage (IA) in gastric cancer. Strong Sp1 expression was more frequently observed among patients with stage IB-IV disease (P = 0.035). Similarly, whereas strong Sp1 expression was uncommonly observed among patients with N0 or N1 disease (19 and 16%), N2/N3 gastric cancer was associated with strong Sp1 expression (48%; P = 0.034). Strong Sp1 expression was also associated with inferior survival. The median survival duration in patients who had a tumor with a negative, weak, and strong Sp1 expression was 44, 38, and 8 months (P = 0.0075), respectively, whereas patients with strong VEGF expression had a shorter survival duration; the difference was not statistically significant. When Sp1 and VEGF expression, stage, completeness of resection, histology, and patient age were entered in a Cox proportional hazards model, strong Sp1 expression (P = 0.021) and an advanced disease stage (P < 0.001) were independently prognostic of poor survival. Given the importance of Sp1 in the expression of VEGF, our data suggest that dysregulated Sp1 expression and activation play important roles in VEGF overexpression and, thus, gastric cancer development and progression.

Construction and analysis of SSH cDNA library of human vascular endothelial cells related to gastrocarcinoma

AIM: To construct subtracted cDNA libraries of human vascular endothelial cells (VECs) related to gastrocarcinoma using suppression substractive hybridization (SSH) and to analyze cDNA libraries of gastrocarcinoma and VECs in Cancer Gene Anatomy Project (CGAP) database.

METHODS: Human VECs related to gastric adenocarcinoma and corresponding normal tissue were separated by magnetic beads coupled with antibody CD31 (Dynabeads CD31). A few amount of total RNA were synthesized and amplified by SMART^TM PCR cDNA Synthesis Kit. Then, using SSH and T/A cloning techniques, cDNA fragments of differentially expressed genes in human VECs of gastric adenocarcinoma were inserted into JM109 bacteria. One hundred positive bacteria clones were randomly picked and identified by colony PCR method. To analyze cDNA libraries of gastrocarcinoma and VECs in CGAP database, the tools of Library Finder, cDNA xProfiler, Digital GENE Expression Displayer (DGED), and Digital Differential Display (DDD) were used.

RESULTS: Forward and reverse subtraction cDNA libraries of human VECs related to gastrocarcinoma were constructed successfully with SSH and T/A cloning techniques. Analysis of CGAP database indicated that no appropriate library of VECs related to carcinoma was constructed.

CONCLUSION: Construction of subtraction cDNA libraries of human VECs related to gastrocarcinoma was successful and necessary, which laid a foundation for screening and cloning new and specific genes of VECs related to gastrocarcinoma.

Role of VEGF and CD44v6 in differentiating benign from malignant ascites

AIM: To detect the vascular endothelial growth factor (VEGF) and soluble splice variant 6 of CD44 (sCD44v6) levels in ascites and to explore their role in differentiating benign from malignant ascites.

METHODS: Cirrhotic ascites (n = 36), tuberculosis ascites (n = 8) and malignant ascites (n = 23) were collected and studied. Concentrations of soluble VEGF and sCD44v6 in various kinds of ascites (n = 67) were measured using a sandwich enzyme-linked immunoadsorbent assay.

RESULTS: VEGF and sCD44v6 levels in malignant ascites were 640.74 ± 264.81 pg/mL and 89.22 ± 38.20 ng/mL, respectively, both of which were significantly higher than those in cirrhotic ascites and tuberculous ascites (q = 18.98, 11.89 and q = 8.92, 5.09; P < 0.01). However, the levels of VEGF and sCD44v6 in cirrhotic and tuberculous ascites had no significant difference (q = 0.48, 0.75; P > 0.05). Furthermore, VEGF levels in malignant ascites in patients with ovarian cancer were higher than those with gastric and colon cancer (q = 5.03, 6.79; P < 0.01, respectively). But differences of VEGF levels between gastric and colon cancer were not significant (q = 1.90, P > 0.05). Whereas, sCD44v6 levels in malignant ascites from patients with ovarian, gastric and colon cancer had no significant difference (q = 0.06, 0.91, 0.35; P > 0.05, respectirely). In comparison with cirrhotic and tuberculous ascites, when the upper limit of its VEGF mean levels 119.44 pg/mL (70.90 ± 48.54) and sCD44v6 mean levels 63.59 ng/mL (44.42 ± 19.17) was taken as the minimum cutoff limit, the sensitivity and specificity of VEGF and sCD44v6 of this assay to the diagnos is of malignant ascites were 91.3%, 90.9% and 73.9%, 88.7% respectively.

CONCLUSION: Elevated levels of VEGF and sCD44v6 may be useful in differential diagnosis of benign and malignant ascites.

Relationship between the expression of iNOS, VEGF, tumor angiogenesis and gastric cancer

AIM: To investigate the relationship between the expression of inducible nitric oxide synthase (iNOS), vascular endothelial growth factor (VEGF), the microvascular density (MVD) and the pathological features and clinical staging of gastric cancer.

METHODS: Immunohistochemical staining was used for detecting the expression of iNOS and VEGF in 46 resected specimens of gastric carcinoma; the monoclonal antibody against CD34 was used for displaying vascular endothelial cells, and MVD was detected by counting of CD34-positive vascular endothelial cells.

RESULTS: Of 46 resected specimens of gastric carcinoma, the rates of expressions of iNOS and VEGF were 58.70% and 76.09%, respectively, and MVD averaged 55.59 ± 19.39. Judged by the standard TNM criteria, the rate of expression of iNOS in stage IV (84.46%) was higher than those in stage I, II, III (Fish exact probabilities test, P = 0.019, 0.023 and 0.033, respectively); the rates of expression of VEGF in stage III, IV (76.0%, 92.31%, respectively) were higher than those in stage I, II (Fish exact probabilities test, P = 0.031, 0.017, 0.022 and 0.019). MVDs in stage III, IV (64.72 ± 14.96, 67.09 ± 18.29, respectively) were higher than those in stage I, II (t = 2.378, 4.015, 2.503 and 2.450, P < 0.05, P < 0.001, P < 0.001, P < 0.05, respectively). In 37 gastric carcinoma specimens with lymph node metastasis, MVD (68.69 ± 18.07) and the rates of expression of iNOS and VEGF (70.27%, 83.78%, respectively) were higher than those in the specimens with absence of metastasis (t = 2.205, χ² = 6.3587, χ² = 6.2584, P < 0.01, P < 0.05, P < 0.05, respectively). MVD and the expressions of iNOS and VEGF were not correlated to the location, size or grade of tumor, nor with the depth of invasion of tumor; MVDs in the positive iNOS and VEGF specimens (59.88 ± 18.02, 58.39 ± 17.73, respectively) were higher than those in the negative iNOS and VEGF specimens (χ² = 6.3587 and 6.1574, P < 0.05, P < 0.05, respectively); thus the expressions of iNOS and VEGF was correlated to MVD, but the expression of iNOS was not correlated to that of VEGF. In addition, of the 46 surviving patients, the 5-year survival rate of patients with positive iNOS or VEGF tumors was significantly less than that of patients with negative iNOS-or VEGF tumors (χ² = 4.3842 and 5.4073, P < 0.05, P < 0.05, respectively).

CONCLUSION: The expressions of iNOS and VEGF are closely related to tumor angiogenesis, and are involved in the advancement and the lymph node metastasis; thus MVD and the expressions of iNOS and VEGF may serve indexes for evaluating staging of gastric carcinoma and forecasting its risk of metastasis, which will help establish a comprehensive therapeutical measure of post-operative patients and provide a new approach to tumor therapy.

High expression of vascular endothelial growth factor predicts early recurrence and poor prognosis after curative resection for ductal adenocarcinoma of the pancreas

INTRODUCTION AND AIMS

Only curative resection for pancreatic adenocarcinoma is related to a favorable prognosis, but the overall survival after surgery still remains poor, and early recurrence is frequently observed. Because recurrence is the limiting factor and the main cause of death after curative resection, the identification of markers that predict early postoperative recurrence is of paramount importance. Angiogenesis is essential for tumor growth and metastases; therefore, we set out to clarify whether vascular endothelial growth factor (VEGF) expression and microvessel density (MVD) correlate with early recurrence and poor prognosis after curative resection. A second goal was to characterize the VEGF-producing cells and the subcellular distribution.

METHODOLOGY

Seventy patients with ductal adenocarcinoma of the pancreas were studied after curative resection with a follow-up of at least 2 years. The MVD quantification was performed immunohistochemically with use of a monoclonal antibody to CD34. The VEGF expression was studied with use of polyclonal antibody. To detect the intracellular localization of specific VEGF mRNA sequences, nonisotopic in situ hybridization was performed. The correlations among VEGF expression and MVD, clinicopathologic parameters, and clinical outcome were then statistically analyzed.

RESULTS

The VEGF immunoreactivity was 88.6%, and positive mRNA signals were obtained in the cytoplasm of carcinoma and endothelial cells in 81.4%. Furthermore, we observed tumor-associated macrophages close to infiltrating carcinoma cells. All endothelial cells showed positive immunoreactivity to the anti-CD34 antibody, and a median distribution of 85 vessels/x200 field was observed. A significant correlation (p < 0.05) was found between the MVD and the International Union Against Cancer (UICC) stage. Statistical analysis showed a significant correlation between VEGF expression and the height of MVD (p < 0.05). Kaplan-Meier analyses revealed that VEGF expression and MVD had a statistically significant correlation with survival after curative resection (p < 0.05). Furthermore, multivariate analysis indicated that VEGF expression is an independent prognostic marker for cancer recurrence within 8 months after curative surgery (p = 0.003).

CONCLUSION

In pancreatic adenocarcinoma, the VEGF expression and the height of MVD are closely correlated, and both-rather than UICC stage and TNM classification (tumor size and nodal involvement)-are markers of prognostic relevance after curative resection. Furthermore, VEGF is a predictor of early recurrence after curative resection. The current study indicates that VEGF may promote the distribution of metastases, leading to early cancer recurrence and poor outcome.

Vascular endothelial growth factor expression correlates with tumour grade and vascularity in gliomas

AIMS

Tumour vascularity and vascular endothelial growth factor (VEGF) expression were studied in 41 primary brain tumours of astrocytic and oligodendroglial origin, in order to define the potential role of VEGF in the vascularization and growth of these tumours.

METHODS AND RESULTS

Two commercial monoclonal antibodies to the VEGF protein (from R&D Systems and NeoMarkers), raised against different isoforms, were utilized. Each monoclonal antibody consistently detected the expression of VEGF in different cell types. The R&D Systems antibody only produced surface staining of endothelial cells in tumour capillaries, whereas staining with the Neomarkers antibody was largely confined to tumour cell cytoplasm. High levels of staining were seen with the R&D Systems and NeoMarkers antibodies in 13 and 14 of 15 glioblastomas, respectively, four and three of five oligodendrogliomas, four and seven of 10 anaplastic astrocytomas, one and three of six low-grade astrocytomas and none and none of five pilocytic astrocytomas. There was a close correlation between VEGF expression, tumour vascularity and grade.

CONCLUSIONS

These findings support a role for VEGF in the angiogenesis of glioblastoma, anaplastic astrocytoma and oligodendroglioma. The distinct immunoreactivities of the two commercial monoclonal antibodies indicate either there is expression of different splice variants of VEGF or that the epitopes are differentially revealed during synthesis, secretion and receptor-binding of the growth factor. This highlights the importance of using more than one antibody in the evaluation of tissue VEGF expression.

Urokinase receptor and vascular endothelial growth factor are synergistically associated with the liver metastasis of colorectal cancer

Considering recent findings that the urokinase plasniinogen activation (PA) system is involved in invasion and vascular endothelial growth factor (VEGF) is involved in angiogenesis of colorectal cancer, we evaluated these factors in the liver metastasis of primary colorectal cancer. Cancer tissues from 71 colorectal cancer patients were assayed quantitatively for antigen levels of urokinase type plasminogen activator (uPA), uPA receptor (uPAR), and plasminogen activator inhibitor‐1 and ‐2 (PAI‐1, PAI‐2), and were also assayed immunohistochemically for expression of VEGF protein. Among the PA system factors, both the levels of uPAR and PAI‐1 were significantly higher in larger tumors than in smaller ones, and were also significantly higher in tumors that invaded subserosa, serosa or adjacent organs than in mucosal, submucosal tumors or in tumors that invaded the muscle layer. The uPAR levels were significantly higher in tumors with liver metastasis than in those without. VEGF overexpression was significantly more frequent in tumors with lymph node involvement or liver metastasis than in those without. Among the PA system factors, the uPAR levels were significantly higher in tumors with VEGF overexpression and a multivariate analysis revealed that high uPA level and VEGF overexpression were independent risk factors for liver metastasis. The combination of high uPAR level and overexpression of VEGF was associated with the worst prognosis in patients with colorectal cancer. These results suggest that uPAR and VEGF might contribute Synergistically to the liver metastasis of colorectal cancer.