肝细胞癌p53和VEGF的表达及其与肿瘤血管形成的关系

目的 :研究p5 3和血管内皮生长因子 (vascularendothelialgrowthfactor ,VEGF)的表达和肿瘤微血管密度 (microvesseldensity ,MVD)测定在人肝细胞癌 (HCC)中的意义。方法 :采用免疫组织化学方法 ,检测 5 0例HCC患者手术切除标本p5 3和VEGF的表达 ,并用抗CD3 4 抗体标记癌组织血管内皮细胞 ,计算MVD。结果 :p5 3、VEGF总阳性表达率分别为 5 4 0 % (2 7 5 0 )和 76 0 % (38 5 0 ) ,p5 3、VEGF的表达和MVD均与HCC组织病理分级呈正相关 ,P <0 0 5。p5 3和VEGF的阳性表达符合率为 74 % (37 5 0 ) ,两者的表达呈相关性 ,P <0 0 5。p5 3阳性和VEGF阳性的癌组织MVD分别为 178± 6 2和 175±5 9 ,而相应的阴性组分别为 12 5± 5 1和 131± 6 1,两者差异有显著意义 ,P <0 0 5。p5 3、VEGF表达均为阳性者 ,MVD为 176± 6 3;p5 3、VEGF的表达均为阴性者 ,MVD为 12 3± 5 2 ;两者差异有显著意义 ,P <0 0 5。结论 :1)p5 3、VEGF的表达以及MVD的测定可作为判断HCC恶性潜能的重要生物学指标 ;2 )p5 3、VEGF的表达对肿瘤血管形成可能起重要作用 ,联合检测p5 3、VEGF的表达对了解肿瘤血管形成的机制有一定意义     

血管内皮生长因子及其受体在大肠癌中的表达

研究血管内皮生长因子及其受体大肠癌中的表达及其临床意义。「方法」应用免疫组化ＳＰ法检测１５５例大肠癌标本ＶＥＧＦ及ＫＤＲ蛋白的表达。分析ＶＥＧＦ和ＫＤＲ与临床病理因素,微血管计数及预后的关系。「结果」ＶＥＧＦ和ＫＤＲ的表达与大肠癌浸润深度、淋巴结转移、血管侵犯、脏脏转移、Ｄｕｋｅｓ’分期密相关,而与组织学分型和肿瘤大小无关。ＶＥＧＦ和ＫＤＲ的表达密切相关。ＶＥＧＦ和ＫＤＲ表达阳性者ＭＶＣ显著高于阴     

Interleukin-8 in non-small cell lung carcinoma: relation with angiogenic pattern and p53 alterations

Progression of solid tumors, including NSCLC, is associated with increase in MVC (microvessel count), as a measure of tumor angiogenesis resulting from an imbalance between angiogenic factors and inhibitors. However, since tumor angiogenesis is a multi-step process under the control of various molecules, the mechanism of angiogenesis has not been fully clarified. Interleukin (IL)-8 has been shown to have a potential angiogenic effect in vitro and in vivo, and is overexpressed in several human solid cancers. Among the various angiogenic factors, vascular endothelial growth factor (VEGF) has been shown to correlate with a high MVC and with adverse prognosis in several human cancers, including NSCLC. Alterations of p53 suppressor gene are the most common genetic changes found in malignant tumors; several studies examined the link between aberrant p53 and angiogenesis in lung cancer, but only a few studies report data regarding a relation between p53 mutations and IL-8 expression. In this study we observed a correlation between IL-8 mRNA expression, intratumoral MVC and VEGF mRNA expression levels; furthermore, an aberrant p53 status was related to IL-8 expression. However, in our samples IL-8 levels did not significantly affect prognosis of NSCLC; more studies are required to elucidate the precise role of IL-8 in a large series of patients with non-small cell lung carcinoma.     

VEGF expression in the colorectal adenoma-carcinoma sequence

Angiogenesis is essential for tumor growth and metastasis. It is controlled by multiple factors, one of the most important being vascular endothelial growth factor (VEGF). VEGF and p53 expression were evaluated in 16 hyperplastic polyps, 35 solitary tubular and tubulovillous adenomas, and 47 cases of sporadic colorectal carcinomas arising on the basis of preexisting adenomas, using immunohistochemistry. In parallel, angiogenesis was assessed by the Chalkley score (CS) method. VEGF positivity was detected in 19/47 carcinoma cases (40%). In the respective adenomatous part of the tumor, VEGF positivity was detected in 11/47 cases (23%). Carcinomas arising from VEGF-positive adenomas were mostly VEGF positive (10/11, 91%), whereas in 28/36 (78%) carcinomas arising from VEGF-negative adenomas VEGF expression was not detected. CS was higher in VEGF-positive compared with VEGF-negative carcinomas (9.1 +/- 1.8 and 7.8 +/- 2.3, respectively, p < 0.05), whereas there was no statistically significant difference between the CS in the VEGF-negative and VEGF-positive adenomatous part of the tumor (3.3 +/- 1.8 and 4.3 +/- 2.3, respectively). Nuclear p53 positivity was detected in 26/47 (55%) cases in the cancerous part and in 14/47 (29%) cases in the adenomatous part of the tissue, and no significant correlation with VEGF expression was observed. We conclude that VEGF associates with angiogenesis in colorectal cancer, and its pattern of expression in adenomas is maintained in the arising carcinomas. Further investigation is warranted to clarify whether these findings could be used as indicators of prognosis in screening programs or in patients with limited stage disease where the usefulness of adjuvant therapies with either cytotoxic drugs or inhibitors of angiogenesis is still unclear.     

Prognostic significance of expression of thymidine phosphorylase and vascular endothelial growth factor in human gastric carcinoma

BACKGROUND AND OBJECTIVES: Both thymidine phosphorylase (dThdPase) and vascular endothelial growth factor (VEGF) are well-characterized inducers of angiogenesis. The purpose of this study was to examine the expression of these antigens and their prognostic significance in gastric carcinoma. METHODS: Medical records of 102 patients with stage II tumor were retrospectively reviewed. Primary tumors were studied by immunohistochemical staining for dThdPase and VEGF. RESULTS: Positive dThdPase expression was observed in 52 (51%) tumors and positive VEGF expression in 53 (52%) tumors. There was a significant correlation between the positive expression of VEGF and lymphatic invasion. The patients with dThdPase-positive carcinoma showed a significantly worse prognosis than those with dThdPase-negative carcinoma in stage II. Moreover, the frequency of hepatic recurrence was significantly higher in the patients with dThdPase-positive and VEGF-positive tumors than in those with dThdPase-negative and VEGF-negative tumors. CONCLUSIONS: Combination analysis of dThdPase and VEGF expression in gastric carcinoma appears to be well-characterized inductors of prognosis and metastasis.     

Expression of vascular endothelial growth factor in renal cell carcinoma and the relation to angiogenesis and p53 protein expression

BACKGROUND AND OBJECTIVES: Vascular endothelial growth factor (VEGF) seems to play an important role in tumor angiogenesis. The tumor-suppressor gene p53 has been thought to regulate VEGF expression. We investigated the effect of VEGF expression on renal cell carcinoma (RCC) and the correlation between the expression of VEGF and tumor angiogenesis and p53 protein expression. METHODS: Sixty-two RCCs were examined by immunohistochemical studies with anti-VEGF, anti-p53, and anti-CD34 antibodies. RESULTS: Forty tumors (80.6%) were classified as VEGF positive, and 28 tumors (45.2%) were positive for p53 protein. The microvessel density was 75.3 +/- 33.5. A significant correlation was found between VEGF expression and both the nuclear grade (P < 0.05) and the TNM stage (P < 0.05). The tumors with VEGF expression had a significantly higher microvessel density than those without VEGF expression (P < 0.01). There was no statistically significant correlation between p53 protein and VEGF expression. No statistically significant differences in survival were found to be associated with microvessel density, VEGF expression or p53 protein expression. By using multivariate survival analyses, nuclear grade (P < 0.05) and TNM stage (P < 0.05) were the only independent prognostic factors. CONCLUSIONS: Our data do not show a direct regulation of VEGF expression by p53. We suggest that VEGF expression plays a role in the promotion of angiogenesis in RCC.     

The intratumoral expression of vascular endothelial growth factor and interleukin-8 associated with angiogenesis in nonsmall cell lung carcinoma patients.

BACKGROUND: Angiogenesis has important effects on tumor growth and metastasis. It is regulated by a variety of angiogenic and angiostatic factors. METHODS: To evaluate the effects of tumor cell-derived angiogenic factors, we performed an immunohistochemic study to evaluate the intratumoral expression of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) in relation to intratumoral microvessel density (IMD) in tumors from 104 nonsmall cell lung carcinoma (NSCLC)patients. RESULTS: Fifty-four carcinomas were VEGF-positive, 47 carcinomas were IL-8-positive, and 53 carcinomas were hypervascular tumors. There was no significant correlation between the percentages of positive VEGF-staining and positive IL-8-staining in NSCLCs (rho = 0.174, P = 0.080). The IMD of VEGF-positive carcinomas was significantly greater than that of VEGF-negative carcinomas (P = 0.023). In addition, the IMD of IL-8-positive carcinomas was significantly greater than that of IL-8-negative carcinomas (P =0.013). The overall survival rate of patients with hypervascular tumors was significantly lower than that of patients with hypovascular tumors (41.0% versus 67.0%, P = 0.004). Cox proportional-hazards regression model also demonstrated that angiogenesis was one of the significant factors in predicting the survival of NSCLC patients (relative risk = 1.944, P = 0.041). CONCLUSIONS: Intratumoral expression of VEGF and IL-8 was associated with angiogenesis in NSCLCs. Tumor angiogenesis significantly affected the prognosis of NSCLC patients.     

The K-ras gene regulates vascular endothelial growth factor gene expression in non-small cell lung cancers

Tumor angiogenesis is an essential step for tumor cell growth, progression and metastasis. Vascular endothelial growth factor (VEGF) is mitogen specific for endothelial cells, and therefore is believed to play a key role in tumor angiogenesis. However, the mechanisms underlying the regulation of VEGF expression remain virtually unknown and the only major regulator of VEGF expression has been reported to be hypoxia. Recently, it was reported that a mutant p53 in#duced the expression of VEGF mRNA, and that wild-type p53 down-regulated endogenous VEGF mRNA levels. In contrast, it has also been reported that mutant ras oncogenes were associated with the marked up-regulation of VEGF in transformed epithelial cells. Based on these results, we performed a retrospective study of the p53 and K-ras genes status and VEGF gene expression in the tumor tissues from 181 patients with non-small cell lung cancer using SSCP, sequencing, RT-PCR and immunohistochemical techniques. Forty-six carcinomas (25.4%) were evaluated as having high VEGF expression, and 135 tumors (74.6%) had low VEGF expression. Of the 181 primary NSCLC studied, 63 carcinomas (34.8%) contained mutations of p53, whereas only 14 carcinomas (7.7%) had mutations of K-ras. There were no significant relationships between VEGF expression and p53 status or each mutant exon of p53. In contrast, a significant difference was found between VEGF expression and K-ras status. Of the 14 tumors with mutant K-ras genes, 7 cases (50.0%) had high VEGF expression whereas only 39 of the 167 tumors with wild-type K-ras (23.4%) had high VEGF expression (p=0.0278). The mean VEGF conservation rate for the 14 tumors with mutant K-ras genes was 0.77+/-0.58 and the rate of the 167 tumors with wild-type K-ras genes was 0.49+/-0.46 (p=0. 0350). Moreover, the overall survival rate of patients with high VEGF expression was lower than patients with low VEGF expression (45.7% vs 60.7%, p=0.0419). On the other hand, there was no significant difference in the overall survival rate between patients with a mutant p53 and those with a wild-type p53; there was also no difference in the overall survival between patients with a mutant K-ras and those with a wild-type K-ras. The Cox regression model analysis indicated that three variables, VEGF status, K-ras status and nodal status, were found to be significant indicators for prognosis (p=0.0236, p=0.0172 and p<0.0001, respectively). Our data suggest that a high expression of VEGF in lung cancer may be associated with a poor prognosis. This may be a clue to improving lung cancer diagnoses and therapies aimed at inhibiting tumor angiogenesis due to VEGF.     

p53和VEGF在食管鳞癌中的表达及其临床意义

背景与目的:实验研究证明p53和血管内皮生长因子(vascularendothelialgrowthfactor,VEGF)协同表达在肿瘤血管生成中有重要作用。本研究的目的是探讨p53如何参与血管生成,以及p53和血管内皮生长因子的表达与食管鳞癌(esophagealsquamouscellcarcinoma,ESCC)临床病理参数和预后的关系。方法:采用免疫组织化学方法,检测76例食管鳞癌患者手术切除标本p53和VEGF的表达,并用FⅧ因子抗体标记癌组织血管内皮细胞,计数肿瘤内微血管密度(microvesseldensity,MVD)。结果:p53和VEGF的阳性表达率分别为60.5%和56.6%,两者共同表达率为42.1%。p53和VEGF阳性表达率与食管鳞癌的远处转移和血管浸润具有显著相关性(P<0.05;P<0.01)。远处转移和血管浸润最常发生于突变型p53和VEGF均阳性表达的患者。p53(+)或VEGF(+)组MVD(31.7±11.5;33.8±11.7)均显著高于p53(-)或VEGF(-)组(22.4±10.6;21.2±9.3,P<0.05),p53和VEGF均阳性表达时MVD最大(35.2±11.9,P<0.05)。结论:突变型p53表达与食管鳞癌的血管生成和远处转移密切相关;p53和VEGF的表达可作为评估食管鳞癌恶性程度的重要生物学指标,联合检测p53和VEGF表达具有重要的临床应用价值。     

p21^WAF1和VEGF在非小细胞肺癌中的表达及临床相关性研究

目的 研究p21WAFI和血管内皮生长因子的表达和肿瘤内微血管密度测定在非小细胞肺癌中的意义。方法用免疫组化方法对45例非小细胞肺癌患者经纤支镜活检、经皮肺活检取得的标本检测p21WAFI和VEGF的表达,并用CD31抗体标记癌组织血管内皮细胞,计算MVD。结果 p21WAFI和VEGF阳性表达率分别为68.9％和77.8％;二者的表达和MVD均与性别、病理类型无关(P>0.05),与临床分期、癌组织MVD呈正相关(P<0.05);p21WAFI阳性、VEGF阴性组的中位生存期(14个月)与p21WAFI阴性、VEGF阳性组的中位生存期(11个月)相比,差异无显著性(P>0.05);p21WAFI阳性、VEGF阳性组的中位生存期(10个月)与p21WAFI阴性、VEGF阴性组的中位生存期(15个月)相比,差异无显著性(P>0.05)。结论p21WAFI和VEGF在非小细胞肺癌的发生和发展中起着重要作用,可反映非小细胞肺癌的恶性程度和进展情况。作为预后指标,p21WAFI作用的发挥是通过上调VEGF的表达水平来实现的,VEGF的表达对肿瘤血管形成、转移起重要作用。     

p53和VEGF蛋白表达与胆囊癌的关系

目的探讨抑癌基因p53和血管内皮生长因子(vascular endothelial growth factor,VEGF)与胆囊癌的关系。方法采用免疫组化方法分别检测50例胆囊癌、35例胆囊腺瘤和26例慢性胆囊炎组织中p53和VEGF蛋白表达。结果胆囊癌组织中p53和VEGF的阳性表达率分别为64.0%和72.0%,明显高于胆囊腺瘤的17.1%和22.9%及慢性胆囊炎的19.2%和23.1%,χ2=4.25,P=0.006,根据Nevin分期,胆囊癌S1、S2、S3期的p53阳性表达率为63.2%,明显高于S4、S5期的35.5%,χ2=7.29,P=0.009,而VEGF在胆囊癌S4、S5期的阳性表达率为87.1%,明显高于S1、S2、S3期的47.4%,χ2=4.29,P=0.007,胆囊癌中p53和VEGF的阳性表达明显相关,r=0.87,P=0.009。它们与胆囊癌病理分级均未发现明显相关性。结论p53和VEGF的过度表达可能对胆囊癌的发生、发展及预后判断有一定作用。     

Modulation of in vivo growth of thyroid tumor-derived cell lines by sense and antisense vascular endothelial growth factor gene.

Vascular endothelial growth factor A (VEGF) is a potent mitogen for endothelial cells in vitro and promotes neo-angiogenesis in vivo. VEGF overexpression occurs in most human malignancies including thyroid carcinomas in which elevated VEGF expression is associated with a high tumorigenic potential. To investigate the role of VEGF in angiogenesis associated with development of thyroid carcinomas, we constitutively expressed VEGF121 into a poorly tumorigenic cell line (NPA) expressing minimal levels of endogenous VEGF. Here we report that VEGF overexpressing NPA cells showed the same growth potential as untransfected NPA in vitro but formed well-vascularized tumors when injected subcutaneously into nude mice with markedly reduced latency compared to parental cells. A complementary approach was to suppress VEGF expression in a highly tumorigenic anaplastic cell line (ARO) by the transfection of an antisense construct. Antisense-transfected ARO cells expressed reduced constitutive levels of VEGF, showed the same growth potential as untransfected ARO cells in vitro and formed small tumors characterized by minimal vascularization, extensive necrosis and longer latency compared to parental or vector-transfected ARO cells in vivo. Finally, we investigated the expression of both VEGF tyrosine kinase receptors (Flt-1 and Flk-1/KDR) in tumor specimens by RT - PCR. Expression of (Flt-1 and Flk-1/KDR) was low in tissue specimens derived from NPA tumors, but was found enhanced in NPA VEGF tumors; conversely, the expression of VEGF receptors was high in tissue specimens derived from ARO tumors but was decreased in tumors derived from VEGF depleted ARO cells. These results clearly demonstrate that VEGF indirectly promotes the growth of thyroid tumors by stimulating angiogenesis.     

In oesophageal squamous cell carcinoma vascular endothelial growth factor is associated with p53 mutation, advanced stage and poor prognosis.

Vascular endothelial growth factor (VEGF) affects malignant tumours by promoting angiogenesis. The tumour-suppressor gene p53 has been thought to regulate VEGF. We investigated the effect of VEGF on oesophageal carcinoma and the connection between VEGF and p53. One hundred and nine resected oesophageal squamous cell carcinomas were examined. VEGF expression was analysed by immunohistochemical staining. Sixty-five tumours (59.6%, 65 out of 109) were classified as VEGF positive. A significant correlation was found between the VEGF expression and both the depth of invasion (P = 0.0001) and lymph node metastasis (P < 0.0001). With regard to p53, we compared the expression of VEGF with the mutation of p53, examined using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and direct sequencing in tumour samples obtained from 36 patients who we have reported previously. The VEGF expression was significantly correlated to p53 mutation (P = 0.0291). To evaluate the angiogenesis, microvascular density (MVD) was counted, and endothelial cells were stained immunohistochemically using anti-CD34 monoclonal antibody against 29 cases with invasion limited to the submucosal layer. The average MVD had a tendency to correlate to VEGF expression (P = 0.1626). The prognoses of patients with VEGF-positive primary tumours were significantly worse than for those with VEGF-negative primary tumours (P = 0.0077). We have assumed that VEGF contributes to aggressive characteristics in oesophageal carcinomas and that VEGF expression might be affected by p53 status.     

Expression of vascular endothelial growth factor,mitogen-activated protein kinase and p53 in human colorectal cancer

BACKGROUND: VEGF is a growth factor involved in the regulation of angiogenesis, a process that plays a central role in tumor growth. It has been suggested that mutations of p53 and activation of the Ras/MAPK pathway may contribute to the up-regulation of VEGF expression and induction of angiogenesis. PATIENTS AND METHODS: We explored the expression of p53 and VEGF and p44MAPK phosphorylation in 43 human colorectal carcinomas, as well as in peritumoral mucosas, and in normal mucosas in order to establish a correlation between VEGF expression and either mutations of p53 or phosphorylation of p44MAPK. Overexpression of p53 in tumor tissues was interpreted as evidence of mutations. RESULTS: p53 was overexpressed in 22 out of 43 tumors; MAPK was phosphorylated in 25 out of 43 cases whereas only 4 out of 22 peritumoral mucosas showed a moderate phosphorylation of p44MAPK VEGF was up-regulated in 22 out of 43 tumors, moderately expressed in 4 out of 22 peritumoral mucosas and not detectable in normal mucosa. Immunohistochemical analysis showed the presence of a phosphorylated form of p44 MAPK only in neoplastic cells. Statistical analysis demonstrated a significant correlation between p53 and VEGF expression (p<0.03) as well as between VEGF expression and p44 MAPK phosphorylation (p<0.002). CONCLUSION: These data suggest that mutations of p53 and activation of the Ras/MAPK pathway may play a role in the induction of VEGF expression in human colorectal cancer.     

Transforming growth factor-beta and Ras regulate the VEGF/VEGF-receptor system during tumor angiogenesis.

The formation of new microvasculature by capillary sprouting, or angiogenesis, is a prerequisite for solid tumor growth. The genetic alterations required to activate the angiogenic program in tumor angiogenesis are still only vaguely known, but dominantly acting oncoproteins may have a much greater impact than previously realized. Here we have studied the consequences of oncogenic transformation on tumor angiogenesis in a mouse mammary carcinoma model. We provide evidence that the expression of vascular endothelial growth factor (VEGF) and of the VEGF receptor-2 (Flk-1), a signaling system centrally involved in tumor angiogenesis, occurs efficiently in tumors formed by Ras-transformed mammary epithelial cells and that both TGF-beta1 and hypoxia are potent inducers of VEGF expression in these cells. VEGF induction in the tumor periphery is mainly triggered by TGF-beta1, whereas VEGF expression in perinecrotic areas is regulated by both hypoxia and TGF-beta1. As the Ras-transformed tumor cells convert into migrating, fibroblastoid cells that start to produce TGF-beta during tumor progression, the TGF-beta effect on VEGF expression becomes propagated throughout the tumor tissue. Thus, in progressed tumors, areas of TGF-beta1 activation and hypoxia may overlap and hence cooperate to induce VEGF expression and angiogenesis. Nevertheless, the overexpression of VEGF in non-Ras-transformed mouse mammary epithelial cells was not sufficient to promote vascularization in vivo. Based on these findings, we conclude that amongst the multiple mutations that render a normal cell tumorigenic, oncogenic Ras is a major player that in conjunction with the tumor's micro-environment sets the stage for tumor cell invasion and angiogenesis.     

VEGF receptor antisense therapy inhibits angiogenesis and peritoneal dissemination of human gastric cancer in nude mice

The efficacy of a phosphorothioate antisense oligonucleotide (ASO) for KDR/Flk-1 (KDR/Flk-1-ASO), an endothelial cell-specific vascular endothelial growth factor (VEGF) receptor, was investigated on the peritoneal dissemination and angiogenesis of a human gastric cancer cell line in nude mice. Green fluorescent protein (GFP)-transduced NUGC-4 (NUGC-4-GFP) human gastric cancer cells were implanted into the peritoneal cavity of nude mice. KDR/Flk-1-ASO, -SO, or phosphate-buffered saline was administrated from days 7 to 14, 200 microg/mouse, once a day. The mice were sacrificed on day 28. Disseminated peritoneal tumor nodules expressing GFP were visualized by fluorescence microscopy. KDR/Flk-1-ASO significantly decreased the extent of peritoneal dissemination of the tumors. The number of cells undergoing apoptosis was significantly increased in the KDR/Flk-1-ASO-treated tumors. Microvessel density was significantly reduced in the KDR/Flk-1-ASO-treated tumor nodules. The KDR/Flk-1 antisense strategy, therefore, decreases tumor dissemination apparently by inhibiting angiogenesis.     

Formation of transformed endothelial cells in the absence of VEGFR-2/Flk-1 by Polyoma middle T oncogene.

The middle T antigen of murine Polyomavirus (PymT) rapidly transforms endothelial cells leading to vascular malformations reminiscent of endothelial tumors or hemangiomas. Flk-1, a receptor tyrosine kinase which is activated upon binding of its ligand VEGF, is predominantly expressed in endothelial cells and essential for the formation of blood vessels since absence of Flk-1 prevents the development of mature endothelial cells in mice and in ES-cell differentiation experiments. To investigate the role of Flk-1 in PymT-induced vascular tumor formation, we studied the expression of Flk-1 and VEGF in PymT-transformed endothelial cells (Endothelioma cells, END. cells). The receptor and its ligand were both expressed in END. cells suggesting that a VEGF/Flk-1 autocrine loop might be causally involved in the formation of vascular tumors. To test this hypothesis, ES cells lacking Flk-1 were generated and the transforming potential of PymT was analysed after in vitro differentiation. Flk-1(-/-) END. cell lines were established which are morphologically identical to flk-1(+/+) END. cells and which express several markers characteristic for endothelial cells. This result suggests that PymT functionally replaces the requirement of Flk-1 in expansion and/or survival of endothelial progenitor cells. Therefore, flk-1(-/-) END. cells provide a powerful tool to dissect the downstream signaling pathways of Flk-1.     

Expression of p53, inducible nitric oxide synthase and vascular endothelial growth factor in gastric precancerous and cancerous lesions: correlation with clinical features

Background  

The growth and metastasis of tumors depend on the development of an adequate blood supply via angiogenesis. Recent studies indicate that the inducible nitric oxide synthase (iNOS), vascular endothelial growth factor (VEGF) and the tumor suppressor p53 are fundamental play-markers of the angiogenic process. Overexpression of iNOS and VEGF has been shown to induce angiogenesis in tumors. P53 suppresses angiogenesis by down-regulating VEGF and iNOS. The correlation of expression of p53, VEGF and iNOS and clinical features in gastric carcinogenesis, however, has not been well characterized.