Angiotensin type 1a receptor signaling-dependent induction of vascular endothelial growth factor in stroma is relevant to tumor-associated angiogenesis and tumor growth

Angiotensin II is a multi-functional bioactive peptide and recent reports have suggested that angiotensin II is a proangiogenic growth factor. A retrospective cohort study revealed that angiotensin converting enzyme inhibitors decreased cancer risk, however, the precise mechanism is unknown. We hypothesized that endogenous angiotensin II plays a crucial role in tumor-associated angiogenesis. Tumors implanted in the subcutaneous tissue of wild-type mice developed intensive angiogenesis with vascular endothelial growth factor (VEGF) induction in tumor stroma. AT1a receptor (AT1a-R), but not AT1b receptor or AT2 receptor was expressed in tumor stroma and systemic administration of an AT1-R antagonist reduced tumor-associated angiogenesis and VEGF expression in tumor stroma. Angiotensin II up-regulates VEGF expression through the pathway including protein kinase C, AP-1 and NF-kappaB in fibroblasts, the major cellular component of tumor stroma. VEGF is a major determinant of tumor-associated angiogenesis in the present model, since angiogenesis was markedly reduced by either a VEGF neutralizing antibody or a VEGF receptor kinase inhibitor. Compared with the wild-type, tumor-associated angiogenesis was reduced in AT1a-R null mice, with reduced expression of VEGF in the stroma, and this reduction in AT1a-R null mice was not inhibited by an AT1-R antagonist. These suggest that host stromal VEGF induction by AT1a-R signaling is a key regulator of tumor-associated angiogenesis and tumor growth. AT1a-R signaling blockade may be a novel and effective therapeutic strategy against cancers.     

Inhibition of DNA synthesis and growth in human breast stromal cells by bradykinin: evidence for independent roles of B1 and B2 receptors in the respective control of cell growth and phospholipid hydrolysis.

The paracrine and intracellular mechanisms controlling stromal cell growth in the normal or neoplastic breast are unknown. This in vitro study uses human breast fibroblasts to investigate a potential role for the inflammatory peptide mediator bradykinin (BK) in the regulation of DNA synthesis and signal transduction in these cells. Bradykinin stimulated a dose-dependent increase in inositol lipid hydrolysis and cytosolic Ca2+ levels in serum-starved fibroblasts derived from both normal and breast tumor tissue. Bradykinin also caused a dose-dependent decrease in cell growth and [3H]thymidine incorporation into DNA in breast fibroblasts. Epidermal growth factor (EGF) and insulin-like growth factor 1 both stimulated DNA synthesis in breast fibroblasts. Bradykinin inhibited this mitogenic effect of EGF but not that due to insulin-like growth factor 1. The binding of 125I-labeled EGF to fibroblasts was also inhibited by BK. Prostaglandin E2 also inhibited fibroblast DNA synthesis, and the cyclooxygenase inhibitor indomethacin partially reversed the inhibitory action of BK on DNA synthesis. Studies with BK receptor antagonists and agonists indicate that inositol lipid signalling and arachidonic acid mobilization in response to BK are B2 receptor-mediated pathways, whereas the inhibition of DNA synthesis appears to be via B1 receptors. Although these data support a role for prostaglandins and EGF receptor down-modulation in the inhibitory action of BK on DNA synthesis in breast fibroblasts, a B1 receptor-mediated pathway is also implicated. This study highlights a potential pathophysiological role for BK as a negative regulator of breast stromal cell growth.     

The VEGF angiogenic switch of fibroblasts is regulated by MMP-7 from cancer cells

Vascular endothelial growth factor (VEGF) production by stromal fibroblasts plays an important role in tumor angiogenesis. However, VEGF is also expressed by normal tissue fibroblasts, raising the question of how the VEGF activity of fibroblasts is regulated. Here we report that the latent VEGF angiogenic activity of fibroblasts is activated by cancer cells, resulting in tumor-selective utilization of fibroblast-derived VEGF. Through the production of VEGF, human VA-13 fibroblasts promote angiogenesis in and growth of human pancreas cancer Capan-1 xenograft tumors, whereas VA-13 fibroblasts alone do not show significant angiogenesis. Treatment of VA-13 fibroblast supernatant with matrix metalloproteinase-7 (MMP-7), an extracellular proteinase characteristically expressed by cancer cells, elicits endothelial tube formation. This effect is abrogated by anti-VEGF antibody or connective tissue growth factor (CTGF), which was previously reported to sequester VEGF and be degraded by MMP-7. Suppression of MMP-7 in Capan-1 cells abrogates the tumor angiogenic activity of VA-13 fibroblasts, which is restored by suppression of CTGF in VA-13 fibroblasts. We further show that these molecular mechanisms that trigger angiogenesis are effective in human primary fibroblasts and human colorectal tissue. These data suggest that fibroblasts may store VEGF in a latent state in the extracellular environment for urgent use in angiogenesis.     

Stromal expression of connective tissue growth factor promotes angiogenesis and prostate cancer tumorigenesis

Our previous studies have defined reactive stroma in human prostate cancer and have developed the differential reactive stroma (DRS) xenograft model to evaluate mechanisms of how reactive stroma promotes carcinoma tumorigenesis. Analysis of several normal human prostate stromal cell lines in the DRS model showed that some rapidly promoted LNCaP prostate carcinoma cell tumorigenesis and others had no effect. These differential effects were due, in part, to elevated angiogenesis and were transforming growth factor (TGF)-beta1 mediated. The present study was conducted to identify and evaluate candidate genes expressed in prostate stromal cells responsible for this differential tumor-promoting activity. Differential cDNA microarray analyses showed that connective tissue growth factor (CTGF) was expressed at low levels in nontumor-promoting prostate stromal cells and was constitutively expressed in tumor-promoting prostate stromal cells. TGF-beta1 stimulated CTGF message expression in nontumor-promoting prostate stromal cells. To evaluate the role of stromal-expressed CTGF in tumor progression, either engineered mouse prostate stromal fibroblasts expressing retroviral-introduced CTGF or 3T3 fibroblasts engineered with mifepristone-regulated CTGF were combined with LNCaP human prostate cancer cells in the DRS xenograft tumor model under different extracellular matrix conditions. Expression of CTGF in tumor-reactive stroma induced significant increases in microvessel density and xenograft tumor growth under several conditions tested. These data suggest that CTGF is a downstream mediator of TGF-beta1 action in cancer-associated reactive stroma and is likely to be one of the key regulators of angiogenesis in the tumor-reactive stromal microenvironment.     

Combining Molecular Targeted Drugs to Inhibit Both Cancer Cells and Activated Stromal Cells in Gastric Cancer

Recent studies have revealed that PDGF plays a role in promoting progressive tumor growth in several cancers, including gastric cancer. Cancer-associated fibroblasts, pericytes, and lymphatic endothelial cells in stroma express high levels of PDGF receptor (PDGF-R); cancer cells and vascular endothelial cells do not. Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that increases the production of proteins that stimulate key cellular processes such as cell growth and proliferation, cell metabolism, and angiogenesis. In the present study, we examined the effects of PDGF-R tyrosine kinase inhibitor (nilotinib) and mTOR inhibitor (everolimus) on tumor stroma in an orthotopic nude mice model of human gastric cancer. Expression of PDGF-B and PDGF-Rβ mRNAs was associated with stromal volume. Treatment with nilotinib did not suppress tumor growth but significantly decreased stromal reactivity, lymphatic invasion, lymphatic vessel area, and pericyte coverage of tumor microvessels. In contrast, treatment with everolimus decreased tumor growth and microvessel density but not stromal reactivity. Nilotinib and everolimus in combination reduced both the growth rate and stromal reaction. Target molecule-based inhibition of cancer-stromal cell interaction appears promising as an effective antitumor therapy.     

Human breast tumors override the antiangiogenic effect of stromal thrombospondin-1 in vivo

The antiangiogenic extracellular matrix protein thrombospondin-1 (TSP-1) inhibits tumor growth and metastasis in animals. However, the clinical relevance of such findings are equivocal as increased stromal TSP-1 expression has been associated with either good or poor prognosis. In an effort to obtain a more integrated understanding of the role of TSP-1 in breast cancer, we first used a breast tumorigenesis model in which tumor-associated stromal fibroblasts were engineered to produce high levels of TSP-1. We demonstrate here that stromal TSP-1 delayed human MDA-MB-231/B02 breast tumor growth. However, this delay in MDA-MB-231/B02 tumor growth upon exposure to TSP-1 was associated with an increased vascular endothelial growth factor (VEGF) expression in tumor cells themselves, leading to a tumor growth rate comparable to that of tumors whose fibroblasts did not overproduce TSP-1. Clinical evidence also suggested that primary breast carcinomas have adapted to escape the effects of stromal TSP-1. TSP-1 was found to be expressed in the stroma of human breast carcinomas where, although its level correlated with decreased vascularization, it was unexpectedly associated with a reduction of relapse-free survival. In metastatic axillary lymph nodes, tumor cells expressed high levels of VEGF and TSP-1 expression were no longer associated with a decreased vascularization. Overall, these results suggest that a resistance may develop early in human breast cancers as a result of high in situ exposure to stromal TSP-1, leading to disease progression.     

癌相关成纤维细胞通过Gro-α激活NF-кB核转位和VEGF表达促进卵巢癌的生长

背景与目的：卵巢癌相关成纤维细胞(cancer-associated fibroblasts,CAF)促进上皮肿瘤的发生,其分泌的趋化因子即生长调节致癌基因α(growth-regulated oncogene alpha,Gro-α)蛋白在肿瘤间质微环境中促进上皮卵巢癌的发生,但其作用机制并不清楚。本研究拟测定Gro-α蛋白是否通过激活间质成纤维细胞中NF-кB核转位和VEGF表达,促进卵巢癌的生长。方法：本研究采用ELISA法测定了两株卵巢癌CAF和两株正常卵巢组织成纤维细胞(normal fibroblasts,NF)条件培养基(conditioned medium,CM)中Gro-α的表达;用CAF-CM或Gro-α分别处理NF,并以NF-кB抑制剂处理作为对照;用蛋白质印迹法(Western blot)测定样品处理前后NF-кB和血管内皮细胞生长因子(vascular endothelial growth factor,VEGF)等分子的变化;然后用CAF或NF分别与卵巢癌细胞系OVCA429混合接种BALB/c裸小鼠,或在有、无NF-кB抑制剂PS1145处理的NF中,用CAFCM或Gro-α处理后,分别与OVCA429混合接种动物,观察和比较动物移植瘤生长及移植瘤组织中微血管形成情况。结果：Gro-α在CAF中比在NF中高5～6倍;与对照组相比,用CAF条件培养基或Gro-α处理的NF中NF-кB p65的核转位升高,且VEGF上升,但血管生成抑制因子-血小板反应蛋白1下降;用NF-кB抑制剂同时处理NF,可以逆转其VEGF和TSP-1的表达水平;动物试验结果发现CAF要比NF更易促进肿瘤生长,而CAF-CM或Gro-α处理的NF细胞可以促进动物移植瘤的快速增长和移植瘤组织中微血管的生成,但用NF-кB抑制剂处理的NF则抑制肿瘤生长和血管形成能力。结论：卵巢癌CAF在肿瘤微环境中通过自分泌Gro-α,激活NF-кB核转位和VEGF表达,促进卵巢癌组织血管增生和肿瘤的生长。     

Multikinase inhibitor regorafenib inhibits the growth and metastasis of colon cancer with abundant stroma

Interaction between tumor cells and stromal cells plays an important role in the growth and metastasis of colon cancer. We previously found that carcinoma‐associated fibroblasts (CAFs) expressed platelet‐derived growth factor receptor‐β (PDGFR‐β) and that PDGFR targeted therapy using imatinib or nilotinib inhibited stromal reaction. Bone marrow‐derived mesenchymal stem cells (MSCs) migrate to tumor stroma and differentiate into CAFs. A novel oral multikinase inhibitor regorafenib inhibits receptor tyrosine kinases expressed on stromal cells (vascular endothelial growth factor receptor 1–3, TIE2, PDGFR‐β, and fibroblast growth factors) and tumor cells (c‐KIT, RET, and BRAF). These molecules are involved in tumor growth, angiogenesis, lymphangiogenesis, and stromal activation. Therefore, we examined whether regorafenib impaired the tumor‐promoting effect of CAFs/MSCs. KM12SM human colon cancer cells alone or KM12SM cells with MSCs were transplanted into the cecal wall of nude mice. Co‐implantation of KM12SM cells with MSCs into the cecal wall of nude mice produced tumors with abundant stromal component and promoted tumor growth and lymph node metastasis. Single treatment with regorafenib inhibited tumor growth and metastasis by inhibiting both tumor cells and stromal reaction. This tumor‐inhibitory effect of regorafenib was more obvious in tumors developed by co‐implanting KM12SM cells with MSCs. Our data suggested that targeting of the tumor microenvironment with regorafenib affected tumor cell–MSC interaction, which in turn inhibited the growth and metastasis of colon cancer.     

Angiogenesis in gastric cancer: importance of the thymidine phosphorylase expression of cancer cells as an angiogenic factor

Thymidine phosphorylase (TP) has been reported to stimulate angiogenesis in a variety of human malignancies. We investigated TP expression and its association with angiogenesis in 73 cases of resected gastric cancer. In addition, we compared the expression of the other angiogenesis related factors (VEGF, eNOS and p53) with that of TP with respect to angiogenesis. TP expression was not detected in most of the non-tumoral glandular epithelial cells except for 5 cases. TP expression of the cancer cells and the stroma was assessed separately. The stromal TP expression was not associated with the TP expression of the cancer cells. The mean percent of TP reactive cancer cells was 18.36+/-2.61 (median, 10.00; range, 0-90) and cases showing a percentage higher than the mean were considered as bearing high reactivity. The mean microvessel score assessed was 90.44+/-3.69 (median, 86; range, 31-174). The TP expression of cancer cells was strongly associated with microvessel density (p=0.030), but the stromal TP expression was not. The microvessel density of the tumor showed strong correlation with VEGF expression (p<0.001), but a marginally significant association with eNOS (p=0.055). On the contrary, there was no association with p53 expression and microvessel density of the tumor. No significant correlation was detected between lymph node metastasis and tumoral or stromal TP expression or VEGF/TP coexpression. In gastric cancer, TP expression of the cancer cells, not stromal cells may play an important role in tumor growth by microvessel formation.     

Vascular stroma formation in carcinoma in situ, invasive carcinoma, and metastatic carcinoma of the breast.

The generation of vascular stroma is essential for solid tumor growth and involves stimulatory and inhibiting factors as well as stromal components that regulate functions such as cellular adhesion, migration, and gene expression. In an effort to obtain a more integrated understanding of vascular stroma formation in breast carcinoma, we examined expression of the angiogenic factor vascular permeability factor (VPF)/vascular endothelial growth factor (VEGF); the VPF/VEGF receptors flt-1 and KDR; thrombospondin-1, which has been reported to inhibit angiogenesis; and the stromal components collagen type I, total fibronectin, ED-A+ fibronectin, versican, and decorin by mRNA in situ hybridization on frozen sections of 113 blocks of breast tissue from 68 patients including 28 sections of breast tissue without malignancy, 18 with in situ carcinomas, 56 with invasive carcinomas, and 8 with metastatic carcinomas. A characteristic expression profile emerged that was remarkably similar in invasive carcinoma, carcinoma in situ, and metastatic carcinoma, with the following characteristics: strong tumor cell expression of VPF/VEGF; strong endothelial cell expression of VPF/VEGF receptors; strong expression of thrombospondin-1 by stromal cells and occasionally by tumor cells; and strong stromal cell expression of collagen type I, total fibronectin, ED-A+ fibronectin, versican, and decorin. The formation of vascular stroma preceded invasion, raising the possibility that tumor cells invade not into normal breast stroma but rather into a richly vascular stroma that they have induced. Similarly, tumor cells at sites of metastasis appear to induce the vascular stroma in which they grow. We conclude that a distinct pattern of mRNA expression characterizes the generation of vascular stroma in breast cancer and that the formation of vascular stroma may play a role not only in growth of the primary tumor but also in invasion and metastasis.     

Myeloid-derived suppressor cells contribute to A2B adenosine receptor-induced VEGF production and angiogenesis in a mouse melanoma model

Vascular endothelial growth factor (VEGF) is an angiogenic factor critically involved in tumor progression. Adenosine A2B receptor plays a pivotal role in promoting tumor growth. The aim of this study was to investigate the role of myeloid-derived suppressor cells (MDSCs) in the pro-angiogenic effects of A2B and to determine whether A2B blockade could enhance the effectiveness of anti-VEGF treatment. Mice treated with Bay60-6583, a selective A2B receptor agonist, showed enhanced tumor VEGF-A expression and vessel density. This effect was associated with accelerated tumor growth, which could be reversed with anti-VEGF treatment. Bay60-6583 increased the accumulation of tumor CD11b+Gr1+ cells. Depletion of MDSCs in mice significantly reduced A2B-induced VEGF production. However, A2B receptor stimulation did not directly regulate VEGF expression in isolated tumor myeloid cells. Mechanistically, Bay60-6583-treated melanoma tissues showed increased STAT3 activation. Inhibition of STAT3 significantly decreased the pro-tumor activity of Bay60-6583 and reduced tumor VEGF expression.Pharmacological blockade of A2B receptor with PSB1115 significantly reduced tumor growth by inhibiting tumor angiogenesis and increasing T cells numbers within the tumor microenvironment. These effects are, at least in part, dependent on impaired tumor accumulation of Gr1+ cells upon A2B receptor blockade. PSB1115 increased the effectiveness of anti-VEGF treatment.     

Extracellular matrix metalloproteinase inducer stimulates tumor angiogenesis by elevating vascular endothelial cell growth factor and matrix metalloproteinases

Matrix metalloproteinases (MMPs) are endopeptidases that play pivotal roles in promoting tumor disease progression, including tumor angiogenesis. In many solid tumors, MMP expression could be attributed to tumor stromal cells and is partially regulated by tumor-stroma interactions via tumor cell-associated extracellular matrix metalloproteinase inducer (EMMPRIN). The role of EMMPRIN during tumor angiogenesis and growth was explored by modulating EMMPRIN expression and activity using recombinant DNA engineering and neutralizing antibodies. In human breast cancer cells, changes in EMMPRIN expression influenced vascular endothelial growth factor (VEGF) production at both RNA and protein levels. In coculture of tumor cells and fibroblasts mimicking tumor-stroma interactions, VEGF expression was induced in an EMMPRIN- and MMP-dependent fashion, and was further enhanced by overexpressing EMMPRIN. Conversely, VEGF expression was inhibited by suppressing EMMPRIN expression in tumor cells, by neutralizing EMMPRIN activity, or by inhibiting MMPs. In vivo, EMMPRIN overexpression stimulated tumor angiogenesis and growth; both were significantly inhibited by antisense suppression of EMMPRIN. Expression of both human and mouse VEGF and MMP, derived from tumor and host cells, respectively, was regulated by EMMPRIN. These results suggest a novel tumor angiogenesis mechanism in which tumor-associated EMMPRIN functionally mediates tumor-stroma interactions and directly contributes to tumor angiogenesis and growth by stimulating VEGF and MMP expression.     

Growth factor-mediated interaction between tumor cells and stromal fibroblasts in an experimental model of human small-cell lung cancer

Malignant tumors induce development of their own stromal tissues during the processes of growth, progression and metastasis. Since the vascular architecture among the various stromal elements is well known to facilitate tumor growth and has been a target of therapy, the importance of stromal fibroblasts has recently been established. To elucidate the interaction between the tumor and its stromal fibroblasts, the present study took advantage of a unique experimental model consisting of a human small-cell lung cancer cell line, WA-ht, and its mouse stromal fibroblast cell line, WA-mFib, both originally derived from a xenograft tumor in a mouse subcutis. Co-culture with the WA-mFib cells significantly augmented the plating efficiency of WA-hT cells in vitro, and their co-inoculation in nude mice shortened latency and tumor doubling time. Histochemical detection of beta-gal, transfected into WA-mFib cells, demonstrated their contribution to the nude mouse xenograft tumor formation as its tumor stroma. Elevated hepatocyte growth factor (HGF) from fibroblasts followed by elevated production of vascular endothelial growth factor (VEGF) from both tumor cells and fibroblasts were demonstrated by ELISA in supernatants of their co-culture, accompanied by enhanced colonogenicity of the tumor cells; these enhanced features were not observed in their respective monocultures. Antisense oligonucleotides to HGF cancelled these augmentation effects with co-culture. The findings highlight the substantial roles of tumor stromal fibroblasts, interacting with soluble growth factors, in promoting the malignant propensity of the tumor.     

Angiogenesis inhibition by vascular endothelial growth factor receptor-2 blockade reduces stromal matrix metalloproteinase expression, normalizes stromal tissue, and reverts epithelial tumor phenotype in surface heterotransplants

Inhibition of vascular endothelial growth factor (VEGF) signaling, a key regulator of tumor angiogenesis, through blockade of VEGF receptor (VEGFR)-2 by the monoclonal antibody DC101 inhibits angiogenesis, tumor growth, and invasion. In a surface xenotransplant assay on nude mice using a high-grade malignant squamous cell carcinoma cell line (A-5RT3), we show that DC101 causes vessel regression and normalization as well as stromal maturation resulting in a reversion to a noninvasive tumor phenotype. Vessel regression is followed by down-regulation of expression of both VEGFR-2 and VEGFR-1 on endothelial cells and increased association of alpha-smooth muscle actin-positive cells with small vessels indicating their normalization, which was further supported by a regular ultrastructure. The phenotypic regression of an invasive carcinoma to a well-demarcated dysplastic squamous epithelium is accentuated by the establishment of a clearly structured epithelial basement membrane and the accumulation of collagen bundles in the stabilized connective tissue. This normalization of the tumor-stroma border coincided with down-regulated expression of the stromal matrix metalloproteinases 9 and 13, which supposedly resulted in attenuated turnover of extracellular matrix components permitting their structural organization. Thus, in this mouse model of a human squamous cell carcinoma cell line, blockade of VEGF signaling resulted in the reversion of the epithelial tumor phenotype through stromal normalization, further substantiating the crucial role of stromal microenvironment in regulating the tumor phenotype.     

VEGF及其受体KDR在宫颈癌的联合表达与局部肿瘤血管生成的关系

目的:探讨血管内皮生长因子及其受体KDR在早期宫颈癌的表达及其对宫颈癌肿瘤血管生成的作用。方法:采用免疫组织化学SP法检测18例宫颈上皮内瘤样病变(cervicalintraepithelialneoplasm,CIN)、75例早期宫颈癌(invasivecarcinomaofcervix,ICC)和15例正常宫颈上皮(normalcervicalepithelium,NCE)中VEGF和KDR的表达情况,并检测其中微血管密度(CD34标记)。结果:在ICC中,VEGF和KDR主要表达于癌细胞膜和(或)细胞浆;而CD34主要表达于癌巢间质血管内皮细胞。从NCE到CIN再到ICC,VEGF与KDR的阳性表达率以及MVD均显著升高(P<0.01)。在ICC中,VEGF、KDR阳性表达者其MVD分别显著高于VEGF、KDR阴性表达者(P<0.05)。VEGF在ICC的表达与KDR显著正相关(r=0.56,P<0.01),并且两者均与MVD显著正相关(前者r=0.60,P<0.01;后者r=0.33,P<0.01)。VEGF与KDR均阳性表达者,其微血管密度显著高于两者均阴性表达者(P<0.01)。结论:VEGF及其受体KDR表达在宫颈癌肿瘤血管生成中起上调作用,两者均过度表达,肿瘤血管生成显著增加。检测VEGF及其受体KDR的联合表达对进一步了解宫颈癌血管生成情况以及寻找抗肿瘤血管生成治疗新靶点有一定价值。     

Over expression of vascular endothelial growth factor and its receptor during the development of estrogen-induced rat pituitary tumors may mediate estrogen-initiated tumor angiogenesis

Estrogens, which have been associated with several types of human and animal cancers, can induce tumor angiogenesis in the pituitary of Fischer 344 rats. The mechanistic details of tumor angiogenesis induction, during estrogen carcinogenesis, are still unknown. To elucidate the role of estrogen in the regulation of tumor angiogenesis in the pituitary of female rats, the density of blood vessels was analysed using factor VIII related antigen (FVIIIRAg) immunohistochemistry and the expression of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) was examined by Western blot and immunohistochemical analysis. The expression of VEGF receptor (VEGFR-2/Flk-1/KDR) was also examined by immunohistochemistry. The results demonstrated that 17beta-estradiol (E2) induces neovascularization, as well as the growth and enlargement of blood vessels after 7 days of exposure. The high tumor angiogenic potential was associated with an elevated VEGF/VPF protein expression in the E2 exposed pituitary of ovariectomized (OVEX) rats. VEGF/VPF and FVIIIRAg immunohistochemistry and endothelial specific lectin (UEA1) binding studies, indicate that the elevation of VEGF protein expression initially occurred in both blood vessels and non-endothelial cells. After 15 days of E2 exposure, VEGF/VPF protein expression, in the non- endothelial cell population, sharply declined and was restricted to the blood vessels. The function of non-endothelial-derived VEGF is not clear. Furthermore, immunohistochemical studies demonstrated that VEGFR- 2 (flk-1/KDR), expression was elevated significantly in the endothelial cells of microblood vessels after 7 days of E2 exposure. These findings suggest that over expression of VEGF and its receptor (VEGFR-2) may play an important role in the initial step of the regulation of estrogen induced tumor angiogenesis in the rat pituitary.      

Thymidine phosphorylase and vascular endothelial growth factor in patients with Stage I lung adenocarcinoma

BACKGROUND: Thymidine phosphorylase (TP) has chemotactic activity in endothelial cells in vitro and angiogenic activity in vivo. However, the clinical significance of TP and cooperative roles of TP with other angiogenic factors have remained unclear in nonsmall cell lung carcinoma (NSCLC). METHODS: The authors stained for TP, vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) in 132 tumors from patients with Stage I NSCLC. They compared TP, VEGF, and bFGF expression levels with microvessel counts (MVCs), macrophage counts, mast cell counts, and clinical outcomes of patients with Stage I NSCLC. RESULTS: In adenocarcinoma samples, only stromal cell-TP expression and tumor cell-VEGF expression were associated with MVCs and mast cell counts but not with macrophage counts. In squamous cell carcinoma samples, there were no significant associations of the expression of any examined angiogenic factors with MVCs, mast cell counts, or macrophage counts. More importantly, only among patients with Stage I adenocarcinoma of the lung did patients in the stromal cell-TP positive tumor group and in the tumor cell-VEGF positive tumor group have a significantly worse prognosis compared with patients in the stromal cell-TP negative tumor group and in the tumor cell VEGF negative group, respectively. In addition, among patients with Stage I adenocarcinoma, patients in the stromal cell-TP positive and tumor cell-VEGF positive tumor group had a significantly worse prognosis among the four groups. CONCLUSIONS: TP induction in tumoral stroma, but not in tumor cells, and tumor cell-VEGF induction may promote angiogenesis cooperatively in adenocarcinoma of the lung. Stromal cell-TP expression and tumor cell-VEGF expression may be important prognostic factors in adenocarcinoma of the lung, and stromal cell-TP expression may be a marker of active remodeling stroma in adenocarcinoma of the lung.     

Interleukin-6 released by colon cancer-associated fibroblasts is critical for tumour angiogenesis: anti-interleukin-6 receptor antibody suppressed angiogenesis and inhibited tumour–stroma interaction

Background:

Interleukin-6 (IL-6) has an important role in cancer progression, and high levels of plasma IL-6 are correlated with a poor prognosis in a variety of cancers. It has also been reported that tumour stromal fibroblasts are necessary for steps in cancer progression, such as angiogenesis. There have been few reports of a correlation between fibroblast actions and IL-6 levels. In this study, we examined the correlation between cancer stromal fibroblasts and IL-6 and the utility of IL-6 as a therapeutic target in human colon cancer.

Methods:

The expression levels of IL-6 and VEGF of fibroblasts and cancer cell lines were evaluated using real-time PCR and ELISA. The anti-angiogenic effect of inhibiting IL-6 signalling was measured in an angiogenesis model and animal experiment.

Results:

We demonstrate that stromal fibroblasts isolated from colon cancer produced significant amounts of IL-6 and that colon cancer cells enhanced IL-6 production by stromal fibroblasts. Moreover, IL-6 enhanced VEGF production by fibroblasts, thereby inducing angiogenesis. In vivo, anti-IL6 receptor antibody targeting stromal tissue showed greater anti-tumour activity than did anti-IL6 receptor antibody targeting xenografted cancer cells.

Conclusion:

Cancer stromal fibroblasts were an important source of IL-6 in colon cancer. IL-6 produced by activated fibroblasts induced tumour angiogenesis by stimulating adjacent stromal fibroblasts. The relationship between IL-6 and stromal fibroblasts offers new approaches to cancer therapy.