Melatonin inhibits the expression of vascular endothelial growth factor in pancreatic cancer cells

Objective:To investigate the effects of melatonin on cellular proliferation and endogenous vascular endothelial growth factor(VEGF) expression in pancreatic carcinoma cells(PANC-1).Methods:PANC-1 cells were cultured for this study.The secreted VEGF concentration in the culture medium was determined using ELISA method,VEGF production in the tumor cells was detected by immunocytochemistry,and VEGF mRNA expression was determined by RT-PCR.Results:Higher melatonin concentrations significantly inhibited cellular proliferation,with 1 mmol/L concentration exhibiting the highest inhibitory effect(P<0.01).VEGF concentrations in the cell culture supernatants and intra-cellules were all significantly reduced after melatonin(1 mmol/L) incubation(P<0.05).VEGF mRNA expression decreased markedly in a time-dependent manner during the observation period(P<0.05).Conclusions:High melatonin concentrations markedly inhibited the proliferation of pancreatic carcinoma cells.The endogenous VEGF expression was also suppressed by melatonin incubation.     

Regulation of vascular endothelial growth factor receptor-1 expression by specificity proteins 1, 3, and 4 in pancreatic cancer cells

Vascular endothelial growth factor receptor-1 (VEGFR1) is expressed in cancer cell lines and tumors and, in pancreatic and colon cancer cells, activation of VEGFR1 is linked to increased tumor migration and invasiveness. Tolfenamic acid, a nonsteroidal anti-inflammatory drug, decreases Sp protein expression in Panc-1 and L3.6pl pancreatic cancer cells, and this was accompanied by decreased VEGFR1 protein and mRNA and decreased luciferase activity on cells transfected with constructs (pVEGFR1) containing VEGFR1 promoter inserts. Comparable results were obtained in pancreatic cancer cells transfected with small inhibitory RNAs for Sp1, Sp3, and Sp4 and all three proteins bound to GC-rich elements in the VEGFR1 promoter. These results show that VEGFR1 is regulated by Sp proteins and that treatment with tolfenamic acid decreases expression of this critical angiogenic factor. Moreover, in vitro studies in Panc-1 cells show that activation of VEGFR1 by VEGFB to increase mitogen-activated protein kinase 1/2 phosphorylation and cell migration on collagen-coated plates is also inhibited by tolfenamic acid. Thus, targeted degradation of Sp proteins is highly effective for inhibiting VEGFR1 and associated angiogenic responses in pancreatic cancer.     

细胞因子和低氧对胰腺癌细胞表达血管内皮生长因子A、C的调节

目的:探讨细胞因子白细胞介素(IL)-1α、IL-6、肿瘤坏死因子(TNF)α、SNAP(S-nitroso-nacetyl-penicillamine)(在培养细胞中可释放NO,使细胞处于低氧状态)对胰腺癌细胞产生和分泌血管内皮生长因子(VEGF)-A、C的调节。方法:用northernblot和westernblot法分别分析人胰腺癌细胞株中VEGF-A、VEGF-C基因和蛋白的表达;以IL-1α(10μg/L)、IL-6(100μg/L)、TNFα(50μg/L)或SNAP(25mg/L)刺激细胞株后用逆转录-聚合酶链式反应技术(RT-PCR)分析其VEGF-A、VEGF-C基因的表达。结果:Northernblot法显示6种胰腺癌细胞株均有4.1kbVEGF-A基因和2.4kbVEGF-C基因的表达;Westernblot法显示这6种胰腺癌细胞株均有相对分子质量为43×103的VEGF-A蛋白和相对分子质量为55×103的VEGF-C蛋白表达。RT-PCR分析法显示:IL-1α使细胞株COLO-357产生VEGF-A、VEGF-CmRNA分别增加1~2倍、1倍;IL-6刺激细胞株CAPAN-1产生VEGF-A、VEGF-CmRNA分别增加2~5倍、1倍;TNF-α使细胞株COLO-357产生VEGF-A、VEGF-CmRNA分别减少1~2.5倍、1~2倍,使细胞株CAPAN-1产生VEGF-A、VEGF-CmRNA分别减少1倍、1.6~2.5倍;而SNAP刺激细胞株COLO-357产生VEGF-AmRNA增加5倍,刺激细胞株CAPAN-1产生VEGF-AmRNA增加4倍。结论:细胞因子IL-1α、IL-6、TNFα和SNAP通过调节血管内皮生长因子A、C的表达而影响胰腺癌细胞的生物学特性。     

Estrogen regulation of vascular endothelial growth factor gene expression in ZR-75 breast cancer cells through interaction of estrogen receptor alpha and SP proteins

Vascular endothelial growth factor (VEGF) is expressed in multiple hormone-dependent cancer cells/tumors. Treatment of ZR-75 breast cancer cells with 17beta-estradiol (E2) induced a greater than fourfold increase of VEGF mRNA levels. ZR-75 breast cancer cells were transfected with pVEGF1, a construct containing a -2018 to +50 VEGF promoter insert, and E2 induced reporter gene (luciferase) activity. Deletion and mutation analysis of the VEGF gene promoter identified a GC-rich region (-66 to -47) which was required for E2-induced transactivation of pVEGF5, a construct containing the minimal promoter (-66 to +54) that exhibited E2-responsiveness. Interactions of nuclear proteins from ZR-75 cells with the proximal GC-rich region of the VEGF gene promoter were investigated by electrophoretic mobility shift and chromatin immunoprecipitation assays. The results demonstrate that both Sp1 and Sp3 proteins bound the GC-rich motif (-66 to -47), and estrogen receptor alpha (ERalpha) interactions were confirmed by chromatin immunoprecipitation. Moreover, E2-dependent activation of constructs containing proximal and distal GC/GT-rich regions of the VEGF promoter was inhibited in ZR-75 cells transfected with small inhibitory RNAs for Sp1 and Sp3. These results were consistent with a mechanism of hormone activation of VEGF through ERalpha/Sp1 and ERalpha/Sp3 interactions with GC-rich motifs.     

Paracrine interactions of vascular endothelial growth factor and platelet-derived growth factor in endothelial and lung cancer cells

While the effects of single growth factors on endothelial cells (ECs) have been extensively studied, the importance of induction of growth factors such as PDGF-BB (platelet derived growth factor) in ECs and its impact on tumor cell functions are only partly understood. Human umbilical vein endothelial cells (HUVECs) were cultured under serum-free conditions and stimulated by 20 ng/ml VEGF (vascular endothelial growth factor) or 20 ng/ml bFGF (basic fibroblastic growth factor). As determined by real-time PCR, both VEGF and bFGF induced a significant (up to 4-fold) increase in PDGF-B RNA expression which was time- and dose-dependent (p<0.05). Similarly, conditioned medium (CM) from lung cancer cells (A549) which is known to contain multiple growth factors including VEGF and bFGF also induced PDGF-B RNA expression. Using ELISA assays, VEGF and bFGF significantly increased PDGF-BB protein secretion in HUVECs (p<0.01). By addition of BIBF 1000, a novel inhibitor of the VEGF and bFGF receptor kinases, the effect of VEGF on PDGF-B RNA induction was significantly antagonized (p<0.01). Furthermore, we studied the biological significance of EC-derived PDGF-BB on lung cancer cells. Interestingly, HUVEC-derived CM significantly stimulated migration of A549 cells (p<0.001) with a trend to further increased migration with the use of VEGF-stimulated (PDGF-BB rich) CM (p=0.2). Collectively, endothelial and lung cancer cells seem to interact via various paracrine pathways, e.g. by the reciprocal induction of VEGF and PDGF-BB. Thus, targeting key molecules would result in expression alterations of multiple factors and alter the biological functions of both stromal and tumor cells.     

beta-Catenin regulates vascular endothelial growth factor expression in colon cancer

To evaluate whether beta-catenin signaling has a role in the regulation of angiogenesis in colon cancer, a series of angiogenesis-related gene promoters was analyzed for beta-catenin/TCF binding sites. Strikingly, the gene promoter of human vascular endothelial growth factor (VEGF, or VEGF-A) contains seven consensus binding sites for beta-catenin/TCF. Analysis of laser capture microdissected human colon cancer tissue indicated a direct correlation between up-regulation of VEGF-A expression and adenomatous polyposis coli (APC) mutational status (activation of beta-catenin signaling) in primary tumors. In metastases, this correlation was not observed. Analysis by immunohistochemistry of intestinal polyps in mice heterozygous for the multiple intestinal neoplasia gene (Min/+) at 5 months revealed an increase and redistribution of VEGF-A in proximity to those cells expressing nuclear beta-catenin with a corresponding increase in vessel density. Transfection of normal colon epithelial cells with activated beta-catenin up-regulated levels of VEGF-A mRNA and protein by 250-300%. When colon cancer cells with elevated beta-catenin levels were treated with beta-catenin antisense oligodeoxynucleotides, VEGF-A expression was reduced by more than 50%. Taken together, our observations indicate a close link between beta-catenin signaling and the regulation of VEGF-A expression in colon cancer.     

Clinical significance of vascular endothelial growth factor expression in gastric cancer

Vascular endothelial growth factor (VEGF) is an angiogenic factor in human cancer tissue. To clarify the clinical significance of this factor, we investigated the VEGF expression in early and advanced gastric cancer. This study included analysis of data on 243 patients with gastric cancer, including 118 in the early stage and 125 in the advanced stage. VEGF was immunohistochemically stained. Of 243 tumors, 102 (42%) were VEGF-positive. The VEGF-positive gastric cancers were larger, more invasive, and classified in the more advanced stage than VEGF negative ones. Patients with VEGF-positive cancers had significantly lower survival rates than did those with negative ones, both in early and advanced stages (P < 0.05, P < 0.01, respectively). The VEGF-positive isolates had more hematogenous metastases than VEGF-negative ones. Multivariate analysis revealed VEGF to be an independent prognostic factor and independent risk factor for liver metastasis. The VEGF expression in cancer cells can serve as a pertinent prognostic indicator both in early and advanced gastric cancer.     

Oncostatin-M induction of vascular endothelial growth factor expression in astroglioma cells

Oncostatin-M (OSM), a hematopoietic cytokine, and vascular endothelial growth factor (VEGF), a quintessential angiogenic signal, are coexpressed in development, cancer and inflammation. Here, we report that OSM treatment of human astroglioma cell lines increases VEGF levels by approximately threefold. Interleukin-1beta (IL-1beta), in combination with OSM, induces up to sevenfold higher VEGF expression, without significantly inducing VEGF on its own. Specifically examining the OSM contribution to VEGF expression, neutralizing antibodies to OSM receptor subunits gp130 and OSMRbeta, but not LIFRbeta, inhibited OSM induction of VEGF, indicating that the OSM-specific receptor OSMRbeta/gp130 transduces the OSM signal for VEGF synthesis. OSM induction of VEGF promoter activity maps to the (-1171, -786) region of the VEGF promoter, which contains a STAT-3-binding site. STAT-3 is indeed essential for this response, since overexpression of a dominant-negative STAT-3 blocks OSM induction of VEGF promoter activity, as well as endogenous VEGF expression. Finally, we demonstrate that OSM is expressed in glioblastoma multiforme tumor biopsies, a particularly malignant form of brain tumor. This novel mechanism of VEGF regulation in astroglioma cells may be active in pathophysiological states where both OSM and IL-1beta are present.     

Significance of phospho‐vascular endothelial growth factor receptor‐2 expression in pancreatic cancer

Vascular endothelial growth factor receptors (VEGFRs) are mainly expressed by endothelial cells, but they are also expressed by some cancer cells, including pancreatic cancer. The objective of this study was to evaluate the significance of VEGFRs expression in pancreatic cancer cells. A total of 107 primary pancreatic tumors were stained with antibodies against VEGFR‐1, VEGFR‐2, phospho‐VEGFR‐2 (pVEGFR‐2), VEGFR‐3, VEGF‐A, VEGF‐C, and VEGF‐D. VEGFR‐2 and pVEGFR‐2 expression were positive in 74 (69%) and 54 (50%) of 107 pancreatic cancers. There was a significant correlation (P < 0.001) between VEGFR‐2 expression and pVEGFR‐2 expression. pVEGFR‐2 was significantly associated with invasion to the anterior capsule of pancreas (P = 0.032) and arterial invasion (P = 0.012). In contrast, VEGFR‐1 and VEGFR‐3 expression was only observed in 13 (12%) and 15 (14%) of 107 pancreatic cancers, and was not associated with any clinicopathological features. The prognosis of pVEGFR‐2 positive patients with stage IIA tumors was significantly (P = 0.0441) poorer than that of pVEGFR‐2‐negative patients. VEGF‐A, VEGF‐C, and VEGF‐D expression was positive in 42 (39%), 82 (77%), and 39 (36%) of 107 pancreatic cancers, respectively. The prognosis for VEGF‐A‐positive patients was significantly (P = 0.0425) poor, but not for VEGF‐C‐positive and VEGF‐D‐positive patients. A multivariate analysis indicated pVEGFR‐2 expression to be an independent prognostic factor, but not VEGF‐A. These findings suggested that VEGFR‐2 signaling might therefore be associated with the prognosis of patients with pancreatic cancer. The expression of pVEGFR‐2 might be a novel predictive prognostic marker for patients with pancreatic cancers, especially at clinical stage IIA. (Cancer Sci 2010)     

Interleukin-8 increases vascular endothelial growth factor and neuropilin expression and stimulates ERK activation in human pancreatic cancer

Interleukin-8 (IL-8) is associated with tumorigenesis by promoting angiogenesis and metastasis. Although up-regulation of IL-8 is indicated in many cancers, its function in pancreatic cancer has not been well characterized. In this study we examined the expression of IL-8 on pancreatic cancer cells and clinical tissue specimens, and investigated the effect of exogenous IL-8 on gene expression, and signaling in human pancreatic cancer cells. We found that pancreatic cancer cells expressed higher amount of IL-8 mRNA than normal human pancreatic ductal epithelium cells. IL-8 mRNA was also substantially overexpressed in 11 of 14 (79%) clinical pancreatic-adenocarcinoma samples compared with that in their surrounding normal tissues. Exogenous IL-8 up-regulated the expression of vascular endothelial growth factor₁₆₅, and neuropilin (NRP)-2 in BxPC-3 cells, one of human pancreatic cancer cell lines. IL-8 expression was inducible by hypoxia mimicking reagent cobalt chloride. In addition, IL-8 activated extracellular signal-regulated kinase (ERK)1/2 signaling pathway in BxPC-3 cells. Our studies suggest that IL-8 might be a malignant factor in human pancreatic cancer by induction of vascular endothelial growth factor and NRP-2 expression and ERK activation. Targeting IL-8 along with other antiangiogenesis therapy could be an effective treatment for this malignancy. ( Cancer Sci 2008, 99: 733–737)     

Stat3 activation regulates the expression of vascular endothelial growth factor and human pancreatic cancer angiogenesis and metastasis

Expression of vascular endothelial growth factor (VEGF), a key angiogenic protein, has been linked with pancreatic cancer progression. However, the molecular basis for VEGF overexpression remains unclear. Immunohistochemical studies have indicated that VEGF overexpression coincides with elevated Stat3 activation in human pancreatic cancer specimens. In our study, more than 80% of the human pancreatic cancer cell lines used exhibited constitutively activated Stat3, with Stat3 activation correlated with the VEGF expression level. Blockade of activated Stat3 via ectopic expression of dominant-negative Stat3 significantly suppressed VEGF expression, angiogenesis, tumor growth, and metastasis in vivo. Furthermore, constitutively activated Stat3 directly activated the VEGF promoter, whereas dominant-negative Stat3 inhibited the VEGF promoter. A putative Stat3-responsive element on the VEGF promoter was identified using a protein-DNA binding assay and confirmed using a promoter mutagenesis assay. These results indicate that Stat3 directly regulates VEGF expression and hence angiogenesis, growth, and metastasis of human pancreatic cancer, suggesting that Stat3 signaling may be targeted for treatment of pancreatic cancer.