Nitric oxide induces cyclooxygenase expression and inhibits cell growth in colon cancer cell lines

The role of nitric oxide (NO) in colon cancer remains controversial. Inducible nitric oxide synthase (iNOS) has been reported to be up regulated and down regulated in colorectal cancer in both animal models and patient tissue samples. Cyclooxygenase-2 (COX-2) is important in colorectal carcinogenesis but its relationship with NO has never been studied in colon cancer. Three colon cancer cell lines (HCA7, HT29 and HCT116) with different COX-2 expression and activities were used to study the effect of the NO donor, S-nitrosoglutathione (GSNO). The effects of GSNO (10-500 micro M) on cell growth, PGE(2) production, COX-1/COX-2 protein expression and cell-cycle distribution were evaluated. GSNO increased PGE(2) production and induced COX-1 and COX-2 protein expression in a dose- and time-dependent manner. Higher concentrations of GSNO also inhibited cell growth and induced apoptosis in all three cell lines, regardless of their COX-2 expression/activities. Inhibition of PGE(2) production did not further improve the inhibitory effect of GSNO.     

The effect of non-steroidal anti-inflammatory drugs on human colorectal cancer cells: evidence of different mechanisms of action

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit proliferation and induce apoptosis in human colorectal cancer cells in vitro. It remains unclear whether individual NSAIDs act by cyclooxygenase-2 (COX-2) inhibition and how NSAIDs exert their anti-proliferative effects. We investigated the effects of NS-398 (a selective COX-2 inhibitor), indomethacin (a non-selective COX inhibitor) and aspirin on four human colorectal cancer cell lines (HT29.Fu, HCA-7, SW480 and HCT116). NS-398 completely inhibited proliferation, induced G1 arrest and promoted apoptosis in COX-2-expressing cells (HT29.Fu and HCA-7). However, indomethacin had similar effects on all cells, regardless of COX-2 expression. NS-398 also had anti-proliferative activity on COX-2-negative cell lines (SW480 and HCT116). Aspirin inhibited proliferation of all cell lines but did not induce apoptosis. Indomethacin decreased beta-catenin protein expression in all cells (unlike NS-398 or aspirin). NSAIDs act on human colorectal cancer cells via different mechanisms. Decreased beta-catenin protein expression may mediate the anti-proliferative effects of indomethacin.     

Cyclooxygenase-2 pathway correlates with VEGF expression in head and neck cancer. Implications for tumor angiogenesis and metastasis

We evaluated the role of COX-2 pathway in 35 head and neck cancers (HNCs) by analyzing COX-2 expression and prostaglandin E2 (PGE2) production in relation to tumor angiogenesis and lymph node metastasis. COX-2 activity was also correlated to vascular endothelial growth factor (VEGF) mRNA and protein expression. COX-2 mRNA and protein expression was higher in tumor samples than in normal mucosa. PGE2 levels were higher in the tumor front zone in comparison with tumor core and normal mucosa (P<.0001). Specimens from patients with lymph node metastasis exhibited higher COX-2 protein expression (P=.0074), PGE2 levels (P=.0011) and microvessel density (P<.0001) than specimens from patients without metastasis. A significant correlation between COX-2 and tumor vascularization (r(s)=0.450, P=.007) as well as between COX-2 and microvessel density with VEGF expression in tumor tissues was found (r(s)=0.450, P=.007; r(s)=0.620, P=.0001, respectively). The induction of COX-2 mRNA and PGE2 synthesis by EGF and Escherichia coli lipopolysaccharide (LPS) in A-431 and SCC-9 cell lines, resulted in an increase in VEGF mRNA and protein production. Indomethacin and celecoxib reversed the EGF- and LPS-dependent COX-2, VEGF, and PGE2 increases. This study suggests a central role of COX-2 pathway in HNC angiogenesis by modulating VEGF production and indicates that COX-2 inhibitors may be useful in HNC treatment.     

PGE2-mediated upregulation of iNOS in murine breast cancer cells through the activation of EP4 receptors

We report here that endogenous prostaglandin E(2) (PGE(2)) resulting from cyclooxygenase (COX)-2 expression in a highly metastatic murine breast cancer cell line C3L5 upregulates IFN-gamma + LPS-induced nitric oxide (NO) synthase (iNOS) expression and NO production. This action of PGE(2) is mediated through the EP(4) receptor in a cAMP-dependent manner. Both nonselective and selective COX-2 inhibitors suppressed IFN-gamma + LPS-induced NO production, which was largely restored by exogenous PGE(2) or EP(4) receptor agonist PGE(1) alcohol. EP(4) antagonist AH-23848B inhibited NO production with a concomitant downregulation of iNOS mRNA in IFN-gamma + LPS-stimulated cells. cAMP dependence of NO production by cells under inducible conditions was demonstrated by the use of known modulators of intracellular cAMP. Since both COX-2 and iNOS are implicated in breast cancer progression, our findings of EP(4) receptor-mediated upregulation of iNOS in COX-2-expressing breast cancer cells suggest that blocking COX-2 and/or EP(4) may provide a simple therapeutic modality in this tumor model.     

一氧化氮合酶和血管内皮生长因子在大肠癌组织中的表达及其与血管生成的关系

目的 研究诱导型与内皮型一氧化氮合酶(iNOS、eNOS)和血管内皮生长因子(VEGF)在大肠癌组织中的表达及其与血管生成的关系。方法 应用免疫组化方法检测72例大肠癌手术切除标本中iNOS、eNOS、vEGF的表达，并与正常大肠黏膜、腺瘤组织相比较。结果 iNOS和eNOS在大肠癌组织中的平均表达阳性率分别为70．83％、36．11％，与正常黏膜、腺瘤比较有显著性差异（P＜0．05)。大肠癌组织中iNOS表达与VEGF表达有一致性(P＜0．05)。结论 iNOS在由VEGF介导的大肠癌血管形成中发挥一定的作用。     

Celecoxib induces cell apoptosis coupled with up-regulation of the expression of VEGF by a mechanism involving ER stress in human colorectal cancer cells

Increasing evidence suggests that celecoxib, a COX-2 inhibitor with potent anticancer activity exerts its effects not only through COX-2, but also through COX-2-independent mechanisms. In the present study, we hypothesized that endoplasmic reticulum stress (ERS) is involved in the up-regulation of VEGF expression induced by celecoxib in colorectal cancer HCT116 cells and that ERS is a major mechanism by which celecoxib triggers tumor cell death in a COX-2-independent manner. HCT116 cells, which do not express COX-2, were cultured in the absence or presence of celecoxib. VEGF expression was detected by quantitative real-time RT-PCR and western blotting. ERS triggered by celecoxib was determined by expression of ER chaperones and other markers. PBA (an inhibitor of ERS) and GRP78 overexpression were both used to prevent ERS. Cell apoptosis was evaluated by TUNEL assay and fluorescence activated cell sorting. In HCT116 cells, celecoxib increased VEGF production with time-course and dose-response curves similar to those observed for the increase of the ER chaperone, GRP78. CHOP, a marker of ERS involved in apoptosis, was also increased by celecoxib. Moreover, celecoxib promoted cell apoptosis. Both apoptosis and up-regulation of VEGF were prevented by protecting cells from ERS. Celecoxib induces cell apoptosis and up-regulation of VEGF in HCT116 cells via activation of the ERS response. Further studies are necessary to evaluate whether the combination of celecoxib with anti-VEGF agents is a promising therapeutic modality for cancer.     

n-3 PUFAs reduce VEGF expression in human colon cancer cells modulating the COX-2/PGE2 induced ERK-1 and -2 and HIF-1alpha induction pathway

n-3 Polyunsaturated fatty acids (PUFAs) inhibit the development of microvessels in mammary tumors growing in mice. Human colorectal tumors produce vascular endothelial growth factor (VEGF) whose expression is up-regulated in tumor cells by both cyclooxygenase-2 (COX-2) and PGE(2) and directly correlated to neoangiogenesis and clinical outcome. The goal of this study was to examine the capability of n-3 PUFAs to regulate VEGF expression in HT-29 human colorectal cells in vitro and in vivo. Constitutive VEGF expression was augmented in cultured HT-29 cells by serum starvation and the effects of eicosapentaenoic (EPA) or docosahexaenoic acid (DHA) on VEGF, COX-2, phosphorylated extracellular signal-regulated kinase (ERK)-1 and -2 and hypoxia-inducible-factor 1-alpha (HIF-1alpha) expression and PGE(2) levels were assessed. Tumor growth, VEGF, COX and PGE(2) analysis were carried out in tumors derived from HT-29 cells transplanted in nude mice fed with either EPA or DHA. Both EPA and DHA reduced VEGF and COX-2 expression and PGE(2) levels in HT-29 cells cultured in vitro. Moreover, they inhibited ERK-1 and -2 phosphorylation and HIF-1alpha protein over-expression, critical steps in the PGE(2)-induced signaling pathway leading to the augmented expression of VEGF in colon cancer cells. EPA always showed higher efficacy than DHA in vitro. Both fatty acids decreased the growth of the tumors obtained by inoculating HT-29 cells in nude mice, microvessel formation and the levels of VEGF, COX-2 and PGE(2) in tumors. The data provide evidence that these n-3 PUFAs are able to inhibit VEGF expression in colon cancer cells and suggest that one possible mechanism involved may be the negative regulation of the COX-2/PGE(2) pathway. Their potential clinical application as anti-angiogenic compounds in colon cancer therapy is proposed.     

Tanshinone II-A Inhibits Angiogenesis through Down Regulation of COX-2 in Human Colorectal Cancer

Angiogenesis plays a significant role in colorectal cancer (CRC) and cyclooxygenase-2 (COX-2) appears tobe involved with multiple aspects of CRC angiogenesis. Our aim was to investigate the inhibitory effects of TanII-A (Tanshinone II-A, Tan II-A) on tumor growth in mice, as well as alteration of expression of COX-2 andVEGF in CRC. We established the mice xenograft model of C26 CRC cell line, and injected 0.5, 1, 2mg/kg ofTan II-A and 1mg/kg of 5-FU in respectively in vivo. Then, we assayed tumor weight and volume, and evaluatedmicrovascular density and expression of VEGF. COX-2 promoter and COX-2 plasmids were transfected intoHCT-116 cells, followed by detection of COX-2 promoter activity by chemiluminescence, and detection of COX-2mRNA expression by fluorescence quantitative PCR. Taken together, the results showed Tan II-A could inhibittumor growth and suppress the VEGF level in vivo. HCT-116 cell experiments showed marked inhibitory effectsof Tan II-A on COX-2 and VEGF in a dose-dependent manner. The results indicate that Tan II-A can effectivelyinhibit tumor growth and angiogenesis of human colorectal cancer via inhibiting the expression level of COX-2and VEGF.     

Antitumor and anti-metastatic effects of cyclooxygenase-2 inhibition by celecoxib on human colorectal carcinoma xenografts in nude mouse rectum

We examined the effects of the preferential cyclooxygenase-2 (COX-2) inhibitor celecoxib on tumorigenesis, angiogenesis, apoptosis, vascular endothelial growth factor (VEGF) protein expression and metastasis in HT-29 human colorectal carcinoma cell xenografts in nude mouse rectum. COX-2 mRNA expression was examined in the xenograft and metastatic sites. The antitumor effect of celecoxib in the xenografts was evaluated by measuring the weight of the peri-ano-rectal tumor. The anti-metastatic effect of celecoxib was assessed by quantification of lymph node and lung metastases by amplification of a cancer-related human DNA by TaqMan PCR. The effects of celecoxib on angiogenesis, apoptosis, prostaglandin E2 (PGE2) production and VEGF protein expression in the xenografts were evaluated by means of microvessel density (MVD) counting, terminal deoxynucleotidyl transferase-mediated nick end labeling assay, quantitative enzyme-linked immunosorbent assay and western blotting, respectively. The rectal xenograft model showed lymph node and lung metastases with enhanced expression of COX-2 mRNA in each organ. Celecoxib inhibited rectal xenograft growth in a dose-dependent manner as follows: 150?ppm, 33.0% (p=0.000220); 750?ppm, 46.4% (p=0.0000292); 1500?ppm, 63.4% (p=0.0000109). Celecoxib inhibited lymph node metastasis in a dose-dependent manner as follows: 150?ppm, 86.7% (p=0.0263); 750?ppm, 90.3% (p=0.00638); 1500?ppm, 96.0% (p=0.000894). Celecoxib also inhibited lung metastasis as follows: 750?ppm, 53.3% (p=0.0107); 1500?ppm, 78.3% (p=0.00022). Celecoxib (1500?ppm) significantly inhibited PGE2 production by 68.4% (p=0.000157) and MVD counting by 48.2% (p=1.3x10-12) and induced apoptosis 2.5-fold (p=3.0x10-14) in the rectal xenograft. Celecoxib suppressed VEGF protein expression in the rectal xenograft. These studies demonstrate that celecoxib reduces the growth and metastatic potential of colorectal carcinoma in mice through COX-2 inhibition, anti-angiogenesis and apoptosis induction. The studies using HT-29 human colorectal carcinoma cell xenografts in nude mouse rectum also provide important information that supports that the COX-2 inhibitor celecoxib has a high potential for use as a clinical agent for inhibition of hematological and lymphatic metastases of colorectal cancer.     

Comparison of oxaliplatin- and curcumin-mediated antiproliferative effects in colorectal cell lines

Colorectal cancer remains a leading cause of cancer death worldwide, despite markedly improved response rates to current systemic therapies. Oxaliplatin either alone or incorporated into 5-fluorouracil/leucovorin regimes has resulted in increased survival rates, particularly with regards to metastatic colorectal carcinoma. The chemopreventive polyphenol curcumin, which is currently in clinical trial, has been advocated for use in colorectal cancer either singly or in combination with chemotherapeutic drugs. In this study, the antiproliferative capacity of both compounds was compared in HCEC (normal-derived), HT29 (p53 mutant adenocarcinoma) and HCT116 (p53wt adenocarcinoma) colorectal cell lines to determine whether effects were cell-type specific at pharmacologically achievable doses, and whether the combination resulted in enhanced efficacy. Both oxaliplatin and curcumin displayed marked antiproliferative capacity at therapeutic concentrations in the two tumor cell lines. Order of sensitivity to oxaliplatin was HCT116>HT29>HCEC, whereas order of sensitivity to curcumin was HT29>HCT116>HCEC. HCT116 cells underwent induction of G2/M arrest in response to both oxaliplatin (irreversible) and curcumin (reversible). Apoptosis was induced by both agents, and up to 16-fold induction of p53 protein was observed in response to the combination. Antiproliferative effects in HT29 cells were largely cell cycle independent, and were mediated by induction of apoptosis. Effects were greatly enhanced in both cell lines when agents were combined. This study provides further evidence that curcumin may be of use in therapeutic regimes directed against colorectal cancer, and suggests that in combination with oxaliplatin it may enhance efficacy of the latter in both p53wt and p53 mutant colorectal tumors.     

Butyrate suppresses expression of neuropilin I in colorectal cell lines through inhibition of Sp1 transactivation

Background  

Neuropilin is a transmembrane receptor for vascular endothelial growth factor (VEGF) and is expressed in normal endothelial cells and upregulated in cancer cells. Neuropilin-1 (NRP-1) has been shown to promote tumour cell migration and survival in colon cancer in response to VEGF binding. The expression profiles of neuropilins, associated co-receptors and known ligands have been mapped in three colorectal cell lines: Caco-2, HCT116 & HT29. We have previously shown that butyrate, a naturally occurring histone deacetylase inhibitor (HDACi) produced by fermentation of fibre in the colon, causes apoptosis of colon cancer cell lines.     

lncRNA CASC2对结直肠癌细胞功能及血管生成的影响

目的 研究lncRNA CASC2过表达对结直肠癌细胞增殖、迁移、血管生成及Wnt/FZD/β-catenin信号通路的影响.方法 qRT-PCR检测lncRNA CASC2在正常结肠上皮细胞(NCM460)及结直肠癌细胞株(DLD-1、HT29、SW620、HCT116、RKO、LOVO、SW480)中的表达情况;H...     

miR-92a 在结直肠癌中的表达及其对肿瘤血管生成的作用*

目的:探讨miR-92a 在结直肠癌中的表达及其对肿瘤血管新生功能的影响和作用机制。方法:采用qRT-PCR方法检测广东医学院附属深圳南山医院2014年6 月至2015年12月经手术切除的25例结直肠癌组织和对应癌旁组织及4 种结直肠癌细胞（HCT 116、SW620、SW480、HT29）中miR-92a 的表达;免疫组织化学法检测结直肠癌和癌旁组织中CD31阳性表达的微血管密度（microvesseldensity,MVD）,Pearson相关性分析探讨miR-92a 表达与肿瘤血管新生MVD的相关性。通过转染miR-92a-mimic、inhibitor 上调或抑制结直肠癌细胞HCT 116、SW620 中miR-92a 的表达水平,采用小管形成实验检测miR-92a 不同表达对HUVEC小管形成的影响,免疫印迹法检测对其下游潜在靶点PTEN的蛋白表达的影响。结果:结直肠癌组织miR-92a 的表达水平显著高于对应癌旁组织（P < 0.01）;4 种人结肠癌细胞系miR-92a 的表达水平均显著高于正常肠上皮组织（P < 0.05）;结直肠癌组织CD31阳性微血管密度显著高于癌旁组织（P < 0.01）,miR-92a 表达水平与结直肠癌血管新生MVD呈显著正相关（r = 0.580,P = 0.01）;上调miR-92a 表达的HCT 116 细胞培养上清液可以显著促进HUVEC小管形成（P < 0.05）;上调miR-92a 表达可以显著抑制HCT116 细胞中PTEN蛋白表达水平（P < 0.01）。 结论:miR-92a 在结直肠癌细胞和组织中高表达,与肿瘤血管新生增加密切相关;miR-92a 可能通过抑制PTEN的表达发挥促进结直肠癌血管新生的生物学功能。      

Expression of inducible nitric oxide synthase and cyclooxygenase-2 in angiogenesis and clinical outcome of human gastric cancer

BACKGROUND AND OBJECTIVES: It has been recognized that inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) produce important endogenous factors of human tumors such as nitric oxide (NO) and prostaglandins, which is involved in the process of carcinogenesis and tumor progression. This study aimed to evaluate the association of clinicopathologic factors, microvessel density, and patient survival with the expression of iNOS and COX-2 in patients with gastric adenocarcinoma. MATERIALS AND METHODS: Seventy-nine specimens, resected from patients with gastric adenocarcinoma, were investigated by immunohistochemical stain against iNOS and COX-2. Microvessels were stained using anti-CD34 antibody and counted as microvessel density. RESULTS: Positive iNOS and COX-2 expressions were significantly correlated with microvessel density by multivariate analysis, respectively (P = 0.0127 vs. P = 0.0214). There was significant difference among the four groups (both iNOS and COX-2 positive, iNOS positive only, COX-2 positive only, and both negative) in serosal invasion (P = 0.038), lymph node metastasis (P = 0.038), Helicobacter pylori infection (P = 0.025), vascular invasion (P = 0.035), and microvessel density (P = 0.019). In patients with gastric cancer that co-expressed iNOS and COX-2, prognosis was significantly poorer than in those that expressed either iNOS or COX-2, or did not express both of them (P = 0.01738). The Cox proportional hazard regression analysis indicated that iNOS expression, vascular invasion, serosal invasion, and microvessel density are independent prognostic factors for patients with gastric cancer. CONCLUSIONS: iNOS and COX-2 expression of gastric cancer are related to tumor angiogenesis, tumor progression, and patient survival in human gastric cancer.     

FOXJ1调控AKT信号通路对结直肠癌细胞凋亡和侵袭能力的影响

目的 探讨叉头框转录因子J1(FOXJ1)对人结直肠癌细胞凋亡和侵袭能力的影响及机制.方法 应用Western Blot方法检测人结直肠癌细胞HCT116、HT29、SW480及人正常肠上皮细胞FHC中FOXJ1的表达水平.细胞中转染pEGFP-N1-FOXJ1和pEGFP-N1,Western Blot检测细胞中FOXJ1、活化的含半胱氨酸的天冬氨酸蛋白水解酶3(Cleaved Caspase-3)、基质金属蛋白酶-2(MMP-2)、蛋白激酶B(AKT)、磷酸化的蛋白激酶B(p-AKT)的表达水平,流式细胞仪检测细胞的凋亡情况,Transwell小室检测细胞的侵袭能力.结果 人结直肠癌细胞HCT116、HT29、SW480中FOXJ1的表达水平均明显低于人正常肠上皮细胞FHC(P﹤0.01).人结直肠癌细胞HCT116中FOXJ1的表达水平下降最多,后续选用HCT116细胞继续研究.转染pEGFP-N1后的细胞凋亡率、侵袭细胞数目及细胞中FOXJ1、Cleaved Caspase-3、MMP-2、AKT、p-AKT的表达水平与对照组比较,差异均无统计学意义(P﹥0.05).转染pEGFP-N1-FOXJ1后的细胞凋亡率及细胞中FOXJ1、Cleaved Caspase-3的表达水平明显高于对照组(P﹤0.01);转染pEGFP-N1-FOXJ1后的侵袭细胞数目及细胞中MMP-2、p-AKT的表达水平明显低于对照组(P﹤0.01).结论 FOXJ1在人结直肠癌细胞中过表达.FOXJ1能够促进结直肠癌细胞凋亡,抑制结直肠癌细胞侵袭,其作用机制可能与AKT信号通路有关.     

Epigenetic silencing BCL6B induced colorectal cancer proliferation and metastasis by inhibiting P53 signaling

BCL6B, a homologue of BCL6, has been reported to be frequently methylated in human gastric cancer. The epigenetic change and the function of BCL6B remains to be elucidated in colorectal cancer. 7 colorectal cancer cell lines (RKO, HT-29, DLD1, LOVO, HCT116, SW480, SW620) and 102 cases of primary colorectal cancer samples were used in this study. Semi-quantitative RT-PCR, methylation specific PCR (MSP), Flow cytometry and western blot were employed. Loss of BCL6B expression was found in HT29, RKO LOVO, SW480, SW620 and DLD1 cells, and reduced expression was found in HCT116 cell line. Complete methylation was found in HT29, RKO, LOVO, SW480, SW620 and DLD1 cells, partial methylation was detected in HCT116 cells. Restoration of BCL6B expression was induced by 5-Aza treatment in these colorectal cancer cells. BCL6B was methylated in 79.4% (81/102) of primary human colorectal cancer and reduced expression was associated with promoter region hypermethylation (p < 0.05). Methylation of BCL6B is associated with late stage (p < 0.05) and lymph node metastasis (p < 0.05). Re-expression of BCL6B inhibited cell proliferation, invasion and migration in RKO and HT29 cells. BCL6B activated P53 signaling and induced apoptosis, Re-expression of BCL6B sensitized RKO and HT29 cells to 5-fluorouracil. In conclusion, BCL6B was frequently methylated in human colorectal cancer and its expression was regulated by promoter region methylation. Methylation of BCL6B is a prognostic and chemo-sensitive marker in colorectal cancer. BCL6B suppresses colorectal cancer growth by activating P53 signaling.     

The histone deacetylase inhibitor trichostatin A induces cell cycle arrest and apoptosis in colorectal cancer cells via p53-dependent and -independent pathways

Many chemotherapeutic agents induce apoptosis via a p53-dependent pathway. However, up to 50% of human cancers have p53 mutation and loss of p53 function. Histone deacetylase inhibitors (HDACIs) are emerging as a potentially important new class of anticancer agents. Here, we report that, Trichostatin A (TSA), a pan-HDAC inhibitor, could induce G2/M cell cycle arrest and apoptosis in both colorectal cancer cell lines with wild-type p53 (HT116 cells) and mutant p53 (HT29 cells), although HCT116 cells had more apoptotic cells than HT29 cells. TSA induces apoptosis in both cell lines via the mitochondrial pathway as indicated by decrease of the mitochondrial membrane potential (MMP) and activation of caspase-3. Additionally, TSA induces expression of the pro-apoptotic protein Bax and decreases the expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL in both cell lines. Bax knockdown by siRNA significantly impaired TSA-induced apoptosis in both cell lines. These data suggest that TSA induces G2/M cell cycle arrest and Bax-dependent apoptosis in colorectal cancer cells (HCT116 cells and HT29 cells) by both p53-dependent and -independent mechanisms. However, cells with normal p53 function are more sensitive to TSA-induced apoptosis.     

Differential involvement of vascular endothelial growth factor in the survival of hypoxic colon cancer cells

The recent approval of bevacizumab (Avastin), a humanized anti-vascular endothelial growth factor (VEGF) monoclonal antibody, in combination with chemotherapy for the treatment of patients with metastatic colorectal cancer, has provided proof of principle of the efficacy of antiangiogenic strategies for cancer therapy. The activity of bevacizumab is primarily attributed to its ability to inhibit endothelial cell survival. Whether anti-VEGF strategies may also have a direct effect on cancer cell survival is poorly understood. We show that serum-starved colon cancer cells differentially respond to autocrine production of VEGF with the induction of hypoxia inducible factor-1 alpha (HIF-1 alpha) and survival under hypoxic conditions. Inhibition of VEGF or VEGF receptor 2 (VEGFR2)/KDR, but not VEGFR1/Flt-1, was sufficient to abrogate VEGF-mediated induction of HIF-1 alpha and survival in sensitive HCT116, but not in resistant HT29, colon cancer cells. These results provide evidence that a VEGF/KDR/HIF-1 alpha autocrine loop differentially mediates survival of hypoxic colon cancer cells, and they suggest that colon cancer cells may be intrinsically sensitive or resistant to anti-VEGF strategies, which may determine the therapeutic efficacy of bevacizumab.