IL-13 regulates cancer invasion and metastasis through IL-13Rα2 via ERK/AP-1 pathway in mouse model of human ovarian cancer

Previously, we have demonstrated that a variety of human cancers including the ovarian cancer express IL-13Rα2, a high affinity receptor for IL-13. Herein, we have examined if IL-13 regulates invasion and metastasis of ovarian cancer through IL-13Rα2 in vitro and in vivo in animal models of human ovarian cancer. We tested cell invasion and protease activity in IL-13Rα2-overexpressing and IL-13Rα2-negative ovarian tumor cell lines. IL-13 treatment significantly augmented both cell invasion and enzyme activities in only IL-13Rα2-positive cells but not in IL-13Rα2-negative cells in vitro. Mechanistically, IL-13 enhanced ERK1/2, AP-1 and MMP activities only in IL-13Rα2-positive cells but not in IL-13Rα2-negative cells. In contrast, other signaling pathways such as IRS1/2, PI3K and AKT do not seem to be involved in IL-13 induced signaling in ovarian cancer cell lines. Highly specific inhibitors for MMP and AP-1 efficiently inhibited both invasion and protease activities without impacting the basal level invasion and protease activities in vitro. In orthotopic animal model of human ovarian cancer, IL-13Rα2-positive tumors metastasized to lymph nodes and peritoneum earlier than IL-13Rα2-negative tumors. Interestingly, the IL-13Rα2-positive tumor bearing mice died earlier than mice with IL-13Rα2-negative tumor. Intraperitoneal injection of IL-13 further shortened survival of IL-13Rα2-positive tumor bearing mice compared to IL-13Rα2-negative tumor mice. IL-13Rα2-positive tumors and lymph node metastasis expressed higher levels of MMPs and higher ERK1/2 activation compared to IL-13Rα2-negative tumors. Taken together, IL-13Rα2 is involved in cancer metastasis through activation of ERK/AP-1 and that targeting IL-13Rα2 might not only directly kill primary tumors but also prevent cancer metastasis.     

IL 6经PI3K/Akt通路诱导卵巢癌细胞对他莫西芬耐药

目的:探讨IL-6诱导卵巢癌细胞对他莫西芬(tamoxifen,TAM)耐药的分子机制.方法:构建内源性过表达IL-6的人卵巢癌A2780细胞系和内源性抑制IL-6表达的人卵巢癌CAOV-3细胞,50 ng/ml外源性IL-6预处理A2780细胞(A2780/preIL-6细胞),Western blotting检测内/外源IL-6对卵巢癌细胞ERα Ser167位磷酸化水平的影响;IL-6与PI3K抑制剂Wort-mannin单独或联合作用于A2780细胞,Western blotting检测其对A2780细胞Akt磷酸化和ERα磷酸化的影响;MTT法检测Wortmannin和内/外源IL-6对A2780细胞TAM敏感性的影响;荧光素酶报告基因检测卵巢癌细胞ERα的转录活性,并分析其可能涉及的信号通路.结果:外源性及内源性过表达IL-6可明显促进A2780细胞ERα Ser167位点磷酸化水平(均P＜0.01),而内源性抑制IL-6表达则可降低CAOV-3细胞ERα Ser167位点的磷酸化水平(P＜0.01);Wortmannin可阻断IL-6诱导的A2780细胞对TAM的耐药及ERα的磷酸化(P ＜0.05);IL-6可促进细胞ERα的转录活性(P＜0.01),而Wortmannin并不能阻断IL-6对ERα的转录活性的影响(P＞0.05).结论:IL-6可经PI3 K/Akt通路引起ERα磷酸化从而活化ER信号通路,进而诱导卵巢癌细胞对TAM耐药.     

The CHK1 inhibitor SRA737 synergizes with PARP1 inhibitors to kill carcinoma cells

Inhibitors of PARP1 are approved therapeutic agents in ovarian carcinomas. We determined whether the novel clinically relevant CHK1 inhibitor SRA737 interacted with PARP1 inhibitors to kill carcinoma cells. In multiple mammary and ovarian cancer lines SRA737 synergized with the PARP1 inhibitors olaparib and niraparib to cause cell death. The [SRA737 + niraparib] drug combination activated an ATM-AMPK-ULK1-mTOR pathway which resulted in the formation of autophagosomes, temporally followed by autolysosome formation. Phosphorylation of ULK1 S317 was essential for kinase activation against ATG13. The drug combination elevated eIF2α phosphorylation which was causal at increasing Beclin1 and ATG5 expression, reducing MCL-1 and BCL-XL levels, and causing CD95 activation. Knock down of CD95, eIF2α, ATM, AMPKα, ULK1, Beclin1 or ATG5 reduced drug combination lethality. Blockade of either caspase 9 function or that of AIF each partially prevented cell death. Expression of activated mTOR or of c-FLIP-s or of BCL-XL reduced cell killing. In vivo, SRA737 and niraparib interacted in an additive fashion to suppress the growth of mammary tumors. Multiplex analyses revealed that drug combination treated tumors had reduced their plasma levels of sERBB1, sERBB2, sVEGFR1, sVEGFR2, sIL-6R, HGF, PDGFAB/BB and CXCL16 and enhanced the levels of CCL26, IL-8 and MIF. Surviving tumors had activated ERK1/2 and AKT. This finding argues that IL-8/ERK/AKT signaling may be an evolutionary survival response to [SRA737 + niraparib].     

Autocrine production of interleukin-6 confers cisplatin and paclitaxel resistance in ovarian cancer cells

It has been shown that IL-6 is elevated in the serum and ascites of ovarian cancer patients, and increased IL-6 concentration correlates with poor prognosis and chemoresistance. However, the role of IL-6 expression in the acquisition of the chemoresistance phenotype and the underlining mechanisms of drug resistance in ovarian cancer cells remain unclear. Here we demonstrate that both exogenous (a relatively short period of treatment with recombination IL-6) and endogenous IL-6 (by transfecting with plasmid encoding for sense IL-6) induce cisplatin and paclitaxel resistance in non-IL-6-expressing A2780 cells, while deleting of endogenous IL-6 expression in IL-6-overexpressing SKOV3 cells (by transfecting with plasmid encoding for antisense IL-6) promotes the sensitivity of these cells to anticancer drugs. IL-6-mediated resistance of ovarian cancer cells exhibits decreased proteolytic activation of caspase-3. Meanwhile, the further study demonstrates that the chemoresistance caused by IL-6 is associated with increased expression of both multidrug resistance-related genes (MDR1 and GSTpi) and apoptosis inhibitory proteins (Bcl-2, Bcl-xL and XIAP), as well as activation of Ras/MEK/ERK and PI3K/Akt signaling. Therefore, modulation of IL-6 expression or its related signaling pathway may be a promising strategy of treatment for drug-resistant ovarian cancer.     

Mesothelin overexpression promotes autocrine IL-6/sIL-6R trans-signaling to stimulate pancreatic cancer cell proliferation

Mesothelin (MSLN) overexpression in pancreatic cancer (PC) leads to enhanced cell survival/proliferation and tumor progression. After screening for a number of growth factors/cytokines, we found that the MSLN expression correlated closely with interleukin (IL)-6 in human PC specimens and cell lines. Stably overexpressing MSLN in different PC cell lines (MIA-MSLN and Panc1-MSLN) led to higher IL-6 production. Silencing MSLN by small interfering RNA (siRNA) significantly reduced IL-6 levels. Blocking the observed constitutive activation of nuclear factor-kappaB (NF-κB) with IKK inhibitor wedelolactone in MIA-MSLN cells also reduced IL-6. Silencing IL-6 by siRNA reduced cell proliferation, cell cycle progression and induced apoptosis with significant decrease of c-myc/bcl-2. Interestingly, recombinant IL-6-induced proliferation of MIA-MSLN cells but not MIA-V cells. Although messenger RNA/protein levels of IL-6R did not vary, soluble IL-6R (sIL-6R) was significantly elevated in MIA-MSLN and was reduced by treatment with the TACE/ADAM17 inhibitor TAPI-1, indicating intramembrane IL-6R cleavage and IL-6 trans-signaling may be operative in MIA-MSLN cells. Blocking the IL-6/sIL-6R axis using sIL-6R antibody abrogated basal proliferation/survival as well as recombinant human IL-6-induced cell proliferation. Our data suggest that MSLN-activated NF-κB induces elevated IL-6 expression, which acts as a growth factor to support PC cell survival/proliferation through a novel auto/paracrine IL-6/sIL-6R trans-signaling. In addition, using a panel of PC cells with varying MSLN/IL-6 expressions, we showed that MSLN/IL-6 axis is a major survival axis in PC supporting tumor cell growth under anchorage-dependent and independent conditions. The close correlation between MSLN and IL-6 provides a new rationale for combination therapy for effective control of MSLN-overexpressing PCs.     

Mitochondrial fission enhances IL-6-induced metastatic potential in ovarian cancer via ERK1/2 activation

Ovarian cancer is a lethal gynecologic cancer mostly diagnosed in an advanced stage with an accumulation of ascites. Interleukin-6 (IL-6), a pro-inflammatory cytokine is highly elevated in malignant ascites and plays a pleiotropic role in cancer progression. Mitochondria are dynamic organelles that undergo fission and fusion in response to external stimuli and dysregulation in their dynamics has been implicated in cancer progression and metastasis. Here, we investigate the effect of IL-6 on mitochondrial dynamics in ovarian cancer cells (OVCs) and its impact on metastatic potential. Treatment with IL-6 on ovarian cancer cell lines (SKOV3 and PA-1) led to an elevation in the metastatic potential of OVCs. Interestingly, a positive association was observed between dynamin-related protein 1 (Drp1), a regulator of mitochondrial fission, and IL-6R in metastatic ovarian cancer tissues. Additionally, IL-6 treatment on OVCs was linked to the activation of Drp1, with a notable increase in the ratio of the inhibitory form p-Drp1(S637) to the active form p-Drp1(S616), indicating enhanced mitochondrial fission. Moreover, IL-6 treatment triggered the activation of ERK1/2, and inhibiting ERK1/2 mitigated IL-6-induced mitochondrial fission. Suppressing mitochondrial fission through siRNA transfection and a pharmacological inhibitor reduced the IL-6-induced migration and invasion of OVCs. This was further supported by 3D invasion assays using patient-derived spheroids. Altogether, our study suggests the role of mitochondrial fission in the metastatic potential of OVCs induced by IL-6. The inhibition of mitochondrial fission could be a potential therapeutic approach to suppress the metastasis of ovarian cancer.     

Inflammatory biomarkers for persistent fatigue in breast cancer survivors.

PURPOSE: This study seeks to define immunologic and inflammatory variables associated with persistent post-treatment fatigue in breast cancer survivors. EXPERIMENTAL DESIGN: Leukocyte subsets, plasma inflammatory markers, and ex vivo proinflammatory cytokine production were assessed in 50 fatigued and nonfatigued breast cancer survivors recruited > or = 2 years after successful primary therapy. Multivariate statistical analyses were used to define a composite immunologic biomarker of fatigue risk. RESULTS: Fatigued breast cancer survivors were distinguished from nonfatigued survivors by increased ex vivo monocyte production of interleukin (IL)-6 and tumor necrosis factor-alpha following lipopolysaccharide stimulation, elevated plasma IL-1ra and soluble IL-6 receptor (sIL-6R/CD126), decreased monocyte cell-surface IL-6R, and decreased frequencies of activated T lymphocytes and myeloid dendritic cells in peripheral blood (all P < 0.05). An inverse correlation between sIL-6R and cell-surface IL-6R was consistent with inflammation-mediated shedding of IL-6R, and in vitro studies confirmed that proinflammatory cytokines induced such shedding. Multivariate linear discriminant function analysis identified two immunologic markers, the ratio of sIL-6R to monocyte-associated IL-6R and decreased circulating CD69+ T lymphocytes, as highly diagnostic of fatigue (P = 0.0005), with cross-validation estimates indicating 87% classification accuracy (sensitivity = 0.83; specificity = 0.83). CONCLUSION: These results extend links between fatigue and inflammatory markers to show a functional alteration in proinflammatory cytokine response to lipopolysaccharide and define a prognostic biomarker of behavioral fatigue.     

Interferon-α sensitizes human gastric cancer cells to TRAIL-induced apoptosis via activation of the c-CBL-dependent MAPK/ERK pathway

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor family that induces apoptosis in cancer cells. However, gastric cancer cells are insensitive to TRAIL. In the present study, we show that pretreatment with IFN-α enhanced TRAIL-induced apoptosis of gastric cancer MGC803 cells. IFN-α up-regulated death receptor 5 (DR5) expression and down-regulated survivin expression. Furthermore, extracellular-regulated protein kinase (ERK1/2) activation was induced by IFN-α, and a combination of IFN-α and TRAIL led to further activation of ERK1/2. Inhibition of the MAPK/ERK signaling pathway partially reversed apoptosis, as well as the expression patterns of DR5 and survivin. Moreover, the expression of the c-casitas B-lineage lymphoma (c-Cbl) family was down-regulated by IFN-α. Transfection of c-Cbl suppressed IFN-α-induced ERK activation. These results indicate that IFN-α enhances TRAIL-induced apoptosis in gastric cancer cells at least partially via downregulation of c-Cbl, and subsequent up-regulation of the MAPK/ERK pathway.     

Tumor-associated lympho-monocytes from neoplastic effusions are immunologically defective in comparison with patient autologous PBMCs but are capable of releasing high amounts of various cytokines

We studied several in vitro activities of tumor-associated lympho-monocytes (TALMs) and the concentrations of interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, tumor necrosis factor (TNF)α, interferon (IFN)γ and soluble IL-2 receptor (sIL-2R) in neoplastic effusions and in the serum of advanced stage cancer patients. Comparisons were made with autologous peripheral blood mononuclear cells (PBMCs). Autologous PBMCs were compared with PBMCs from normal subjects used as controls. TALMs were collected from 13 peritoneal and 18 pleural neoplastic effusions, secondary to primary tumors of different sites. After PHA stimulation, concentrations of IL-1α, IL-1β and TNFα in culture media of TALMs both from peritoneal and pleural effusions were lower than those of autologous PBMCs and, similarly, concentrations of IL-4 and IL-10 in culture media of TALMs from peritoneal effusions were lower than those of autologous PBMCs, whereas concentrations of IL-4 and IL-10 in culture media of TALMs from pleural effusions were in the same range as those of autologous PBMCs. On the contrary, IL-2, IL-6 and IFNγ amounts (only from pleural effusions) were significantly higher. IL-1α, IL-1β, IL-2, IL-6 and TNFα production from patient PBMCs was lower than that of control PBMCs, whereas production of IL-4, IL-10 and IFNγ was higher than that of control PBMCs. Both in peritoneal and in pleural effusions concentrations of IL-1α, IL-1β and IL-4 were not different from those measured in autologous serum, whereas those of IL-6, IL-10, TNFα, IFNγ and sIL-2R were significantly higher. The amounts of IL-2 in pleural effusions were not different from those of autologous serum, but in peritoneal effusions they were higher than those of autologous serum. The amounts of IL-1α, IL-1β, IL-2, IL-6, TNFα and sIL-2R were higher in patient than in control sera, whereas those of IL-4, IL-10 and IFNγ were in the same range in patient and in control sera. Cell cycle analysis of cultured TALMs and PBMCs (from 3 patients) showed a significant accumulation of TALMs in the non-cycling G₀/G₁ cell population compared with autologous PBMCs.Int. J. Cancer 71:724-731, 1997. © 1997 Wiley-Liss Inc.     

Comprehensive serum cytokine analysis identifies IL-1RA and soluble IL-2Rα as predictors of event-free survival in T-cell lymphoma

BackgroundT-cell malignancies are heterogeneous in their clinical presentation and pathology, and have a poor prognosis. New biomarkers are needed to predict prognosis and to provide insights into signal pathways used by these cells. The goal of this study was to evaluate pretreatment serum cytokines in patients with newly diagnosed T-cell neoplasms and correlate with clinical outcome.Patients and methodsWe evaluated 30 cytokines in pretreatment serum from 68 untreated patients and 14 normal controls. Significantly elevated cytokines were correlated with patterns of abnormalities, event-free survival (EFS) and overall survival (OS).ResultsOur data demonstrated significantly elevated levels (versus controls) of seven cytokines—epidermal growth factor (EGF), IL-6, IL-12, interferon gamma-induced protein (IP)-10, soluble interleukin (sIL)-2Rα, monokine induced by gamma interferon (MIG), and IL-1RA—in all T-cell neoplasms (P < 0.05). In the angioimmunoblastic subset, all seven cytokines except IP-10 and in the peripheral T-cell lymphoma (TCL)-not otherwise specified subset, only IP-10, sIL-2Rα, MIG, and IL-8 were statistically elevated compared with control. Of these, elevated cytokines all but EGF were predictive of an inferior EFS; IL-1RA, sIL-2Rα, and MIG predicted an inferior OS. In a multivariate analysis, sIL-2Rα [hazard ratio (HR) = 3.95; 95% confidence interval (CI) 1.61–8.38] and IL-1RA (HR = 3.28; 95% CI 1.47–7.29) levels remained independent predictors of inferior EFS. TCL cell lines secreted high levels of sIL-2Rα and expressed the IL-2Rα surface receptor.ConclusionsThis report describes the cytokines relevant to prognosis in patients with untreated TCL and provides the rationale to include serum IL-1RA and sIL-2Rα as biomarkers in future trials. Inhibition of these cytokines may also be of therapeutic benefit.     

CTCL患者外周血淋巴细胞亚群、血清sIL-2R及炎性因子的水平变化特点及意义

目的:探讨皮肤T细胞淋巴瘤（CTCL）患者外周血淋巴细胞亚群及血清可溶性白细胞介素2受体（sIL-2R）、炎性因子的水平变化特点及意义。方法:选取2013年1月至2018年1月在我院治疗的CTCL患者35例（CTCL组）,同时选取炎症性皮肤病患者35例作为对照组,检测两组血清sIL-2R、B淋巴细胞、T淋巴细胞和NK细胞水平以及白细胞介素-6（IL-6）、肿瘤坏死因子 （TNF-α）和C反应蛋白（CRP）。结果:CTCL组血清sIL-2R为（770.15±87.44）U/ml,明显高于对照组（P＜0.05）,而B淋巴细胞为6.10（0.15～10.57）%,明显低于对照组（P＜0.05）;CTCL组和对照组T淋巴细胞和NK细胞比较差异无统计学意义（P＞0.05）;CTCL组血清IL-6、TNF-α和CRP分别为110.02(67.39,230.03)pg/ml、（31.29±7.28）pg/ml和（36.60±6.10）mg/L,明显高于对照组（P＜0.05）;皮损改善患者治疗后sIL-2R为（230.04±78.11）U/ml,明显低于皮损未改善患者（P＜0.05）。结论:CTCL患者血清sIL-2R、IL-6、TNF-α和CRP升高,而B淋巴细胞水平降低,其中sIL-2R与治疗效果有一定关系,值得进一步研究。     

Role of PKC-ERK signaling in tamoxifen-induced apoptosis and tamoxifen resistance in human breast cancer cells

This study was designed to investigate the role of protein kinase C (PKC) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling in tamoxifen (TAM)-induced apoptosis and drug resistance in human breast cancer cells. Drug-sensitive, or estrogen receptor (ER)-positive human breast carcinoma cells (MCF-7) and the multi-drug-resistant variant (ER-negative) MCF-7/ADR cells were treated with doses of TAM for various periods of time. Cell viability and apoptosis were assessed using cell counting, DNA fragmentation and flow cytometric analysis. We found that TAM administration caused a significant increase in apoptosis of MCF-7 cells but not MCF-7/ADR cells. Western blot analysis revealed enhanced expression of PKCδ but decreased expression of PKCα in ER-positive MCF-7 cells; while ER-negative MCF-7/ADR cells had decreased levels of PKCδ and increased levels of PKCα. Interestingly, we observed that in MCF-7 cells, TAM stimulated apoptosis by promoting rapid activation of PKCδ, antagonizing downstream signaling of ERK phosphorylation; while in MCF-7/ADR cells, TAM upregulated PKCα, which promoted ERK phosphorylation. These results suggest that PKCδ enhances apoptosis in TAM-treated MCF-7 cells by antagonizing ERK phosphorylation; while the PKCα pathway plays an important role in TAM-induced drug resistance by activating ERK signaling in MCF-7/ADR cells. The combination of TAM with PKCα and ERK inhibitors could promote TAM-induced apoptosis in breast cancer cells.     

Quantitative and functional alterations of plasmacytoid dendritic cells contribute to immune tolerance in ovarian cancer

In ovarian cancer, the immune system fails to eradicate established tumors partly due to the induction of immune tolerance within tumor microenvironment. In this study, we investigated the contribution of plasmacytoid dendritic cells (pDC) in the establishment of immune tolerance in a cohort of 44 ovarian cancer patients. In the tumor and malignant ascites, CD4(+)CD123(+)BDCA2(+) pDC were the most abundant dendritic cell subset; however, they were profoundly depleted in peripheral blood. The presence of pDC in primary ovarian cancer, but not ascites, was an independent prognostic factor associated with early relapse. Following chemotherapy, we observed a partial restoration of blood pDC levels in patients in complete remission. These findings show preferential recruitment of pDC into tumors where they express a partially mature phenotype that may reflect an in situ activation. Importantly, compared with pDC found in ascites or blood, tumor-associated pDC (TApDC) produced less IFN-α, TNF-α, IL-6, macrophage inflammatory protein-1β, and RANTES in response to toll-like receptor stimulation, and alterations in pDC functions were mainly mediated through tumor-derived TNF-α and TGF-β. Unlike ascites-derived pDC, TApDC induced IL-10 production from allogeneic naive CD4(+) T lymphocytes, suggesting the existence of a paracrine immunosuppressive loop. Taken together, our findings indicate that both local and systemic dysfunction of pDC play a critical role in the progression of ovarian cancer via induction of immune tolerance.     

缺氧诱导的结直肠癌外泌体通过激活PTEN/PI3Kγ信号通路介导巨噬细胞极化

目的:探究缺氧条件下,结直肠癌细胞外泌体对巨噬细胞极化的影响及机制。方法:差速离心法提取正常条件下和缺氧条件下结直肠癌细胞HT-29所分泌的外泌体（HT-29 N-exo和HT-29 H-exo）,透射电镜和Western blot鉴定外泌体,荧光显微镜下观察外泌体的摄取。将U937细胞与100 ng/mL的PMA共孵育的同时分别与1 μg/mL的HT-29 N-exo和HT-29 H-exo以及等体积的PBS共孵育,记为PBS组、HT-29 N-exo组、HT-29 H-exo组。qRT-PCR检测各组细胞CD163、IL-10、IL-1Rα、TGF-β1、CCL2、TNF-α mRNA的表达,Elisa检测各组细胞IL-10 和 TNF-α 分泌,流式细胞术鉴定各组细胞CD163和CD11b表达,Western blot检测各组细胞PTEN/PI3Kγ信号通路激活情况。结果:差速离心法所提取的外泌体符合其结构和生物学特征,并且可被U937细胞摄取;相比于HT-29 N-exo组, HT-29 H-exo组细胞CD163、IL-10、IL-1Rα、TGF-β1、CCL2表达显著增加（P＜0.05）,IL-10分泌显著增加,TNF-α 表达以及分泌显著减少（P＜0.01）,CD163+CD11b+巨噬细胞数显著增加（P＜0.001）,PTEN/PI3Kγ信号通路显著激活（P＜0.001）。结论:缺氧条件下结直肠癌细胞外泌体能够显著促进巨噬细胞M2型极化,其机制为激活PTEN/PI3Kγ信号通路。     

Inhibition of malignant ascites and growth of human ovarian carcinoma by oral administration of a potent inhibitor of the vascular endothelial growth factor receptor tyrosine kinases

We determined whether inhibition of the catalytic tyrosine kinase activity of the receptors for vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) inhibits the formation of malignant ascites and the progressive growth of human ovarian carcinoma cells implanted into the peritoneal cavity of nude mice. The novel protein tyrosine inhibitor PTK 787 was evaluated in two models of human ovarian cancer: Hey-A8 cells, which express low levels of VEGF/VPF and grow as solid tumor foci on the surface of peritoneal organs, and SKOV3 i.p.1 cells, which express high levels of VEGF/VPF and grow as solid peritoneal tumors and ascites. Treatment of nude mice by daily oral administration of 50 mg/kg PTK 787 was not effective against Hey-A8 tumors. In sharp contrast, it significantly inhibited growth of SKOV3 i.p.1 cells and formation of ascites, significantly increasing survival of mice with the implants. Tumor-induced vascular hyperpermeability in the peritoneum of tumor-bearing mice was inhibited by PTK 787, which accounted for its inhibition of ascites formation. Our results suggest that blockade of the VEGF/VPF receptor may be an efficient strategy to inhibit formation of malignant ascites and growth of VEGF/VPF-dependent human ovarian carcinomas.