c-Met and hepatocyte growth factor: Potential as novel targets in cancer therapy

Receptor tyrosine kinases have come to fruition as therapeutic targets in a variety of malignancies. In this group of targets, the c-Met receptor tyrosine kinase plays an important role in increased cell growth, reduced apoptosis, altered cytoskeletal function, increased metastasis, and other biologic changes. The ligand for c-Met is hepatocyte growth factor (HGF), also known as scatter factor. Met is overexpressed and mutated in a variety of malignancies, among which germline mutations are of particular interest. Most mutations of Met have been found in the juxtamembrane, the tyrosine kinase, and the semaphorin domain. Met gain-of-function mutations lead to deregulated or prolonged tyrosine kinase activity, which is instrumental to its transforming activity. This review summarizes the biologic functions regulated by Met and its structural requirements as well as related developments in targeted therapy. Treatment approaches, including antagonism of HGF binding to Met, targeting of RNA and the Met protein, and inhibition of the tyrosine kinase domain of Met, are highlighted. Targeting of the HGF/Met pathway, alone or in combination with standard therapies, is likely to improve current therapies in Met-dependent malignancies.     

NK4 (HGF-antagonist/angiogenesis inhibitor) in cancer biology and therapeutics

Invasion and subsequent establishment of metastasis are devastating events for patients with cancer, but past therapeutic approaches have paid relatively little attention to these important issues. Hepatocyte growth factor (HGF) and its receptor, the c-Met tyrosine kinase, play roles in cancer invasion and metastasis in a wide variety of tumor cells. Activation of the c-Met receptor integrates multiple signal transduction pathways involved in cell-cell and cell-matrix interactions, cellular migration, and breakdown of the extracellular scaffold. Paracrine activation of the c-Met receptor by stromal-derived HGF mediates tumor-stromal interactions that facilitate invasion and metastasis. Likewise, aberrant expression of the c-Met receptor and autocrine or mutational activation of c-Met receptor tyrosine kinase are closely associated with the progression of malignant tumors. Based on this background, NK4, a competitive antagonist of HGF-c-Met association was prepared so as to block cancer invasion and metastasis. NK4, an internal fragment of HGF, binds to but does not activate the c-Met receptor, thereby competitively antagonizing the biological activities of HGF. Unexpectedly, NK4 was subsequently shown to be an angiogenesis inhibitor as well, and this angioinhibitory activity is independent of its action as an HGF-antagonist. Importantly, NK4 protein or NK4 gene therapy have been shown to inhibit tumor invasion, metastasis and angiogenesis, effectively converting malignant tumors into benign tumors. Targeting tumor invasion-metastasis and angiogenesis with NK4 seems to have considerable therapeutic potential for cancer patients. (Cancer Sci 2003; 94: 321–327)     

Mutations of the epidermal growth factor receptor gene in gastrointestinal tract tumor cell lines

The epidermal growth factor receptor (EGFR) is commonly overexpressed in many human tumors including gastrointestinal tract tumors. Gefitinib is a selective inhibitor of EGFR tyrosine kinase, and blocks several signal transduction pathways including those involved in tumor cell proliferation, angiogenesis and metastasis. Recent mutational and biological studies have suggested that mutations in the tyrosine kinase domain of the EGFR gene are well correlated with the response to gefitinib, and that these mutations are frequently observed in non-small cell lung cancers affecting women, East Asians and non-smokers. This led us to speculate that EGFR gene mutations may occur frequently in gastrointestinal tract carcinomas (GITCs) because overexpression is observed in these tumor types. To investigate EGFR mutations in GICTs, we studied 11 esophageal, 6 gastric, and 12 colorectal cancer cell lines. We found a missense mutation in a gastric cancer cell line, and 10 single nucleotide polymorphisms. The occurrence of rare mutations in the tyrosine kinase domain of the EGFR gene suggests that gefitinib is unlikely to be reliable as single-drug therapy for GITCs.     

Mechanisms of translational deregulation in human tumors and therapeutic intervention strategies

Analysis of the recurrent genetic aberrations present in human tumors provides insight into how normal cells escape appropriate proliferation and survival cues. Commonly mutated genes encode proteins that monitor DNA damage (e.g., p53), proteins that regulate the cell cycle (such as Rb), and proteins that regulate signal transduction pathways (such as APC, PTEN and Ras). Analysis of the relevant targets and downstream events of these genes in normal and tumor cells will clearly highlight important pathways for tumorigenesis. However, more infrequent mutations are also informative in defining events critical for the process of tumorigenesis, and often delineate important pathways lying downstream of commonly mutated oncogenes and tumor suppressors. Together, these studies have led to the conclusion that deregulated protein synthesis plays an important role in human cancer. This review will discuss the evidence implicating mRNA translation as an important downstream consequence of signal transduction pathways initiated by mutated oncogenes and tumor suppressors, as well as additional genetic findings implicating the importance of global and specific translational control in human cancer. It will also discuss therapeutic strategies that take advantage of differences in translational regulation between normal and tumor cells.     

Targeting of membrane receptor tyrosine kinases: is there resistance in the HER?

Human Epidermal growth factor Receptors (HER) play an important role in cellular proliferation, and differentiation. Their overexpression in tumor tissues is often associated with a poor prognosis. Consequently, HER receptors are interesting therapeutic targets for cancer treatment. Two strategies are proposed. First, monoclonal antibodies can be used to inhibit the binding of one ligand to its receptor. The second approach is based upon the designing of tyrosine kinase inhibitors capable to bind into the phosphorylation site of the receptor. Consequently, both approaches block the signal transduction downstream. Resistance to anti receptor tyrosine kinase therapy can lead to enhanced morbidity associated with high therapeutic cost. Different mechanisms can be implicated. Non specific mechanisms include alterations of the signal transduction pathways (PI3K/AKT), recruitment of alternative receptor tyrosine kinase pathways (IGFR, VEGFR) and proteasome degradation inhibition. Other mechanisms are specific to HER and rely on inhibition of the binding of monoclonal antibodies (sialomucin-MUC4), heterodimerisation of HER, truncated soluble receptors intervention and mutated variants, as demonstrated very recently with EGF receptors, or genetic polymorphism. This paper reviews these different resistance mechanisms that have been identified in preclinical and clinical situations.     

KIT overexpression induces proliferation in astrocytes in an imatinib-responsive manner and associates with proliferation index in gliomas

Activating gene mutations, gene amplifications and overexpressed proteins may be useful as targets for novel therapies. Alterations at chromosome locus 4q12 are associated with gliomas and the region harbors the receptor tyrosine kinase gene KIT, which is frequently amplified in gliomas, and also overexpressed in a subset of gliomas. KIT and its ligand stem cell factor are widely expressed in embryonic and adult mouse brain, and they play a role in many signal transduction pathways involved in cellular proliferation, differentiation and cancer cell metastasis. However, the function of KIT in gliomagenesis or disease progression remains unresolved as well as its role in neural and brain tumor development. In this study, we utilized lentivirus-mediated gene transfer to deliver the KIT gene into mouse astrocytes. The growth properties of KIT overexpressing cells were analyzed using several in vitro functional assays. The effect of receptor tyrosine kinase inhibitor imatinib on astrocyte growth was also investigated. Our results indicate that overexpression of KIT in mouse astrocytes promotes cell proliferation, and the increased proliferation is partly inhibited by imatinib treatment. Furthermore, KIT overexpression induces phenotypic changes in the cells suggesting that KIT may play a role in astrocyte growth regulation.     

An orally available small-molecule inhibitor of c-Met, PF-2341066, exhibits cytoreductive antitumor efficacy through antiproliferative and antiangiogenic mechanisms

The c-Met receptor tyrosine kinase and its ligand, hepatocyte growth factor (HGF), have been implicated in the progression of several human cancers and are attractive therapeutic targets. PF-2341066 was identified as a potent, orally bioavailable, ATP-competitive small-molecule inhibitor of the catalytic activity of c-Met kinase. PF-2341066 was selective for c-Met (and anaplastic lymphoma kinase) compared with a panel of >120 diverse tyrosine and serine-threonine kinases. PF-2341066 potently inhibited c-Met phosphorylation and c-Met-dependent proliferation, migration, or invasion of human tumor cells in vitro (IC(50) values, 5-20 nmol/L). In addition, PF-2341066 potently inhibited HGF-stimulated endothelial cell survival or invasion and serum-stimulated tubulogenesis in vitro, suggesting that this agent also exhibits antiangiogenic properties. PF-2341066 showed efficacy at well-tolerated doses, including marked cytoreductive antitumor activity, in several tumor models that expressed activated c-Met. The antitumor efficacy of PF-2341066 was dose dependent and showed a strong correlation to inhibition of c-Met phosphorylation in vivo. Near-maximal inhibition of c-Met activity for the full dosing interval was necessary to maximize the efficacy of PF-2341066. Additional mechanism-of-action studies showed dose-dependent inhibition of c-Met-dependent signal transduction, tumor cell proliferation (Ki67), induction of apoptosis (caspase-3), and reduction of microvessel density (CD31). These results indicated that the antitumor activity of PF-2341066 may be mediated by direct effects on tumor cell growth or survival as well as antiangiogenic mechanisms. Collectively, these results show the therapeutic potential of targeting c-Met with selective small-molecule inhibitors for the treatment of human cancers.     

New paradigms in anticancer therapy: targeting multiple signaling pathways with kinase inhibitors

Signal transduction in cancer cells is a sophisticated process that involves receptor tyrosine kinases (RTKs) that eventually trigger multiple cytoplasmic kinases, which are often serine/threonine kinases. A number of tumor models have identified several key cellular signaling pathways that work independently, in parallel, and/or through interconnections to promote cancer development. Three major signaling pathways that have been identified as playing important roles in cancer include the phosphatidyl inositol-3-kinase (PI3K)/AKT, protein kinase C (PKC) family, and mitogen-activated protein kinase (MAPK)/Ras signaling cascades. In clinical trials, highly selective or specific blocking of only one of the kinases involved in these signaling pathways has been associated with limited or sporadic responses. Improved understanding of the complexity of signal transduction processes and their roles in cancer has suggested that simultaneous inhibition of several key kinases at the level of receptors and/or downstream serine/threonine kinases may help to optimize the overall therapeutic benefit associated with molecularly targeted anticancer agents. Using targeted agents to inhibit multiple signaling pathways has emerged as a new paradigm for anticancer treatment based on preclinical and clinical data showing potent anti-tumor activity of single drugs inhibiting multiple molecular targets or combination therapies involving multiple drugs with selective or narrow target specificity. Preclinical and clinical studies point to molecules on vascular endothelial cells and pericytes as being important targets for anticancer therapies, as well as molecules on or within tumor cells themselves. This suggests that optimal therapeutic approaches to cancer may involve targeting multiple molecules found in both the tumor and supportive tissues. In this review, we will use the most recent preclinical and clinical data to describe this emerging paradigm for anticancer therapy involving targeting multiple signaling pathways with tyrosine or serine/threonine kinase inhibitors.     

FAK 在恶性肿瘤中的研究进展

黏着斑激酶（ Focal adhesion kinase,FAK）是细胞内重要的骨架蛋白,属于一种非受体型酪氨酸蛋白激酶,也是多种信号通路的关键性分子。在肿瘤发生、发展、迁移以及侵袭的各个阶段FAK都具有重要作用。近年来,人们对FAK的研究越来越多,综合国内外研究资料表明,FAK在许多肿瘤组织中表达增高,提示FAK可能与肿瘤的发生发展密切相关,可能是肿瘤治疗的潜在靶点。该综述将对FAK分子结构及功能特点,与肿瘤的关系进行系统阐述。     

KRC-408, a novel c-Met inhibitor,suppresses cell proliferation and angiogenesis of gastric cancer

Among many cancer therapeutic targets, c-Met receptor tyrosine kinase has recently given particular attention. This kinase and its ligand, hepatocyte growth factor (HGF), play a central role in cell proliferation and the survival of several human cancers. Thus, we developed KRC-408 as a novel c-Met inhibitor and investigated its anti-cancer effects on human gastric cancer. KRC-408 inhibited the phosphorylation of c-Met and its constitutive downstream effectors such as phosphatidylinositol 3-kinase (PI3K), Akt, Mek, and Erk. This compound was found to exert anti-cancer effects stronger than those of 5-fluorouracil (5-FU) on gastric cancer cells, especially cell lines that overexpressed c-Met. Interestingly, cytotoxicity of KRC-408 was lower than that of 5-FU in normal gastric cells. Apoptosis induced by KRC-408 was accompanied by increased levels of cleaved caspase-3 and PARP as well as DNA condensation and fragmentation. Flow cytometry analysis showed an accumulation of gastric cancer cells in the G2/M phase with concomitant loss of cells in the S phase following treatment with this drug. In the angiogenesis studies, KRC-408 inhibited tube formation and migration of human umbilical vein endothelial cells (HUVECs), and suppressed microvessel sprouting from rat aortic rings ex vivo along with blood vessel formation in a Matrigel plug assay in mice. Results of an in vivo mouse xenograft experiment showed that the administration of KRC-408 significantly delayed tumor growth in a dose-dependent manner, and suppressed Akt and Erk phosphorylation as well CD34 expression in tumor tissues. These findings indicate that KCR-408 may exert anti-tumor effects by directly affecting tumor cell growth or survival via the c-Met receptor tyrosine kinase pathway. We therefore suggest that KRC-408 is a novel therapeutic candidate effective against gastric cancers that overexpress c-Met.     

mda-9/Syntenin: a positive regulator of melanoma metastasis

Metastasis is a significant event in cancer progression and continues to pose the greatest challenge for a cancer cure. Defining genes that control metastasis in vivo may provide new targets for intervening in this process with profound therapeutic implications. Melanoma differentiation associated gene-9 (mda-9) was initially identified by subtraction hybridization as a novel gene displaying biphasic expression during terminal differentiation in human melanoma cells. Mda-9, also known as syntenin, is a PDZ-domain protein overexpressed in many types of human cancers, where it is believed to function in tumor progression. However, a functional role of mda-9/syntenin in tumor growth and metastasis and the signaling pathways involved in mediating these biological activities remain to be defined. Evidence is now provided, using weakly and highly metastatic isogenic melanoma variants, that mda-9/syntenin regulates metastasis. Expression of mda-9/syntenin correlates with advanced stages of melanoma progression. Regulating mda-9/syntenin expression using a replication-incompetent adenovirus expressing either sense or antisense mda-9/syntenin modifies the transformed phenotype and alters metastatic ability in immortal human melanocytes and metastatic melanoma cells in vitro and in vivo in newborn rats. A direct relationship is observed between mda-9/syntenin expression and increased phosphorylation of focal adhesion kinase, c-Jun-NH2-kinase, and p38. This study provides the first direct link between mda-9/syntenin expression and tumor cell dissemination in vivo and indicates that mda-9/syntenin expression activates specific signal transduction pathways, which may regulate melanoma tumor progression. Based on its ability to directly alter metastasis, mda-9/syntenin provides a promising new focus for melanoma cancer research with potential therapeutic applications for metastatic diseases.     

c-Met信号通路在多种恶性肿瘤中的研究进展

近年来,恶性肿瘤的治疗已进入了个体化和分子靶向时代,因此,研发针对肿瘤病人个体新的治疗靶点已成为重中之重。大量临床和基础实验研究发现,由间质细胞产生的肝细胞生长因子(Hepatocyte growth factor receptor,HGF)与上皮细胞中的特异受体间质——上皮细胞转化因子(Mesenchymal-epithelial transition factor,c-Met)结合并激活该受体的酪氨酸活性,促进多种类型细胞的生长、迁移和形态学改变,继而促进肿瘤的侵袭、转移和血管生成。在甲状腺癌、乳腺癌、肺癌、头颈部鳞癌、中枢神经系统肿瘤及消化系统肿瘤的发生、发展中,HGF及其受体c-Met起着重要作用。HGF/c-Met信号通路作为多种实体瘤的新靶点,被认为是近年来最有前景的治疗靶点,已成为目前研究的热点之一。本文将主要就HGF及c-Met受体的结构、功能、激活机制及在多种恶性肿瘤中的研究进展做一综述。     

The impact of gefitinib on epidermal growth factor receptor signaling pathways in cancer

The ErbB family of receptor tyrosine kinases, of which the epidermal growth factor receptor (EGFR) is the prototype, is associated with the formation and malignant progression of most of the common solid tumors. These molecules play a key role in a complex network of signal transduction pathways that function in normal development as well as in neoplastic transformation. The EGFR and other family members are therefore promising targets for new anticancer therapies. In normal tissues, EGFR-tyrosine kinase (TK) activity is strictly controlled. However, in tumor cells, there are multiple mechanisms that can lead to increased or inappropriate EGFR-TK activity, including altered expression of EGFR, its ligand, or interacting molecules; decreased deactivation through phosphatases or downregulation; or mutation of the EGFR protein. Novel therapeutic approaches aimed at inhibiting increased EGFR-TK activity include antibodies that block the extracellular ligand-binding site, antibody or ligand fusion proteins that specifically target toxins to the tumor cells, or small-molecule TK inhibitors (TKIs) that act intracellularly to block downstream signal transduction from EGFR. Studies have shown that such blockade can lead to reduced cellular proliferation, inhibition of survival signals, and inhibition of tumor metastasis and angiogenesis. Additionally, some agents, including EGFR antibodies and TKIs such as gefitinib have been demonstrated to be effective against various human solid tumors in preclinical models and have shown activity in advanced non-small-cell lung cancer and other solid tumors.     

Radiation stimulates HGF receptor/c-Met expression that leads to amplifying cellular response to HGF stimulation via upregulated receptor tyrosine phosphorylation and MAP kinase activity in pancreatic cancer cells

Hepatocyte growth factor (HGF) is a stromal-derived cytokine that plays a crucial role in invasion and metastasis of tumor cells through the interaction with HGF receptor, c-Met, which is frequently overexpressed in pancreatic cancer. The present study was designed to investigate the change in HGF receptor and HGF-mediated signaling after irradiation in pancreatic cancer cells. Six cell lines from human pancreatic cancer were included in the study. Gamma-radiation was used for irradiation treatment. The changes in expression levels of c-Met were evaluated by immunoblot and confirmed morphologically by indirect immunofluorescence staining. Whether the resultant alteration in c-Met would cascade as biologically usable signals upon HGF ligation was traced by receptor tyrosine phosphorylation analysis and mitogen activated protein kinase (MAP kinase or MAPK) activity assay. The various biological responses to HGF (including cell proliferation, cell scattering, migration and invasion) were evaluated as well. We also used a 4-kringle antagonist of HGF, NK4, to block the HGF/c-Met signaling pathway. Both immunoblot and immunofluorescent analysis showed moderate increased expression of c-Met in 3 of 6 pancreatic cancer cell lines after irradiation. The actions seemed to be dose-responsible, which began at 3 hr and reached its peak value at 24 hr following irradiation. The radiation-increased expression of c-Met could transform into magnifying receptor tyrosine phosphorylation reaction and MAP kinase activity once the ligand was added, fairly corresponding with alteration in the receptor. Sequentially, the cellular responses to HGF, including scattering and invasion but not proliferation, were enhanced. Also, in the presence of HGF, the elevated receptor could help to recover the radiation-compromised cell migration. A recombinant HGF antagonist, NK4 could effectively block these aberrant effects activated by irradiation both in molecular and cellular levels, thus suggesting the deep involvement of the c-Met/HGF pathway in the enhanced malignant potential after irradiation. These results suggest that radiation may promote HGF-induced malignant biological behaviors of certain pancreatic cancer cells through the up-regulated HGF/c-Met signal pathway. Selectively targeted blockade of the HGF/c-Met pathway could help to abolish the enforced malignant behavior of tumor cells by irradiation and therefore may improve the efficacy of radiotherapy for pancreatic cancer.     

Tyrosine kinase inhibitors: Multi-targeted or single-targeted?

Since in most tumors multiple signaling pathways are involved, many of the inhibitors in clinical development are designed to affect a wide range of targeted kinases. The most important tyrosine kinase families in the development of tyrosine kinase inhibitors are the ABL, SCR, platelet derived growth factor, vascular endothelial growth factor receptor and epidermal growth factor receptor families. Both multi-kinase inhibitors and single-kinase inhibitors have advantages and disadvantages, which are related to potential resistance mechanisms, pharmacokinetics, selectivity and tumor environment. In different malignancies various tyrosine kinases are mutated or overexpressed and several resistance mechanisms exist. Pharmacokinetics is influenced by interindividual differences and differs for two single targeted inhibitors or between patients treated by the same tyrosine kinase inhibitor. Different tyrosine kinase inhibitors have various mechanisms to achieve selectivity, while differences in gene expression exist between tumor and stromal cells. Considering these aspects, one type of inhibitor can generally not be preferred above the other, but will depend on the specific genetic constitution of the patient and the tumor, allowing personalized therapy. The most effective way of cancer treatment by using tyrosine kinase inhibitors is to consider each patient/tumor individually and to determine the strategy that specifically targets the consequences of altered (epi)genetics of the tumor. This strategy might result in treatment by a single multi kinase inhibitor for one patient, but in treatment by a couple of single kinase inhibitors for other patients.     

Reduced c-Met expression by an adenovirus expressing a c-Met ribozyme inhibits tumorigenic growth and lymph node metastases of PC3-LN4 prostate tumor cells in an orthotopic nude mouse model.

PURPOSE: The expression of c-Met, the receptor protein tyrosine kinase for hepatocyte growth factor/scatter factor, frequently increases during prostate tumor progression. However, whether reduced c-Met expression inhibits tumor growth and metastasis has not been ascertained. EXPERIMENTAL DESIGN: c-Met expression was reduced by infection of an adenovirus expressing a c-Met ribozyme into the highly metastatic human prostate cancer cell line PC3-LN4. In vitro, effects on c-Met, Akt, and extracellular signal-regulated kinase 1/2 expression and phosphorylation, Src expression and activity, and vascular endothelial growth factor expression were determined, as were effects on cell migration and invasion. Prostate tumor formation and metastasis to regional lymph nodes in nude mice were examined after both ex vivo and in vivo infection of cells. RESULTS: Infection of PC3-LN4 cells with the Ad-c-Met-expressing ribozyme decreased steady-state c-Met levels, decreased Src kinase activity, decreased vascular endothelial growth factor expression, and decreased migration and invasion versus the pU1 (control) virus. Significant inhibition of tumorigenicity (histologically confirmed tumors in only 1 of 10 mice) and consequent lymph node metastasis were observed upon ex vivo infection of Ad-c-Met. Similarly, gene therapy experiments led to complete inhibition of tumor growth in 7 of 8 mice. CONCLUSIONS: Reduction in c-Met expression substantially inhibits both tumor growth and lymph node metastasis of PC3-LN4 cells in orthotopic nude mouse models. Therefore, targeting the c-Met signaling pathways may be important in controlling tumor growth and metastasis in human prostate cancers.     

E7050: A dual c-Met and VEGFR-2 tyrosine kinase inhibitor promotes tumor regression and prolongs survival in mouse xenograft models

c-Met is the cellular receptor for hepatocyte growth factor (HGF) and is known to be dysregulated in various types of human cancers. Activation of the HGF/c-Met pathway causes tumor progression, invasion, and metastasis. Vascular endothelial growth factor (VEGF) is also known as a key molecule in tumor progression through the induction of tumor angiogenesis. Because of their key roles in tumor progression, these pathways provide attractive targets for therapeutic intervention. We have generated a novel, orally active, small molecule compound, E7050, which inhibits both c-Met and vascular endothelial growth factor receptor (VEGFR)-2. In vitro studies indicate that E7050 potently inhibits phosphorylation of both c-Met and VEGFR-2. E7050 also potently represses the growth of both c- met amplified tumor cells and endothelial cells stimulated with either HGF or VEGF. In vivo studies using E7050 showed inhibition of the phosphorylation of c-Met and VEGFR-2 in tumors, and strong inhibition of tumor growth and tumor angiogenesis in xenograft models. Treatment of some tumor lines containing c- met amplifications with high doses of E7050 (50–200 mg/kg) induced tumor regression and disappearance. In a peritoneal dissemination model, E7050 showed an antitumor effect against peritoneal tumors as well as a significant prolongation of lifespan in treated mice. Our results indicate that E7050 is a potent inhibitor of c-Met and VEGFR-2 and has therapeutic potential for the treatment of cancer. ( Cancer Sci 2009)     

An Orally Available Small-Molecule Inhibitor of c-Met,PF-2341066, Reduces Tumor Burden and Metastasis in a Preclinical Model of Ovarian Cancer Metastasis

Deregulated expression of the hepatocyte growth factor (HGF) receptor, c-Met, in cancer contributes to tumor progression and metastasis. The objective of this study was to determine whether blocking c-Met with an orally available c-Met inhibitor, PF-2341066, reduces tumor burden and increases survival in a xenograft model of ovarian cancer metastasis. Treatment of mice injected interperitoneally with SKOV3ip1 cells showed reduced overall tumor burden. Tumor weight and the number of metastases were reduced by 55% (P < .0005) and 62% (P < .0001), respectively. Treatment also increased median survival from 45 to 62 days (P = .0003). In vitro, PF-2341066 reduced HGF-stimulated phosphorylation of c-Met in the tyrosine kinase domain as well as phosphorylation of the downstream signaling effectors, Akt and Erk. It was apparent that inhibition of the pathways was functionally important because HGF-induced branching morphogenesis was also inhibited. In addition, proliferation and adhesion to various extracellular matrices were inhibited by treatment with PF-2341066, and the activity of matrix metalloproteinases was decreased in tumor tissue from treated mice compared with those receiving vehicle. Overall, these data indicate that PF-2341066 effectively reduces tumor burden in an in vivo model of ovarian cancer metastasis and may be a good therapeutic candidate in the treatment of patients with ovarian cancer.