AZ12756122, a novel fatty acid synthase inhibitor, decreases resistance features in EGFR-TKI resistant EGFR-mutated NSCLC cell models.

Different EGFR tyrosine kinase inhibitors (TKIs) have been developed for the treatment of non-small cell lung cancer (NSCLC) patients harboring sensitizing mutations in the EGFR gene. Apart from acquired secondary mutations, multiple resistance mechanisms have been reported, such as the overexpression of fatty acid synthase (FASN), a multi-functional enzyme essential for the de novo lipogenesis, or the increase of cancer stem cells, a small subpopulation within the tumor responsible for relapse, metastasis, and resistance to therapies. Hence, the purpose of this work is to evaluate the novel FASN inhibitor AZ12756122, both alone and in combination with gefitinib and osimertinib, in EGFR-mutated (EGFRm) lung adenocarcinoma cell models sensitive and resistant to EGFR-TKIs. The molecular effect of AZ12756122 (alone and in combination with EGFR-TKI) on FASN, EGFR/STAT3, Akt/mTOR, and MAPK signaling pathways was analyzed using RT-qPCR and Western blot. FASN expression was also evaluated in samples from patients with EGFRm NSCLC through immunohistochemistry. Our findings revealed that AZ12756122 caused cytotoxic effects inducing apoptosis, downregulated FASN expression and activity, decreased the activation of EGFR and Akt/mTOR pathway, and reduced cancer stem-like cells. Furthermore, the combination of AZ12756122 and osimertinib sensitized cells to EGFR-TKI, showing a synergistic effect that resulted in a reduction in the activation of EGFR, Akt/mTOR, and MAPK signaling pathways. Our study also showed that FASN+ EGFRm NSCLC patients exhibited a longer mPFS in patients who responded to EGFR-TKI treatment. In conclusion, FASN inhibition should be further studied for the treatment, alone or in combination with EGFR-TKIs, for EGFRm NSCLC patients.

Polycaprolactone Electrospun Scaffolds Produce an Enrichment of Lung Cancer Stem Cells in Sensitive and Resistant EGFRm Lung Adenocarcinoma.

The establishment of a three-dimensional (3D) cell culture model for lung cancer stem cells (LCSCs) is needed because the study of these stem cells is unable to be done using flat surfaces. The study of LCSCs is fundamental due to their key role in drug resistance, tumor recurrence, and metastasis. Hence, the purpose of this work is the evaluation of polycaprolactone electrospun (PCL-ES) scaffolds for culturing LCSCs in sensitive and resistant EGFR-mutated (EGFRm) lung adenocarcinoma cell models. We performed a thermal, physical, and biological characterization of 10% and 15%-PCL-ES structures. Several genes and proteins associated with LCSC features were analyzed by RT-qPCR and Western blot. Vimentin and CD133 tumor expression were evaluated in samples from 36 patients with EGFRm non-small cell lung cancer through immunohistochemistry. Our findings revealed that PC9 and PC9-GR3 models cultured on PCL-ES scaffolds showed higher resistance to osimertinib, upregulation of ABCB1, Vimentin, Snail, Twist, Sox2, Oct-4, and CD166, downregulation of E-cadherin and CD133, and the activation of Hedgehog pathway. Additionally, we determined that the non-expression of CD133 was significantly associated with a low degree of histological differentiation, disease progression, and distant metastasis. To sum up, we confirmed PCL-ES scaffolds as a suitable 3D cell culture model for the study of the LCSC niche.

FGFR a promising druggable target in cancer: Molecular biology and new drugs.

INTRODUCTION: The Fibroblast Growth Factor Receptor (FGFR) family consists of Tyrosine Kinase Receptors (TKR) involved in several biological functions. Recently, alterations of FGFR have been reported to be important for progression and development of several cancers. In this setting, different studies are trying to evaluate the efficacy of different therapies targeting FGFR. AREAS COVERED: This review summarizes the current status of treatments targeting FGFR, focusing on the trials that are evaluating the FGFR profile as inclusion criteria: Multi-Target, Pan-FGFR Inhibitors and anti-FGF (Fibroblast Growth Factor)/FGFR Monoclonal Antibodies. EXPERT OPINION: Most of the TKR share intracellular signaling pathways; therefore, cancer cells tend to overcome the inhibition of one tyrosine kinase receptor by activating another. The future of TKI (Tyrosine Kinase Inhibitor) therapy will potentially come from multi-targeted TKIs that target different TKR simultaneously. It is crucial to understand the interaction of the FGF-FGFR axis with other known driver TKRs. Based on this, it is possible to develop therapeutic strategies targeting multiple connected TKRs at once. One correct step in this direction is the reassessment of multi target inhibitors considering the FGFR status of the tumor. Another opportunity arises from assessing the use of FGFR TKI on patients harboring FGFR alterations.

Erlotinib and bevacizumab in patients with advanced non-small-cell lung cancer and activating EGFR mutations (BELIEF): an international, multicentre, single-arm, phase 2 trial.

BACKGROUND: The tyrosine kinase inhibitor erlotinib improves the outcomes of patients with advanced non-small-cell lung carcinoma (NSCLC) harbouring epidermal growth factor receptor (EGFR) mutations. The coexistence of the T790M resistance mutation with another EGFR mutation in treatment-naive patients has been associated with a shorter progression-free survival to EGFR inhibition than in the absence of the T790M mutation. To test this hypothesis clinically, we developed a proof-of-concept study, in which patients with EGFR-mutant NSCLC were treated with the combination of erlotinib and bevacizumab, stratified by the presence of the pretreatment T790M mutation. METHODS: BELIEF was an international, multicentre, single-arm, phase 2 trial done at 29 centres in eight European countries. Eligible patients were aged 18 years or older and had treatment-naive, pathologically confirmed stage IIIB or stage IV lung adenocarcinoma with a confirmed, activating EGFR mutation (exon 19 deletion or L858R mutation). Patients received oral erlotinib 150 mg per day and intravenous bevacizumab 15 mg/kg every 21 days and were tested centrally for the pretreatment T790M resistance mutation with a peptide nucleic acid probe-based real-time PCR. The primary endpoint was progression-free survival. The primary efficacy analysis was done in the intention-to-treat population and was stratified into two parallel substudies according to the centrally confirmed pretreatment T790M mutation status of enrolled patients (T790M positive or negative). The safety analysis was done in all patients that have received at least one dose of trial treatment. This trial was registered with ClinicalTrials.gov, number NCT01562028. FINDINGS: Between June 11, 2012, and Oct 28, 2014, 109 patients were enrolled and included in the efficacy analysis. 37 patients were T790M mutation positive and 72 negative. The overall median progression-free survival was 13·2 months (95% CI 10·3-15·5), with a 12 month progression-free survival of 55% (95% CI 45-64). The primary endpoint was met only in substudy one (T790M-positive patients). In the T790M-positive group, median progression-free survival was 16·0 months (12·7 to not estimable), with a 12 month progression-free survival of 68% (50-81), whereas in the T790M-negative group, median progression-free survival was 10·5 months (9·4-14·2), with a 12 month progression-free survival of 48% (36-59). Of 106 patients included in the safety analysis, five had grade 4 adverse events (one acute coronary syndrome, one biliary tract infection, one other neoplasms, and two colonic perforations) and one died due to sepsis. INTERPRETATION: The BELIEF trial provides further evidence of benefit for the combined use of erlotinib and bevacizumab in patients with NSCLC harbouring activating EGFR mutations. FUNDING: European Thoracic Oncology Platform, Roche.

Response of brain metastasis from lung cancer patients to an oral nutraceutical product containing silibinin.

Despite multimodal treatment approaches, the prognosis of brain metastases (BM) from non-small cell lung cancer (NSCLC) remains poor. Untreated patients with BM have a median survival of about 1 month, with almost all patients dying from neurological causes. We herein present the first report describing the response of BM from NSCLC patients to an oral nutraceutical product containing silibinin, a flavonoid extracted from the seeds of the milk thistle. We present evidence of how the use of the silibinin-based nutraceutical Legasil® resulted in significant clinical and radiological improvement of BM from NSCLC patients with poor performance status that progressed after whole brain radiotherapy and chemotherapy. The suppressive effects of silibinin on progressive BM, which involved a marked reduction of the peritumoral brain edema, occurred without affecting the primary lung tumor outgrowth in NSCLC patients. Because BM patients have an impaired survival prognosis and are in need for an immediate tumor control, the combination of brain radiotherapy with silibinin-based nutraceuticals might not only alleviate BM edema but also prove local control and time for either classical chemotherapeutics with immunostimulatory effects or new immunotherapeutic agents such as checkpoint blockers to reveal their full therapeutic potential in NSCLC BM patients. New studies aimed to illuminate the mechanistic aspects underlying the regulatory effects of silibinin on the cellular and molecular pathobiology of BM might expedite the entry of new formulations of silibinin into clinical testing for progressive BM from lung cancer patients.

Neoadjuvant Chemoradiotherapy Treatment for a Classic Biphasic Pulmonary Blastoma with High PD-L1 Expression.

Pulmonary blastomas are rare malignant tumors, comprising only 0.25-0.5% of all malignant lung neoplasms. The prognosis of pulmonary blastoma is very poor, with an overall five-year survival of 16%. No standard treatment has been defined for unresectable disease. We present the case of a 25-year-old woman with unresectable locally advanced classic biphasic pulmonary blastoma (CBPB) successfully treated with neodjuvant chemoradiotherapy based on two chemotherapy induction cycles of cisplatin plus etoposide, followed by concurrent weekly cisplatin to 50.4 Gy radiotherapy treatment. The patient had a significant reduction in tumor size, allowing for complete resection by pneumonectomy. Molecular study for epidermal growth factor receptor (EGFR) mutations, anaplastic lymphoma kinase (ALK), proto-oncogene receptor tyrosine kinase (ROS1) and rearranged during transfection (RET) rearrangements, and programmed death ligand 1 (PD-L1) expression was performed in the pre-treatment tumor sample. Our patient presented a high expression (>90% of tumor cells) of PD-L1. To our knowledge, this is the first report of PD-L1 expression in CBPB. This could lead to new treatment options based on new immunotherapy agents blocking the PD-1/PD-L1 pathway for this rare disease with poor prognosis.

Paraneoplastic limbic encephalitis in a male with squamous cell carcinoma of the lung.

BACKGROUND: Paraneoplastic limbic encephalitis (PLE) is a rare syndrome characterized by memory impairment, symptoms of hypothalamic dysfunction, and seizures. It commonly precedes the diagnosis of cancer. Small-cell lung cancer is the neoplasm that is most frequently reported as the etiology underlying PLE. CASE REPORT: This report describes a male patient who presented with neurologic symptoms consistent with anterograde amnesia, apathy, and disorientation. MRI revealed diffuse hyperintensities located predominantly in the medial bitemporal lobes, basal ganglia, frontal lobes, and leptomeninges on fluid attenuated inversion recovery images, suggesting PLE. Study of the primary tumor revealed squamous cell carcinoma of the lung. The patient was treated with neoadjuvant chemotherapy followed by surgery and adjuvant chemoradiotherapy, which resulted in his neurologic symptoms gradually improving. CONCLUSIONS: PLE might be a rare debut of squamous cell carcinoma of the lung. Treatment of the primary tumor may improve the neurologic symptoms.

Assessment of ALK status by FISH on 1000 Spanish non-small cell lung cancer patients.

INTRODUCTION: Patients with non-small cell lung cancer (NSCLC) harboring anaplastic lymphoma kinase (ALK) rearrangement selectively respond to ALK inhibitors. Thus, identification of ALK rearrangements has become a standard diagnostic test in advanced NSCLC patients. Our institution has been a referral center in Spain for ALK determination by Fluorescent in situ hybridization (FISH). The aim of our study was to assess the feasibility and the FISH patterns of the ALK gene and to evaluate the clinical and pathological features of patients with ALK alterations. METHODS: Between 2010 and 2014, 1092 samples were evaluated for ALK using FISH technique (927 histological samples, 165 cytological samples). Correlation with available clinical-pathological information was assessed. RESULTS: ALK rearrangement was found in 35 patients (3.2%). Cytological samples (using either direct smears or cell blocks), were more frequently non-assessable than histological samples (69% versus 89%, respectively) (p < 0.001). Within the ALK-rearranged cases the majority were female, non-smokers, and stage IV. CONCLUSIONS: Although assessable in cytological samples, biopsies are preferred when available for ALK evaluation by FISH. The ALK translocation prevalence and the associated clinico-pathological features in Spanish NSCLC patients are similar to those previously reported.

Successful empirical erlotinib treatment of a mechanically ventilated patient newly diagnosed with metastatic lung adenocarcinoma.

BACKGROUND: Lung cancer is the most common solid tumor in critically ill cancer patients who are admitted to intensive care units (ICUs). An ICU trial consists of unlimited ICU support for a limited time period. CASE REPORT: We present the case of a 60-year-old woman with newly diagnosed metastatic lung adenocarcinoma who required mechanical ventilation due to respiratory failure. Empirical erlotinib treatment was administered through a nasogastric feeding tube as part of an ICU trial, which led to a dramatic and durable response. CONCLUSION: Empirical erlotinib should be considered when epidermal growth factor receptor (EGFR) mutations are suspected in ICU newly diagnosed patients with lung adenocarcinoma.

Fatty acid synthase expression is strongly related to menopause in early-stage breast cancer patients.

OBJECTIVE: Overexpression of fatty acid synthase (FASN), the enzyme involved in the de novo synthesis of fatty acids, has been reported in several human carcinomas, including breast cancer, and has been related to poor prognosis. Our aim was to analyze the association of FASN tumor tissue expression with clinicopathological and anthropometrical features in early-stage breast cancer patients. METHODS: We prospectively studied 53 women with early-stage breast cancer who were treated with surgical operation and postoperative chemotherapy. RESULTS: Menopause status and age were strongly associated with higher levels of FASN tumor expression (P < 0.005 and P = 0.038, respectively). Body mass index and pathological stage were also related to FASN tumor expression. CONCLUSIONS: Our findings suggest that FASN could be a potential therapeutic target in postmenopausal breast cancer patients. However, further studies are needed.

Erlotinib versus standard chemotherapy as first-line treatment for European patients with advanced EGFR mutation-positive non-small-cell lung cancer (EURTAC): a multicentre, open-label, randomised phase 3 trial.

BACKGROUND: Erlotinib has been shown to improve progression-free survival compared with chemotherapy when given as first-line treatment for Asian patients with non-small-cell lung cancer (NSCLC) with activating EGFR mutations. We aimed to assess the safety and efficacy of erlotinib compared with standard chemotherapy for first-line treatment of European patients with advanced EGFR-mutation positive NSCLC. METHODS: We undertook the open-label, randomised phase 3 EURTAC trial at 42 hospitals in France, Italy, and Spain. Eligible participants were adults (> 18 years) with NSCLC and EGFR mutations (exon 19 deletion or L858R mutation in exon 21) with no history of chemotherapy for metastatic disease (neoadjuvant or adjuvant chemotherapy ending ≥ 6 months before study entry was allowed). We randomly allocated participants (1:1) according to a computer-generated allocation schedule to receive oral erlotinib 150 mg per day or 3 week cycles of standard intravenous chemotherapy of cisplatin 75 mg/m(2) on day 1 plus docetaxel (75 mg/m(2) on day 1) or gemcitabine (1250 mg/m(2) on days 1 and 8). Carboplatin (AUC 6 with docetaxel 75 mg/m(2) or AUC 5 with gemcitabine 1000 mg/m(2)) was allowed in patients unable to have cisplatin. Patients were stratified by EGFR mutation type and Eastern Cooperative Oncology Group performance status (0 vs 1 vs 2). The primary endpoint was progression-free survival (PFS) in the intention-to-treat population. We assessed safety in all patients who received study drug (≥ 1 dose). This study is registered with ClinicalTrials.gov, number NCT00446225. FINDINGS: Between Feb 15, 2007, and Jan 4, 2011, 174 patients with EGFR mutations were enrolled. One patient received treatment before randomisation and was thus withdrawn from the study; of the remaining patients, 86 were randomly assigned to receive erlotinib and 87 to receive standard chemotherapy. The preplanned interim analysis showed that the study met its primary endpoint; enrolment was halted, and full evaluation of the results was recommended. At data cutoff (Jan 26, 2011), median PFS was 9·7 months (95% CI 8·4-12·3) in the erlotinib group, compared with 5·2 months (4·5-5·8) in the standard chemotherapy group (hazard ratio 0·37, 95% CI 0·25-0·54; p < 0·0001). Main grade 3 or 4 toxicities were rash (11 [13%] of 84 patients given erlotinib vs none of 82 patients in the chemotherapy group), neutropenia (none vs 18 [22%]), anaemia (one [1%] vs three [4%]), and increased amino-transferase concentrations (two [2%] vs 0). Five (6%) patients on erlotinib had treatment-related severe adverse events compared with 16 patients (20%) on chemotherapy. One patient in the erlotinib group and two in the standard chemotherapy group died from treatment-related causes. INTERPRETATION: Our findings strengthen the rationale for routine baseline tissue-based assessment of EGFR mutations in patients with NSCLC and for treatment of mutation-positive patients with EGFR tyrosine-kinase inhibitors. FUNDING: Spanish Lung Cancer Group, Roche Farma, Hoffmann-La Roche, and Red Temática de Investigacion Cooperativa en Cancer.

[Oxidative stress in patients with cancer: two sides of the same coin]. / Estrés oxidativo en pacientes con cáncer: dos caras de una misma moneda.

Oxidative stress is a biochemical condition of imbalance between free radicals and antioxidant defence mechanisms. Cancer is an inducing oxidative stress disease. Metabolic changes in neoplastic cells, tumor infiltration by inflammatory cells, malnutrition and specific cancer treatment contribute to high levels of oxidative stress in cancer patients. The toxic effects of oxidative stress on normal cells could be counteracted by use of antioxidants, even though they may abrogate the harmful effects of oxidative stress on tumor cells and prevent apoptosis. Thus, currently, there is not enough scientific evidence to support the use of antioxidants in patients with cancer.

Predictive biomarkers in the management of EGFR mutant lung cancer.

Activating mutations in the form of deletions in exon 19 (del 19) or the missense mutation L858R in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) predict outcome to use of EGFR tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib. Pooled data from several phase II studies show that gefitinib and erlotinib induce responses in over 70% of NSCLC patients harboring EGFR mutations, with progression-free survival (PFS) ranging from 9 to 13 months. Two studies in Caucasian and Asian patients have confirmed that these subgroups of patients attain PFS up to 14 months. These landmark outcomes have been accompanied by new challenges, primarily the additional role of chemotherapy and the management of tumors with the secondary T790M mutation that confers resistance to EGFR TKIs. Mechanisms of resistance to reversible EGFR TKIs should be further clarified and could be related to modifications in DNA repair.

Screening for epidermal growth factor receptor mutations in lung cancer.

BACKGROUND: Activating mutations in the epidermal growth factor receptor gene (EGFR) confer hypersensitivity to the tyrosine kinase inhibitors gefitinib and erlotinib in patients with advanced non-small-cell lung cancer. We evaluated the feasibility of large-scale screening for EGFR mutations in such patients and analyzed the association between the mutations and the outcome of erlotinib treatment. METHODS: From April 2005 through November 2008, lung cancers from 2105 patients in 129 institutions in Spain were screened for EGFR mutations. The analysis was performed in a central laboratory. Patients with tumors carrying EGFR mutations were eligible for erlotinib treatment. RESULTS: EGFR mutations were found in 350 of 2105 patients (16.6%). Mutations were more frequent in women (69.7%), in patients who had never smoked (66.6%), and in those with adenocarcinomas (80.9%) (P<0.001 for all comparisons). The mutations were deletions in exon 19 (62.2%) and L858R (37.8%). Median progression-free survival and overall survival for 217 patients who received erlotinib were 14 months and 27 months, respectively. The adjusted hazard ratios for the duration of progression-free survival were 2.94 for men (P<0.001); 1.92 for the presence of the L858R mutation, as compared with a deletion in exon 19 (P=0.02); and 1.68 for the presence of the L858R mutation in paired serum DNA, as compared with the absence of the mutation (P=0.02). The most common adverse events were mild rashes and diarrhea; grade 3 cutaneous toxic effects were recorded in 16 patients (7.4%) and grade 3 diarrhea in 8 patients (3.7%). CONCLUSIONS: Large-scale screening of patients with lung cancer for EGFR mutations is feasible and can have a role in decisions about treatment.

[Fatty acid synthase: a new anti-tumor target]. / Sintasa de ácidos grasos como nueva diana antitumoral.

Fatty acid synthase (FASN), an enzyme capable of de novo fatty acid synthesis, is highly expressed and activated in most human carcinomas. FASN is associated with poor prognosis in prostate and breast cancer and its inhibition is selectively cytotoxic to human cancer cells. Thus, FASN and fatty acid metabolism have become an important focus for the diagnostic and treatment of cancer. In this sense, there is an increasing interest in identifying and developing new antitumor compounds that inhibit FASN.

Fatty acid metabolism in breast cancer cells: differential inhibitory effects of epigallocatechin gallate (EGCG) and C75.

Endogenous fatty acid metabolism is crucial to maintain the cancer cell malignant phenotype. Lipogenesis is regulated by the enzyme fatty acid synthase (FASN); and breakdown of fatty acids is regulated by carnitine palmitoyltransferase-1 (CPT-I). FASN is highly expressed in breast cancer and most common human carcinomas. Several compounds can inhibit FASN, although the degree of specificity of this inhibition has not been addressed. We have tested the effects of C75 and (-)-epigallocatechin-3-gallate (EGCG) on fatty acid metabolism pathways, cellular proliferation, induction of apoptosis and cell signalling in human breast cancer cells. Our results show that C75 and EGCG had comparable effects in blocking FASN activity. Treating cancer cells with EGCG or C75 induced apoptosis and caused a decrease in the active forms of oncoprotein HER2, AKT and ERK1/2 to a similar degree. We observed, in contrast, marked differential effects between C75 and EGCG on the fatty acid oxidation pathway. While EGCG had either no effect or a moderate reduction in CPT-I activity, C75 stimulated CPT-I activity (up to 129%), even in presence of inhibitory levels of malonyl-CoA, a potent inhibitor of the CPT-I enzyme. Taken together, these findings indicate that pharmacological inhibition of FASN occurs uncoupled from the stimulation of CPT-I with EGCG but not with C75, suggesting that EGCG might be free of the CPT-I related in vivo weight-loss that has been associated with C75. Our results establish EGCG as a potent and specific inhibitor of fatty acid synthesis (FASN), which may hold promise as a target-directed anti-cancer drug.

Inhibition of epidermal growth factor receptor signaling elevates 15-hydroxyprostaglandin dehydrogenase in non-small-cell lung cancer.

Evidence indicates that the induction of cyclooxygenase-2 (COX-2) and high prostaglandin E2 (PGE2) levels contribute to the pathogenesis of non-small-cell lung cancer (NSCLC). In addition to overproduction by COX-2, PGE2 concentrations also depend upon the levels of the PGE2 catabolic enzyme 15-hydroxyprostaglandin dehydrogenase (15-PGDH). We find a dramatic down-regulation of PGDH protein in NSCLC cell lines and in resected human tumors when compared with matched normal lung. Affymetrix array analysis of 10 normal lung tissue samples and 49 resected lung tumors revealed a much lower expression of PGDH transcripts in all NSCLC histologic groups. In addition, treatment with the epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) erlotinib increased the expression of 15-PGDH in a subset of NSCLC cell lines. This effect may be due in part to an inhibition of the extracellular signal-regulated kinase (ERK) pathway as treatment with mitogen-activated protein kinase kinase (MEK) inhibitor U0126 mimics the erlotinib results. We show by quantitative reverse transcription-PCR that the transcript levels of ZEB1 and Slug transcriptional repressors are dramatically reduced in a responsive cell line upon EGFR and MEK/ERK inhibition. In addition, the Slug protein, but not ZEB1, binds to the PGDH promoter and represses transcription. As these repressors function by recruiting histone deacetylases to promoters, it is likely that PGDH is repressed by an epigenetic mechanism involving histone deacetylation, resulting in increased PGE2 activity in tumors. This effect is reversible in a subset of NSCLC upon treatment with an EGFR TKI.

Host and direct antitumor effects and profound reduction in tumor metastasis with selective EP4 receptor antagonism.

Prostaglandin E(2) (PGE(2)), one of the major metabolites of cyclooxygenase-2, has been implicated in tumorigenesis and tumor progression in several human cancers, including colorectal and lung. Here, we show that one of the PGE(2) receptors, the EP4 receptor, plays an important role in metastasis in both of these tumor types. Using i.v. injected Lewis lung carcinoma (3LL), we found that tumor metastasis to lung was significantly reduced when mice were treated with a specific EP4 antagonist ONO-AE3-208 or when EP4 receptor expression was knocked down in the tumor cells using RNA interference technology. Host EP4 receptors also contributed to tumor metastasis and tumor growth with decreased metastasis and tumor growth observed in EP4 receptor knockout animals. In vitro tumor cell adhesion, motility, invasion, colony formation, and Akt phosphorylation were all significantly inhibited when 3LL cells were treated with the EP4 receptor-specific antagonist. When the cells were treated with an EP4-specific agonist (AE1-734), we observed a worsening of these same features in vitro. Treatment with ONO-AE3-208 also profoundly decreased liver metastases after intrasplenic injection of MC26 colon cancer cells. Our data show that selective antagonism of EP4 receptor signaling results in a profound reduction in lung and colon cancer metastasis. Selective antagonism of the EP4 receptor may thus represent a novel therapeutic approach for the treatment of cancer and especially its propensity to metastasize.