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Background: MYC is an attractive therapeutic target in lung cancer. ICX-101 is a novel potent, selective small molecule that directly inhibits the binding of MYC/MAX dimers to the DNA binding sequence E-box. Here, we show that ICX-101 shows antitumor activity in patient-derived cells (PDC) of advanced lung cancer and that the drug responses are correlated with the MYC expression levels. Methods: PDCs of lung cancer were treated with ICX-101, and the area under the dose-response curve (AUC) was measured as the readout for antitumor efficacy. MYC expression level of each PDC was measured with the fold expression of mRNA compared to the normal lung tissue. The patient’s clinical data and survival outcomes were analyzed to correlate with the drug responses of PDCs. Results: We collected 100 PDCs from 82 lung cancer patients. The histologic types included adenocarcinoma (N = 82), squamous cell carcinoma (N = 10), non-small cell lung cancer (NSCLC) not otherwise specified (NOS) (N = 4), and small cell lung cancer (SCLC, N = 4). PDCs derived from SCLC showed higher MYC expression levels than NSCLC (P = 0.004). MYC was a prognostic factor, as the patient groups with the top and bottom 25 percentiles of MYC mRNA expression had an overall survival of 932.5 and 256 days, respectively (P = 0.029). However, MYC expression was predictive for the response to ICX-101, as the PDCs with the top 25 percentiles of MYC levels showed markedly lower AUC values than those with the bottom 25 percentile (P < 0.001). Additionally, the MYC mRNA levels and AUC values were inversely correlated with statistical significance (R = -0.46, P < 0.001). Conclusion: ICX-101 is a potent MYC inhibitor that shows antitumor activity in lung cancer PDCs. Our results suggest the potential of ICX-101 as a possible therapeutic option in advanced lung cancer with high MYC expressions. Citation Format: Wonyoung Choi, Kyung-Chae Jeong, Seog-Yun Park, Sunshin Kim, Eun Hye Kang, Mihwa Hwang, Ji-Youn Han. ICX-101, a novel MYC inhibitor, shows antitumor activity in patient-derived cells of advanced lung cancer with high MYC expression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4929.

Herein, we describe a novel approach for the practical synthesis of tetrasubstituted thiophenes 8. The developed method was particularly used for the facile preparation of thienyl heterocycles 8. The mechanism for this reaction is based on the formation of a sulfur ylide-like intermediate. It was clearly suggested by (i) the intramolecular cyclization of ketene N,S-acetals 7 to the corresponding thiophenes 8, (ii) 1H NMR studies of Meldrum’s acid-substituted aminothioacetals 9, and (iii) substitution studies of the methoxy group on Meldrum’s acid containing N,S-acetals 9b. Notably, in terms of structural effects on the reactivity and stability of sulfur ylide-like intermediates, 2-pyridyl substituted compound 7a exhibited superior properties over those of others.

// Ho Kyung Seo 1, 2, * , Sung Han Kim 1, 3, * , Kyung-Ohk Ahn 3 , Sang-Jin Lee 4 , Weon Seo Park 5 , Sohee Kim 6 , Sang-Hyun Hwang 7 , Do Hoon Lee 8 , Jae Young Joung 1 , Jinsoo Chung 1 , Jungnam Joo 6 and Kyung-Chae Jeong 3 1 Department of Urology, Center for Prostate Cancer, Hospital, National Cancer Center, Goyang, Gyeonggi-do, Korea 2 Biomarker Branch, Research Institute, National Cancer Center, Goyang, Gyeonggi-do, Korea 3 Translational Research Branch, Research Institute, National Cancer Center, Goyang, Gyeonggi-do, Korea 4 Immunotherapeutics Branch, Research Institute, National Cancer Center, Goyang, Gyeonggi-do, Korea 5 Department of Pathology, Center for Prostate Cancer, Hospital, National Cancer Center, Goyang, Gyeonggi-do, Korea 6 Biometrics Research Branch, Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi, Korea 7 Department of Laboratory Medicine, Center for Diagnostic Oncology, National Cancer Center, Goyang-si, Korea 8 Department of Laboratory Medicine and Hematologic Malignancy Branch, Research Institute and Hospital of National Cancer Center, Goyang-si, Korea * These authors have contributed equally to this work Correspondence to: Kyung-Chae Jeong, email: jeongkc@ncc.re.kr Keywords: administration; intravesical therapy; mitomycin C; neoplasm; urinary bladder Received: March 17, 2017 Accepted: June 30, 2017 Published: October 09, 2017 ABSTRACT Objective: Sodium bicarbonate has been reported to maximize the efficacy of intravesical instillation of mitomycin-C (IVI-MMC) therapy by urine alkalinization in non-muscle-invasive bladder cancer (NMIBC). This study aimed to analyze the changes in MMC concentration according to urinary pH and evaluate the efficacy of sodium bicarbonate to maintain the concentration of active form of MMC during IVI-MMC. Methods: We prospectively enrolled 26 patients with NMIBC after transurethral resection of bladder tumor. Patients with very high-risk and low-risk NMIBC were excluded. Urinary creatinine, volume, pH, and concentrations of MMC and its degraded form were measured immediately before and after IVI-MMC. The patients were administered 1.5 g of oral sodium bicarbonate during the preceding evening, in the morning, and immediately before the fourth cycle of the six-cycle IVI-MMC. The correlation between MMC concentration and urinary pH changes was explored with or without oral bicarbonate therapy. Results: Recurrence without progression to muscle-invasive disease was noted in 4 of 26 patients in a 23.7-month follow-up. The mean urinary pH before and after the therapy increased from 6.03 to 6.50, and 6.46 to 7.24, without or with oral SB therapy, respectively. Despite this increase, the concentration of active form of MMC did not change significantly. No correlation was found between urinary pH and MMC concentration. Urine alkalinization by SB administration did not maintain the high concentration of urinary MMC. Conclusions: Urine alkalinization by sodium bicarbonate administration for IVI-MMC did not maintain the high concentration of active urinary MMC in NMIBC.

We compared progression-free survival (PFS) and overall survival (OS) among 292 metastatic renal cell carcinoma (mRCC) patients either undergoing nephrectomy (Nx, 61.6%) or not (non-Nx, 38.4%), stratified according to the MSKCC and Heng risk models, treated with either immunotherapy (IT, 45.2%) or targeted therapy (TT, 54.8%) between 2000 and 2015. During the follow-up duration of 16.6 months, PFS/OS of the Nx (6.0/30 months) and non-Nx (3.0/6.0 months) groups were significantly different despite differences among baseline parameters (p 0.05). In both synchronous and metachronous mRCC patients, both PFS and OS showed similar survivals; the Nx group had significantly longer PFS and OS than the non-Nx group, even after considering each systemic therapy and prognostic model. Nx showed a significant positive benefit in PFS and OS compared to no Nx upon patient stratification according to the MSKCC and Heng risk models. The metastatic type did not significantly affect survival between the two groups.

In a previous report, 3-aminopropyl functionalized magnesium phyllosilicate (aminoclay) improved adenovirus transduction efficiency by shielding the negative surface charges of adenovirus particles. The present study analyzed the physicochemical characterization of the electrostatic complex of adenoviruses with aminoclay and explored whether it could be utilized for enhancing tumor suppressive activity in the bladder. As a result of aminoclay-adenovirus nanobiohybridization, its transduction was enhanced in a dose-dependent manner, increasing transgene expression in bladder cancer cells and in in vivo animal models. Physicochemical studies demonstrated that positively charged aminoclay led to the neutralization of negative surface charges of adenoviruses, protection of adenoviruses from neutralizing antibodies and lowered transepithelial electrical resistance (TEER). As expected from the physicochemical properties, the aminoclay enabled tumor-targeting adenoviruses to be more potent in killing bladder cancer cells and suppressing tumor growth in orthotopic bladder tumors, suggesting that aminoclay would be an efficient, versatile and biocompatible delivery carrier for intravesical instillation of adenoviruses.

// Ho Kyung Seo 1 , Jeong Bin Seo 2 , Jae-Kook Nam 3 , Kyung-Chae Jeong 4 , Seung-Pil Shin 3 , In-Hoo Kim 5 , Sang Don Lee 2 and Sang-Jin Lee 3 1 Center for Prostate Cancer, Gyeonggi-do, Biomedical Research Institute, Pusan National University and Research Institute for Convergence of Biomedical Science and Technology, Pusan 2 Pusan National University and Biomedical Research Institute, Pusan National University and Research Institute for Convergence of Biomedical Science and Technology, Pusan 3 Genitourinary Cancer Branch, Research Institute National Cancer Center, Gyeonggi-do, Korea 4 Biomolecular Function Research Branch, Research Institute National Cancer Center, Gyeonggi-do, Korea 5 Molecular Imaging and Therapy Branch, Research Institute National Cancer Center, Gyeonggi-do, Korea Correspondence: Sang-Jin Lee, email: // Sang-Don Lee, email: // Keywords : bladder cancer, gene therapy, adenovirus, survivin Received : April 6, 2014 Accepted : June 29, 2014 Published : June 30, 2014 Abstract Survivin is a member of the inhibitors of apoptosis protein family. Here, we examined survivin expression and confirmed abundant survivin expression in bladder cancer cells. This expression pattern indicated that the transcriptional regulatory elements that control survivin expression could be utilized to discriminate cancer from normal cells. We therefore generated a novel adenovirus termed Ad5/35E1apsurvivinE4 with the following characteristics: 1) E1A and E4 protein expression was dependent on survivin promoter activity; 2) the green fluorescence protein gene was inserted into the genome under the control of the CMV promoter; 3) most of the E3 sequences were deleted, but the construct was still capable of expressing the adenovirus death protein with potent cytotoxic effects; and 4) the fiber knob was from serotype 35 adenovirus. As expected from the abundant survivin expression observed in bladder cancer cells, Ad5/35E1apsurvivinE4 replicated better in cancer cells than in normal cells by a factor of 10 6 to 10 2 . Likewise, Ad5/35E1apsurvivinE4 exerted greater cytotoxic effects on all bladder cancer cell lines tested. Importantly, Ad5/35E1apsurvivinE4 inhibited the growth of Ku7-Luc orthotopic xenografts in nude mice. Taken together, Ad5/35E1apsurvivinE4 indicates that the survivin promoter may be utilized for the development of a replication-competent adenovirus to target bladder cancers.

$('.header-date').hide();$('#titleAuthors').hide(); $('#abstractHeader').hide(); Ho Kyung Seo 1 , Kyung-Ohk Ahn 2 , Nae-Rae Jung 3 , Ji-Sun Shin 3 , Weon Seo Park 1 , Kang Hyun Lee 1 , Sang-Jin Lee 3 , and Kyung-Chae Jeong 2 1 Center for Prostate Cancer, Hospital, National Cancer Center, Goyang, Gyeonggi-do, Korea 2 Biomolecular Function Research Branch, Research Institute, National Cancer Center, Goyang, Gyeonggi-do, Korea 3 Genitourinary Cancer Branch, Research Institute, National Cancer Center, Goyang, Gyeonggi-do, Korea Correspondence: Kyung-Chae Jeong, e-mail: jeongkc@ncc.re.kr Sang-Jin Lee, e-mail: leesj@ncc.re.kr Key words: Bladder cancer, c-Myc, inhibitor, gemcitabine, gemcitabine resistance Received : October 28, 2013 Accepted : December 12, 2013 Published : January 16, 2014 ABSTRACT Intravesical instillation of chemotherapeutic agents is a well-established treatment strategy to decrease recurrence following transurethral resection in non-muscle invasive bladder cancer. Gemcitabine is a recently developed treatment option. However, the curative effects of gemcitabine are far from satisfactory due to de novo or acquired drug resistance. In a previous study, we reported that intravesical administration of the c-Myc inhibitor KSI-3716 suppresses tumor growth in an orthotopic bladder cancer model. Here, we explored whether KSI-3716 inhibits gemcitabine-resistant bladder cancer cell proliferation. As expected from the in vitro cytotoxicity of gemcitabine in several bladder cancer cell lines, gemcitabine effectively suppressed the growth of KU19-19 xenografts in nude mice, although all mice relapsed later. Long-term in vitro exposure to gemcitabine induced gemcitabine-specific resistance. Gemcitabine-resistant cells, termed KU19-19/GEM, formed xenograft tumors even in the presence of 2 mg/kg gemcitabine. Interestingly, KU19-19/GEM cells up-regulated c-Myc expression in the presence of the gemcitabine and resisted to the gemcitabine, however was suppressed by the KSI-3716. The sequential addition of gemcitabine and KSI-3716 inhibited gemcitabine-resistant cell proliferation to a great extent than each drug alone. These results suggest that sequential treatment with gemcitabine and KSI-3716 may be beneficial to bladder cancer patients.

// Ho Kyung Seo 1, 2 , Seung-Phil Shin 2 , Na-Rae Jung 2 , Whi-An Kwon 3 , Kyung-Chae Jeong 4 and Sang-Jin Lee 2 1 Center for Prostate Cancer, Hospital, National Cancer Center, Goyang, Gyeonggi-do, Korea 2 Genitourinary Cancer Branch, Research Institute, National Cancer Center, Goyang, Gyeonggi-do, Korea 3 Department of Urology, School of Medicine, Institute of Wonkwang Medical Science, Wonkwang University, Wonkwang University Sanbon Hospital, Gunpo, Gyeonggi-do, Korea 4 Biomolecular Function Research Branch, Research Institute, National Cancer Center, Goyang, Gyeonggi-do, Korea Correspondence to: Sang-Jin Lee, email: leesj@ncc.re.kr Ho Kyung Seo, email: seohk@ncc.re.kr Keywords: bladder cancer, c-myc, orthotopic bladder cancer model, MBT-2 Received: April 20, 2016 Accepted: June 17, 2016 Published: July 22, 2016 ABSTRACT To properly evaluate the biological effects of immunotherapy, it is critical to utilize a model of cancer in immune-competent mice. Currently, MBT-2 is the most common murine bladder cancer cell line used in orthotopic bladder cancer models, even though this cell type often has an inappropriate genetic mutation landscape. In these models, after tumors are detected with in vivo imaging, the mouse usually dies within two to three weeks due to post-renal azotemia caused by the rapidly growing mass. This event prohibits the evaluation of tumor behavior upon intravesical drug treatment. We explored whether an shRNA-induced decrease in the expression of the c-myc oncogene in MBT-2 cells could slow down their in vitro proliferation and in vivo tumor growth. We transduced MBT-2 cells with shRNA lentiviruses that bound c-myc, established MBT2.cMYCshRNA and confirmed the retardation of the growth of tumors implanted in C3H/He mice. Accordingly, this study suggests that this novel orthotopic bladder cancer model in immune-competent mice may be more appropriate for the analysis of the effects of the intravesical instillation of immunotherapeutic agents.

Aim of this study was to evaluate HRQoL of patients affected by NMIBC underwent intravesical instillations of Bacillus Calmette-Gu erin (BCG) or Mytomicin C (MMC) with a short-term follow-up. METHODS: From December 2011 to December 2014 we recruited 108 consecutive patients in a single academic center with a first-time diagnosis of NMIBC at intermediate or high risk. The median age was 73 years (38-94) and 55.3% (N 57) patients underwent BCG and 44.7% (N 46) patients underwent MMC after TURBT respectively. The assessment of HRQoL was performed using two questionnaires from EORTC: QLQ-C30 and QLQ-BLS24 specific for NMIBC. Patients self-completed the questionnaires in three different times: T0 (before intravesical instillation), T1 (after intravesical instillation), T2 (at three months after last instillation). The above analysis was stratified by gender, age (?70 years and >70 years), tumour degree risk (intermediate and high risk) and type of intravesical therapy (MMC and BCG). Wilcoxon two sample test was used to verify differences. Statistical significance was achieved if pvalue was 1⁄40.05 (two-sides). RESULTS: Treatment was well tolerated in both groups of patients underwent intravesical instillations of BCG and MMC respectively. Grade I and II side effects, as CTCAE classification, were reported by 46.6% of patients at T1 and 47.5% at T2. 5 patients dropped out of the study (3 lost in follow-up and 2 developed side effects of BCG). At T1 we founded a drop in QoL, with reference to Physical, Role, Emotional and Social functioning domains and a worsening of urinary bladder symptoms with a generally decrease of Global Quality of Life Score. The sexual sphere was affected by adjuvant therapy with persistence or worsening of sexual disorders. At T2 patients showed a progressive return to baseline QoL, in particular in the Social and clinical symptoms domains. Male gender, age>70 years, high-risk tumours and BCG seem to be the factors that worsening HRQoL of these patients. CONCLUSIONS: Intravesical instillations seem to modify the HRQoL of these patients with a return at 3 months to baseline conditions.

Pyrococcus furiosus PF2050 is an uncharacterized putative protein that contains two DUF2666 domains. Functional and structural studies of PF2050 have not previously been performed. In this study, we determined the crystal structure of PF2050. The structure of PF2050 showed that the two DUF2666 domains interact tightly, forming a globular structure. Each DUF2666 domain comprises an antiparallel β-sheet and an α-helical bundle. One side of the PF2050 structure has a positively charged basic cleft, which may have a DNA-binding function. Furthermore, we confirmed that PF2050 interacts with circular and linear dsDNA.

Apoptosis inhibitor 5 (API5) is an anti-apoptotic protein that is up-regulated in various cancer cells. Here, we present the crystal structure of human API5. API5 exhibits an elongated all α-helical structure. The N-terminal half of API5 is similar to the HEAT repeat and the C-terminal half is similar to the ARM (Armadillo-like) repeat. HEAT and ARM repeats have been implicated in protein-protein interactions, suggesting that the cellular roles of API5 may be to mediate protein-protein interactions. Various components of multiprotein complexes have been identified as API5-interacting protein partners, suggesting that API5 may act as a scaffold for multiprotein complexes. API5 exists as a monomer, and the functionally important heptad leucine repeat does not exhibit the predicted a dimeric leucine zipper. Additionally, Lys-251, which can be acetylated in cells, plays important roles in the inhibition of apoptosis under serum deprivation conditions. The acetylation of this lysine also affects the stability of API5 in cells.

E-mail: nskang@cnu.ac.kr Received August 30, 2011, Accepted November 7, 2011Androgen receptor (AR) is ligand-inducible nuclear hormone receptor which has been focused on keymolecular target in growth and progression of prostate cancer. We synthesized a series of 4-aryl 2-substitutedaniline-thiazole analogs and evaluated their anti-cancer activity in AR-dependent human prostate cancerLNCap cells. Among them, the compound 6 inhibited the tumor growth in LNCap-inoculated xenograft model.Key Words : Androgen receptor, Antagonist, LNCap cell, Prostate cancerIntroductionAndrogen receptor (AR) is androgen inducible nuclearhormone receptor and a key molecular target in growth andprogression of prostate cancer, even at the castration-resistant status.

The cellular response to DNA damage is emerging as a promising target for cancer therapy. In the present study, the authors exploited the relationship between the level of the phosphorylated form of histone H2AX (γH2AX) and the extent of DNA damage and developed a quantitative, cell-based, high-content screening system for measuring the DNA damage response (DDR). In this system, the authors quantified the level of γH2AX by measuring DNA damage-induced γH2AX nuclear foci using an automated cell imager. They found that the total area of γH2AX foci per cell exhibited a good correlation with the concentration of DNA damage-inducing agents, including etoposide. The effects of 2 well-known inhibitors of DNA damage could be quantified using this system, suggesting the suitability of the γH2AX-foci quantification method for large-scale screening applications. This was confirmed by using this method to screen a chemical library; the resulting "hits" included compounds that inhibited early signaling events in DDR, as well those that inhibited subsequent DNA damage repair processes. Overall, this γH2AX foci-measuring system may be an effective screening method for identifying DNA damage response inhibitors that could eventually be used to develop novel anticancer drugs.

Although many efforts on revealing mechanism of the constitutive activation of NF-κB in cancer cells contributed to understanding canonical pathways, largely it remains to be determined for therapeutic approaches. Recently, we found that increased expression of transglutaminase 2 (TGase 2) appears to be responsible for constitutive activation of NF-κB in certain types of cancer cells. In previous studies, we demonstrated that TGase 2 inhibition markedly increases anti-cancer drug sensitivity in drug resistance cancer cells. Therefore, we develop safe and effective TGase 2 inhibitors for therapeutic approach.We screened a chemical library of natural compounds using in vitro TGase 2 activity assay. The salient discovery was that glucosamine (GlcN), a known anti-inflammatory substance, inhibited the cross-linking activity of TGase 2. We tested, through a biochemical analysis including kinetics, whether the GlcN and GlcN analogs specifically inhibit TGase 2. We also determined the inhibitory mechanism using conformational change of TGase 2.We found that the primary amine of GlcN plays a key role in TGase 2 inhibition. We also demonstrated that GlcN reversed TGase 2-mediated I-κBα polymerization in vitro. Interestingly, the metabolite of GlcN, glucosamine-6-phosphate (GlcN6P), inhibited TGase 2 activity via binding to the GTP-binding site with better efficiency than GlcN. In the native gel electrophoresis, it was clearly observed that GlcN6P binds to TGase 2 directly as an allosteric inhibitor.We concluded that GlcN inhibits TGase 2 activity by direct contact. GlcN and its metabolite GlcN6P can down-regulate constitutive activation of NF-κB in vivo via inhibition of TGase 2.

Post-transcriptional regulation of mRNA stability by Hu proteins is an important mechanism for tumorigenesis. We focused on the molecular interactions between the HuC protein and AU-rich elements (AREs) to find chemical inhibitors of RNA-protein interactions using RNA electrophoretic mobility shift assay with non-radioactive probes. Screening of 52 natural compounds identified 14 candidate compounds that displayed potent inhibitory activity. Six (quercetin, myricetin, (-)-epigallocatechin gallate, ellagic acid, (-)-epicatechin gallate, and rhamnetin) were categorized as phytochemicals, and their IC(50) values were low (0.2-1.8 microM). [BMB reports 2009; 42(1): 41-46].

In our previous studies, we have observed that curcumin and momordin I isolated from Ampelopsis radix inhibit the formation of Fos-Jun-activation protein-1 (AP-1) DNA complex. We have screened more effective compounds which have a 5-membered ring framework like momordin I and have modified disaccharide or carboxylic acid portions in momordin I. We synthesized momordin I derivatives according to the published method with slight modification. Synthetic momordin I derivatives showed remarkable inhibitory activities on Fos-Jun-AP-1 DNA complex formation results in in vitro assays. The IC 50 values of momordin I derivatives were about 4.0 μM in an electrophoretic mobility shift assay (EMSA). This value is about 125 times higher than that of curcumin and about 12 times higher than that for curcumin derivative Cl, and moreover about 30 times higher than that for momordin I. We found momordin I derivatives (a) and (b) are the strongest inhibitory compound for Fos-Jun-AP-1 DNA complex formation.

Recently, three types of missense mutations (M330R,I331N, N333S) in transglutaminase 2 were found in patientswith early-onset type 2 diabetes. Mutated residues, more-over, were located near the catalytic site, and the mutationsresulted in loss of the transamidation activity of trans-glutaminase 2 from the

Although trastuzumab is a successful targeted therapy for breast cancer patients with tumors expressing HER2 (ERBB2), many patients eventually progress to drug resistance. Here, we identified subpathways differentially expressed between trastuzumab-resistant vs. -sensitive breast cancer cells, in conjunction with additional transcriptomic preclinical and clinical gene datasets, to rigorously identify overexpressed, resistance-associated genes. From this approach, we identified 32 genes reproducibly upregulated in trastuzumab resistance. 25 genes were upregulated in drug-resistant JIMT-1 cells, which also downregulated HER2 protein by >80% in the presence of trastuzumab. 24 genes were downregulated in trastuzumab-sensitive SKBR3 cells. Trastuzumab sensitivity was restored by siRNA knockdown of these genes in the resistant cells, and overexpression of 5 of the 25 genes was found in at least one of five refractory HER2 + breast cancer. In summary, our rigorous computational approach, followed by experimental validation, significantly implicate ATF4, CHEK2, ENAH, ICOSLG, and RAD51 as potential biomarkers of trastuzumab resistance. These results provide further proof-of-concept of our methodology for successfully identifying potential biomarkers and druggable signal pathways involved in tumor progression to drug resistance.

Background A major problem with the use of current chemotherapy regimens for several cancers, including breast cancer, is development of intrinsic or acquired drug resistance, which results in disease recurrence and metastasis. However, the mechanisms underlying this drug resistance are unknown. To study the molecular mechanisms underlying the invasive and metastatic activities of drug-resistant cancer cells, we generated a doxorubicin-resistant MCF-7 breast cancer cell line (MCF-7/DOX). Methods We used MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays, flow cytometry assays, DNA fragmentation assays, Western blot analysis, cell invasion assays, small interfering RNA (siRNA) transfection, reverse transcription-polymerase chain reaction, experimental lung metastasis models, and gelatin and fibrinogen/plasminogen zymography to study the molecular mechanism of metastatic activities in MCF-7/DOX cells. Results We found that MCF-7/DOX acquired invasive activities. In addition, Western blot analysis showed increased expression of epidermal growth factor receptor (EGFR) and Cox-2 in MCF-7/DOX cells. Inhibition of Cox-2, phosphoinositide 3-kinase (PI3K)/Akt, or mitogen-activated protein kinase (MAPK) pathways effectively inhibited the invasive activities of MCF-7/DOX cells. Gelatin and fibrinogen/plasminogen zymography analysis showed that the enzymatic activities of matrix metalloproteinase-2 (MMP-2), MMP-9, and urokinase-type plasminogen activator were markedly higher in MCF-7/DOX cells than in the MCF-7 cells. In vitro invasion assays and mouse models of lung metastasis demonstrated that MCF-7/DOX cells acquired invasive abilities. Using siRNAs and agonists specific for prostaglandin E (EP) receptors, we found that EP1 and EP3 played important roles in the invasiveness of MCF-7/DOX cells. Conclusions We found that the invasive activity of MCF-7/DOX cells is mediated by Cox-2, which is induced by the EGFR-activated PI3K/Akt and MAPK pathways. In addition, EP1 and EP3 are important in the Cox-2-induced invasion of MCF-7/DOX cells. Therefore, not only Cox-2 but also EP1 and EP3 could be important targets for chemosensitization and inhibition of metastasis in breast cancers that are resistant to chemotherapy.