AG

AA

bst

ract

sM1639

Guggulsterone Induces Apoptosis in Colon Cancer Cells and Inhibits TumorGrowth in a Murine Xenograft Model: Therapeutic Potential in the Treatmentof Colorectal CancerMin Ji An, Jae Hee Cheon, TAE IL KIM, Won Ho Kim

Background & Aims: The plant sterol guggulsterone (GGS) has been shown to exert anti-inflammatory effects through NF-κB inhibition. Furthermore, it has been recently reportedto have anti-tumor effects by enhancing apoptosis in some cancer cell types. However, it isunknown whether GGS is effective in the treatment of colorecal cancer. Moreover, theprecise nature of their anti-tumor effects and their modes of action vis-à-vis mechanismsremain unknown. Therefore, we investigated the anti-tumor effects of GGS on colon cancercells and elucidated its molecular mechanisms in terms of apoptosis and determined itseffect of on the tumor growth of murine xenograft model. Methods: Human HT-29 cellsand IEC-18 cells were treated with GGS for various times. The apoptotic effects of GGSwere examined by cell survival assay including Hoechst 33258 staining and fluorescence-activated cell sorting analysis (FACS). Western blot analyses were used to determine thelevels of various down-stream intracellular proteins involved in apoptosis In Vitro. For InVivo study, male nude mice were assigned to tumor control, GGS 20mg/kg group, or GGS40mg/Kg group. Tumor xenograft was induced by subcutaneous injection with HT-29 cells.After the tumors reached an approximate volume of 100-150 mm3, the mice received dailyintraperitoneal injections of GGS. Weight changes and tumor size were assessed daily. Atday 15 after GGS injection, mice were sacrificed. Results: GGS significantly decreased cellviability and increased the numbers of apoptotic cells in colon cancer cells in a dose dependentmanner but in nontransformed intestinal epithelial cells. Furthermore, it provoked chromatincondensation in colon cancer cells. GGS increased the activation of caspases-3, 8 and thelevels of truncated Bid, Fas, p-JNK, and p-c-Jun, but decreased those of bcl-2 and IAPs.Xenograft tumors were significantly smaller in GGS-treated mice (both GGS 20 and GGS40 groups) than in mice treated with the vehicle. Conclusion: Our data demonstrate thatGGS induces apoptosis in colon cancer cells and inhibits growth of HT-29 xenografts InVivo, which suggests that it has a therapeutic potential in the treatment of colorectal cancer.

M1640

CK2 Inhibition Sensitizes Chemopreventive-Induced Apoptosis of ColonCarcinoma CellsSerge Dionne, Denise Levesque, Ernest G. Seidman

Background: Colon cancer is often resistant to apoptosis induced by single agents. Targetingseveral apoptosis pathways with combined therapy represents a promising therapeutic strat-egy. CK2 is a highly pleiotropic kinase whose activity is aberrantly elevated in diverse tumortypes including colorectal carcinomas (CRC). Specific CK2 inhibitors were recently developedallowing study of affected signaling pathways and their role in proliferation and apoptosis.Aim: To investigate the effect of 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole(DMAT) in combination with other anticancer drugs on apoptosis of CRC cells. Methods:HT-29 and Caco-2 cells were cultured with DMAT +/- suboptimal doses of TRAIL, TWEAK,15dPGJ2, rosiglitazone, GW9662, butyrate and sulindac sulfide. Apoptosis was measuredwith the M30 assay which specifically recognizes caspase cleaved cytokeratin 18. ROS weremeasured using H2DCFDA and loss of mitochondrial potential (MP) was measured withthe cationic dye JC-1 by flow cytometry. Results: DMAT dose-dependently decreased CRCcell viability. This effect was partially antagonized in the presence of FCS. DMAT (40 µM)did not affect viability in presence of 10% FCS, as assessed by MTT assay. CRC cell viabilityafter 72 h incubation with TRAIL 100 ng/ml (93%), TWEAK 100 ng/ml (91%), 15d-PGJ29 µM (67%), rosiglitazone 15 µM (105%), GW9662 15 µM (109%) and sulindac sulfide35 µM (116%) was significantly decreased in the presence of 40 µM DMAT (80%, 81%,41%, 82%, 89%, and 85%, respectively). Sensitization with combined treatment was lessmarked with butyrate 2.5 mM (79% vs 68%). Apoptosis rate (48 h) was enhanced by 1.6to 4 fold in the presence of DMAT. Combined treatment resulted in enhanced caspase-3and 8 activation, dissipation of MP and ROS production. Modulation of ERK phosphorylation,as well as prolonged JNK phosphorylation were also observed. Apoptosis was decreased byover 60% by pre-treatment with the caspase inhibitor zVAD and 30-50% by the antioxidantNAC. Notably, combined treatment resulted in decreased levels of the β-catenin/LCF targetsurvivin and NF-kB target c-FLIP. Conclusions: We hypothesized that CK2 inhibition facilit-ates apoptotic commitment by decreasing NF-kB and β-catenin/LCF activities in cancer cellswhich resulted in decreased expression of c-FLIP and survivin. This in turn favors increasedROS production, JNK and caspases activation leading to cell death. Our results shows thatsensitization of CRC cells to low doses of chemo preventive agents is achievable in thepresence of suboptimal CK2 inhibition. Supported by the Dairy Foundation of Canada andthe Canadian Institutes of Health Research.

M1641

Anti-Gastric Cancer Effect of Celecoxib, a Selective COX-2 Inhibitor, ThroughInhibition of AKT SignalingNayoung Kim, Chung Hyun Kim, Ji Hyun Park, Mi Kyung Lee, Soo-Jeong Cho, Joo SungKim, Hyun Chae Jung, In Sung Song

Background and aim: Previously we found that the anti-cancer effects of celecoxib on gastriccancer cells appeared to be mediated by cell cycle arrest and apoptosis, and not by anti-COX-2 effect or PGE2 suppression alone. This study was carried out In Vitro and In Vivoto investigate the mechanism of celecoxib associated anti-cancer effect. Methods: In Vitroexperiment Western blot analysis of total Akt, phosphorylated Akt, fork head transcriptionalfactor, phosphorylated GSK3 and caspase-9 was performed in the condition of celecoxib orindomethacin-treatment in AGS cells. In Vivo experiment, vehicle (control) or celecoxib (5and 10 mg/kg/day) was gavaged for 40 weeks to 45 Wistar rats, which had been treatedby MNNG (N-mehtyl-N'-nitro-Nnitrosoguanidine) and 10% NaCl for 6 weeks as a gastriccancer inducer. Western blot analysis of tAkt and pAkt was performed In Vivo experiment.Results: The expression of phosphorylated Akt but not total Akt became lower in the

T : 11501$$CH204-02-08 16:47:09 Page 388Layout: 11501B : e

A-388AGA Abstracts

celecoxib treated-AGS cells in dose dependent manner (0, 5, 10, 25, or 50 uM) (P < 0.05).The expression of FKHR and phosphorylated GSK3 also decreased in dose dependent mannerin AGS cells. Procaspase 9 (47 kDa) has been cleaved into 37, 35, and 17 kDa fragmentsin the celecoxib-treatment group. However, these changes of cell signal transduction werenot observed in the indometacin treated cells. In Vivo study, only one rat of 29 rats treatedwith MNNG had carcinoma at squamo-columnar junction, and microscopic glandular disten-sion was frequently found in the MNNG treated rats than in control (P = 0.042). Theexpression of phosphorylated Akt was lower in the celecoxib-treated rats than control (P <0.05). Conclusion: Anti-cancer effects of celecoxib on gastric cancer cells might be mediatedby down-regulation of Akt, fork head transcriptional factor and phosphorylated GSK3 andup-regulation of caspase-9, In Vitro. The mediation of Akt-pathway was also supported byIn Vivo experiment.

M1642

Simvastatin Potentiates Sensitivity to Apoptosis in Microsatellite-UnstableColon Cancer CellsYeon Sil Jang, Eun Suk Choi, Dong Kyung Chang, Young-Ho Kim, Poong-lyul Rhee, JaeJ. Kim, Jong Chul Rhee

Background/Aim: Genetic or epigenetic inactivation of DNA mismatch repair (MMR) genesresults in a strong mutator phenotype, known as the microsatellite instability (MSI). Thedefective MMR system occurs in about 15% of colorectal cancer and has been shown toconfer resistance to various chemotherapeutic reagents. Numerous recent reports suggest thatstatins (hydroxyl-3-methylglutaryl-CoA reductase inhibitors) exhibit potential to suppresstumorigenesis through a mechanism that is not fully understood. This study aims to comparethe anticancer efficacy of simvastatin in between MMR-profient and -deficient colon cancercells. Methods: MMR-deficient colon cell lines HCT116, HCT116/p53-/-, HCT116/p21-/-and its MMR-proficient colon cell lines HCT116+ch3, HCT116+ch3/E6 were treated withsimvastatin dose-and time-dependently. Results: MMR-deficient HCT116 cells were moresensitive to simvastatin than to MMR-proficient HCT116+ch3 as cytotoxicity was determinedby MTT assay and apoptotic cell death was measured by annexin-V/PI staining. Apoptosisoccurred time- and dose-dependently in both cells as indicated by Bcl-xL down-regulation,caspase-3 activation and PARP cleavage. However, their levels of changes were not differentbased on the existence or nonexistence of MLH1 and p53. On the other hand, simvastatinstimulated phosphorylation of c-jun which was completely abolished by the c-jun NH2-terminal kinase (JNK) inhibitor SP600125, which also reduced the cytotoxic effect of simvas-tatin in both MMR-deficient and -proficient colon cells to the similar degree. Conclusion:Simvastatin seems to induce apotosis more in MMR-deficient cells. Its apoptotic effectinvolves JNK in HCT116 colon cancer cell series independent of their MLH1 and p53expression status. Some other mechanisms may contribute to the higher level of apoptosisin MMR-deficient cells. Our findings suggest a potential of simvastatin for the therapies ofmicrosatellite-unstable colon cancers resistant to currently used chemotherapeutic drugs.

M1643

GSK3 Activity Regulates Proliferation and Survival of Human PancreaticCancer CellsBenoit Marchand, Marie-Josee Boucher

The glycogen synthase kinase-3 (GSK3) was initially described as a key enzyme involvedin glycogen metabolism. Since then, it has been found to regulate a diverse range of cellfunctions including proliferation, differentiation and apoptosis. The role of GSK3 greatlydepends on cellular context. Thus, the aim of the study was to clarify the role of GSK3 withrespect to pancreatic cancer cell proliferation and survival. Methods. Cell proliferation andcell survival were evaluated in different human pancreatic cancer cell lines (BxPC-3, PANC-1, MiaPaCa-2) following inhibition of GSK3 activity by different specific inhibitors (AR-A014418, BIO, SB216763). Results. Inhibition of GSK3 activity led to a marked reductionin cell proliferation (evaluated by reduced cell number) of all pancreatic cancer cell linestested. Further analysis revealed a hypophosphorylated status of pRb suggesting that inhibi-tion of GSK3 activity induced a blockade of cell proliferation in the G1-phase of the cellcycle. Also, reduced cyclinD1 and cyclinE protein expressions were observed while theexpression of the cell cycle inhibitor p21 was increased. Reduction in cyclin A proteinexpression was also observed. Furthermore, prolonged inhibition of GSK3 activity (24h)induced apoptosis, an effect that was visualized by DNA fragmentation, PARP cleavage andinduction of caspase-7 activity. Importantly, cell apoptosis induced by GSK3 inhibitioncould not be rescue by addition of serum. Taking together, our results demonstrated thatthe activity of GSK3 contributes to the proliferation of human pancreatic cancer cells andis imperative for their survival. Hence, GSK3 activity could be an attractive new therapeutictarget in the treatment of unresectable pancreatic cancer.

M1644

Characterisation of Progenitor Cells in Colorectal Cancer and the AdultHuman ColonJamie Murphy, Sahira Khalaf, Rebecca Hands, Jun Tian, Norman S. Williams, Stephen A.Bustin

Background: A subset of mutated stem cells within each colorectal cancer appear to initiateand sustain tumour growth. Prominin-1, which encodes the CD133 cell surface antigen,has been proposed as a marker for these cells. The purpose of this study was to clarifyCD133 expression patterns in the normal human bowel, primary colorectal cancer, andcolorectal cancer metastases. Methods: Normal intestinal tissue was obtained from 20 patientsundergoing surgery for benign disease. Full thickness colorectal cancer samples were obtainedfrom 20 patients, while matched samples of laser micro-dissected non-malignant adjacentepithelium, central and peripheral primary colorectal cancer, vascular invasion, and lymphnode and liver metastasises were obtained from a further 13 patients. Assessment of prominin-1 mRNA / CD133 protein expression was performed by RT-qPCR, immunohistochemistry,