safety of delta-tocotrienol (D-T3) in pancreatic cancer. This study evaluated the role of D- T3 in CRC. D-T3 is one of 8 isomers of Vitamin E. Unlike the common Vitamin E - tocopherol, D-T3 is unsaturated and possesses an isoprenoid side chain. Recent studies demonstrate this structural distinction gives it potent selective activity against cancer cells. Methods: Effects of D-T3 in CRC cell proliferation were investigated using MTT assay in normal human colon cells (NCM460) and human CRC cells (HCT-116, SW-620, SW-480, and HT-29). Anchorage independent growth was measured by soft agar colony formation assay. Cellular migration and invasion were assessed using a wound healing assay and invasion assay through Matrigel. Cell apoptosis was measured by Annexin V-FITC. Expression of proteins were measured by Western blot. Effect on carcinogenesis was assessed in the rat Azoxymethane (AOM) colon carcinogenesis model. Statistical analysis included unpaired t-tests or one-way ANOVA where appropriate. ANOVA was followed by Duncan's multiple range tests using SAS statistical software for comparison between different treatment groups. Statistical significance was set at p<0.05. Results: D-T3 was the most bioactive vitamin E isomer in CRC cells (p<0.001). D-T3 selectively inhibits CRC cells, but not normal colorectal cells (p<0.001). In HCT-116 and SW-620 CRC cells, D-T3 inhibits malignant transformation (p<0.02, p<0.001), cell migration (0<0.02, p<0.05), invasion (p<0.05, p<0.01), and protein biomarkers of metastasis and angiogenesis compared to vehicle. D-T3 induced apoptosis significantly in SW-620 cells, HCT-116 cells, and HT-29 cells compared to vehicle and did not induce apoptosis in normal colon cells NCM460. D-T3 inhibits colorectal polyps by 70% (figure 1) and CRC by almost 100% (figure 2) in the AOM carcinogenesis rat model compared to no treatment or vehicle (p<0.02, p<0.001). D-T3 is more active than sulindac and aspirin in growth inhibition and induction of apoptosis in CRC cells (HCT-116) and CRC stem cells (CCSC). Discussion: Taken together, these data demonstrate that D-T3 is a potential chemopreventive agent in CRC and warrants further investigation for its clinical use in the prevention and treatment of CRC. A. Delta tocotrienol (DT-3) inhibits colorectal polyps by 70% in AOM carcinogenesis model of Fisher 344 rats. B. Effects of DT-3 and Sulindac on chemoprevention of colon premalignant aberrant crypt foci. The histopathological data show invasive cancer in untreated group (NT), invasive cancer singlet ring type in vehicle treated group (V), normal to adenoma in Sulindac treated group and hyperplasia and normal mucosa in DT-3 treated group. H & E staining of colon (10 X). H & E - hematoxylin & eosin. A. Delta tocotrienol inhibits colorectal carcinoma by almost 100% in AOM carcinogenesis model of Fisher 344 rats. B. Histopathological data show evidence of a very rare signet ring carcinoma invading the colonic sub mucosa (arrows) in NT or vehicle (V) group. The aberrant crypt foci, the earliest stage of development of pre-malignant lesions, were seen in Vehicle (V) and Sulindac group (arrows). Whereas VEDT group had a completely normal colonic mucosa. H & E staining of colon (10 X). H & E - hematoxylin and eosin. Mo1987 RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED IMMUNOPREVENTION TRIAL WITH MUC1 VACCINE IN PATIENTS WITH NEWLY DIAGNOSED ADVANCED ADENOMAS Robert E. Schoen, Lisa A. Boardman, Marcia R. Cruz-Correa, Ajay Bansal, David M. Kastenberg, Chin Hur, Lynda Dzubinski, L. M. Rodriguez, Andres Salazar, John McKolanis, Pamela Beatty, Reet Pai, Drew Seisler, Nathan R. Foster, Mei-Yin Polley, Paul Limburg, Olivera J. Finn Background: Immunotherapy targeting tumor-associated antigens on colorectal cancers and polyps offers the potential for a relatively non-invasive, non-toxic prevention strategy, and the potential for prolonged protection. We are evaluating MUC1 vaccine with the TLR-3 agonist polyICLC (HiltonolÒ) as an adjuvant, for immunogenicity and effect on colorectal adenoma recurrence, in a double-blind, placebo-controlled randomized trial in patients with advanced adenomas within the previous year. Aim: To evaluate MUC1 immunogenicity at week 12 (following injection at 0, 2, and 10 weeks), and to assess determinants of the immune response. Methods: Response to the vaccine was assessed by comparing IgG anti- MUC1 antibody titer ratio defined as t12/t0, where t0 is the initial titer measured prior to vaccination, and t12 is the titer drawn at 12 weeks. A ratio of $2.0 was the primary S-873 AGA Abstracts definition of immune response. Because the level of immunogenicity that corresponds to a clinical response is unknown, lower ratios were also examined. T Regulatory and myleoid derived suppressor cell (MDSC) levels at baseline were assessed in relation to vaccine response. Results: 102 subjects were randomized at 6 centers, 52 received MUC1 vaccine and 50 placebo. Subjects had a mean age of 59.4±7.0 (range 40-70) years, 60.8% were male, 88.2% were white, and 18.6% Hispanic or Latino. At 12 weeks the mean (SD) IgG ratio was 3.0 (4.3) in the MUC1 arm and 1.0 (0.2) in the placebo arm (p=0.0004). MUC1 vaccine patients had a t12/t0 ratio $2.0, in 13/52 (25%) (ratio range among responders 2.9-17.3), vs. 0/50 in placebo group (Fisher's exact P=.0001), and was $1.5 in 19/52 (36.5%) of vaccine recipients compared to 1/50 (2%) in placebo group (P<.0001). In the vaccinated group, the IgG ratio was $2.0 in 45% of women (9/20) vs. 12.5% of men (4/ 32) (P=0.009) and $1.5 in 55% of women (11/20) vs. 25% of men (8/32) (P=0.03). In the vaccinated group, reduced levels of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) pre-vaccination were associated with response, 0.2%±0.1 among responders (n=13) vs. 0.8%±1.1 among non-responders (N=39) (p=0.0006) whereas monocytic MDSC and T regulatory cells (CD4+CD25, Foxp3) were not associated with response. There were no grade 3 AEs possibly or probably related to the vaccine. The most common AE was an injection site reaction (grade 1 or 2) which occurred in 80.8% (n=42/52) in vaccine group vs. 6.0% in the placebo group (3/50). Conclusions: Subjects with an advanced adenoma receiving MUC1 vaccine compared with a placebo are significantly more likely to develop an anti-IgG MUC1 immune response at 12 weeks. Women and subjects with lower circulating PMN-MDSC levels at baseline were more likely to respond. Follow up for the effect of the vaccine on adenomatous polyp recurrence is ongoing. Mo1988 METFORMIN PREVENTS KRAS-MUTANT PANCREATIC DUCTAL ADENOCARCINOMA PROMOTED BY DIET-INDUCED OBESITY Hui-Hua Chang, James Sinnett-Smith, Andrea I. Schmidt, Oscar J. Hines, Guido Eibl, Enrique Rozengurt Background: Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with virtually no efficacious treatments. Chronic conditions such as obesity and type-2 diabetes are known risk factors, thus making PDAC amenable for preventive strategies. Metformin, a widely used anti-diabetic drug shown to improve metabolic dysfunction, has been linked epidemiol- ogically with reduced incidence, recurrence and mortality of cancer in diabetic patients. However, the efficacy and mechanisms of metformin in obesity-promoted PDAC are much less known. Here, we characterized, the chemo-preventive effects of metformin on PDAC development using the KrasG12D model subjected to a high-fat, high calorie diet (HFCD). Results: Offspring of p48-Cre and LSL-KrasG12D mice have been randomly allocated to either HFCD (~4,535 kcal/kg; 40% of calories from fats) or control diet (CD; ~3,725 kcal/ kg; 12% of calories from fats) and treated without or with metformin (5 mg/ml in the drinking water) for either 3 or 9 months. Analysis of the 3-month cohort showed that HFCD induced a marked decrease in intact acini, reflecting acinar-to-ductal metaplasia (ADM) that was completely prevented by metformin. Metformin also prevented HFCD-induced formation of PanIN-3 lesions and stimulation of ERK, mTORC1 and PKD but activated AMPK as determined by phosphorylation of acetyl-CoA carboxylase (ACC) at Ser79, a direct substrate of AMPK. Analysis of the 9-month cohort indicates that HFCD induced extensive depletion of intact acini, formation of PanIN-3 lesions and a striking increase in PDAC incidence accompanied by strong desmoplastic reaction. Metformin prevented the depletion of intact acini the formation of PanIN3 lesions and PDAC development induced by HFCD in KC mice Specifically, PDAC was identified in 2 of 13 mice (15%) in control diet (CD) but in 7 of 12 mice (58%) subjected to HFCD (CD vs. HFCD, p=0.04). In sharp contrast, only 1 out of 14 mice (7%) treated with HFCD and metformin developed PDAC (HFCD vs. HFCD + metformin, p = 0.01). Conclusion: Our results show that metformin effectively prevents the progression of advanced PanINs and the development of KRAS-driven PDAC promoted by diet-induced obesity. These results are also consistent with the notion that the cancer preventive effects of metformin are mediated, at least in part, through direct effects on pancreatic epithelial cells harboring Kras G12D . Given that metformin is FDA-approved, our findings will have a strong translational impact for the development of novel chemo-preven- tive strategies for PDAC. Mo1989 -MANGOSTIN, A NATURAL XANTHONE DERIVATIVE TARGETS WNT SIGNALING IN FAMILIAL ADENOMATOUS POLYPOSIS PATIENT DERIVED CELL LINES Balaji Krishnamachary, Prabhu Ramamoorthy, Dharmalingam Subramaniam, Pugazhendhi Srinivasan, Scott J. Weir, Sufi M. Thomas, Trevor Cole, Seth Septer, Thomas M. Attard, Shrikant Anant Background & Aim: Familial adenomatous polyposis (FAP) is an inherited condition caused by germline mutation in the adenomatous polyposis coli (APC) gene on chromosome 5q22, resulting in aberrant Wnt/b-catenin signaling. FAP has a nearly 100% lifetime risk of colon cancer by the age of forty and total colectomy is required to prevent the development of colon cancer. Considering the universal risk for colon cancer with FAP and to delay or prevent colectomy, there is an increasing interest among the scientific community to identify natural products available from medicinal plants. -Mangostin is a major bioactive compound present in Mangosteen ( Garcinia mangostana) which possess significant anti-cancer activity. In the present study, the effects of -Mangostin has been investigated against FAP patient derived cell lines. Methods: FAP patient derived cells were isolated from different FAP patients' colonic biopsy samples. Cell proliferation were assessed by hexosaminidase and clonogenicity assays. Cell cycle was analyzed by FACS analysis using propidium iodide staining. Apoptotic proteins were measured by western blot analysis. The growth of spheroids was also evaluated. In addition, Wnt signaling proteins were measured by western blot analysis. Further, proteosomal degradation of -catenin was assessed by MG132 treatment. Results: -Mangostin inhibits proliferation and colony formation in a dose and time depend- ent manner in both FAP patient derived cell lines. In addition, -Mangostin induces S-phase and G2/M arrest, thereby reducing cyclin D1 levels. Furthermore, it inhibits the expression AGA Abstracts