588 Effect of Flexible Sigmoidoscopy Screening on Incidence and Mortality From Colorectal Cancer in the PLCO Screening Trial

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Optimizing the Response to Thiopurine Therapy: A Search for Novel Explanations for Thiopurine Hypermethylation Paul A. Blaker, Annemieke M. Peters van Ton, Monica Arenas, Melissa A. Smith, Catherine H. Smith, Peter M. Irving, Anthony M. Marinaki, Jeremy D. Sanderson

Effect of Flexible Sigmoidoscopy Screening on Incidence and Mortality From Colorectal Cancer in the PLCO Screening Trial Robert E. Schoen, Paul Pinsky, Joel Weissfeld, Lance A. Yokochi, Timothy R. Church, Adeyinka O. Laiyemo, Robert S. Bresalier, Thomas L. Riley, Philip C. Prorok, Christine Berg

Background. Thiopurines are not effective in up to 1/3 of patients with inflammatory bowel disease (IBD) and 1/5 have to discontinue therapy due to side effects. The most important cause of these problems is thiopurine hypermethylation. This is a catabolic process leading to an unfavourable thiopurine metabolite profile (high methyl-mercaptopurine (6-MeMP) to low thioguanine nucleotide (TGN) ratio; >11:1). This is observed in 15% of patients and is not predicted by pre-treatment measurement of thiopurine-S-methyltransferase (TPMT) activity. Importantly thiopurine hypermethylation can be circumvented with the use allopurinol in combination with low dose AZA/6-MP. The aim of this research is to establish the mechanism of thiopurine hypermethylation and identify predictive genetic markers to allow early combination therapy. We hypothesized that thiopurine hypermethylation occurs as a result of genetic factors that affect methylation flux and the cellular transport of methylated metabolites. Methods. A well-defined cohort of 168 age and dose-matched patients prescribed AZA/6-MP was identified from the records of the Purine Research Laboratory (PRL). Genomic DNA was extracted from EDTA blood samples of 76 patients demonstrating thiopurine hypermethylation and 92 patients with normal methylation profiles. Polymorphic sequence variants in genes predicted to affect thiopurine methylation flux and cellular metabolite transport were identified from single nucleotide polymorphism (SNP) databases and genotyped by Taqman assay. Associations were tested using Fisher's Exact test. Results. We found a significant association between the haplotype of rs9332377 T and rs4646316 C, which encodes a low-activity synonymous Catechol-O-methyltransferase (COMT) variant, and protection from thiopurine hypermethylation (rs9332377 T, p=0.0178, rs4646316 C, p=0.03). A polymorphism in the nucleo-base transporter, ABCB5, was significantly associated with thiopurine hypermethylation (rs2031641 G/G, p=0.0098). The association was strengthened when patients with 6-MeMP levels >5000 pmol/L versus 6-MeMP <5000 pmol/L were compared (p=0.0065). In keeping with this we have previously reported that polymorphism in the ABCB5 gene is associated with a lack of clinical response to thiopurines. Conclusions. Changes in methylation flux due to the activity of methyltransferases other than TPMT affect the formation of thiopurine methylated metabolites, likely through direct competition for the essential co-factor S-adenosylmethionine. Furthermore, polymorphism in the ABCB5 gene, which affects the nucleotide-binding domain of this transporter, is associated with thiopurine hypermethylation, suggesting reduced cellular efflux of methylated metabolites. Further studies are now indicated to establish the role of these genetic markers in clinical practice.

Studies in the UK and Italy demonstrate a reduction in distal CRC incidence and mortality with FSG screening. No significant effect in the proximal colon was observed, but only 58% of subjects underwent colonoscopy. In the U.S., the multi-center, randomized Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial compared FSG with usual care. Most subjects with abnormal FSG underwent colonoscopy for diagnostic follow up. Aim: To evaluate the effect of flexible sigmoidoscopy on CRC incidence and mortality. Methods: From 1993 to 2001, men and women age 55-74 were randomized to FSG screening with a repeat exam at 3 or 5 years, versus usual care. Colorectal cancers and deaths were ascertained and cause of death was evaluated in a formal adjudication process. Results: A total of 77,445 participants were randomized to intervention and 77,455 to usual care. Mean follow-up time (11.2 years) in the two arms was similar, and extended maximally to 13 years. Over 86% of subjects (67,071/77,445) underwent ≥1 screen, 50.9% (39,440/ 77,445) had two, and 28.5% (N=22083) had ≥1 exam positive for a polyp or mass. Of subjects with an abnormal screen, 80.5% (17,772/22,083) underwent diagnostic intervention within 1 year, 95.6% (N=16,990/17,772) of whom underwent colonoscopy, for a colonoscopy rate of 21.9% (16,990/77,445) as a direct effect of FSG screening. The incidence of CRC was 11.9/10,000 person years (PY) in the intervention arm compared to 15.2/10,000 in usual care, a 21% reduction (RR=0.79; 95% CI .72-.85, P<0.0001). Mortality due to CRC was observed in 3.9/10,000 PY in the usual care arm (341 deaths) compared with 2.9/ 10,000 PY in the intervention arm (252 deaths), a 26% reduction (RR=0.74; 95% CI .63.87, P=0.0003). Conclusions: Screening with flexible sigmoidoscopy resulted in a statistically significant and clinically important decrease in overall CRC incidence and mortality. Information on the effect of the intervention in the distal and the proximal colon will be forthcoming. 589 Modulation of the Brain-Gut Axis After 4-Week Intervention With a Probiotic Fermented Dairy Product Kirsten Tillisch, Jennifer S. Labus, Bahar Ebrat, Jean Stains, Bruce D. Naliboff, Denis Guyonnet, Sophie Legrain-Raspaud, Beatrice Trotin, Emeran A. Mayer BACKGROUND: Preclinical studies in rodents show that changes in gut microbiota alter central signaling mechanisms and emotional behavior (1, 2). However, such changes have never been demonstrated in humans by modulating the gut microbiota with probiotics or antibiotics. AIM: To determine whether consumption of a probiotic fermented dairy product alters response in emotional arousal and visceral afferent brain regions during an Emotional Reactivity Task (ERT) in healthy women. METHODS: In this double-blind, controlled, parallel study, 45 healthy women, age 18-50, were screened to rule out medical or psychiatric illness. They were randomly assigned to three intervention groups, no product (NoP), control milk-based non-fermented dairy product (CTRL), or probiotic dairy product (TEST) consisting in a fermented dairy product containing B. lactis CNCM I-2494, a yoghurt symbiosis L. bulgaricus and S. thermophilus, as well as L. lactis. CTRL and TEST groups consumed twice daily 125 gram products for 4 weeks. All groups performed the ERT during functional magnetic resonance imaging (fMRI) at randomization and at the end of the 4week intervention period. The ERT consisted of viewing negative emotional faces and viewing shapes as a control. fMRI blood oxygen level-dependent (BOLD) response was measured using a 3 Tesla scanner. Pre-post intervention BOLD subtraction images were compared using the general linear model implemented in SPM. Small volume corrections were performed in pre-hypothesized regions (amygdala, anterior cingulate, insula, prefrontal cortex-PFC). Partial least squares analysis was performed to assess intervention related connectivity between insula based and amygdala based networks. RESULTS: The TEST group exhibited less BOLD response in the mid/posterior insula during the ERT compared to CTRL (pFWE=.002; MNI 46, 2, 6) and NoP (pFWE=.016; MNI 36, -18, 20) groups. No BOLD differences were noted in the cingulate, PFC, or amygdala. The TEST group showed decreased connectivity of an amygdala-centered network with the insula, dorsal striatum and lateral PFC. CONCLUSIONS: To our knowledge, this is the first study in humans demonstrating that consumption of a probiotic fermented dairy product can be associated with modulations of brain activity. The findings suggest that changes in the gut microbiota by regular intake of a probiotic can (i) affect brain regions concerned with the central processing of afferent signals from the gut, and (ii) reduce the impact of the brain regions involved in emotional arousal on the central processing of gut afferent signals. One may speculate that the observed changes are mediated by effects on sensory encoding mechanisms in the gut. References: 1) Bravo JA, et al. PNAS USA 2011 2) Diaz Heijtz, R, et al. PNAS USA 2011

568 Therapeutic Diagnostic: Identification of Molecular Mechanisms Underlying Ulcerative Colitis in Infliximab Non-Responders at Baseline Michael Macoritto, Ty Thomson, Jennifer S. Park, David Drubin, Renee Deehan-Kenney, David De Graaf, Daphna Laifenfeld One fundamental challenge in the treatment of patients is heterogeneity of the molecular mechanisms of disease resulting in a varied response to treatment among individuals. In patients with ulcerative colitis (UC), anti-TNF therapy is successful, with 61-69% of patients responding in the first two months of treatment with infliximab, presumably because their disease is driven by TNF. There remain 31-39% of patients who do not respond, and may have alternative disease mechanisms. Another challenge is the co-development of a therapeutic diagnostic (TDx) to select patients most likely to respond prior to availability of clinical outcome data. We applied a systems biology methodology to identify: 1. Alternate molecular mechanisms of UC in infliximab non-responders 2. Candidate TDx to identify patients with a greater prospect of responding to therapies targeting these alternate mechanisms in the absence of clinical outcomes data Over 2000 “molecular footprints” (MF) (molecular, context dependent activation patterns (e.g., TNF)) were used to infer measures of activity for all entities in each patient of a public UC transcriptomic data set. Grouping patients with similar activity patterns identified two subpopulations of patients that differ on their levels of three main mechanisms, Il6, Vegf, and Il1b, and patients with high activity levels are nonresponders to infliximab. The patients were then stratified by the activities of each of these molecular mechanisms and the stratification was used to train classifiers for high and low activity for each mechanism. The classifiers were applied to UC patients in an independent test data set, using infliximab response as a basis of successful prediction in lieu of actual response data for targeted therapies to these mechanisms. Infliximab non-responders had relatively high levels of signaling for these disease mechanisms with a high degree of consistency in the test set. Using patient stratification by target activity as a substrate, candidate biomarkers for predicting therapeutic response can be discovered without a priori knowledge of outcome. We verified this approach retrospectively using data for Inflammatory Bowel Disease (IBD) patients treated with infliximab. Using the TNF MF, we stratified a training set of IBD patients by inferred TNF activity, then generated gene expression and mechanism-based classifiers from patients with high and low TNF signaling. When applied to a test set, the mechanism and gene expression classifiers predicted responders with positive and negative predictive values of 79/88% and 71/100% respectively. This method can be applied to other diseases and may facilitate target pathway identification and TDx development and enabling the selection of appropriate patient populations prior to treatment and clinical trial participation.

590 One-Year Effectiveness and Costs of Six Alternative H. pylori Test/Treat and Retest/Retreat Strategies Using Triple, Concomitant or Sequential Drug Regimens in Seven Latin American Sites (SWOG Trial S0701) Javier Torres, Douglas R. Morgan, E. R. Greenberg, Eduardo Salazar-Martinez, Ricardo Dominguez, Catterina Ferreccio, Luis Eduardo Bravo, Rodolfo Peña, Rolando Herrero, Mercedes Meza-Montenegro, Maria E. Martinez, Pelayo Correa, Manuel Valdivieso, Garnet L. Anderson, William D. Chey, John Crowley, Laurence H. Baker BACKGROUND: The potential feasibility of H. pylori (Hp) eradication strategies to prevent gastric cancer depends on the prevalence of infection in the community, the longer-term probability of remaining uninfected following treatment, and the program cost per person who is freed of infection. We assessed the effectiveness and costs of different strategies using data from a large clinical trial in Latin America where gastric cancer risks are high. METHODS: We recruited 1852 adults (ages 21-65) from the general populations of seven communities and screened them with a urea breath test (UBT). 1463 individuals (79.4%) tested positive

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AGA Abstracts

AGA Abstracts

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