DeMars, Cathrine J.

Abstract Background: In patients with Barrett's esophagus, chronic reflux injury and inflammation are associated with esophageal adenocarcinoma, one of the most rapidly increasing lethal cancers. Epidemiological and preclinical studies support decreased risk of esophageal adenocarcinoma with NSAID use. Gastroesophageal refluxate contents can promote carcinogenesis in Barrett's metaplasia by activating AKT, which up regulates COX-2 expression and prostaglandin biosynthesis. We recently noted that neoplastic transformation in Barrett's esophagus is associated with increased AKT expression, particularly isoform AKT1. The AIM of this study is to investigate the effect of NSAID (Aspirin) use in patients with Barrett's esophagus on AKT1 expression using frozen tissue from the randomized, phase II trial of aspirin and esomeprazole for esophageal cancer chemoprevention in Barrett's esophagus patients and to assess the functional consequences of AKT1 expression in-vitro. Methods and Results: In a subset of patients (12 of 120 patients) with Barrett's esophagus who were randomized to placebo, lower dose (81 mg) or higher dose (325 mg) Aspirin for 4 weeks, both PCR and Western blot revealed marked reduction in AKT1 expression in patients who received 325 mg of Aspirin daily compared to patients who received placebo. Our in-vitro experiments support that AKT1 expression is functionally relevant to the process of carcinogenesis in Barrett's epithelial cells. Using adenovirus to induce AKT1 expression, we show that increased AKT1 expression increases Barrett's epithelial cell growth, facilitates RAS-mediated transformation of pre-neoplastic epithelial cells and promotes colony formation. Since AKT1 is known as Warburg kinase and regulates cellular glucose uptake to support aerobic glycolysis during growth de-regulation and neoplasia, we examined the uptake of fluorescent deoxyglucose analog (2-NBDG) in Barrett's epithelial cells transduced with AKT1 adenovirus. At 48 hrs, compared to control, AKT1 overexpression resulted in increased glucose uptake both by metaplastic and neoplastic Barrett's epithelial cells. Transcriptional repression of AKT1 abrogated the 2-NBDG uptake by these cells. Finally, we did pathway specific qPCRs and noted that use of Aspirin is associated with altered expression of chromatin remodelers that could down-regulate AKT1 expression. Conclusion: Collectively, our results demonstrate that Aspirin mediated down-regulation of Warburg kinase AKT1 in patients with Barrett?s esophagus is a novel mechanism for the regulation of Barrett?s epithelial cell growth. The in-depth characterization of molecular mechanisms is currently underway. This abstract is also presented as Poster A82. Citation Format: Navtej S. Buttar, Gary W. Falk, Cathrine J. DeMars, Sonia Chowdhury, Ahmed Elebiary, Anamay Sharma, Sidhartha Chaudhry, Nathan R. Foster, Katie L. Allen Ziegler, Yvonne Romero, Norman E. Marcon, Thomas Schnell, Douglas A. Corley, Prateek Sharma, Marcia R. Cruz-Correa, Chin Hur, David E. Fleischer, Amitabh Chak, Kenneth R. DeVault, David S. Weinberg, Gary Della’Zanna, Ellen Richmond, Thomas C. Smyrk, Sumithra Mandrekar, Paul J. Limburg. Aspirin mediated downregulation of Warburg kinase AKT1 in patients with Barrett's esophagus: Implications in neoplastic transformation. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr PR-03.

SP/KLF (Specificity protein/Krüppel-like factor) transcription factors comprise an emerging group of proteins that may behave as tumour suppressors. Incidentally, many cancers that display alterations in certain KLF proteins are also associated with a high incidence of KRAS (V-Ki-ras2 Kirsten rat sarcoma viral oncogene homologue) mutations. Therefore in the present paper we investigate whether SP/KLF proteins suppress KRAS-mediated cell growth, and more importantly, the potential mechanisms underlying these effects. Using a comprehensive family-wide screening of the 24 SP/KLF members, we discovered that SP5, SP8, KLF2, KLF3, KLF4, KLF11, KLF13, KLF14, KLF15 and KLF16 inhibit cellular growth and suppress transformation mediated by oncogenic KRAS. Each protein in this subset of SP/KLF members individually inhibits BrdU (5-bromo-2-deoxyuridine) incorporation in KRAS oncogenic-mutant cancer cells. SP5, KLF3, KLF11, KLF13, KLF14 and KLF16 also increase apoptosis in these cells. Using KLF11 as a representative model for mechanistic studies, we demonstrate that this protein inhibits the ability of cancer cells to form both colonies in soft agar and tumour growth in vivo. Molecular studies demonstrate that these effects of KLF11 are mediated, at least in part, through silencing cyclin A via binding to its promoter and leading to cell-cycle arrest in S-phase. Interestingly, similar to KLF11, KLF14 and KLF16 mechanistically share the ability to modulate the expression of cyclin A. Collectively, the present study stringently defines a distinct subset of SP/KLF proteins that impairs KRAS-mediated cell growth, and that mechanistically some members of this subset accomplish this, at least in part, through regulation of the cyclin A promoter.

Abstract Reflux-induced injury promotes esophageal adenocarcinoma, one of the most rapidly increasing, highly lethal cancers in Western countries. Here, we investigate the efficacy of a combinatorial chemoprevention strategy for esophageal adenocarcinoma and characterize the underlying molecular mechanisms. Specifically, our approach involves the use of ursodeoxycholic acid (Urso) due to its ability to decrease injury-inducing bile salts in combination with Aspirin to mitigate the consequences of injury. We find that Urso-Aspirin combination reduces the risk of adenocarcinoma in vivo in animals with reflux, decreases the proliferation of esophageal adenocarcinoma cells, and downregulates a key cell cycle regulator, CDK2. Mechanistically, using cell growth, luciferase reporter, expression, and chromatin immunoprecipitation assays, we identify GLI1, a Hedgehog-regulated transcription factor, as a novel target of Urso-Aspirin combination. We show that GLI1 is upregulated during esophageal carcinogenesis, and GLI1 can bind to the CDK2 promoter and activate its expression. Although the Urso-Aspirin combination downregulates GLI1, the GLI1 overexpression not only abrogates the effect of this combination on proliferation but it also restores CDK-2 expression. These findings support that the chemopreventive effect of the Urso-Aspirin combination occurs, at least in part, through a novel GLI1-CDK2–dependent mechanism. To further understand the regulation of CDK2 by GLI1, both pharmacologic and RNAi-mediated approaches show that GLI1 is a transcriptional activator of CDK2, and this regulation occurs independent of Smoothened, the central transducer of the Hedgehog canonical pathway. Collectively, these results identify a novel GLI1-to-CDK2 pathway in esophageal carcinogenesis, which is a bona fide target for effective combinatorial chemoprevention with Urso and Aspirin. Cancer Res; 70(17); 6787–96. ©2010 AACR.