Abstract 38: Chemoprevention with COX2 and EGFR inhibition in familial adenomatous polyposis patients: mRNA signatures of duodenal neoplasia

Background and Purpose: Nearly 80% of colon cancers arise after acquired mutations in the adenomatous polyposis coli (APC) gene. Familial adenomatous polyposis (FAP) is an autosomal dominant inherited disorder caused by a germline mutation in the APC gene, leading to a nearly 100% risk of colorectal cancer and a 12% lifetime risk of duodenal cancer. Since prophylactic colectomy is now the standard of care when colorectal polyposis increases beyond endoscopic management, duodenal cancer has now become the leading cause of cancer death in FAP. Efficacious chemoprevention of duodenal neoplasia is, therefore, an unmet clinical need. As part of a Phase II double blind, randomized placebo-controlled trial of cyclooxygenase (COX) and epidermal growth factor receptor (EGFR) inhibition therapy with sulindac and erlotinib respectively, in FAP patients, we showed a profound 40% decrease in duodenal polyp burden at 6 months (p = 3 X10-9). For most patients on drug, both duodenal polyp number and size were decreased. However, the mechanisms by which COX and EGFR inhibition protects against duodenal neoplasia remain incompletely understood. Methods: To better understand the molecular changes in duodenal tissue caused by sulindac and erlotinib, RNA sequencing was performed on normal and polyp (≥3mm) biopsies from the duodenum of FAP patients obtained 6-month endpoint endoscopy. Ten FAP patients on placebo and ten FAP patients on sulindac and erlotinib were selected for this preliminary analysis. Differential RNA expression in paired baseline and endpoint normal colon tissue and paired normal and polyp tissue was determined using negative binomial statistics (DESeq2). Variations in RNA expression patterns between biopsy samples was determined by principal component analysis and unsupervised hierarchical clustering. Biological pathways affected by sulindac and erlotinib treatment were determined using Ingenuity Pathway Analysis (IPA) software. Results: Comparing paired polyp and normal tissue from patients on placebo, we identified more than 1100 differentially expressed genes (Fold ≥ 1.5, FDR Conclusions: Animal models and molecular studies have supported a link between Wnt and EGFR signaling pathways and COX-2 expression in intestinal neoplasia. A chemoprevention trial in patients with germline APC mutations leading to familial adenomatous polyposis tested the potential for combined COX and EGFR inhibition to hinder growth of duodenal neoplasia. Sequencing of mRNA from tissue obtained at endpoint of the trial demonstrated inhibition of COX2, EGFR and Wnt/β-catenin signaling in duodenal neoplasia of patients treated with sulindac and erlotinib. The successful observed regression of duodenal neoplasia in drug-treated FAP patients on the trial is supported by differential expression in the mRNA. Citation Format: Deborah Neklason, Don Delker, Jewel Samadder, Austin Wood, Randall Burt, Phil Bernard. Chemoprevention with COX2 and EGFR inhibition in familial adenomatous polyposis patients: mRNA signatures of duodenal neoplasia. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Integrating Clinical Genomics and Cancer Therapy; Jun 13-16, 2015; Salt Lake City, UT. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(1_Suppl):Abstract nr 38.