Abstract B71: Potential role of hemoglobin in colorectal cancer initiation in inflammatory bowel disease setting.

Abstract

Abstract Background: Inflammatory bowel disease (IBD) is a recognized high risk condition to develop colorectal cancer (CRC) and other intestinal cancers. Several risk factors have been described, allowing preventive strategies to focus on these patients: extensive long-standing disease, severity of inflammation, family history of CRC and primary sclerosing cholangitis (PSC). Aims: While using MALDI MS tissue profiling, we found a unique spectral peak at mass-to-charge ratio (m/z) 5045 to be more intense in inflamed colon samples from IBD patients compared to adjacent normal tissue and/ or diverticulosis (DV). We investigated this signal as a possible transforming factor in CRC initiation, in the setting of IBD. Methods: We profiled colonic mucosal and submucosal layers of 99 IBD patients for biomarkers that differentiated ulcerative colitis (UC) from Crohn's colitis (CC). We determined these unique differentiating proteins by histology-directed proteomic profiling using MALDI MS; protein identification utilized LC/MS/MS. We tested DNA damage by exposing an identified protein to a normal colonic epithelial cell-line (NCM 356). DNA damage was tested by comet assay. Results: LC-MS/MS identified m/z 5045 in CC/UC subjects as triply charged free hemoglobin ion chain (Hb). Validation studies used protein extracts and tissues from full thickness samples from UC, CC, and diverticulosis (DV, controls) subjects. Both CC and UC mucosal and submucosal samples were strongly positive for Hb-α. However, DV staining was restricted to erythrocytes found in submucosal capillaries. There was no significant difference in Hb-α level between UC and CC; however UC and CC levels were significantly higher than those in DV samples (p< 0.006 and p< 0.0001, respectively). When normal colonocytes (1x105 cells/ml) were exposed to Hb (300μM for 4 hours), there was clear DNA damage analyzed by comet assay. We noted macrophage erythrophagocytosis of extravasated erythrocytes. Conclusion: Free Hb was found in UC/CC but not DV mucosa/submucosa tissue. Free Hb resulted from extravasated macrophage erythrophagocytosis. Hb significantly induced DNA-damage of normal epithelial colonocytes (NCM356). DNA-damage could potentially increase risks for CRC transformation. Further elucidative studies are underway. Citation Format: Laura A. Franklin, Joan C. Smith, Billy R. Ballard, Erin H. Seeley, Mary K. Washington, Jeremy L. Norris, Kevin L. Schey, Harold L. Moses, Richard M. Caprioli, Samuel E. Adunyah, Amosy E. M'Koma. Potential role of hemoglobin in colorectal cancer initiation in inflammatory bowel disease setting. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr B71.