Inflammatory Bowel Disease-Associated Colorectal Cancer: Translational and Transformational Risks from Exogenous Free Hemoglobin Alpha Chain: A By-product of Extravasated Erythrocyte Macrophage Erythrophagocytosis

Abstract

The aggregate aftermath of persistent inflammation in patients with inflammatory bowel disease (IBD) places them at increased risk for the advancement to colitis-associated colorectal cancer (CACRC). CACRC is preceded by IBD, the highly heterogenous, pharmacologically incurable, pertinacious, reverting/worsening, and immune-mediated inflammatory pathologies of the colon and rectum. The molecular and immunological basis of CACRC is highly correlated with the length/duration and stringency/severity of colon inflammation predisposed by the exogenous/free hemoglobin alpha chain (HbαC) the byproduct of infiltrating immune cells, extravasated erythrocytes, and macrophage erythrophagocytosis. The exogenous free HbαC prompts oxygen-free radical-arbitrated DNA damage (DNAD) through increased cellular reactive oxygen species (ROS) exacerbated by decreased tissue antioxidant defenses. Mitigation of Fenton reaction via pharmaceutical therapy would attenuate the ROS, promote apoptosis, DNAD repair, and subsequent prevent the incidence of CACRC. Three pharmaceutical options that attenuate hemoglobin toxicity include haptoglobin, deferoxamine, and flavonoids (vitamins C/E). Haptoglobin’s clearance rare from plasma is inversely correlated with its size; the smaller the size, the faster the clearance. Thus, the administration of Hp1-1 may prove to be beneficial. Furthermore, deferoxamine’s hydrophilic structure limits its ability to cross cell membranes. Thus, it may be beneficial if administered intracellularly to avoid the higher plasma concentrations and longer incubation periods associated with extracellular administration. Finally, the effectiveness of flavonoids and natural herb antioxidants is associated with high reactivity of hydroxyl substituents. Multiple analyses are currently underway to assess the clinical context of CACRC and outline the molecular basis of HbαC-induced ROS pathogenesis by exposing colonocytes and/or colonoids to HbαC. These cells are then treated with haptoglobin, deferoxamine (DFO), and flavonoids in order to separate free HbαC and measure their impact on hydroxyl radical formation therapies. The molecular pathogenesis of sporadic colorectal cancer (SCRC) i.e., “inflammation-dysplasia-carcinoma” progression sequence is well described, but the immunopathogenesis of CACRC herein reviewed is broadly still in prodromal stage/phase to be validated and understood. Therefore this timely review outlines the molecular and immunological basis of disease pathogenesis and the pharmaceutical intervention as a protective measure for CACRC.