Molecular aspects of chronic radiation enteritis

Abstract

Purpose: Chronic radiation enteritis (CRE) is one of the most feared complications of abdominal or pelvic radiation therapy and the treatment of CRE is difficult and often controversial. Recent progress in molecular biology has shed some light on the pathogenesis of CRE, which is characterized by fibrosis. The purpose of this article is to summarize the current state of knowledge of molecular aspects of radiation induced intestinal fibrosis and to discuss potential therapeutic targets. Methods: A review of the up-to-date published literature involving the possible molecular cascades in radiation-induced intestinal fibrosis and prospective targets for CRE were performed using the Pub-Med search engine. Results: Fibrosis development is correlated with transforming growth factor β1 (TGF-β1) and its downstream effector Smad3, which stimulates fibrogenic downstream mediators, such as connective tissue growth factor (CTGF). Ras homologue (Rho) and Rho-associated kinase (ROCK) signaling pathway have been shown to play important roles in the development of CRE. The inhibition of these pathways ameliorated radiation-induced intestinal fibrosis in vitro and in animal studies; however, the relationship between the Smad3 and Rho signaling pathways has not been elucidated. Conclusions: Rho/ROCK and TGF-β1/Smad3 signaling pathways have been shown to play a key role in intestinal fibrogenesis, which might provide with effective possibilities for clinical intervention. Understanding the cooperation between Smad3 and Rho, may therefore be critical to our overall understanding of fibrosis development and maintenance of CRE.