TMT-labelled quantitative proteomic analysis to identify the proteins underlying radiation-induced colorectal fibrosis in rats.

Radiation-induced colorectal fibrosis (RICF) after pelvic radiotherapy can lead to stenosis and affect patients' quality of life. However, to date, few effective prevention and treatment methods for RICF have been implemented in clinical practice. Therefore, there is a strong need to investigate the molecular events underlying radiation-induced intestinal fibrosis. This study aimed to identify the comprehensive protein expression profiles related to RICF in rats. We performed tandem mass tag (TMT)-labelling proteomic analysis to examine RICF in rats after a single dose of 20 Gy conformal irradiation via X-ray and confirmed the altered proteins with parallel reaction monitoring (PRM). In total, we identified 6692 proteins, of which 5756 were quantified. When the p-value was <0.05, a protein fold change >1.5 or < 0.67 was considered to indicate a differentially abundant protein (DAP). Finally, we detected 227 upregulated proteins and 93 downregulated DAPs. The DAPs were involved in several pathways, including those involved in extracellular space, complement and coagulation cascades pathway, and regulation of response to wounding. Nine proteins in three main pathways were validated by parallel reaction monitoring. Our findings could accelerate the understanding of the mechanism underlying RICF and provide some clues for the identification of potential candidate targets for anti-fibrosis treatment. SIGNIFICANCE: Radiation-induced intestinal fibrosis is a significant problem that causes higher morbidity and affects patients' quality of life. However, there are few effective methods implemented in clinics to prevent and reverse this disease to date. The mechanism of radiation-induced colorectal fibrosis remains unclear, and the proteomic study is very limited. Here, we performed a large-scale comparative quantitative proteomics study on radiation-induced colorectal fibrosis in rats. The results provide an improved understanding of radiation-induced intestinal fibrosis and some clues for the identification of potential candidate targets for anti-fibrosis treatment.