Figure 1.

Large intestine morphology, radiotoxicity, and cancer radioresistance. The large intestine exhibits a unique physiology that facilitates its absorption and waste storage functions. The epithelial barrier, which separates the lumen and the lamina propria, is linked by junctions and is covered by a mucus layer. The oxygen gradient within the large intestine, ranging from 3 to 40 pO2 (mmHg), creates an anaerobic environment in the lumen and an aerobic environment in the lamina propria. During radiotherapy, both healthy and cancerous colorectal tissue can be adversely affected by radiation. Radiotoxicity of healthy tissues is mediated by a series of interconnected events, while radioresistance in cancer tissues can result in an increase in tumor growth. This can be attributed to a facilitated microenvironment and tumor-enhancing mutations [20,21,22,23].