Roles of growth factors in chemotherapy-induced intestinal mucosal damage repair.

Chemotherapy agents induce apoptotic cell death and loss of cell proliferation in the intestinal crypt epithelium, resulting in intestinal mucosal damage called "mucositis". Small intestinal mucositis is characterized structurally by crypt loss and villus atrophy, and functionally by absorptive and barrier impairments. The increased use of chemotherapy in cancer treatment and the clinical importance of the intestinal mucositis as a common side effect have stimulated more active research into understanding the pathophysiology of intestinal mucositis and developing agents for preventing or treating this condition. Rodent studies have shown that, following the chemotherapy-induced initial apoptosis and loss of crypt cell proliferation, many different growth factors or their receptors are upregulated locally at the crypts, preceding or coinciding with the epithelial hyperproliferative repair response. Aiming to reduce crypt cell apoptotic sensitivity to cytotoxic chemotherapy and/or to enhance crypt epithelial proliferative repair, several exogenous growth factor treatments have been tested, either preclinically and/or clinically, and are showing promise for their efficacy or safety in preventing or treating chemotherapy-induced mucositis. These tested growth factors include keratinocyte growth factor, interleukin-11, transforming growth factor beta, milk-derived growth factor extract, macrophage/granulocyte colony stimulating factors, and glucagon-like peptide 2. Further research on the basic and discovery levels and subsequent translational studies are needed to understand more about chemotherapy-induced intestinal mucositis and to identify candidates of growth factors or other agents that will potentially prevent or treat chemotherapy-induced mucositis more effectively, specifically, safely, and practically in chemotherapy patients.