Rho/ROCK pathway as a molecular target for modulation of intestinal radiation-induced toxicity.

More than half of cancer patients are treated with radiation therapy. Despite its high therapeutic index, radiation therapy can cause disabling injuries to normal tissues, especially in long-term survivors. Thus, one of the great challenges of modern radiation therapy is to increase tolerance of normal tissue to ionizing radiation in order to improve the quality of life of cancer survivors and/or enhance local control using dose escalation. The physiopathological aspects of normal tissue toxicity have been widely explored; however, none of these descriptive findings has led to the development of effective therapeutic strategies. Several empirical treatments have also been used in clinical trials (superoxide dismutase, pentoxifylline-tocopherol); however, the results are still controversial, and their mechanisms of action have not been clearly defined. The recent development of high-throughput biological approaches will contribute greatly to the characterization of the molecular pathways associated with normal tissue toxicity and the identification of specific and effective molecular targets for therapeutic interventions using already known or new pharmacological compounds. In this paper, we will discuss recent advances made in the characterization of one of the most serious complications of radiation therapy, late intestinal toxicity, using molecular profiling. We will focus on the involvement of the Rho/ROCK pathway in the development and maintenance of late radiation enteropathy. The role of the Rho/ROCK pathway in tissue response to radiation injury will be reviewed, as well as therapeutic perspectives.