Colorectal cancer (CRC) is one of the common malignancies worldwide, accounting for a significant percentage of cancer mortality. Concurrent chemoradiation (CCRT) is now a standard treatment for unresectable malignancies of anorectum. To improve quality of life, CCRT is also commonly applied in treatment of lower rectal and anal canal cancer to preserve anal sphincter function. The most commonly used chemotherapeutic drugs combined with radiation as radiosensitizers is 5-fluorouracil (5-FU). Circulating endothelial progenitor cells (EPC), which contribute to the tumor vessel formation, reflect the response to chemotherapy both in animal model and clinical trial. Thus, circulating EPC can be used as a marker for optimizing and monitoring the anti-angiogenesis therapy including angiogenesis inhibitors and chemotherapy. Whether circulating EPC can be served as a marker of CCRT efficacy or not remains undetermined. Since CCRT is now a standard treatment of locally advanced and high-risk CRC, the development of a surrogate marker for monitoring CCRT response and optimize treatment intensity is very important.

In this grant we intent to monitor the levels of circulating EPC in locally advanced and high-risk CRC patients before, during and after CCRT. To further characterize the changes in function and biology of EPC caused by CCRT, a syngeneic animal model will be also used to evaluate the clonogenecity and specific gene expression of EPC in tumor-bearing mice receiving CCRT.