Therefore, although the data inconsistent has still existed in the literatures, the accumulating data has indicated that the resistance of CRC to CPT-11 might be developed by the activity modulation of these enzymes and the copy number change/mutation of TOP1. Moreover, it should also be noted that most of these results have come from the in vitro studies, therefore, the further in vivo evidences about the CPT-11 resistance of CRCs are still needed to exam for the improvement of CPT-11 therapy of CRC patients. The gene discussed is TOP1; the disease is colorectal carcinoma.