ABSTRACT
Colorectal cancer is one of the most common malignant tumors in the digestive tract and the morbidity increase annually. Surgery is still the main method for treating colorectal cancer, supplemented by chemotherapy. However, chemotherapy resistance is the predominant cause for failed chemotherapy treatment against colorectal cancer. Exploring the resistance mechanisms against existing chemotherapy may be a key step for getting more effective chemotherapies against malignancies. The underlying mechanisms of resistance are complicated and interfered by numerous factors. This paper summarized the previous studies focusing on drug resistance mechanism, with the emphasize factors including mediation of membrane transporter proteins, abnormal changes in the activity of drug resistance-related transferase, apoptosis-related regulation, DNA repair, changes in microenvironment, and signal transduction pathways and activating transcription factors.