Figure 1.

General mechanisms of drug resistance in colorectal cancer (CRC). Drug resistance is caused by multiple mechanisms, such as the decrease in delivery of drug to cancer cells, increase in an efflux out of the cells mediated by ATP-dependent transporters, decrease in uptake into the cells, change in enzymes involved in metabolism, genetic, or epigenetic modifications in the cells, and upregulation, mutation, or activation of downstream of signaling molecules.