Figure 1.

Underlying mechanism of drug resistance in CSCs. To survive in a harsh tumor microenvironment and to withstand the cell death mechanisms CSCs alter the expression of several genes. ABC transporters are one among them which serve as drug efflux pumps. It is believed that upregulation of these drug exports makes CSCs to escape from the effects of anti-neoplastic drugs. This picture describes the mode of action of various drugs in normal cells and CSCs. Usually, under normal conditions, the drug efflux pumps are usually inactivated in the affected cell so that the drug that comes from the circulation would be easily absorbed by that cell with help of certain drug uptake channels. However, in CSCs due to overexpression of ABC transports, although the drug would be absorbed it would be immediately pushed back to the circulation.