FIGURE 4.

Molecular mechanisms of tumor chemoresistance and radioresistance. (A) Abnormal expression of ABC family contribute to drugs being pumped out of the cell, which causes intracellular drug concentrations too low to sensitive to drugs. (B) Changes in the expression of transport proteins in drug absorption lead to a decreased drug absorption rate and chemoresistance. (C) DNA damaged by chemotherapy and radiotherapy is repaired quickly, which is closely related to the acquisition of chemoresistance and radioresistance. (D) Cell death is inhibited, indicating that the balance between apoptosis and cell growth is disrupted, affected by the major gene families such as p53 and Bcl. (E) The production of cellular EMT properties causes resistance to chemotherapy and radiotherapy. (F) The molecular targets of drugs can be altered in tumor cells. (G) Drug inactivation, some detoxification‐related proteins deactivate drugs in cells, which is followed by chemoresistance acquisition