Figure 1.

Mechanisms of drug resistance in ovarian cancer. Cancer cells can become resistant to the administered drug during chemotherapy. Several mechanisms cause resistance to chemotherapy. (A) Activation of a drug occurs when resistance genes (MDR) code for enzymes that chemically modify the drug. (B) Efflux pump overexpression inhibits the accumulation of a chemotherapeutic drug. (C) Enhanced DNA damage repair is triggered by DNA repair mechanisms, nucleotide excision repair, and homologous recombination. These processes reverse drug damage and increase drug resistance. (D) Alteration of drug targets occurs because chemotherapeutic drugs have specific targets, and changes may render the drug ineffective. (E) Inhibition of drug uptake occurs due to modifications in the cell wall proteins, preventing drugs from entering the cell. By targeting these resistance mechanisms, cancer cells can become sensitive to the drugs and increase their effectiveness.