Platinum drug resistance - Ursus arctos horribilis (North American brown bear)

Platinum-based drugs cisplatin, carboplatin and oxaliplatin are widely used in the therapy of solid malignancies, including testicular, ovarian, head and neck, colorectal, bladder and lung cancers. The mechanism of action of Platinum-based drugs involves covalent binding to purine DNA bases, which primarily leads to cellular apoptosis. Their clinical success is, however, limited due to severe side effects and intrinsic or acquired resistance to the treatment. Platinum resistance could arise from decreased drug influx, increased drug efflux, intracellular detoxification by glutathione, etc., decreased binding (e.g., due to high intracellular pH), increased DNA repair, decreased mismatch repair, defective apoptosis, and altered oncogene expression.