[MDR (Multiple Drug Resistant) type of resistance to chemotherapy in clinical practice].

Multifactorial resistance is the main mechanism of chemotherapy failure in cancers. Multidrug resistance (MDR) is related to the expression of a 170 kDa membrane glycoprotein, the so-called P-glycoprotein (P-gp). This protein is able to extrude drugs of various structures and mechanisms out of the cytoplasm. P-gp is a pronostic value in hemopathy as well as in child sarcoma, osteosarcoma and neuroblastoma. Modulator agents of different generations are capable of inhibiting P-gp. MDR modulation is obtained in hemopathies and is associated with an eradication of the P-gp (+) cell clones. In solid tumors, clinical trials using verapamil or cyclosporin are not so convincing. It is likely that other mechanisms of resistance are responsible for tumor progression, such as the MRP system, glutathion and topoisomerases. A better knowledge of multifactorial resistance and drug synthesis counteracting these resistance mechanisms will allow to elaborate new therapeutic basis for cancer therapy.