MDR gene acts by -
Block drug activation
Block intracellular DNA synthesis
Causes efflux of drug
DNA repair inhibition
Ans. is 'c' i.e., Causes efflux of drug Multi drug resistance o Resistance develops to a variety of anticancer drugs. o It is associated with increased expression of a normal gene MDR1 gene. o MDR I gene encodes for P-glycoprotein Pcgp). P glycoprotein is a protective mechanism possessed by normal cells. o Pgp is an ATP dependent membrane efflux pump. o Its function is to expel a variety offoreign molecules including antitumour drugs from the cell. o Long lived cells such as the haemopoietic stem cells, Cells on excretory surfaces such as biliary hepatocytes, proximal renal tubules and intestinal cells and the cells of the blood-brain barrier, all have high expression of Pgp. o The MDR phenomenon illustrates how tumour cells adapt and enhance normal cell mechanism to deal with the effects of chemotherapy and how repeated cycles of chemotherapy select out a population of cells which have developed adaptive survival mechanism e.g. in myeloma where MDR proteins are rare at diagnosis but common at progression.