Awtar Krishan

Flow Cytometric Monitoring of Drug Resistance in Human Solid Tumors

Resistance to cancer chemotherapy continues to be a major hurdle in successful management of refractory human malignancies. Drug resistance may be intrinsic or acquired after chemotherapy. Several well-known extracellular factors such as drug metabolism and pharmacokinetics may be responsible for failure of chemotherapy. However, a major reason for drug resistance resides at the cellular level and often involves cellular mechanisms which under normal conditions may have other protective and important biological roles. Tumor cell resistance is believed to be multifactorial involving altered drug transport (influx, retention and efflux), and biochemical mechanisms such as xenobiotic detoxification/ alternate metabolic pathways, and altered targets (1–3). Multiple drug resistance (MDR) has been recently described as a phenomenon in which tumor cells are resistant to a variety of unrelated natural products such as alkaloids and antibiotics used as cancer chemotherapeutic agents (1,3).