Cellular models for multiple drug resistance in cancer

Conclusion Considerable progress has been made toward understanding some of the molecular mechanisms underlying MDR in cancer cells in vitro, and sensitive techniques such as immunocytochemistry and RT-PCR indicate that these mechanisms may also play a role in resistance in human cancers. It does seem, however, that there are many different patterns and mechanisms of MDR, not all of which are currently well understood. Identification of chemicals which, at non-toxic doses, circumvent MDR, and of new drugs to which MDR cells are not cross resistant, remains a priority in this area of research. Also, it is important to remember that, although inherent resistance at the molecular level is possibly the most serious barrier to successful chemotherapy, other issues including tumor cell kinetics, drug metabolism, drug penetration within the tumor, and side effects on normal tissues are also critical factors in determining how an individual may respond to chemotherapy.