Abstract
The term “multidrug resistance” has come to mean different things to different people. Initially, it was coined to describe the laboratory phenomenon of cross-resistance to various natural products, and this phenomenon was later found to relate to increased expression of P-glycoprotein (gp170) ( 1 ). Since then, many laboratory scientists and some clinicians have mistakenly assumed that the clinical observation of drug resistance to a wide range of cytotoxic agents has the same basis. Are the two in fact related? In this issue of the Journal, Trock et al. ( 2 ) have conducted an exhaustive review of the literature in an attempt to answer this question as it relates to breast cancer. There has been a plethora of studies with widely varying conclusions, and an attempt to distill them into a single review article is indeed praiseworthy. But there are problems.