Flow cytometric analysis of the multiple drug resistance phenotype.

Laser flow cytometry is increasingly used for quantitation of cellular fluorescent drug retention, effect of efflux blockers and for expression of drug resistance related cellular surface markers. Several intrinsic and extrinsic factors can affect the results obtained from drug retention functional assays and lead to artifacts. In the present study, we have used a panel of well-characterized parental and drug resistant cell lines, fluorochromes and efflux blockers to identify the possible sources of artefacts in flow cytometric analysis of the multiple drug resistance phenotype.