Rapid detection assays for multidrug resistance

In attempts to develop simple and rapid assays for detection of multidrug resistance (MDR) doxorubicin-resistant S180 (S180DOX), colchicine-resistant CHO (CHOCOL) and cytarabine (cytosine-arabinoside)-resistant L1210 cell lines (L1210AraC) were investigated. S180DOX and CHOCOL cells express the MDR-phenotype while L1210AraC does not. Using a previously described short-term assay firstly, inhibition of incorporation of radioactive nucleic acid precursors into tumour cells after addition of doxorubicin was measured. Secondly, the accumulation of the fluorescent dye rhodamine 123 (R123) in the different cell lines were analyzed. It could be observed that the resistant S180DOX and CHOCOL cells needed significantly more time to accumulate R123 than their sensitive parental cell lines or L1210AraC cells. Therefore, both assays are adequate tools for the rapid detection of MDR.