[Methods for diagnosing MDR: immunohistochemistry versus molecular biology]

The methods of multidrug resistance (MDR) detection in human malignant tumors are numerous. The process of molecular biology (Slot Blot, Northern Blot, Reverse Transcription Polymerase Chain Reaction, PCR) and the process of in situ hybridization or immunohistochemistry are complementary. The process of molecular biology are quantitative and especially sensitive for PCR, by contrast they fail in specificity. This specificity is obtained by in situ hybridization and immunohistochemistry. However, none of these methods give knowledge of GP170 functional activity. The detection of functional GP170 can be identified by rhodamine or daunorubicin intracellular accumulation with flux cytometry or by scintigraphically imaging GP170 expression in vivo with Tc-Sestamibi. The multiplicity of methods for detecting multidrug resistance show that there is no consensus about the best process to employ commonly. In consequence, the alone MDR biological diagnosis should not be the rationale of choice for second line chemotherapy or for using MDR revertant agents. In other words, the MDR biological diagnosis, keeping in mind that other chemoresistant mechanisms (topoisomerases, glutathione system, etc) could be present simultaneously or successively during tumor spreading or during successive antineoplastic treatments.