Establishment of criteria for measuring MDR-1 gene expression level in breast cancer by RT-PCR

Abstract

Objective: To formulate criteria of multidrug resistance (mdr-1) gene expression for predicting chemotherapy response and prognosis. Methods: Using reverse transcription-polymerase chain reaction (RT-PCR) assay, the expression of mdr-1 gene in 82 breast cancer samples were detected. Results: The data were treated by statistic analysis system (SAS)-singlevariate analysis. It showed that the level of mdr-1 gene expression clearly deviated from normal to right distribution (P<0.0001), and thus might be divided by quantiles P50 (mdr-1/β2-MG=0.2) and P75 (mdr-1/β2-MG=0.6), which were taken as the preliminary criteria for analyzing 56 patients’ chemosensitivity to ADM, VDS and VCRin vitro and 32 relapsed metastatic patients’ chemotherapy responsein vivo, seperately. When mdr-1/β2-MG<0.2, the ratios of resistance gradually escalated, but there were about 30%∼50% of the cases who showed sensitive to the drugsin vitro and effective to chemotherapyin vivo. When mdr-1/β2-MG≥0.6, the most of patients showed drug resistance bothin vitro andin vivo. Conclusion: According to the above-mentioned results, criteria of evaluating mdr-1 gene expression level was formulated: the mdr-1/β2-MG<0.2 (P50) was considered as negative expression, the ratio≥0.2∼<0.6 (P75) was weakly positive expression, ≥0.6 was strongly positive expression. This indicated that different levels of mdr-1 gene expression may reflect objectively drug resistancein vitro and chemotherapy responsein vivo.