Expression of the gene for the multidrug resistance-associated protein in human prostate tissue

To characterize the clinical relevance of MRP gene in the chemoresistance o f prostate carcinomas we determined the multidrug resistance-associated pro tein (MRP) expression in 30 samples from organ-confined prostate carcinoma, 9 samples from adjacent normal tissue and 4 hormone unresponsive cancers. The measurement of MRP expression was carried out by reverse transcription polymerase chain reaction (RT-PCR) in combination with capillary electropho resis. Incorporated fluorescence-labeled primers were disclosed by a laser- operated fluorescence detection module. MRP expression was quantified by in tegration of the peak area and correlated to the ubiquitously expressed bet a 2 microglobulin. As positive control served the adriamycin-resistant HL60 -ADR cell line, which overexpresses MRP. MRP expression was found in all sa mples. All samples showed a lower MRP/beta 2 ratio than HL60-ADR cells. The expression of the MRP gene was 30% higher in organ-confined tumors than in hormone-unresponsive anaplastic tumors. Normal tissue showed the same MRP mRNA level as the adriamycin-sensitive HL60 cells. A higher tumor stage cor related with an increase of MRP expression (> factor 2), whereas G3 tumors displayed a MRP expression 30% lower than in G2 tumors. The small alteratio ns indicate that MRP expression seems not be involved in the chemoresistanc e of prostate carcinomas.