EXPRESSION OF THE MULTIDRUG RESISTANCE-ASSOCIATED PROTEIN (MRP) GENE IN COLORECTAL CARCINOMAS

To determine the clinical significance of MRP in patients with colorec tal carcinomas, we have studied the expression of the MRP gene by reve rse transcription-polymerase chain reaction (RT-PCR) (n = 105) and by immunohistochemistry (n = 30). MRP mRNA expression was observed in 92 (88%) tumour specimens. Positive MRP staining with monoclonal antibodi es QCRL-1 and QCRL-3 was detected in all samples studied with strong s taining in seven (23%) and weak staining in 23 (77%) specimens. Strong MRP staining in these samples did not appear to be related to the age and sex of the patients, localization of the primary tumour, histolog ical grade, tumour size, lymph node metastasis, distant metastasis and tumour stage. Strong MRP staining was not associated with MDR1 RNA or P-glycoprotein (P-gp) expression. Kaplan-Meier curves revealed that o verall survival of patients with strong MRP-staining tumours was simil ar to the survival of patients with weak-staining tumours. These data indicate that the MRP gene is expressed in primary colorectal carcinom as but is neither related to known prognostic factors nor a prognostic factor by itself.