EXPRESSION OF MDR1 P-GLYCOPROTEIN AND MULTIDRUG RESISTANCE-ASSOCIATEDPROTEIN IN CHILDHOOD SOLID TUMORS/

We evaluated the expression of MDRl/p-glycoprotein in paediatric rumou rs using reverse transcriptase polymerase chain reaction (RT-PCR), RNA dot blot analysis, and immunohistochemistry on formalin fixed paraffi n-embedded material with JSB-1 and C-219 monoclonal antibodies, and co mpared these three techniques. The expression of multidrug resistance- associated protein (MRP) gene was examined by RT-PCR assay. We studied MDRl/p-glycoprotein and MRP expression in 13 samples from 10 neurobla stoma patients, 11 samples from 10 nephroblastoma patients, 2 rhabdomy osarcomas, 1 adrenocortical carcinoma and 10 benign tumours or tumour- like lesions. Eleven of 13 neuroblastomas, 7 of 11 nephroblastomas, 2 rhabdomyosarcomas, 1 adrenocortical carcinoma, and 7 of 10 benign rumo urs or tumour-like lesions showed MDR1 PCR products. By RNA dot blot a nalysis, MDR1 transcripts were detectable in 11 of 34 specimens. Immun ohistochemically, we detected positive reaction products for JSB-1 in 26 of 36 samples. There was a significant correlation between the immu noreactivity for JSB-1 and the expression of MDR1 mRNA expression by R T-PCR (P=0.0001). However, the presence of p-glycoprotein immunostaini ng does not correlate with the MDR1 expression shown by RT-PCR in ever y case. As for MRP mRNA expression, 9 of 13 neuroblastomas and 10 of 1 1 nephroblastomas revealed PCR products.