We evaluated the MDR1 expression levels in 77 osteosarcomas and investigated whether MDR1 mRNA expression in osteosarcomas varies with location within the tumour, following chemotherapy, or after metastasis.
No significant relationship was found between the expression of the resistance-related proteins P-glycoprotein or glutathione S-transferase-pi and the incidence of metastases.
Two patients with increased levels of MDR1 before chemotherapy did not respond to the treatment and distant metastasis and death occurred in these patients.
We sought to determine how often P-glycoprotein is involved in the drug-resistance of urothelial cancer, and whether MDR1 gene expression is correlated with tumor grade, invasiveness, or metastasis.
MDR1 levels in early stage, clear cell tumors (n = 14) were lower than in tumors that had spread into perinephric tissue or had metastasized (n = 6) (0.77 +/- 0.08 versus 1.24 +/- 0.30, P < 0.05).
This study offers compelling evidence that (a) IGR-N-91 is a human neuroblastoma xenograft model able to induce metastasis in nude mice, (b) an increase in MYCN and MDR1 transcripts levels is associated with the metastatic process, and (c) IGR-N-91 provides a biological tool for the study of gene activations during tumor dissemination in neuroblastoma.
However, MDR1 RNA expression was less frequent in locally advanced tumors and was absent in the primary tumors of all six patients who had distant metastases.
By using a sensitive immunoperoxidase method, increased P-glycoprotein was detected in five multidrug-resistant and two selectively plant alkaloid-resistant retinoblastoma cell lines and in the intraocular and metastatic tumors from which they were derived.