Resistance to chemotherapy significantly affects the treatment results in various cancers. Multidrug resistance caused by P-glycoprotein expression is now widely studied in human malignancies. We present the results of P-glycoprotein expression examination in 91 tumor tissue samples obtained from children treated for different malignant tumors in the Dept. of Pediatric Oncology, Prague. The correlation between the level of P-glycoprotein expression and tumor histology, clinical outcome, use of therapy, relapse rate and metastatic disease was made. P-glycoprotein expression was found significantly more frequent in soft tissue sarcomas, neuroblastomas, and hepatoblastomas, and generally in disseminated disease. On the contrary, a high expression of P-glycoprotein was not found in malignant brain tumors and nephroblastomas. The data strongly support the possibility that the percentage of P-glycoprotein expressing cells in selected tumors (soft tissue sarcomas, neuroblastomas), may have a clinical importance.

Department of Pediatric Oncology 2nd Medical Faculty Charles University and University Hospital Motol Prague Czech Republic

DNA and histone deacetylases as targets for neuroblastoma treatment