Expression of N-myc, c-myc, and MDR-1 proteins in newly established neuroblastoma cell lines: a study by immunofluorescence staining and flow cytometry.
Because expression of mdr-1 is increased in neuroblastoma cell lines by differentiating agents, the authors hypothesized a similar correlation with differentiation in vivo in neuroblastomas.
Many of the neuroblastoma samples were also evaluated for N-myc amplification but there was no correlation between N-myc copy number and the level of MDR1 mRNA expression.
MDR1 RNA levels were occasionally elevated in other untreated cancers, including neuroblastoma, acute lymphocytic leukemia (ALL) in adults, acute nonlymphocytic leukemia (ANLL) in adults, and indolent non-Hodgkin's lymphoma.
The results indicate that the level of MDR1 mRNA expression is associated with previous chemotherapy, including drugs that select the multidrug resistance phenotype in vitro regardless of neuroblastoma tissue origin or N-myc content in the genome.