Neuroblastoma is a
tumor accounting for approximately 10% of
all childhood malignancies and 50% of
all childhood cancer-related deaths. MYCN gene copy number variation represents the most important prognostic factor in
neuroblastoma. Prognostic significance of MYCN gene expression is more complicated and may depend on other factors such as MYCN gene copy number status. In the present study, we assessed MYCN gene expression using real-time RT-PCR following
cisplatin treatment in three human
neuroblastoma cell lines (UKF-NB-3, UKF-NB-4 and SK-N-AS) and their
cisplatin-resistant counterparts. We also examined MYCN gene status and copy number (gain and amplification) variations using interphase and metaphase fluorescent in situ hybridization (FISH) and multiplex
ligation-dependent probe amplification (MLPA). Only
cisplatin-sensitive UKF-NB-4 cells exhibited decreased MYCN expression following treatment with
cisplatin. Other sensitive
neuroblastoma cells did not exhibit a change in MYCN expression. In contrast,
cisplatin-resistant UKF-NB-4 and SK-N-AS cells exhibited increased MYCN expression irrespective of the number of MYCN copies or concentration of
cisplatin in the medium. In MYCN-amplified
neuroblastoma cells we did not observe any significant change in the number of MYCN copies after
cisplatin treatment, whereas MYCN-non-amplified SK-N-AS cells revealed during
cisplatin treatment an increased number of MYCN gene copies caused by 2p gain in the majority of cells by FISH. We postulated that
cisplatin treatment does not result directly in altered transcription of MYCN. A functional change in MYCN
mRNA levels and increased MYCN expression in
cisplatin-resistant
neuroblastoma cells do not have a clear relationship to MYCN copy numbers. These findings may further contribute to the understanding of
cisplatin chemotherapy in connection with MYCN expression, and the possible copy number variations in MYCN
neuroblastoma cells may be of importance since targeting of MYCN is being tested as
neuroblastoma therapy.