Effect of cytotoxic agents and retinoic acid on Myc-N protein expression in neuroblastoma.
OBJECTIVE
Neuroblastoma is an important pediatric tumor in which Myc-N amplification is a well-known poor prognostic indicator. It has a great diversity in clinical behavior. The effect of pharmacologic agents used in neuroblastoma treatment on Myc-N expression is still unclear.


METHODS
We analyzed Myc-N expression changes by immunocytochemistry in Myc-N-positive Kelly human neuroblastoma cell line using retinoic acid and cytotoxic drugs (cisplatin, vincristine, cyclophosphamide, etoposide, and doxorubicin) and their combinations compared with control conditions. First, concentration of drugs were determined as LD50 doses. Kelly cells and drugs were incubated for 24 hours in 5% CO2, 37 degrees C in 96-well plates. Myc-N expression was scored semiquantitatively as negative, mild, moderate, or high positive.


RESULTS
Myc-N amplification did not change with any agent or combination. It was higher than 20 copies in all conditions. Myc-N protein expression was high in control and doxorubicin group. It was moderate in retinoic acid, cyclophosphamide, retinoic acid combined with cyclophosphamide and retinoic acid combined with doxorubicin groups. The expression was mild in cisplatin, vincristine, etoposide, retinoic acid combined with etoposide, and retinoic acid combined with cisplatin groups. Myc-N expression was negative in retinoic acid combined with vincristine group.


CONCLUSIONS
Myc-N expression is reduced with cytotoxic agents and retinoic acid in neuroblastoma although Myc-N amplification remains the same. Retinoic acid combined with vincristine is the most effective combination to reduce Myc-N expression. Our results suggest that therapeutic applications of these agents as low dose maintenance therapy might be useful.
Aktas
Safiye
S
Institute of Oncology, Dokuz Eylul University, Izmir, Turkey. safiyeaktas@yahoo.com
Altun
Zekiye
Z
Erbayraktar
Zubeyde
Z
Aygun
Nevim
N
Olgun
Nur
N
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002648:Child; D005784:Gene Amplification / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D009447:Neuroblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D016271:Proto-Oncogene Proteins c-myc / Q000032:analysis / Q000187:drug effects*; D014212:Tretinoin / Q000494:pharmacology*; D014750:Vincristine / Q000494:pharmacology
C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; D014212:Tretinoin; D014750:Vincristine