Heterogeneity of the MYCN oncogene in neuroblastoma.
OBJECTIVE
MYCN amplification is an important therapy-stratifying marker in neuroblastoma. Fluorescence in situ hybridization with signal detection on the single-cell level allows a critical judgement of MYCN intratumoral heterogeneity.


METHODS
The MYCN status was investigated by fluorescence in situ hybridization at diagnosis and relapse. Heterogeneity was defined as the simultaneous presence of amplified cells (>/=5 cells per slide) and nonamplified cells within one tumor or sequential change of the amplification status during the course of the disease. Likewise, heterogeneity can be detected between primary tumor and metastasis.


RESULTS
From 1,341 patients analyzed, 1,071 showed no amplification, 250 showed homogeneous amplification, and 20 patients showed MYCN heterogeneity. Of the patients with heterogeneity, 12 of 20 had clusters of MYCN amplifications, 3 of 20 had amplified single cells, 3 of 20 showed MYCN amplifications in the bone marrow but not in the primary tumor, and 2 of 20 acquired MYCN amplification during the course of the disease. All stage 4 patients were treated according to high-risk protocols; 7 of 8 later progressed. Four patients with localized disease were treated according to high-risk protocol because of MYCN-amplified clusters; 1 of 4 later progressed. One patient treated with mild chemotherapy experienced progression. Seven patients with localized/4S disease underwent no chemotherapy: 4 of 5 patients with MYCN heterogeneity at diagnosis remained disease-free, and 1 of 5 experienced local progression. Two patients had normal MYCN status at diagnosis but acquired MYCN amplification during the course of the disease.


CONCLUSIONS
MYCN heterogeneity is rare. Our results suggest that small amounts of MYCN-amplified cells are not correlated to adverse outcomes. More patients with heterogeneity are warranted to clarify the role of MYCN heterogeneity for risk classification.
Theissen
Jessica
J
Department of Pediatric Oncology and Hematology, Children's Hospital, University of Cologne, Cologne, Germany. jessica.theissen@uk-koeln.de
Boensch
Marc
M
Spitz
Ruediger
R
Betts
David
D
Stegmaier
Sabine
S
Christiansen
Holger
H
Niggli
Felix
F
Schilling
Freimut
F
Schwab
Manfred
M
Simon
Thorsten
T
Westermann
Frank
F
Berthold
Frank
F
Hero
Barbara
B
D005784:Gene Amplification; D006801:Humans; D000071447:N-Myc Proto-Oncogene Protein; D009367:Neoplasm Staging; D009447:Neuroblastoma / Q000235:genetics* / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics*; D015513:Oncogene Proteins / Q000235:genetics*; D009857:Oncogenes
C459801:MYCN protein, human; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins