Clinical implications of a slight increase in the gene dosage of MYCN in neuroblastoma determined using quantitative PCR

Abstract

Introduction: Recently, determining the MYCN status in neuroblastoma (NB) using the quantitative PCR (Q-PCR) and FISH instead of the Southern blotting (SB) has been recommended. In order to assess the implications of the gene dosage of MYCN in NB, the MYCN status was evaluated using Q-PCR on DNA extracted from small areas of NB specimens obtained using laser capture microdissection (LCM).

Materials and methods: MYCN gene dosages (MYCN/NAGK) were determined in 63 primary NB block samples, as well as in 243 microdissected tissues from 63 samples using Q-PCR. In 23 of 63 cases, the MYCN gene status was evaluated using FISH.

Results: Nine block samples with the amplification of MYCN based on SB showed a remarkable increase of the MYCN gene dosage using Q-PCR. Twelve of 54 block samples with no amplification of MYCN based on SB showed a slight increase of the MYCN gene dosage (3.56 > or == MYCN/NAGK > 1.84), and 8 of these 12 cases were in the advanced stage. Among these 12 cases, 1 case had several LCM areas with a high copy number of MYCN and several LCM areas which showed no increase of MYCN gene. Another case showed a slight increase in the MYCN gene dosage (3.65 < or == MYCN/NAGK < or == 4.82) in all LCM areas. In addition, a large number of cells with the MYCN gain were found using FISH in the block sample. In 2 other cases of 12 cases, although no LCM areas showed an increased gene dosage of MYCN, a small number of cells with MYCN amplification were found using FISH were found in the block sample.

Conclusion: A slight increase in the gene dosage of MYCN detected by Q-PCR may indicate that the NB tissue contains a small number of cells with the MYCN amplification or a large number of cells with the MYCN gain, which are associated with the aggressive progression of NB.