Determination of Chromosomal Alterations in Nasal NK/T-cell Lymphomas by DOP-PCR and Comparative Genomic Hybridization

Park, Sang Jin; Ha, Mahn Joon; Kim, Hyon Ju; Park, Kwang Hwa; Kim, Hyun Soo; Yang, Woo Ik; Kim, Hugh Chul

Abstract

PURPOSE: Because of difficulty of obtaining metaphase cells from tumor specimens, there are only a few cytogenetic studies in nasal NK/T-cell lymphomas, and so far no consistent specific chromosomal abnormalities have been described. In this study, we have used degenerate oligonucleotide primed PCR (DOP-PCR) and comparative genomic hybridization (CGH) to deter mine chromosomal alterations from 6 nasal NK/T-cell lymphoma tissues dissected from formalin- fixed paraffin-embedded slide sections.
MATERIALS AND METHODS
For the isolation of tumor DNA, four 7-micrometer-thick tissue sections from each sample were dewaxed and rehydrated, and areas of high tumor cell content (more than 60%) were dissected and pooled into a tube. Normal DNA was prepared from the peripheral blood of a healthy volunteer. Tumor DNA was labeled with biotin-16-dUTP by DOP-PCR and normal DNA was labeled with digoxigenin-dUTP using a nick translation kit. In CGH, equal amounts of differently labeled DNA from the tumors and normal reference DNA were hybridized simul taneously to normal metaphase chromosomes. They were visualized by different fluordegrees Chromes, and the signal intensities were quantitated separately as gray levels for each chromosome. The over- and underrepresented DNA segments were determined by computation of image ratios and average ratio profiles.
RESULTS
Our results show that gains of DNA copy number were more prevalence than DNA losses. The most commonly observed gains were mapped to chromosomal regions of 1p32.2 ter,19 and 20 in 4 of 6 cases (67%). The other frequent gains were found on chromosomes 12q in 3 of 6 cases. The most frequent loss was detected on 6q in 4 of 6 cases(67%), and less fre quently observed on 13q21.1 q34 and 13q14 q34.
CONCLUSION
These genomic changes found in specific chromosomal regions are likely to harbor genes of importance in nasal NK/T-cell lymphomagenesis, therefore such cytogenetic mapping of genomic imbalance may be of value for further molecular delineation of NK/T-cell lymphoma.