Detection of karyotype changes in interphase cells: oligonucleotide-primed in situ labelling versus fluorescence in situ hybridization.

Interphase cytogenetics is a rapidly developing technique which is usually performed by fluorescence in situ hybridization (FISH). Recently, oligonucleotide-primed in situ synthesis (PRINS) has become established as a method of labelling centromeric regions of chromosomes in metaphase spreads. We tested the suitability of PRINS in detecting the exact copy number of chromosomes 1, 3, 7 and 8 in intact interphase cells of 17 cytological preparations derived from normal and neoplastic tissues. Control procedures consisted in preparation of metaphase spreads of lymphocytes of healthy donors, conventional cytogenetics in some of the specimens, and omission of the primers or Taq polymerase from the reaction mixture. All specimens were additionally examined by FISH and analysed blind by two experienced observers. Both PRINS and FISH revealed a corresponding distribution of hybridization signals for all chromosomes examined in specimens of normal bone marrow (n = 5), normal liver cells (n = 5), three samples of acute nonlymphocytic leukaemia in which conventional chromosome analyses had shown monosomy 7 or trisomy 8, and in four hepatocellular carcinomas that displayed trisomy 1. Overall, statistical analysis revealed no significant difference in the signal distribution between the two techniques. Our results demonstrate that PRINS is as reliable as FISH for detecting chromosome copy numbers in interphase nuclei of intact cells. The PRINS method, however, is easier to perform, faster and less expensive, holding great potential for future applications in diagnostic pathology.