Applications of single-color and double-color oligonucleotide primed in situ labeling in cytology.

Interphase cytogenetics is mostly performed with use of fluorescence in situ hybridization (FISH), using long DNA probes of several hundred or thousand base pairs in length. Recently, oligonucleotide primed in situ labeling (PRINS) was established for staining centromeres and telomeres of chromosomes in metaphase spreads by Taq-polymerase-mediated incorporation of labeled nucleotides. We investigated the use of PRINS in intact interphase cells of various cytologic preparations, targeting chromosomes 1, 8, and 9. Examining cell smears (n = 3), touch preparations (n = 20), and cytospins (n = 11) of non-neoplastic and neoplastic tissues, PRINS was as sensitive and reliable as the FISH method in assessing the exact chromosome number. Aneuploidy in tumor cells was confirmed by double-color PRINS in a part of the specimens. The PRINS reaction, which requires heating of the cell preparations to as high as 96 degrees C, did not affect the cytomorphologic details. Because PRINS is much faster and approximately 10 times less expensive than FISH, this method allows an increased application of interphase cytogenetics in diagnostic cytopathology.