Multinucleation of koilocytes is in fact multilobation and is related to aberration of the G2 checkpoint

Abstract

AIMS: To clarify the fine structure of koilocytes and correlate this with genetic aberration of the G2 checkpoint. METHODS: Three dimensional reconstruction from confocal fluorescent images, together with functional assays for key molecules of the G2 checkpoint-cdc2 and cyclin B1-was performed in human uterine cervical samples. After confirming 22 human papillomavirus (HPV) types using a DNA chip from 30 cervical swabs, previously confirmed as 15 cervical low grade and 15 high grade intraepithelial lesions, the activity of molecules involved in the G2 checkpoint was evaluated using western blotting for cyclin B1, cdc2, and phospho-cdc2 (Y15 and T161), a nuclear extraction fractional assay, and a reverse transcription polymerase chain reaction assay. In addition, three dimensional confocal image restoration was performed on confirmed cervical intraepithelial neoplasia tissue samples. RESULTS: T161 phospho-cdc2 and cyclin B1 expression was higher in HPV infected cervical lesions than in normal samples. Immunofluorescence, revealed that cyclin B1 was present predominantly in the nuclei of HPV infected cells, confirming the results of the nuclear fractional assay. On restoration of three dimensional confocal images, the multinucleation of koilocytes was revealed to be multilobation of a single nucleus, rather than true multinucleation. This multilobation appeared to be associated with chromosomal instability and aberration of the G2 checkpoint. CONCLUSIONS: The multiple nuclei of koilocytes are in fact multilobation of a single nucleus, and this phenomenon is associated with upregulation of gene products related to the G2 checkpoint.