Elucidation of proliferative capability of mononuclear tetraploid cells, emerging spontaneously from diploid cells, using image cytometry and fluorescence in situ hybridization

Abstract Objectives Proliferation of tetraploid cells ( TC s) emerging from diploid cells is considered to be a critical event toward tumourigenesis, or cancer progression. Recently, several studies have reported that binuclear TC s emerging from normal cells are capable of mitosis, however, it has not been confirmed directly whether mononuclear TC s emerging from normal cells could proliferate, even cancer cells. The aim of this study is to detect mononuclear TC s in vitro , spontaneously emerging from diploid cells and to elucidate their proliferative capability directly. For this purpose, we have developed a novel method. Materials and methods In this study, two completely disomic cell lines were used, TIG ‐7, a fibroblast cell line and CAL ‐51, a breast cancer cell line. Cells were cultured on microscope slides and their DNA content was determined using an image cytometer. On the same slides, chromosome numbers were scored using centromere fluorescence in situ hybridization ( FISH ). For evaluating proliferative capability of TC s, bromodeoxyuridine (BrdUrd) incorporation and colony‐forming ability were examined. Results Using our method, spontaneous emergence of mononuclear TC s was detected in both TIG ‐7 and CAL ‐51. Colonies of TIG ‐7 TC s were not observed, but were observed of CAL ‐51 TC s. Conclusions Our method enables detection of mononuclear TC s and elucidation of their proliferative capability, directly; this evidence reveals that mononuclear TIG ‐7 TC s do not proliferate but that mononuclear CAL ‐51 TC s are able to.