Cell fusion in tumor progression: the isolation of cell fusion products by physical methods

Here we describe a simple improvement in PEG-mediated cell fusion that was obtained by modifying the standard single-step procedure. We found that the use of two PEG undertreatments obtains a better yield of cell fusion products than the standard method, and most of these products are bi- or trinucleated polykaryocytes. Fusion rate was quantified using fluorescent cell staining microscopy. We used this improved cell fusion and cell isolation method to compare giant cells obtained in vitro and giant cells obtained in vivo from patients with Hodgkin's disease and erythroleukemia.In the present study we show how to improve PEG-mediated cell fusion and that cell separation by velocity sedimentation offers a simple alternative for the efficient purification of cell fusion products and to investigate giant cell formation in tumor development.The study of cell fusion has gained momentum in modern cell biology through several lines of investigation [1-3]. Somatic cell hybrids have been used by a number of investigators to analyse the genetic basis of cancer [4-7] and for gene mapping [8-11]. Cell hybridisation provided the method for generating monoclonal antibodies [12] and fusion of virus-transformed cells has been instrumental in the isolation of transforming viruses [13]. Tumour-dendritic cell fusion technology is applied to immunotherapy strategies [14-16]. The idea that cell fusion plays a role in the transition from polyploidy to aneuploidy and hence in tumour progression has been the subject of several reviews [7,3], but experimental evidence in favour of this hypothesis is difficult to obtain. As noted by Brenda M. Ogle in a review on cell fusion, "the origin of a cell as the product of a fusion event can be difficult or impossible to deduce" [2].In previous investigations we have explored the possibilities that lymphocyte-lymphocyte fusion plays a role in the cytogenesis of giant polykaryons in Hodgkin's disease (HD) [17] and that erythroblast fusion might be a so