Human monocyte x mouse melanoma fusion hybrids express human gene.

Artificial fusion of human monocyte with Cloudman S91 mouse melanoma cells resulted in hybrids that showed increased motility in vitro, enhanced metastatic potential in vivo, and also tended to be super melanotic (Rachkovsky et al., Clin. Exp. Metastasis 16 (1998) 299). However, no gene derived from monocytes has been shown to be expressed in these hybrids until now. Similar observations have also been noted in hybrids originating from mouse macrophage and mouse melanoma cells. Having the advantage of species differences in mouse x human hybrids, we are able, this time, to show by RT-PCR that some genes specific to the human genome are expressed in these hybrids, indicating that not only is the genomic DNA from parental monocytes integrated in the hybrids but also some genes are being expressed. This observation may lead us to find contributory genes from monocyte and/or macrophage that are responsible for modulating the genotypes and hence the phenotypes in the hybrids.