Figure 2.

Melanoma cells spontaneously fused with primary human dermal fibroblasts and monocytes. (a,b) A melanoma (CTO)–fibroblast (CTG) (a) and a melanoma (CTO)–monocyte (CTG) (b) hybrid visualized with a confocal microscope in X-Y and X-Z planes. The Z-stacking confirms that double positivity does not result from cells lying on each other. Black arrows indicate the crossline of planes; white bars indicate 20 µm (a) and 10 µm (b). (c) A melanoma (CTO)–fibroblast (CTG) hybrid confirmed with confocal microscopy contains a nucleus from a female melanoma cell and another from a fibroblast from a male donor (upper row). Fluorescent in situ hybridization visualizing three X (red) and one Y (green) chromosome in the same cell (lower row). White bars indicate 30 µm (upper row) and 10 µm (lower row). (d) Fluorescent in situ hybridization visualizing two X (red) and one Y (green) chromosome in a melanoma (female)–monocyte (male) hybrid cell. White bar indicates 10 µm. (e) The percentage of hybrid cells compared to the total number of melanoma cells and fibroblasts or to the total number of melanoma cells and monocytes after 24 h of co-culture measured with flow cytometry. All investigated melanoma cell lines fuse spontaneously with human dermal fibroblasts (left panel) and peripheral blood-derived monocytes (right panel). Means of three experiments + SD are shown. * indicates significant differences between the marked groups. # indicates a significant difference between the marked group and all the other groups. p < 0.05. DAPI: 4′,6-Diamidin-2-phenylindol.