Aggregation assay of M07e and M07e.Axl cells. M07e and M07e.Axl cells were labeled with ethidium bromide and acridine orange and incubated in the presence or absence of rhGAS6 (400 ng/mL). Yellow-green (acridine orange) color aggregates of at least five living cells were counted in 20 microscopic fields, using a fluorescence microscope. Aggregates of dead cells were red-stained by ethidium bromide and excluded. The mean ± SD of five experiments is reported.