Figure 1.

YB-1 is secreted by melanoma cells in a progression stage-dependent manner. (a,b) Immunoblot analysis of 48 h-conditioned serum-free cell culture supernatants of benign control cells (melanocytes (FM), fibroblasts (FF), keratinocytes (FK)) and of melanoma cell lines derived from metastatic melanomas or primary melanomas in the radial (RGP) or vertical growth phase (VGP). A representative immunoblot using an antibody targeting the C-terminus of YB-1 is shown (a, uncropped Western blot in Figure S1a). An arrowhead marks the boundary between the two in parallel processed gels. Densitometric analysis was conducted on four independent experiments (relative values of the prevalent experiment indicated below the immunoblot). YB-1 concentrations in the supernatants was approximated with the help of a recombinant YB-1 protein standard included on each gel (b; mean values for individual cell lines (points) and group means (vertical lines) are shown). Significance was determined with one-way ANOVA and subsequent Tukey’s multiple comparison test (ns = non-significant, * for p < 0.05, ** for p < 0.01, *** for p < 0.001 and **** for p < 0.0001). Relative viability was assessed by LDH release and trypan blue uptake (a).