Acknowledgments We thank Dr Giuseppe
Loreto for his expert assistance with figures and tables, Agostino Eusepi for his help in the treatment and maintenance of mice, and Paola Di Matteo and Stefano Guida for providing general technical support. We finally thank Dr Tania Merlino for the text editing. Grant support This work was supported by grants from Cariplo and from the Italian Association for Cancer Research. Electronic supplementary material Additional file 1: Figure S1: Phenotypic characterization of melanospheres. A) Flow cytometric analysis of melanospheres for the indicated stem cell-associated antigens. White histograms Ganetespib are negative controls, grey histograms are specific GSK1120212 in vivo antibody stainings. B) RT-PCR analysis for the expression of ABCB-5 in the following samples: (M) marker, melanospheres sample 1 to 5, melanocytes, positive control (lung cancer stem cells), negative control. C) RT-PCR analysis for the expression of Nanog and Oct-4 in the samples indicated as in B. D) Flow cytometric analysis of CD44 variant 6 in melanospheres, differentiated cells, fresh xenografts and melanocytes as indicated. Each type of cells
was stained with unspecific antibody as negative control in the upper panels (control). (TIFF 774 Alpelisib purchase KB) Additional file 2: Figure S2: In vitro stem cell properties of melanospheres. A) Proliferative potential of melanospheres. Growth curve of melanospheres at early passages (kept in culture for few weeks after the isolation and before the experiment) or at late passages (after 6 month-culture). Cells were counted each week by trypan blue exclusion. B) Self renewing ability (percentage of clonogenic cells) of melanospheres. Percentage of cells able to form new spheres after single cell plating in limiting dilution Glycogen branching enzyme analysis for the indicated samples (first panel). Percentage of self-renewing cells obtained from primary, secondary or tertiary spheres in limiting dilution analysis (second panel).
Percentage of self renewing in undifferentiated (spheres) or differentiated cells obtained under stem cell culture conditions (undifferentiative) or under differentiative conditions as indicated (third panel). Comparison of self-renewing cells in cells previously expanded under stem cell conditions (SC medium) or under standard conditions for differentiated melanoma cells (RPMI) (last panel). The values represent mean +/- SD of three independent experiments. Student’ s T test was used to determine p-value (*p<0,1; **p<0,01; ***p<0,001). C) Multidifferentiation potential of melanospheres. (left) Melanogenic differentiation (S-100); (middle) Adipogenic differentiation (Oil-red-O); (right) Osteogenic differentiation (Alcaline Phosphatase activity).