Learning the ABCs of melanoma-initiating cells.

Tumor stem or initiating cells have been proposed to exist for melanoma. Stem-like cells have been propagated from melanoma cell lines and specimens. Additionally, classical stem cell markers, including ABCG2 and CD133, have been identified in clinical melanomas. However, definitive markers for the purification and further characterization of melanoma-initiating cells remained elusive. Recently, Schatton et al. provided solid evidence that the doxorubicin-resistant ATP-binding cassette transporter ABCB5 marks primitive cells capable of recapitulating melanomas in xenotransplantation models. The identification of melanoma-initiating cells has far-reaching implications, as new therapeutic strategies can be envisioned that specifically target these cells.