ABCG2 and melanoma: To test this hypothesis, we used multiple human melanoma cells—SK-MEL-30, MDA-MB-435, SK-MEL-28, and MALME-3M, and we found that in both melanotic and amelanotic melanoma, the GH–GHR system upregulates both ABC-transporter levels as well as MITF-directed processes of melanosome formation and tyrosinase activity, differentially, following multiple chemotherapy treatments.