Drug resistance of melanosphere and pathway activation. A) Cell viability of undifferentiated melanospheres of the indicated samples and melanocytes treated with the indicated drugs. Mean ± SD of 3 independent experiments is shown. ** p < 0,01. B) Cell viability of melanospheres (undifferentiated) and their progeny (differentiated) exposed to the indicated chemotherapeutic agents. A representative sample is shown. Mean ± SD of 3 independent experiments is shown. *** p < 0,001. C) Cell viability of melanospheres exposed to the indicated kinase inhibitors. Mean ± SD of 3 independent experiments is shown. ** p < 0,01; * p < 0,05 D) Immunoblot analysis of the indicated proteins or phosphoproteins in melanospheres. U251 and T98G glioblastoma cell lines were used as p-ERK positive and negative control, respectively.