Identification of ACA-28, a 1'-acetoxychavicol acetate analogue compound, as a novel modulator of ERK MAPK signaling, which preferentially kills human melanoma cells.

The extracellular signal-regulated kinase (ERK) signaling pathway is essential for cell proliferation and is frequently deregulated in human tumors such as melanoma. Melanoma remains incurable despite the use of conventional chemotherapy; consequently, development of new therapeutic agents for melanoma is highly desirable. Here, we carried out a chemical genetic screen using a fission yeast phenotypic assay and showed that ACA-28, a synthetic derivative of 1'-acetoxychavicol acetate (ACA), which is a natural ginger compound, effectively inhibited the growth of melanoma cancer cells wherein ERK MAPK signaling is hyperactivated due to mutations in the upstream activating regulators. ACA-28 more potently inhibited the growth of melanoma cells than did the parental compound ACA. Importantly, the growth of normal human epidermal melanocytes (NHEM) was less affected by ACA-28 at the same 50% inhibitory concentration. In addition, ACA-28 specifically induced apoptosis in NIH/3T3 cells which were oncogenically transformed with human epidermal growth factor receptor-2 (HER2/ErbB2), but not in the parental cells. Notably, the ACA-28-induced apoptosis in melanoma and HER2-transformed cells was abrogated when ERK activation was blocked with a specific MEK inhibitor U0126. Consistently, ACA-28 more strongly stimulated ERK phosphorylation in melanoma cells, as compared in NHEM. ACA-28 might serve as a promising seed compound for melanoma treatment.