Comparative gene expression study in WM164 melanoma cells treated with dimethylacrylshikonin.

Currently, one in every three cancers diagnosed is a skin cancer. Melanoma accounts for only 4% of all skin cancers but is responsible for ca. 79% of skin cancer deaths. Moreover, the incidence of malignant melanoma is rising faster than any other solid tumor type. Even though the survival rate is 100% at a very early stage, it drops dramatically at an advanced stage and leaves melanoma then as one of the most aggressive and incurable types of solid cancer. This reflects the need for the discovery and development of new respective anti-cancer drugs. In a previous study [1], we discovered that dimethylacrylshikonin, isolated from the roots of Onosma paniculata Bur.&Franch. (Boraginaceae), exhibited the lowest IC₅₀ of several isolated shikonin derivatives and was most active towards melanoma cell lines. Therefore, it was chosen for more in-depth investigations. We did a comprehensive gene expression study using the metastatic melanoma cell line WM164. Cells were treated with 8µM dimethylacrylshikonin for 24h and the gene expression signature was compared to vehicle-treated control cells (vehicle: 0.5% DMSO). 1192 distinct mRNAs could be identified as expressed in all three biological replicates out of which 89 were 2-fold differentially expressed (n = 3). Testing for significantly differentially expressed genes following the Benjamini-Hochberg correction for multiple testing resulted in 31 distinct mRNAs. The most interesting candidates (among other things sequestosome 1) are known to be involved in apoptosis, cell proliferation, survival and/or drug resistance and were validated and confirmed by semi-quantitative real-time PCR. Additional experiments are in progress to study the changes in different signaling pathways in more detail to reveal the exact mode of action.

[1] Kretschmer et al, J Nat Prod, 2012, 75:865 – 9.