In the present study, we investigated the activity and modes of action of cajanin stilbene acid (CSA) and its derivatives in terms of cytotoxicity, gene expression profile, and transcription factor activity. XTT assays on MCF7 cells were performed upon treatment with CSA or derivatives. After the determination of IC50 values, gene expression profiling was performed with Agilent microarray experiments. Deregulated genes were determined with Chipster software, pathway and functional analyses were performed with Ingenuity pathway software. In order to identify the potential upstream regulators, MatInspector software was used to perform transcription factor binding motif search in the promoter regions of the deregulated genes. Molecular docking on MYC/MAX complex and reporter cell line experiments were performed to validate the MYC inhibitory activity of CSA and its derivatives. Two known MYC inhibitors: 10058-F4 and 10074-G5 were used as positive control. All compounds showed cytotoxicities in the micromolar range. Microarray analyses pointed to cell cycle, DNA damage, and DNA repair as mainly affected cellular functions. Promoter motif analysis of the deregulated genes further supported the microarray gene expression analysis results emphasizing the relevance of transcription factors regulating cell cycle and proliferation, with MYC as being the most pronounced one. Luciferase-based reporter cell line experiments and molecular docking studies yielded supportive results emphasizing the inhibitory activity of CSA and its derivatives on MYC. CSA and its derivatives are shown to be promising anticancer compounds with low toxicity. They inhibit MYC activity comparable to 10058-F4 and 10074-G5. Further studies are warranted to analyze the therapeutic applicability of these compounds in more detail.
Keywords: Breast cancer; Cajanin stilbene acid; Microarray; Pharmacogenomics; c-MYC.