Differential phosphorylation and gene expression patterns induced by the polyisoprenylated benzophenone “CLU-502” in cells with different histology

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Polyisoprenylated benzophenones are recently published as anticancer agents. We have characterized CLU-502 a new polyisoprenylated benzophenone isolated from Clusia sp. Analyses of cell proliferation, cell cycle arrest, protein phosphorylation and gene expression were performed in cell lines with different histology including leukemia (HL60, K562, Tanoue and Jurkat), prostate cancer (PC3, LNCap and DU145), colon carcinoma (HCT8), neuroblastoma (LAN1) and breast carcinoma (MCF-7). Using the SRB cell proliferation assay, the mean IC50 concentration of CLU-502 was determined to 2.5 μM (min: 2.0 μM; max: 5.0 μM). In contrast, non-tumoral cell lines like human and murine fibroblasts demonstrated a certain resistance to CLU-502 (IC50: 40 - 80 μM). Cell cycle analyses revealed an arrest in G1/S-Phase. Western-Blot analyses of different regulatory pathways including the Src, Wnt/β-Catenine, MAP-kinase and Akt-pathway in addition to topoisomerase assays (Topo I, Topo IIalpha, Topo IIbeta, phosphorylated Topo II alpha) and expression of the proto-oncogenes N-Myc, L-myc, c-myc, c-kit and c-myb were performed. Putting the results together, no universal pattern of gene expression, phosphorylation of distinct regulatory proteins of the signal transduction cascades or of apoptosis were detectable after exposure of the different cancer cell lines with the polyisoprenylated benzophenone CLU-502.