Isolation of a novel thioflavin S-derived compound that inhibits BAG-1-mediated protein interactions and targets BRAF inhibitor-resistant cell lines

• Published in: Molecular cancer therapeutics 2013-11, Vol.12 (11), p.2400-2414
• Main Authors: Enthammer, Marion, Papadakis, Emmanouil S, Salomé Gachet, Maria, Deutsch, Martin, Schwaiger, Stefan, Koziel, Katarzyna, Ashraf, Muhammad Imtiaz, Khalid, Sana, Wolber, Gerhard, Packham, Graham, Cutress, Ramsey I, Stuppner, Hermann, Troppmair, Jakob
• Format: Article
• Language: English
• Subjects: Aniline Compounds - isolation & purification; Aniline Compounds - metabolism; Aniline Compounds - pharmacology; Animals; Antineoplastic Agents - isolation & purification; Antineoplastic Agents - metabolism; Antineoplastic Agents - pharmacology; Benzothiazoles - isolation & purification; Benzothiazoles - metabolism; Benzothiazoles - pharmacology; Binding Sites - drug effects; Butadienes - pharmacology; Cell Line; Cell Proliferation - drug effects; DNA-Binding Proteins - antagonists & inhibitors; DNA-Binding Proteins - metabolism; Fluorescent Dyes - metabolism; Fluorescent Dyes - pharmacology; HEK293 Cells; HSC70 Heat-Shock Proteins - metabolism; Humans; Indoles - pharmacology; MCF-7 Cells; Mice; Molecular Docking Simulation; Neoplasms - drug therapy; Neoplasms - pathology; NIH 3T3 Cells; Nitriles - pharmacology; Protein Binding - drug effects; Proto-Oncogene Proteins B-raf - antagonists & inhibitors; Proto-Oncogene Proteins B-raf - metabolism; Sulfonamides - pharmacology; Thiazoles - chemistry; Transcription Factors - antagonists & inhibitors; Transcription Factors - metabolism; Vemurafenib
• ISSN: 1535-7163; 1538-8514
• DOI: 10.1158/1535-7163.MCT-13-0142

Protein-protein interactions mediated through the C-terminal Bcl-2-associated athanogene (BAG) domain of BAG-1 are critical for cell survival and proliferation. Thioflavin S (NSC71948)-a mixture of compounds resulting from the methylation and sulfonation of primulin base-has been shown to dose-dependently inhibit the interaction between BAG-1 and Hsc70 in vitro. In human breast cancer cell lines, with high BAG-1 expression levels, Thioflavin S reduces the binding of BAG-1 to Hsc70, Hsp70, or CRAF and decreases proliferation and viability. Here, we report the development of a protocol for the purification and isolation of biologically active constituents of Thioflavin S and the characterization of the novel compound Thio-2. Thio-2 blocked the growth of several transformed cell lines, but had much weaker effects on untransformed cells. Thio-2 also inhibited the proliferation of melanoma cell lines that had become resistant to treatment with PLX4032, an inhibitor of mutant BRAF. In transformed cells, Thio-2 interfered with intracellular signaling at the level of RAF, but had no effect on the activation of AKT. Thio-2 decreased binding of BAG-1 to Hsc70 and to a lesser extent BRAF in vitro and in vivo, suggesting a possible mechanism of action. Given that tumors frequently develop resistance to kinase inhibitors during treatment, Thio-2 and related compounds may offer promising alternative strategies to currently available therapies.