Isolation of a novel thioflavin S-derived compound that inhibits BAG-1-mediated protein interactions and targets BRAF inhibitor-resistant cell lines.
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.
Corresponding Author: Jakob Troppmair, Innsbruck Medical University, Innrain 66, Innsbruck 6020, Austria. Jakob.troppmair@i-med.ac.at.
Marion
M
Enthammer
Emmanouil S
ES
Papadakis
Maria
M
Salomé Gachet
Martin
M
Deutsch
Stefan
S
Schwaiger
Katarzyna
K
Koziel
Muhammad Imtiaz
MI
Ashraf
Sana
S
Khalid
Gerhard
G
Wolber
Graham
G
Packham
Ramsey I
RI
Cutress
Hermann
H
Stuppner
Jakob
J
Troppmair
D000814:Aniline Compounds / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D052160:Benzothiazoles / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites / Q000187:drug effects; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism* / Q000494:pharmacology; D057809:HEK293 Cells; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D061986:MCF-7 Cells; D051379:Mice; D062105:Molecular Docking Simulation; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000188:drug therapy* / Q000473:pathology; D009570:Nitriles / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D013844:Thiazoles / Q000737:chemistry*; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000077484:Vemurafenib
D000814:Aniline Compounds; D000970:Antineoplastic Agents; C091732:BCL2-associated athanogene 1 protein; D052160:Benzothiazoles; D002070:Butadienes; D004268:DNA-Binding Proteins; D005456:Fluorescent Dyes; D050883:HSC70 Heat-Shock Proteins; D007211:Indoles; C000589256:N-ethyl-4-(6-methylbenzo(d)thiazol-2-yl)aniline; D009570:Nitriles; D013449:Sulfonamides; D013844:Thiazoles; D014157:Transcription Factors; C113580:U 0126; D000077484:Vemurafenib; C009462:thioflavin T; D048493:Proto-Oncogene Proteins B-raf