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

Mol Cancer Ther. 2013 Nov;12(11):2400-14. doi: 10.1158/1535-7163.MCT-13-0142. Epub 2013 Sep 18.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 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
  • NIH 3T3 Cells
  • Neoplasms / drug therapy*
  • Neoplasms / pathology
  • 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


  • Aniline Compounds
  • Antineoplastic Agents
  • BCL2-associated athanogene 1 protein
  • Benzothiazoles
  • Butadienes
  • DNA-Binding Proteins
  • Fluorescent Dyes
  • HSC70 Heat-Shock Proteins
  • Indoles
  • N-ethyl-4-(6-methylbenzo(d)thiazol-2-yl)aniline
  • Nitriles
  • Sulfonamides
  • Thiazoles
  • Transcription Factors
  • U 0126
  • Vemurafenib
  • thioflavin T
  • Proto-Oncogene Proteins B-raf