A novel HSP-90 inhibitor with highly selective activity against papillary and anaplastic thyroid cancers

Abstract

Background

HSP90 is a chaperone protein regulating several client proteins involved in thyroid cancer development. The purpose of this study is to mechanisticially evaluate a novel natural-product HSP90 inhibitor in thyroid cancer cell lines for future translational applications.

Methods

285 plant-extracts/compounds were evaluated for anti-cancer activity by MTS assay. Apoptosis and cell-cycle-arrest were characterized by annexinV-PI flow cytometry. HSP90 and client-protein inhibition along with apoptosis confirmation was demonstrated by Western blot analysis.

Results

45 of 285extracts/compounds demonstrated anti-proliferative activity in thyroid cancers by MTS assay. BTIMNP_D004 demonstrated the highest inhibition [IC50(NPA)=0.19±0.02mM, IC50(DRO)=0.26±0.03mM]vs. 17-AAG [IC50(NPA)=0.51±0.02mM; IC50(DRO)=0.75±0.04mM;p<0.001]. D004 induced cell-cycle-arrest after 18hours (G1/G0→S and G2/M) with 26%DRO cells shifted and 23%NPA cells shifted vs. controls (p<0.001 and <0.01 respectively). 1mM D004 induced significant apoptosis with 76%DRO cells gated after 18hrs. (Annexin V/PI staining) vs <2% in controls;p<0.001 and 80%NPA cells vs. 4%controls(p<0.001). Western analysis demonstrated inhibition of HSP90, HSF-1, AKT, and cleavage of procaspase3 and PARP in both NPA and DRO cells.

Conclusion

BTIMNP_D004 is a potent, novel HSP90inhibitor with selective activity against papillary and anaplastic thyroid cancers through modulation of client proteins, induction of apoptosis and cell cycle arrest. These data support future pre-clinical studies for translational applications.