Y‐632 inhibits heat shock protein 90 (Hsp90) function by disrupting the interaction between Hsp90 and Hsp70/Hsp90 organizing protein, and exerts antitumor activity in vitro and in vivo

Abstract

Heat shock protein 90 (Hsp90) stabilizes a variety of proteins required for cancer cell survival and has been identified as a promising drug target for cancer treatment. To date, several Hsp90 inhibitors have entered into clinical trials, but none has been approved for cancer therapy yet. Thus, exploring new Hsp90 inhibitors with novel mechanisms of action is urgent. In the present study, we show that Y‐632, a novel pyrimidine derivative, inhibited Hsp90 in a different way from the conventional Hsp90 inhibitor geldanamycin. Y‐632 induced degradation of diverse Hsp90 client proteins through the ubiquitin–proteasome pathway, as geldanamycin did; however, it neither directly bound to Hsp90 nor inhibited Hsp90 ATPase activity. Y‐632 inhibited Hsp90 function mainly through inducing intracellular thiol oxidation, which led to disruption of the Hsp90–Hsp70/Hsp90 organizing protein complex and further induced cell adhesion inhibition, G0/G1 cell cycle arrest, and apoptosis. Moreover, Y‐632 efficiently overcame imatinib resistance mediated by Bcr‐Abl point mutations both in vitro and in vivo. We believe that Y‐632, acting as a novel small‐molecule inhibitor of the Hsp90–Hsp70/Hsp90 organizing protein complex, has great potential to be a promising Hsp90 inhibitor for cancer therapy, such as for imatinib‐resistant leukemia.

Heat-shock protein 90 (Hsp90) promotes opioid-induced anti-nociception by an ERK mitogen-activated protein kinase (MAPK) mechanism in mouse brain

“…For signaling protein expression changes, we found that Hsp70 was induced in all four cell lines, which is a canonical effect of this class of Hsp90 inhibitors and serves as a marker of Hsp90 inhibition (Fig. 1, A and B) (24,25). We also found that Hsp90 inhibition altered the protein expression levels of the MOR itself and of the signaling regulator ␤arr2 and the kinase Akt.…”

Aberrant intracellular metabolism of T‐DM1 confers T‐DM1 resistance in human epidermal growth factor receptor 2‐positive gastric cancer cells

“…Western blotting was carried out as described previously . In brief, cells were lysed in SDS sample buffer, then separated by SDS‐PAGE, and transferred to PVDF membranes (Millipore, Bedford, MA, USA).…”

“…Western blotting was carried out as described previously. (16) In brief, cells were lysed in SDS sample buffer, then separated by SDS-PAGE, and transferred to PVDF membranes (Millipore, Bedford, MA, USA). Membranes were incubated with primary antibodies at 4°C overnight and then with secondary antibodies for 2 h at room temperature.…”

“…Cell proliferation was determined by sulforhodamine B assay, as described previously . In brief, cells seeded in 96‐well plates were incubated for approximately 24 h and then treated with different concentrations of drugs for 72 or 120 h in culture medium containing 10% FBS.…”

Solution structure of the Hop TPR2A domain and investigation of target druggability by NMR, biochemical and in silico approaches

“…However, these toxoflavins are compromised in their usefulness by being ubiquitous ‘frequent hitters’ in HTS campaigns as well as very toxic to cells 40 – 43 . More recently, a structurally related chemical series of thiol-reactive acrylamide-containing compounds has also been published 44 . These compounds do not bind Hsp90 or its cochaperones, but exert their activity through intracellular thiol oxidation.…”