Novel Small Molecule Hsp90/Cdc37 Interface Inhibitors Indirectly Target K-Ras-Signaling

Abstract

The ATP-competitive inhibitors of Hsp90 have been tested predominantly in kinase addicted cancers; however, they have had limited success. A mechanistic connection between Hsp90 and oncogenic K-Ras is not known. Here, we show that K-Ras selectivity is enabled by the loss of the K-Ras membrane nanocluster modulator galectin-3 downstream of the Hsp90 client HIF-1α. This mechanism suggests a higher drug sensitivity in the context of KRAS mutant, HIF-1α-high and/or Gal3-high cancer cells, such as those found, in particular, in pancreatic adenocarcinoma. The low toxicity of conglobatin further indicates a beneficial on-target toxicity profile for Hsp90/Cdc37 interface inhibitors. We therefore computationally screened >7 M compounds, and identified four novel small molecules with activities of 4 μM —44 μM in vitro. All of the compounds were K-Ras selective, and potently decreased the Hsp90 client protein levels without inducing the heat shock response. Moreover, they all inhibited the 2D proliferation of breast, pancreatic, and lung cancer cell lines. The most active compounds from each scaffold, furthermore, significantly blocked 3D spheroids and the growth of K-Ras-dependent microtumors. We foresee new opportunities for improved Hsp90/Cdc37 interface inhibitors in cancer and other aging-associated diseases.

Targeting Chaperone/Co-Chaperone Interactions with Small Molecules: A Novel Approach to Tackle Neurodegenerative Diseases

“…To identify novel Hsp90-Cdc37 interaction inhibitors, Siddiqui et al recently established a mammalian cell lysate-based, medium-throughput amenable split Renilla luciferase assay, which employs N-terminal and C-terminal fragments of Renilla luciferase fused to full-length human Hsp90 and Cdc37, respectively [106]. Later, the same group screened more than 120,000 compounds via an FW-04-806 (conglobatin A)-based pharmacophore model and molecular docking, and confirmed the hits' in vitro effects using their formerly established mammalian cell lysate-based split Renilla luciferase assay [85]. The active compounds 26 and 27 were identified with K-Ras selectivity.…”

“…Chemoproteomics and computational approaches together reveal that FW-04-806 binds to the NTD of Hsp90 without affecting ATP binding of Hsp90 [84]. Recent computational docking results indicate that FW-04-806 sterically blocks and disturbs critical interactions, notably between Glu47 of Hsp90 NTD and Arg167 of Cdc37 at the interface of the complex (PDB: 1US7) [85].…”

Interfacial Peptides as Affinity Modulating Agents of Protein-Protein Interactions

“…It is pertinent to note that there are a number of successful design solutions of effective PPI modulators based on low molecular weight non-peptide compounds [ 17 , 18 , 19 ]. Nevertheless, the scientific community is faced with a number of controversial questions addressed to the specificity of their action and sensitivity to disease-associated mutations in the interfaces of PPIs [ 20 , 21 , 22 ].…”

A study of lipid-mediated clustering of oncogenic Ras proteins on cell membrane using nanotopography engineering

“…). [27][28][29][30][31] Ras nanoclusters are recognized as the effector binding sites along the RAF/MEK/ERK cascade 22,[32][33][34][35] and are therefore crucial for signal transmission.…”

“…To measure Ras nanoclustering, EM coupled with spatial mapping [24][25][26][27] and FLIM-FRET [27][28][29][30][31] are two of the most frequently adopted techniques (Fig. 1.4).…”