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

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• ATP-competitive inhibitors of Heat Shock Protein 90 (Hsp90) have shown limited success in clinical trials for cancer treatment.
• The mechanistic link between Hsp90 and oncogenic K-Ras remains largely unknown.
• Galectin-3 (Gal3) acts as a K-Ras membrane nanocluster modulator, and its loss is implicated in Hsp90-mediated K-Ras regulation.

Purpose of the Study:

• To investigate the mechanistic connection between Hsp90 and oncogenic K-Ras.
• To identify novel Hsp90/Cdc37 interface inhibitors with K-Ras selectivity for cancer therapy.
• To evaluate the efficacy and toxicity profile of these novel inhibitors.

Main Methods:

• Computational screening of over 7 million compounds to identify potential Hsp90/Cdc37 inhibitors.
• In vitro assays to determine compound activity, K-Ras selectivity, and effects on Hsp90 client proteins.
• Cell-based assays to assess inhibition of 2D proliferation, 3D spheroid growth, and microtumor development.
• Evaluation of heat shock response induction by the identified compounds.

Main Results:

• Four novel small molecules were identified with in vitro activities ranging from 4 μM to 44 μM.
• All identified compounds demonstrated K-Ras selectivity and potently reduced Hsp90 client protein levels without inducing heat shock response.
• Compounds inhibited 2D proliferation in breast, pancreatic, and lung cancer cell lines, and significantly blocked 3D spheroids and K-Ras-dependent microtumor growth.
• The mechanism suggests enhanced drug sensitivity in cancer cells with KRAS mutations, high HIF-1α, and/or high Gal3 levels, particularly pancreatic adenocarcinoma.

Conclusions:

• Loss of galectin-3 downstream of HIF-1α enables K-Ras selectivity for Hsp90 inhibitors.
• Novel Hsp90/Cdc37 interface inhibitors exhibit potent anti-cancer activity and a favorable on-target toxicity profile.
• These findings present new therapeutic opportunities for Hsp90/Cdc37 inhibitors in KRAS-mutant cancers and potentially other aging-associated diseases.