Mitochondrial-targeted Hsp90 C-terminal inhibitors manifest anti-proliferative activity

The development of C-terminal heat shock protein 90 kDa (Hsp90) inhibitors has emerged as a potential treatment for cancer. Similarly, small molecules that target the mitochondria have proven to be efficacious towards cancer, as the reprogramming of mitochondrial function is often associated with oncogenic transformation. Herein, we report the development of triphenylphosphonium (TPP)-conjugated Hsp90 C-terminal inhibitors, their anti-proliferative activity, and accumulation in the mitochondria. In general, TPP-conjugated Hsp90 C-terminal inhibitors were found to manifest increased activity against various cancer cell lines when compared to the parent compounds.

Synthesis and evaluation of a ring-constrained Hsp90 C-terminal inhibitor that exhibits neuroprotective activity

KU-596 is a second-generation C-terminal heat shock protein 90 KDa (Hsp90) modulator based on the natural product, novobiocin. KU-596 has been shown to induce Hsp70 levels and manifest neuroprotective activity through induction of the heat shock response. A ring-constrained analog of KU-596 was designed and synthesized to probe its binding orientation and ability to induce Hsp70 levels. Compound 2 was found to exhibit comparable or increased activity compared to KU-596, which is under clinical investigation for the treatment of neuropathy.

A Chemogenomic Screening Platform Used to Identify Chemotypes Perturbing HSP90 Pathways

Compounds that modulate the heat shock protein (HSP) network have potential in a broad range of research applications and diseases. A yeast-based liquid culture assay that measured time-dependent turbidity enabled the high-throughput screening of different Saccharomyces cerevisae strains to identify HSP modulators with unique molecular mechanisms. A focused set of four strains, with differing sensitivities to Hsp90 inhibitors, was used to screen a compound library of 3680 compounds. Computed turbidity curve functions were used to classify strain responses and sensitivity to chemical effects across the compound library. Filtering based on single-strain selectivity identified nine compounds as potential heat shock modulators, including the known Hsp90 inhibitor macbecin. Haploid yeast deletion strains (360), mined from previous Hsp90 inhibitor yeast screens and heat shock protein interaction data, were screened for differential sensitivities to known N-terminal ATP site-directed Hsp90 inhibitors to reveal functional distinctions. Strains demonstrating differential sensitivity (13) to Hsp90 inhibitors were used to prioritize primary screen hit compounds, with NSC145366 emerging as the lead hit. Our follow-up biochemical and functional studies show that NSC145366 directly interacts and inhibits the C-terminus of Hsp90, validating the platform as a powerful approach for early-stage identification of bioactive modulators of heat shock-dependent pathways.