Showing papers by "Susan Lindquist published in 2019"

Mitochondrial metabolism promotes adaptation to proteotoxic stress.

Abstract: The mechanisms by which cells adapt to proteotoxic stress are largely unknown, but are key to understanding how tumor cells, particularly in vivo, are largely resistant to proteasome inhibitors. Analysis of cancer cell lines, mouse xenografts and patient-derived tumor samples all showed an association between mitochondrial metabolism and proteasome inhibitor sensitivity. When cells were forced to use oxidative phosphorylation rather than glycolysis, they became proteasome-inhibitor resistant. This mitochondrial state, however, creates a unique vulnerability: sensitivity to the small molecule compound elesclomol. Genome-wide CRISPR-Cas9 screening showed that a single gene, encoding the mitochondrial reductase FDX1, could rescue elesclomol-induced cell death. Enzymatic function and nuclear-magnetic-resonance-based analyses further showed that FDX1 is the direct target of elesclomol, which promotes a unique form of copper-dependent cell death. These studies explain a fundamental mechanism by which cells adapt to proteotoxic stress and suggest strategies to mitigate proteasome inhibitor resistance.

Structural basis for species-selective targeting of Hsp90 in a pathogenic fungus.

Abstract: New strategies are needed to counter the escalating threat posed by drug-resistant fungi. The molecular chaperone Hsp90 affords a promising target because it supports survival, virulence and drug-resistance across diverse pathogens. Inhibitors of human Hsp90 under development as anticancer therapeutics, however, exert host toxicities that preclude their use as antifungals. Seeking a route to species-selectivity, we investigate the nucleotide-binding domain (NBD) of Hsp90 from the most common human fungal pathogen, Candida albicans. Here we report structures for this NBD alone, in complex with ADP or in complex with known Hsp90 inhibitors. Encouraged by the conformational flexibility revealed by these structures, we synthesize an inhibitor with >25-fold binding-selectivity for fungal Hsp90 NBD. Comparing co-crystals occupied by this probe vs. anticancer Hsp90 inhibitors revealed major, previously unreported conformational rearrangements. These insights and our probe’s species-selectivity in culture support the feasibility of targeting Hsp90 as a promising antifungal strategy. The chaperone Hsp90 is a potential target for the development of drugs against fungal pathogens. Here the authors determine the structure of the Hsp90 nucleotide-binding domain from Candida albicans, which they use to design an inhibitor and demonstrate its selectivity for the fungal enzyme, both biochemically and in cells.

Rebalancing Protein Homeostasis Enhances Tumor Antigen Presentation.

Abstract: Purpose: Despite the accumulation of extensive genomic alterations, many cancers fail to be recognized as "foreign" and escape destruction by the host immune system. Immunotherapies designed to address this problem by directly stimulating immune effector cells have led to some remarkable clinical outcomes, but unfortunately, most cancers fail to respond, prompting the need to identify additional immunomodulatory treatment options. Experimental Design: We elucidated the effect of a novel treatment paradigm using sustained, low dose HSP90 inhibition in vitro and in syngeneic mouse models using genetic and pharmacological tools. Profiling of treatment associated tumor cell antigens was performed using immunoprecipitation followed by peptide mass spectrometry. Results: We show that sustained, low-level inhibition of HSP90 both amplifies and diversifies the antigenic repertoire presented by tumor cells on MHC-I molecules through an interferon gamma-independent mechanism. In stark contrast, we find that acute, high dose exposure to HSP90 inhibitors, the only approach studied in the clinic to date, is broadly immunosuppressive in cell culture and in cancer patients. In mice, chronic non-heat shock-inducing HSP90 inhibition slowed progression of colon cancer implants, but only in syngeneic animals with intact immune function. Addition of a single dose of non-specific immune adjuvant to the regimen dramatically increased efficacy, curing a subset of mice receiving combination therapy. Conclusions:These highly translatable observations support reconsideration of the most effective strategy for targeting HSP90 to treat cancers and suggest a practical approach to re-purposing current orally bioavailable HSP90 inhibitors as a new immunotherapeutic strategy.

Author Correction: Mitochondrial metabolism promotes adaptation to proteotoxic stress.

Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper

Combination treatments of hsp90 inhibitors for enhancing tumor immunogenicity and methods of use thereof

Abstract: It has been established that exposure to cytotoxic doses of HSP90 inhibitor is broadly immunosuppressive, whereas continuous exposure to low-dosages of the same inhibitor exerts anti-tumor activity. The anti-tumor activity is mediated by the host immune system. Compositions and methods for continuous, low-dose exposure to HSP90 inhibitors in combination with one or more immunostimulatory agents for the treatment of cancer are described. Typically, the HSP90 inhibitor is administered in an amount that is between 1% and 20% of the clinically-determined maximum tolerate dose. The immunostimulatory agent can be administered simultaneously with the HSP90 inhibitor, or at some time before or after the HSP90 inhibitor. Compositions including a sub-toxic dose of HSP90 inhibitor in combination with an immunostimulatory agent in an amount effective to treat cancer are also provided.