How Much Longer Will We Put Up With $100,000 Cancer Drugs?

The spiraling cost of new drugs mandates a fundamentally different approach to keep lifesaving therapies affordable for cancer patients. We call here for the formation of new relationships between academic drug discovery centers and commercial partners, which can accelerate the development of truly transformative drugs at sustainable prices.

Native Size-Exclusion Chromatography-Based Mass Spectrometry Reveals New Components of the Early Heat Shock Protein 90 Inhibition Response Among Limited Global Changes.

The molecular chaperone heat shock protein 90 (HSP90) works in concert with co-chaperones to stabilize its client proteins, which include multiple drivers of oncogenesis and malignant progression. Pharmacologic inhibitors of HSP90 have been observed to exert a wide range of effects on the proteome, including depletion of client proteins, induction of heat shock proteins, dissociation of co-chaperones from HSP90, disruption of client protein signaling networks, and recruitment of the protein ubiquitylation and degradation machinery-suggesting widespread remodeling of cellular protein complexes. However, proteomics studies to date have focused on inhibitor-induced changes in total protein levels, often overlooking protein complex alterations. Here, we use size-exclusion chromatography in combination with mass spectrometry (SEC-MS) to characterize the early changes in native protein complexes following treatment with the HSP90 inhibitor tanespimycin (17-AAG) for 8 h in the HT29 colon adenocarcinoma cell line. After confirming the signature cellular response to HSP90 inhibition (e.g., induction of heat shock proteins, decreased total levels of client proteins), we were surprised to find only modest perturbations to the global distribution of protein elution profiles in inhibitor-treated HT29 cells at this relatively early time-point. Similarly, co-chaperones that co-eluted with HSP90 displayed no clear difference between control and treated conditions. However, two distinct analysis strategies identified multiple inhibitor-induced changes, including known and unknown components of the HSP90-dependent proteome. We validate two of these-the actin-binding protein Anillin and the mitochondrial isocitrate dehydrogenase 3 complex-as novel HSP90 inhibitor-modulated proteins. We present this dataset as a resource for the HSP90, proteostasis, and cancer communities (https://www.bioinformatics.babraham.ac.uk/shiny/HSP90/SEC-MS/), laying the groundwork for future mechanistic and therapeutic studies related to HSP90 pharmacology. Data are available via ProteomeXchange with identifier PXD033459.

canSAR: update to the cancer translational research and drug discovery knowledgebase.

canSAR (https://cansar.ai) is the largest public cancer drug discovery and translational research knowledgebase. Now hosted in its new home at MD Anderson Cancer Center, canSAR integrates billions of experimental measurements from across molecular profiling, pharmacology, chemistry, structural and systems biology. Moreover, canSAR applies a unique suite of machine learning algorithms designed to inform drug discovery. Here, we describe the latest updates to the knowledgebase, including a focus on significant novel data. These include canSAR's ligandability assessment of AlphaFold; mapping of fragment-based screening data; and new chemical bioactivity data for novel targets. We also describe enhancements to the data and interface.

The Chemical Probes Portal: an expert review-based public resource to empower chemical probe assessment, selection and use.

We describe the Chemical Probes Portal (https://www.chemicalprobes.org/), an expert review-based public resource to empower chemical probe assessment, selection and use. Chemical probes are high-quality small-molecule reagents, often inhibitors, that are important for exploring protein function and biological mechanisms, and for validating targets for drug discovery. The publication, dissemination and use of chemical probes provide an important means to accelerate the functional annotation of proteins, the study of proteins in cell biology, physiology, and disease pathology, and to inform and enable subsequent pioneering drug discovery and development efforts. However, the widespread use of small-molecule compounds that are claimed as chemical probes but are lacking sufficient quality, especially being inadequately selective for the desired target or even broadly promiscuous in behaviour, has resulted in many erroneous conclusions in the biomedical literature. The Chemical Probes Portal was established as a public resource to aid the selection and best-practice use of chemical probes in basic and translational biomedical research. We describe the background, principles and content of the Portal and its technical development, as well as examples of its applications and use. The Chemical Probes Portal is a community resource and we therefore describe how researchers can be involved in its content and development.

canSAR: update to the cancer translational research and drug discovery knowledgebase.

canSAR (http://cansar.icr.ac.uk) is the largest, public, freely available, integrative translational research and drug discovery knowledgebase for oncology. canSAR integrates vast multidisciplinary data from across genomic, protein, pharmacological, drug and chemical data with structural biology, protein networks and more. It also provides unique data, curation and annotation and crucially, AI-informed target assessment for drug discovery. canSAR is widely used internationally by academia and industry. Here we describe significant developments and enhancements to the data, web interface and infrastructure of canSAR in the form of the new implementation of the system: canSARblack. We demonstrate new functionality in aiding translation hypothesis generation and experimental design, and show how canSAR can be adapted and utilised outside oncology.

Modulation of Biliary Cancer Chemo-Resistance Through MicroRNA-Mediated Rewiring of the Expansion of CD133+ Cells.

BACKGROUND AND AIMS: Changes in single microRNA (miRNA) expression have been associated with chemo-resistance in biliary tract cancers (BTCs). However, a global assessment of the dynamic role of the microRNome has never been performed to identify potential therapeutic targets that are functionally relevant in the BTC cell response to chemotherapy. APPROACH AND RESULTS: High-throughput screening (HTS) of 997 locked nucleic acid miRNA inhibitors was performed in six cholangiocarcinoma cell lines treated with cisplatin and gemcitabine (CG) seeking changes in cell viability. Validation experiments were performed with mirVana probes. MicroRNA and gene expression was assessed by TaqMan assay, RNA-sequencing, and in situ hybridization in four independent cohorts of human BTCs. Knockout of microRNA was achieved by CRISPR-CAS9 in CCLP cells (MIR1249KO) and tested for effects on chemotherapy sensitivity in vitro and in vivo. HTS revealed that MIR1249 inhibition enhanced chemotherapy sensitivity across all cell lines. MIR1249 expression was increased in 41% of cases in human BTCs. In validation experiments, MIR1249 inhibition did not alter cell viability in untreated or dimethyl sulfoxide-treated cells; however, it did increase the CG effect. MIR1249 expression was increased in CD133+ biliary cancer cells freshly isolated from the stem cell niche of human BTCs as well as in CD133+ chemo-resistant CCLP cells. MIR1249 modulated the chemotherapy-induced enrichment of CD133+ cells by controlling their clonal expansion through the Wnt-regulator FZD8. MIR1249KO cells had impaired expansion of the CD133+ subclone and its enrichment after chemotherapy, reduced expression of cancer stem cell markers, and increased chemosensitivity. MIR1249KO xenograft BTC models showed tumor shrinkage after exposure to weekly CG, whereas wild-type models showed only stable disease over treatment. CONCLUSIONS: MIR1249 mediates resistance to CG in BTCs and may be tested as a target for therapeutics.

canSAR: update to the cancer translational research and drug discovery knowledgebase.

canSAR (http://cansar.icr.ac.uk) is a public, freely available, integrative translational research and drug discovery knowlegebase. canSAR informs researchers to help solve key bottlenecks in cancer translation and drug discovery. It integrates genomic, protein, pharmacological, drug and chemical data with structural biology, protein networks and unique, comprehensive and orthogonal 'druggability' assessments. canSAR is widely used internationally by academia and industry. Here we describe major enhancements to canSAR including new and expanded data. We also describe the first components of canSARblack-an advanced, responsive, multi-device compatible redesign of canSAR with a question-led interface.

Structural and functional characterisation of human RNA helicase DHX8 provides insights into the mechanism of RNA-stimulated ADP release.

DHX8 is a crucial DEAH-box RNA helicase involved in splicing and required for the release of mature mRNA from the spliceosome. Here, we report the biochemical characterisation of full-length human DHX8 and the catalytically active helicase core DHX8Δ547, alongside crystal structures of DHX8Δ547 bound to ADP and a structure of DHX8Δ547 bound to poly(A)6 single-strand RNA. Our results reveal that DHX8 has an in vitro binding preference for adenine-rich RNA and that RNA binding triggers the release of ADP through significant conformational flexibility in the conserved DEAH-, P-loop and hook-turn motifs. We demonstrate the importance of R620 and both the hook-turn and hook-loop regions for DHX8 helicase activity and propose that the hook-turn acts as a gatekeeper to regulate the directional movement of the 3' end of RNA through the RNA-binding channel. This study provides an in-depth understanding of the activity of DHX8 and contributes insights into the RNA-unwinding mechanisms of the DEAH-box helicase family.

Correction to: Reflections and Outlook on Targeting HSP90, HSP70 and HSF1 in Cancer: A Personal Perspective.

The original version of the book was revised: Chapter 11 is now available open access under a CC BY 4.0 license and the copyright holder has been changed to 'The Author(s)'.

Reflections and Outlook on Targeting HSP90, HSP70 and HSF1 in Cancer: A Personal Perspective.

This personal perspective focuses on small-molecule inhibitors of proteostasis networks in cancer-specifically the discovery and development of chemical probes and drugs acting on the molecular chaperones HSP90 and HSP70, and on the HSF1 stress pathway. Emphasis is on progress made and lessons learned and a future outlook is provided. Highly potent, selective HSP90 inhibitors have proved invaluable in exploring the role of this molecular chaperone family in biology and disease pathology. Clinical activity was observed, especially in non small cell lung cancer and HER2 positive breast cancer. Optimal use of HSP90 inhibitors in oncology will likely require development of creative combination strategies. HSP70 family members have proved technically harder to drug. However, recent progress has been made towards useful chemical tool compounds and these may signpost future clinical drug candidates. The HSF1 stress pathway is strongly validated as a target for cancer therapy. HSF1 itself is a ligandless transcription factor that is extremely challenging to drug directly. HSF1 pathway inhibitors have been identified mostly by phenotypic screening, including a series of bisamides from which a clinical candidate has been identified for treatment of ovarian cancer, multiple myeloma and potentially other cancers.

MIR21 Drives Resistance to Heat Shock Protein 90 Inhibition in Cholangiocarcinoma.

BACKGROUND & AIMS: Cholangiocarcinomas (CCA) are resistant to chemotherapy, so new therapeutic agents are needed. We performed a screen to identify small-molecule compounds that are active against CCAs. Levels of microRNA 21 (MIR21 or miRNA21) are increased in CCAs. We investigated whether miRNA21 mediates resistance of CCA cells and organoids to HSP90 inhibitors. METHODS: We performed a high-throughput screen of 484 small-molecule compounds to identify those that reduced viability of 6 human CCA cell lines. We tested the effects of HSP90 inhibitors on cells with disruption of the MIR21 gene, cells incubated with MIR21 inhibitors, and stable cell lines with inducible expression of MIR21. We obtained CCA biopsies from patients, cultured them as organoids (patient-derived organoids). We assessed their architecture, mutation and gene expression patterns, response to compounds in culture, and when grown as subcutaneous xenograft tumors in mice. RESULTS: Cells with IDH1 and PBRM1 mutations had the highest level of sensitivity to histone deacetylase inhibitors. HSP90 inhibitors were effective in all cell lines, irrespective of mutations. Sensitivity of cells to HSP90 inhibitors correlated inversely with baseline level of MIR21. Disruption of MIR21 increased cell sensitivity to HSP90 inhibitors. CCA cells that expressed transgenic MIR21 were more resistant to HSP90 inhibitors than cells transfected with control vectors; inactivation of MIR21 in these cells restored sensitivity to these agents. MIR21 was shown to target the DnaJ heat shock protein family (Hsp40) member B5 (DNAJB5). Transgenic expression of DNAJB5 in CCA cells that overexpressed MIR21 re-sensitized them to HSP90 inhibitors. Sensitivity of patient-derived organoids to HSP90 inhibitors, in culture and when grown as xenograft tumors in mice, depended on expression of miRNA21. CONCLUSIONS: miRNA21 appears to mediate resistance of CCA cells to HSP90 inhibitors by reducing levels of DNAJB5. HSP90 inhibitors might be developed for the treatment of CCA and miRNA21 might be a marker of sensitivity to these agents.

Wnt signalling modulates transcribed-ultraconserved regions in hepatobiliary cancers.

OBJECTIVE: Transcribed-ultraconserved regions (T-UCR) are long non-coding RNAs which are conserved across species and are involved in carcinogenesis. We studied T-UCRs downstream of the Wnt/ß-catenin pathway in liver cancer. DESIGN: Hypomorphic Apc mice (Apcfl/fl) and thiocetamide (TAA)-treated rats developed Wnt/ß-catenin dependent hepatocarcinoma (HCC) and cholangiocarcinoma (CCA), respectively. T-UCR expression was assessed by microarray, real-time PCR and in situ hybridisation. RESULTS: Overexpression of the T-UCR uc.158- could differentiate Wnt/ß-catenin dependent HCC from normal liver and from ß-catenin negative diethylnitrosamine (DEN)-induced HCC. uc.158- was overexpressed in human HepG2 versus Huh7 cells in line with activation of the Wnt pathway. In vitro modulation of ß-catenin altered uc.158- expression in human malignant hepatocytes. uc.158- expression was increased in CTNNB1-mutated human HCCs compared with non-mutated human HCCs, and in human HCC with nuclear localisation of ß-catenin. uc.158- was increased in TAA rat CCA and reduced after treatment with Wnt/ß-catenin inhibitors. uc.158- expression was negative in human normal liver and biliary epithelia, while it was increased in human CCA in two different cohorts. Locked nucleic acid-mediated inhibition of uc.158- reduced anchorage cell growth, 3D-spheroid formation and spheroid-based cell migration, and increased apoptosis in HepG2 and SW1 cells. miR-193b was predicted to have binding sites within the uc.158- sequence. Modulation of uc.158- changed miR-193b expression in human malignant hepatocytes. Co-transfection of uc.158- inhibitor and anti-miR-193b rescued the effect of uc.158- inhibition on cell viability. CONCLUSIONS: We showed that uc.158- is activated by the Wnt pathway in liver cancers and drives their growth. Thus, it may represent a promising target for the development of novel therapeutics.

RNAi screen reveals synthetic lethality between cyclin G-associated kinase and FBXW7 by inducing aberrant mitoses.

BACKGROUND: F-box and WD40 repeat domain-containing 7 (FBXW7) is an E3 ubiquitin ligase involved in the ubiquitination and degradation of multiple oncogenic substrates. The tumour suppressor function is frequently lost in multiple cancers through genetic deletion and mutations in a broad range of tumours. Loss of FBXW7 functionality results in the stabilisation of multiple major oncoproteins, culminating in increased cellular proliferation and pro-survival pathways, cell cycle deregulation, chromosomal instability and altered metabolism. Currently, there is no therapy to specifically target FBXW7-deficient tumours. METHODS: We performed a siRNA kinome screen to identify synthetically lethal hits to FBXW7 deficiency. RESULTS: We identified and validated cyclin G-associated kinase (GAK) as a potential new therapeutic target. Combined loss of FBXW7 and GAK caused cell cycle defects, formation of multipolar mitoses and the induction of apoptosis. The synthetic lethal mechanism appears to be independent of clathrin-mediated receptor endocytosis function of GAK. CONCLUSIONS: These data suggest a putative therapeutic strategy for a large number of different types of human cancers with FBXW7 loss, many of which have a paucity of molecular abnormalities and treatment options.

A selective chemical probe for exploring the role of CDK8 and CDK19 in human disease.

There is unmet need for chemical tools to explore the role of the Mediator complex in human pathologies ranging from cancer to cardiovascular disease. Here we determine that CCT251545, a small-molecule inhibitor of the WNT pathway discovered through cell-based screening, is a potent and selective chemical probe for the human Mediator complex-associated protein kinases CDK8 and CDK19 with >100-fold selectivity over 291 other kinases. X-ray crystallography demonstrates a type 1 binding mode involving insertion of the CDK8 C terminus into the ligand binding site. In contrast to type II inhibitors of CDK8 and CDK19, CCT251545 displays potent cell-based activity. We show that CCT251545 and close analogs alter WNT pathway-regulated gene expression and other on-target effects of modulating CDK8 and CDK19, including expression of genes regulated by STAT1. Consistent with this, we find that phosphorylation of STAT1(SER727) is a biomarker of CDK8 kinase activity in vitro and in vivo. Finally, we demonstrate in vivo activity of CCT251545 in WNT-dependent tumors.

E3 ubiquitin ligase Cullin-5 modulates multiple molecular and cellular responses to heat shock protein 90 inhibition in human cancer cells.

The molecular chaperone heat shock protein 90 (HSP90) is required for the activity and stability of its client proteins. Pharmacologic inhibition of HSP90 leads to the ubiquitin-mediated degradation of clients, particularly activated or mutant oncogenic protein kinases. Client ubiquitination occurs via the action of one or more E3 ubiquitin ligases. We sought to identify the role of Cullin-RING family E3 ubiquitin ligases in the cellular response to HSP90 inhibition. Through a focused siRNA screen of 28 Cullin-RING ligase family members, we found that CUL5 and RBX2 were required for degradation of several HSP90 clients upon treatment of human cancer cells with the clinical HSP90 inhibitor 17-AAG. Surprisingly, silencing Cullin-5 (CUL5) also delayed the earlier loss of HSP90 client protein activity at the same time as delaying cochaperone dissociation from inhibited HSP90-client complexes. Expression of a dominant-negative CUL5 showed that NEDD8 conjugation of CUL5 is required for client degradation but not for loss of client activity or recruitment of clients and HSP90 to CUL5. Silencing CUL5 reduced cellular sensitivity to three distinct HSP90 inhibitors, across four cancer types driven by different protein kinases. Our results reveal the importance of CUL5 in multiple aspects of the cellular response to HSP90 inhibition.

Distinctive Behaviors of Druggable Proteins in Cellular Networks.

The interaction environment of a protein in a cellular network is important in defining the role that the protein plays in the system as a whole, and thus its potential suitability as a drug target. Despite the importance of the network environment, it is neglected during target selection for drug discovery. Here, we present the first systematic, comprehensive computational analysis of topological, community and graphical network parameters of the human interactome and identify discriminatory network patterns that strongly distinguish drug targets from the interactome as a whole. Importantly, we identify striking differences in the network behavior of targets of cancer drugs versus targets from other therapeutic areas and explore how they may relate to successful drug combinations to overcome acquired resistance to cancer drugs. We develop, computationally validate and provide the first public domain predictive algorithm for identifying druggable neighborhoods based on network parameters. We also make available full predictions for 13,345 proteins to aid target selection for drug discovery. All target predictions are available through canSAR.icr.ac.uk. Underlying data and tools are available at https://cansar.icr.ac.uk/cansar/publications/druggable_network_neighbourhoods/.

Fused imidazoles as potential chemical scaffolds for inhibition of heat shock protein 70 and induction of apoptosis. Synthesis and biological evaluation of phenanthro[9,10-d]imidazoles and imidazo[4,5-f][1,10]phenanthrolines.

The imidazole ring is widespread in biologically active compounds, and hence imidazole-containing scaffolds are useful starting points for drug discovery programmes. We report the synthesis of a series of novel imidazole-containing compounds fused with either phenanthrene or phenanthroline, which show enhanced growth inhibitory potency against human colon, breast and melanoma cancer cell lines, as well as evidence of inhibition of the molecular chaperone heat shock protein 70 (Hsp70) pathway in cells, as shown by depletion of downstream oncogenic client proteins of the Hsp90 chaperone pathway, and induction of apoptosis.

Hsp90-dependent activation of protein kinases is regulated by chaperone-targeted dephosphorylation of Cdc37.

Activation of protein kinase clients by the Hsp90 system is mediated by the cochaperone protein Cdc37. Cdc37 requires phosphorylation at Ser13, but little is known about the regulation of this essential posttranslational modification. We show that Ser13 of uncomplexed Cdc37 is phosphorylated in vivo, as well as in binary complex with a kinase (C-K), or in ternary complex with Hsp90 and kinase (H-C-K). Whereas pSer13-Cdc37 in the H-C-K complex is resistant to nonspecific phosphatases, it is efficiently dephosphorylated by the chaperone-targeted protein phosphatase 5 (PP5/Ppt1), which does not affect isolated Cdc37. We show that Cdc37 and PP5/Ppt1 associate in Hsp90 complexes in yeast and in human tumor cells, and that PP5/Ppt1 regulates phosphorylation of Ser13-Cdc37 in vivo, directly affecting activation of protein kinase clients by Hsp90-Cdc37. These data reveal a cyclic regulatory mechanism for Cdc37, in which its constitutive phosphorylation is reversed by targeted dephosphorylation in Hsp90 complexes.

Exploiting the cancer genome: strategies for the discovery and clinical development of targeted molecular therapeutics.

Our biological understanding of the molecular basis of cancer has benefited from advances in basic research, accelerated recently by cancer genome sequencing and other high-throughput, genome-wide profiling technologies. Given the diverse heterogeneity among tumors, the traditional cytotoxic chemotherapy and one-size-fits-all approaches to cancer discovery and development are not appropriate for molecularly targeted agents. Selection of new drug targets is based on achieving cancer selectivity through exploiting specific dependencies and vulnerabilities predicted from tumor genetics. Discovery of highly target-selective agents is enhanced by integrating multiple modern technologies, particularly structure-based design. Efficient clinical evaluation requires smart, hypothesis-testing studies using validated pharmacodynamic and predictive biomarkers. We discuss and exemplify biomarker-driven clinical development and the concept of the Pharmacologic Audit Trail. We detail the exciting approaches offered by drugging the cancer genome, focusing on blocking oncogene addiction, drugging the oncogenic lipid kinome, addressing nononcogene addiction, exploiting synthetic lethality, and overcoming apoptotic resistance, leading to personalized molecular medicine.

ATP-competitive inhibitors block protein kinase recruitment to the Hsp90-Cdc37 system.

Protein kinase clients are recruited to the Hsp90 molecular chaperone system via Cdc37, which simultaneously binds Hsp90 and kinases and regulates the Hsp90 chaperone cycle. Pharmacological inhibition of Hsp90 in vivo results in degradation of kinase clients, with a therapeutic effect in dependent tumors. We show here that Cdc37 directly antagonizes ATP binding to client kinases, suggesting a role for the Hsp90-Cdc37 complex in controlling kinase activity. Unexpectedly, we find that Cdc37 binding to protein kinases is itself antagonized by ATP-competitive kinase inhibitors, including vemurafenib and lapatinib. In cancer cells, these inhibitors deprive oncogenic kinases such as B-Raf and ErbB2 of access to the Hsp90-Cdc37 complex, leading to their degradation. Our results suggest that at least part of the efficacy of ATP-competitive inhibitors of Hsp90-dependent kinases in tumor cells may be due to targeted chaperone deprivation.