Systems level profiling of chemotherapy-induced stress resolution in cancer cells reveals druggable trade-offs.

Cancer cells can survive chemotherapy-induced stress, but how they recover from it is not known. Using a temporal multiomics approach, we delineate the global mechanisms of proteotoxic stress resolution in multiple myeloma cells recovering from proteasome inhibition. Our observations define layered and protracted programs for stress resolution that encompass extensive changes across the transcriptome, proteome, and metabolome. Cellular recovery from proteasome inhibition involved protracted and dynamic changes of glucose and lipid metabolism and suppression of mitochondrial function. We demonstrate that recovering cells are more vulnerable to specific insults than acutely stressed cells and identify the general control nonderepressable 2 (GCN2)-driven cellular response to amino acid scarcity as a key recovery-associated vulnerability. Using a transcriptome analysis pipeline, we further show that GCN2 is also a stress-independent bona fide target in transcriptional signature-defined subsets of solid cancers that share molecular characteristics. Thus, identifying cellular trade-offs tied to the resolution of chemotherapy-induced stress in tumor cells may reveal new therapeutic targets and routes for cancer therapy optimization.

The HDAC6 inhibitor C1A modulates autophagy substrates in diverse cancer cells and induces cell death.

BACKGROUND: Cytosolic deacetylase histone deacetylase 6 (HDAC6) is involved in the autophagy degradation pathway of malformed proteins, an important survival mechanism in cancer cells. We evaluated modulation of autophagy-related proteins and cell death by the HDAC6-selective inhibitor C1A. METHODS: Autophagy substrates (light chain-3 (LC-3) and p62 proteins) and endoplasmic reticulum (ER) stress phenotype were determined. Caspase-3/7 activation and cellular proliferation assays were used to assess consequences of autophagy modulation. RESULTS: C1A potently resolved autophagy substrates induced by 3-methyladenine and chloroquine. The mechanism of autophagy inhibition by HDAC6 genetic knockout or C1A treatment was consistent with abrogation of autophagosome-lysosome fusion, and decrease of Myc protein. C1A alone or combined with the proteasome inhibitor, bortezomib, enhanced cell death in malignant cells, demonstrating the complementary roles of the proteasome and autophagy pathways for clearing malformed proteins. Myc-positive neuroblastoma, KRAS-positive colorectal cancer and multiple myeloma cells showed marked cell growth inhibition in response to HDAC6 inhibitors. Finally, growth of neuroblastoma xenografts was arrested in vivo by single agent C1A, while combination with bortezomib slowed the growth of colorectal cancer xenografts. CONCLUSIONS: C1A resolves autophagy substrates in malignant cells and induces cell death, warranting its use for in vivo pre-clinical autophagy research.

Differential role of pannexin-1/ATP/P2X7 axis in IL-1ß release by human monocytes.

IL-1ß release is integral to the innate immune system. The release of mature IL-1ß depends on 2 regulated events: the de novo induction of pro-IL-1ß, generally via NF-κB-dependent transduction pathways; and the assembly and activation of the NLRP3 inflammasome. This latter step is reliant on active caspase-1, pannexin-1, and P2X7 receptor activation. Pathogen-associated molecular patterns in gram-positive and gram-negative bacteria activate IL-1ß release from immune cells via TLR2 and TLR4 receptors, respectively. We found that pro-IL-1ß and mature IL-1ß release from human monocytes is stimulated by the TLR2 agonists Pam3CSK4 or FSL-1, as well as the TLR4 agonist LPS in the absence of additional ATP. TLR2 agonists required pannexin-1 and P2X7 receptor activation to stimulate IL-1ß release. In contrast, IL-1ß release stimulated by the TLR4 agonist LPS is independent of both pannexin-1 and P2X7 activation. In the absence of exogenous ATP, P2X7 activation requires endogenous ATP release, which occurs in some cells via pannexin-1. In line with this, we found that LPS-stimulated human monocytes released relatively low levels of ATP, whereas cells stimulated with TLR2 agonists released high levels of ATP. These findings suggest that in human monocytes, both TLR2 and TLR4 signaling induce pro-IL-1ß expression, but the mechanism by which they activate caspase-1 diverges at the level of the pannexin-1/ATP/P2X7 axis.-Parzych, K., Zetterqvist, A. V., Wright, W. R., Kirkby, N. S., Mitchell, J. A., Paul-Clark, M. J. Differential role of pannexin-1/ATP/P2X7 axis in IL-1ß release by human monocytes.

The coordinated action of VCP/p97 and GCN2 regulates cancer cell metabolism and proteostasis during nutrient limitation.

VCP/p97 regulates numerous cellular functions by mediating protein degradation through its segregase activity. Its key role in governing protein homoeostasis has made VCP/p97 an appealing anticancer drug target. Here, we provide evidence that VCP/p97 acts as a regulator of cellular metabolism. We found that VCP/p97 was tied to multiple metabolic processes on the gene expression level in a diverse range of cancer cell lines and in patient-derived multiple myeloma cells. Cellular VCP/p97 dependency to maintain proteostasis was increased under conditions of glucose and glutamine limitation in a range of cancer cell lines from different tissues. Moreover, glutamine depletion led to increased VCP/p97 expression, whereas VCP/p97 inhibition perturbed metabolic processes and intracellular amino acid turnover. GCN2, an amino acid-sensing kinase, attenuated stress signalling and cell death triggered by VCP/p97 inhibition and nutrient shortages and modulated ERK activation, autophagy, and glycolytic metabolite turnover. Together, our data point to an interconnected role of VCP/p97 and GCN2 in maintaining cancer cell metabolic and protein homoeostasis.

An engineered, quantifiable in vitro model for analysing the effect of proteostasis-targeting drugs on tissue physical properties.

Cellular function depends on the maintenance of protein homeostasis (proteostasis) by regulated protein degradation. Chronic dysregulation of proteostasis is associated with neurodegenerative and age-related diseases, and drugs targeting components of the protein degradation apparatus are increasingly used in cancer therapies. However, as chronic imbalances rather than loss of function mediate their pathogenesis, research models that allow for the study of the complex effects of drugs on tissue properties in proteostasis-associated diseases are almost completely lacking. Here, to determine the functional effects of impaired proteostatic fine-tuning, we applied a combination of materials science characterisation techniques to a cell-derived, in vitro model of bone-like tissue formation in which we pharmacologically perturbed protein degradation. We show that low-level inhibition of VCP/p97 and the proteasome, two major components of the degradation machinery, have remarkably different effects on the bone-like material that human bone-marrow derived mesenchymal stromal cells (hMSC) form in vitro. Specifically, whilst proteasome inhibition mildly enhances tissue formation, Raman spectroscopic, atomic force microscopy-based indentation, and electron microscopy imaging reveal that VCP/p97 inhibition induces the formation of bone-like tissue that is softer, contains less protein, appears to have more crystalline mineral, and may involve aberrant micro- and ultra-structural tissue organisation. These observations contrast with findings from conventional osteogenic assays that failed to identify any effect on mineralisation. Taken together, these data suggest that mild proteostatic impairment in hMSC alters the bone-like material they form in ways that could explain some pathologies associated with VCP/p97-related diseases. They also demonstrate the utility of quantitative materials science approaches for tackling long-standing questions in biology and medicine, and could form the basis for preclinical drug testing platforms to develop therapies for diseases stemming from perturbed proteostasis or for cancer therapies targeting protein degradation. Our findings may also have important implications for the field of tissue engineering, as the manufacture of cell-derived biomaterial scaffolds may need to consider proteostasis to effectively replicate native tissues.

Author Correction: Bi-directional cell-pericellular matrix interactions direct stem cell fate.

The original version of this Article contained an error in the author affiliations. The affiliation of Marjan Enayati with 'Ludwig Boltzmann Cluster for Cardiovascular Research at the Center for Biomedical Research, Medical University of Vienna, Austria' was inadvertently omitted. This has now been corrected in both the PDF and HTML versions of the Article.

Author Correction: Bi-directional cell-pericellular matrix interactions direct stem cell fate.

In the original version of this Article the dataset identifier in the Data Availability statement was incorrect. The correct dataset identifier is PXD009500. This has been corrected in the HTML and PDF versions of this Article.

Bi-directional cell-pericellular matrix interactions direct stem cell fate.

Modifiable hydrogels have revealed tremendous insight into how physical characteristics of cells' 3D environment drive stem cell lineage specification. However, in native tissues, cells do not passively receive signals from their niche. Instead they actively probe and modify their pericellular space to suit their needs, yet the dynamics of cells' reciprocal interactions with their pericellular environment when encapsulated within hydrogels remains relatively unexplored. Here, we show that human bone marrow stromal cells (hMSC) encapsulated within hyaluronic acid-based hydrogels modify their surroundings by synthesizing, secreting and arranging proteins pericellularly or by degrading the hydrogel. hMSC's interactions with this local environment have a role in regulating hMSC fate, with a secreted proteinaceous pericellular matrix associated with adipogenesis, and degradation with osteogenesis. Our observations suggest that hMSC participate in a bi-directional interplay between the properties of their 3D milieu and their own secreted pericellular matrix, and that this combination of interactions drives fate.

Inflammatory transcriptome profiling of human monocytes exposed acutely to cigarette smoke.

BACKGROUND: Cigarette smoking is responsible for 5 million deaths worldwide each year, and is a major risk factor for cardiovascular and lung diseases. Cigarette smoke contains a complex mixture of over 4000 chemicals containing 10(15) free radicals. Studies show smoke is perceived by cells as an inflammatory and xenobiotic stimulus, which activates an immune response. The specific cellular mechanisms driving cigarette smoke-induced inflammation and disease are not fully understood, although the innate immune system is involved in the pathology of smoking related diseases. METHODOLOGY/PRINCIPLE FINDINGS: To address the impact of smoke as an inflammagen on the innate immune system, THP-1 cells and Human PBMCs were stimulated with 3 and 10% (v/v) cigarette smoke extract (CSE) for 8 and 24 hours. Total RNA was extracted and the transcriptome analysed using Illumina BeadChip arrays. In THP-1 cells, 10% CSE resulted in 80 genes being upregulated and 37 downregulated by ≥1.5 fold after 8 hours. In PBMCs stimulated with 10% CSE for 8 hours, 199 genes were upregulated and 206 genes downregulated by ≥1.5 fold. After 24 hours, the number of genes activated and repressed by ≥1.5 fold had risen to 311 and 306 respectively. The major pathways that were altered are associated with cell survival, such as inducible antioxidants, protein chaperone and folding proteins, and the ubiquitin/proteosome pathway. CONCLUSIONS: Our results suggest that cigarette smoke causes inflammation and has detrimental effects on the metabolism and function of innate immune cells. In addition, THP-1 cells provide a genetically stable alternative to primary cells for the study of the effects of cigarette smoke on human monocytes.