p53 promotes revival stem cells in the regenerating intestine after severe radiation injury

Ionizing radiation induces cell death in the gastrointestinal (GI) epithelium by activating p53. However, p53 also prevents animal lethality caused by radiation-induced acute GI syndrome. Through single-cell RNA-sequencing of the irradiated mouse small intestine, we find that p53 target genes are specifically enriched in regenerating epithelial cells that undergo fetal-like reversion, including revival stem cells (revSCs) that promote animal survival after severe damage of the GI tract. Accordingly, in mice with p53 deleted specifically in the GI epithelium, ionizing radiation fails to induce fetal-like revSCs. Using intestinal organoids, we show that transient p53 expression is required for the induction of revival stem cells and is controlled by an Mdm2-mediated negative feedback loop. Together, our findings reveal that p53 suppresses severe radiation-induced GI injury by promoting fetal-like reprogramming of irradiated intestinal epithelial cells.

YAP targetome reveals activation of SPEM in gastric pre-neoplastic progression and regeneration

Peptic ulcer disease caused by environmental factors increases the risk of developing gastric cancer (GC), one of the most common and deadly cancers in the world. However, the mechanisms underlying this association remain unclear. A major type of GC uniquely undergoes spasmolytic polypeptide-expressing metaplasia (SPEM) followed by intestinal metaplasia. Notably, intestinal-type GC patients with high levels of YAP signaling exhibit a lower survival rate and poor prognosis. YAP overexpression in gastric cells induces atrophy, metaplasia, and hyperproliferation, while its deletion in a Notch-activated gastric adenoma model suppresses them. By defining the YAP targetome genome-wide, we demonstrate that YAP binds to active chromatin elements of SPEM-related genes, which correlates with the activation of their expression in both metaplasia and ulcers. Single-cell analysis combined with our YAP signature reveals that YAP signaling is activated during SPEM, demonstrating YAP as a central regulator of SPEM in gastric neoplasia and regeneration.

p53 promotes revival stem cells in the regenerating intestine after severe radiation injury

Ionizing radiation induces cell death in the gastrointestinal (GI) epithelium by activating p53. However, p53 also prevents animal lethality caused by radiation-induced GI injury. Through single-cell RNA-sequencing of the irradiated mouse intestine, we find that p53 target genes are specifically enriched in stem cells of the regenerating epithelium, including revival stem cells that promote animal survival after GI damage. Accordingly, in mice with p53 deleted specifically in the GI epithelium, ionizing radiation fails to induce revival stem cells. Using intestinal organoids, we show that transient p53 expression is required for the induction of revival stem cells that is controlled by an Mdm2-mediated negative feedback loop. These results suggest that p53 suppresses severe radiation-indued GI injury by promoting intestinal epithelial cell reprogramming.

One-Sentence Summary

After severe radiation injury to the intestine, transient p53 activity induces revival stem cells to promote regeneration.

Integrated single-cell analysis defines the epigenetic basis of castration-resistant prostate luminal cells

Understanding prostate response to castration and androgen receptor signaling inhibitors (ARSI) is critical to improving long-term prostate cancer (PCa) patient survival. Here we use a multi-omics approach on 229,794 single cells to create a mouse single-cell reference atlas better suited to interpreting mouse prostate biology and castration response. Our reference atlas refines single-cell annotations and provides chromatin context, which, when coupled with mouse lineage tracing demonstrates that the castration-resistant luminal cells are distinct from the pre-existent urethra-proximal stem/progenitor cells. Molecular pathway analysis and therapeutic studies further implicate JUN/FOS, WNT/B-Catenin, FOXQ1, NFkB, and JAK/STAT pathways as the major drivers of castration-resistant luminal populations with high relevance to human PCa. Importantly, we demonstrate the utility of our datasets, which can be explored through an interactive portal (https://visportal.roswellpark.org/data/tang/), to aid in developing novel combination treatments with ARSI for advanced PCa patients.

Absolute scaling of single-cell transcriptomes identifies pervasive hypertranscription in adult stem and progenitor cells

Hypertranscription supports biosynthetically demanding cellular states through global transcriptome upregulation. Despite its potential widespread relevance, documented examples of hypertranscription remain few and limited to early development. Here, we demonstrate that absolute scaling of single-cell RNA-sequencing data enables the estimation of total transcript abundances per cell. We validate absolute scaling in known cases of developmental hypertranscription and apply it to adult cell types, revealing a remarkable dynamic range in transcriptional output. In adult organs, hypertranscription marks activated stem/progenitor cells with multilineage potential and is redeployed in conditions of tissue injury, where it precedes bursts of proliferation during regeneration. Our analyses identify a common set of molecular pathways associated with both adult and embryonic hypertranscription, including chromatin remodeling, DNA repair, ribosome biogenesis, and translation. These shared features across diverse cell contexts support hypertranscription as a general and dynamic cellular program that is pervasively employed during development, organ maintenance, and regeneration.

Loss of Epigenetic Regulation Disrupts Lineage Integrity, Induces Aberrant Alveogenesis, and Promotes Breast Cancer

Systematically investigating the scores of genes mutated in cancer and discerning disease drivers from inconsequential bystanders is a prerequisite for precision medicine but remains challenging. Here, we developed a somatic CRISPR/Cas9 mutagenesis screen to study 215 recurrent "long-tail" breast cancer genes, which revealed epigenetic regulation as a major tumor-suppressive mechanism. We report that components of the BAP1 and COMPASS-like complexes, including KMT2C/D, KDM6A, BAP1, and ASXL1/2 ("EpiDrivers"), cooperate with PIK3CAH1047R to transform mouse and human breast epithelial cells. Mechanistically, we find that activation of PIK3CAH1047R and concomitant EpiDriver loss triggered an alveolar-like lineage conversion of basal mammary epithelial cells and accelerated formation of luminal-like tumors, suggesting a basal origin for luminal tumors. EpiDriver mutations are found in ∼39% of human breast cancers, and ∼50% of ductal carcinoma in situ express casein, suggesting that lineage infidelity and alveogenic mimicry may significantly contribute to early steps of breast cancer etiology.

SIGNIFICANCE

Infrequently mutated genes comprise most of the mutational burden in breast tumors but are poorly understood. In vivo CRISPR screening identified functional tumor suppressors that converged on epigenetic regulation. Loss of epigenetic regulators accelerated tumorigenesis and revealed lineage infidelity and aberrant expression of alveogenesis genes as potential early events in tumorigenesis. This article is highlighted in the In This Issue feature, p. 2711.

Systematic exploration of dynamic splicing networks reveals conserved multistage regulators of neurogenesis

Alternative splicing (AS) is a critical regulatory layer; yet, factors controlling functionally coordinated splicing programs during developmental transitions are poorly understood. Here, we employ a screening strategy to identify factors controlling dynamic splicing events important for mammalian neurogenesis. Among previously unknown regulators, Rbm38 acts widely to negatively control neural AS, in part through interactions mediated by the established repressor of splicing, Ptbp1. Puf60, a ubiquitous factor, is surprisingly found to promote neural splicing patterns. This activity requires a conserved, neural-differential exon that remodels Puf60 co-factor interactions. Ablation of this exon rewires distinct AS networks in embryonic stem cells and at different stages of mouse neurogenesis. Single-cell transcriptome analyses further reveal distinct roles for Rbm38 and Puf60 isoforms in establishing neuronal identity. Our results describe important roles for previously unknown regulators of neurogenesis and establish how an alternative exon in a widely expressed splicing factor orchestrates temporal control over cell differentiation.

A single cell survey of the microbial impacts on the mouse small intestinal epithelium

The small intestinal epithelial barrier inputs signals from the gut microbiota in order to balance physiological inflammation and tolerance, and to promote homeostasis. Understanding the dynamic relationship between microbes and intestinal epithelial cells has been a challenge given the cellular heterogeneity associated with the epithelium and the inherent difficulty of isolating and identifying individual cell types. Here, we used single-cell RNA sequencing of small intestinal epithelial cells from germ-free and specific pathogen-free mice to study microbe-epithelium crosstalk at the single-cell resolution. The presence of microbiota did not impact overall cellular composition of the epithelium, except for an increase in Paneth cell numbers. Contrary to expectations, pattern recognition receptors and their adaptors were not induced by the microbiota but showed concentrated expression in a small proportion of epithelial cell subsets. The presence of the microbiota induced the expression of host defense- and glycosylation-associated genes in distinct epithelial cell compartments. Moreover, the microbiota altered the metabolic gene expression profile of epithelial cells, consequently inducing mTOR signaling thereby suggesting microbe-derived metabolites directly activate and regulate mTOR signaling. Altogether, these findings present a resource of the homeostatic transcriptional and cellular impact of the microbiota on the small intestinal epithelium.

Regulation of homeostasis and regeneration in the adult intestinal epithelium by the TGF-β superfamily

The delicate balance between the homeostatic maintenance and regenerative capacity of the intestine makes this a fascinating tissue of study. The intestinal epithelium undergoes continuous homeostatic renewal but is also exposed to a diverse array of stresses that can range from physiological processes such as digestion, to exposure to infectious agents, drugs, radiation therapy, and inflammatory stimuli. The intestinal epithelium has thus evolved to efficiently maintain and reinstate proper barrier function that is essential for intestinal integrity and function. Factors governing homeostatic epithelial turnover are well described, however, the dynamic regenerative mechanisms that occur following injury are the subject of intense ongoing investigations. The TGF-β superfamily is a key regulator of both homeostatic renewal and regenerative processes of the intestine. Here we review the roles of TGF-β and BMP on the adult intestinal epithelium during self-renewal and injury to provide a framework for understanding how this major family of morphogens can tip the scale between intestinal health and disease. This article is protected by copyright. All rights reserved.

A scalable serology solution for profiling humoral immune responses to SARS-CoV-2 infection and vaccination

Objectives

Antibody testing against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has been instrumental in detecting previous exposures and analyzing vaccine‐elicited immune responses. Here, we describe a scalable solution to detect and quantify SARS‐CoV‐2 antibodies, discriminate between natural infection‐ and vaccination‐induced responses, and assess antibody‐mediated inhibition of the spike‐angiotensin converting enzyme 2 (ACE2) interaction.

Methods

We developed methods and reagents to detect SARS‐CoV‐2 antibodies by enzyme‐linked immunosorbent assay (ELISA). The main assays focus on the parallel detection of immunoglobulin (Ig)Gs against the spike trimer, its receptor binding domain (RBD) and nucleocapsid (N). We automated a surrogate neutralisation (sn)ELISA that measures inhibition of ACE2‐spike or ‐RBD interactions by antibodies. The assays were calibrated to a World Health Organization reference standard.

Results

Our single‐point IgG‐based ELISAs accurately distinguished non‐infected and infected individuals. For seroprevalence assessment (in a non‐vaccinated cohort), classifying a sample as positive if antibodies were detected for ≥ 2 of the 3 antigens provided the highest specificity. In vaccinated cohorts, increases in anti‐spike and ‐RBD (but not ‐N) antibodies are observed. We present detailed protocols for serum/plasma or dried blood spots analysis performed manually and on automated platforms. The snELISA can be performed automatically at single points, increasing its scalability.

Conclusions

Measuring antibodies to three viral antigens and identify neutralising antibodies capable of disrupting spike‐ACE2 interactions in high‐throughput enables large‐scale analyses of humoral immune responses to SARS‐CoV‐2 infection and vaccination. The reagents are available to enable scaling up of standardised serological assays, permitting inter‐laboratory data comparison and aggregation.

NUAK1 promotes organ fibrosis via YAP and TGF-β/SMAD signaling

Fibrosis is a central pathway that drives progression of multiple chronic diseases, yet few safe and effective clinical antifibrotic therapies exist. In most fibrotic disorders, transforming growth factor-β (TGF-β)-driven scarring is an important pathologic feature and a key contributor to disease progression. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are two closely related transcription cofactors that are important for coordinating fibrogenesis after organ injury, but how they are activated in response to tissue injury has, so far, remained unclear. Here, we describe NUAK family kinase 1 (NUAK1) as a TGF-β-inducible profibrotic kinase that is up-regulated in multiple fibrotic organs in mice and humans. Mechanistically, we show that TGF-β induces a rapid increase in NUAK1 in fibroblasts. NUAK1, in turn, can promote profibrotic YAP and TGF-β/SMAD signaling, ultimately leading to organ scarring. Moreover, activated YAP and TAZ can induce further NUAK1 expression, creating a profibrotic positive feedback loop that enables persistent fibrosis. Using mouse models of kidney, lung, and liver fibrosis, we demonstrate that this fibrogenic signaling loop can be interrupted via fibroblast-specific loss of NUAK1 expression, leading to marked attenuation of fibrosis. Pharmacologic NUAK1 inhibition also reduced scarring, either when initiated immediately after injury or when initiated after fibrosis was already established. Together, our data suggest that NUAK1 plays a critical, previously unrecognized role in fibrogenesis and represents an attractive target for strategies that aim to slow fibrotic disease progression.

Myofibroblast YAP/TAZ activation is a key step in organ fibrogenesis

Fibrotic diseases account for nearly half of all deaths in the developed world. Despite its importance, the pathogenesis of fibrosis remains poorly understood. Recently, the two mechanosensitive transcription cofactors YAP and TAZ have emerged as important profibrotic regulators in multiple murine tissues. Despite this growing recognition, a number of important questions remain unanswered, including which cell types require YAP/TAZ activation for fibrosis to occur and the time course of this activation. Here, we present a detailed analysis of the role that myofibroblast YAP and TAZ play in organ fibrosis and the kinetics of their activation. Using analyses of cells, as well as multiple murine and human tissues, we demonstrated that myofibroblast YAP and TAZ were activated early after organ injury and that this activation was sustained. We further demonstrated the critical importance of myofibroblast YAP/TAZ in driving progressive scarring in the kidney, lung, and liver, using multiple transgenic models in which YAP and TAZ were either deleted or hyperactivated. Taken together, these data establish the importance of early injury-induced myofibroblast YAP and TAZ activation as a key event driving fibrosis in multiple organs. This information should help guide the development of new antifibrotic YAP/TAZ inhibition strategies.

Somatic driver mutation prevalence in 1844 prostate cancers identifies ZNRF3 loss as a predictor of metastatic relapse

Driver gene mutations that are more prevalent in metastatic, castration-resistant prostate cancer (mCRPC) than localized disease represent candidate prognostic biomarkers. We analyze 1,844 localized (1,289) or mCRPC (555) tumors and quantify the prevalence of 113 somatic driver single nucleotide variants (SNVs), copy number aberrations (CNAs), and structural variants (SVs) in each state. One-third are significantly more prevalent in mCRPC than expected while a quarter are less prevalent. Mutations in AR and its enhancer are more prevalent in mCRPC, as are those in TP53, MYC, ZNRF3 and PRKDC. ZNRF3 loss is associated with decreased ZNRF3 mRNA abundance, WNT, cell cycle & PRC1/2 activity, and genomic instability. ZNRF3 loss, RNA downregulation and hypermethylation are prognostic of metastasis and overall survival, independent of clinical and pathologic indices. These data demonstrate a strategy for identifying biomarkers of localized cancer aggression, with ZNRF3 loss as a predictor of metastasis in prostate cancer.

Enteric glial cell heterogeneity regulates intestinal stem cell niches

The high turnover and regenerative capacity of the adult intestine relies on resident stem cells located at the bottom of the crypt. The enteric nervous system consists of an abundant network of enteric glial cells (EGCs) and neurons. Despite the close proximity of EGCs to stem cells, their in vivo role as a stem cell niche is still unclear. By analyzing the mouse and human intestinal mucosa transcriptomes at the single-cell level, we defined the regulation of EGC heterogeneity in homeostasis and chronic inflammatory bowel disease. Ablation of EGC subpopulations revealed that the repair potential of intestinal stem cells (ISCs) is regulated by a specific subset of glial fibrillary acidic protein (GFAP)⁺ EGCs. Mechanistically, injury induces expansion of GFAP⁺ EGCs, which express several WNT ligands to promote LGR5⁺ ISC self-renewal. Our work reveals the dynamically regulated heterogeneity of EGCs as a key part of the intestinal stem cell niche in regeneration and disease.

YAP establishes epiblast responsiveness to inductive signals for germ cell fate

The germ cell lineage in mammals is induced by the stimulation of pluripotent epiblast cells by signaling molecules. Previous studies have suggested that the germ cell differentiation competence or responsiveness of epiblast cells to signaling molecules is established and maintained in epiblast cells of a specific differentiation state. However, the molecular mechanism underlying this process has not been well defined. Here, using the differentiation model of mouse epiblast stem cells (EpiSCs), we have shown that two defined EpiSC lines have robust germ cell differentiation competence. However, another defined EpiSC line has no competence. By evaluating the molecular basis of EpiSCs with distinct germ cell differentiation competence, we identified YAP, an intracellular mediator of the Hippo signaling pathway, as crucial for the establishment of germ cell induction. Strikingly, deletion of YAP severely affected responsiveness to inductive stimuli, leading to a defect in WNT target activation and germ cell differentiation. In conclusion, we propose that the Hippo/YAP signaling pathway creates a potential for germ cell fate induction via mesodermal WNT signaling in pluripotent epiblast cells.

Summary: YAP, an intracellular mediator of the Hippo signaling pathway, establishes epiblast competency for germ cell differentiation through activation of the WNT pathway.

Binary pan-cancer classes with distinct vulnerabilities defined by pro- or anti-cancer YAP/TEAD activity

Cancer heterogeneity impacts therapeutic response, driving efforts to discover over-arching rules that supersede variability. Here, we define pan-cancer binary classes based on distinct expression of YAP and YAP-responsive adhesion regulators. Combining informatics with in vivo and in vitro gain- and loss-of-function studies across multiple murine and human tumor types, we show that opposite pro- or anti-cancer YAP activity functionally defines binary YAP^on or YAP^off cancer classes that express or silence YAP, respectively. YAP^off solid cancers are neural/neuroendocrine and frequently RB1^-/-, such as retinoblastoma, small cell lung cancer, and neuroendocrine prostate cancer. YAP silencing is intrinsic to the cell of origin, or acquired with lineage switching and drug resistance. The binary cancer groups exhibit distinct YAP-dependent adhesive behavior and pharmaceutical vulnerabilities, underscoring clinical relevance. Mechanistically, distinct YAP/TEAD enhancers in YAP^off or YAP^on cancers deploy anti-cancer integrin or pro-cancer proliferative programs, respectively. YAP is thus pivotal across cancer, but in opposite ways, with therapeutic implications.

The hippo pathway: A master regulator of liver metabolism, regeneration, and disease

The liver is the only visceral organ in the body with a tremendous capacity to regenerate in response to insults that induce inflammation, cell death, and injury. Liver regeneration is a complicated process involving a well-orchestrated activation of non-parenchymal cells in the injured area and proliferation of undamaged hepatocytes. Furthermore, the liver has a Hepatostat, defined as adjustment of its volume to that required for homeostasis. Understanding the mechanisms that control different steps of liver regeneration is critical to informing therapies for liver repair, to help patients with liver disease. The Hippo signaling pathway is well known for playing an essential role in the control and regulation of liver size, regeneration, stem cell self-renewal, and liver cancer. Thus, the Hippo pathway regulates dynamic cell fates in liver, and in absence of its downstream effectors YAP and TAZ, liver regeneration is severely impaired, and the proliferative expansion of liver cells blocked. We will mainly review upstream mechanisms activating the Hippo signaling pathway following partial hepatectomy in mouse model and patients, its roles during different steps of liver regeneration, metabolism, and cancer. We will also discuss how targeting the Hippo signaling cascade might improve liver regeneration and suppress liver tumorigenesis.

Comparison of SARS-CoV-2 indirect and direct RT-qPCR detection methods

BACKGROUND

Sensitive, rapid, and accessible diagnostics continue to be critical to track the COVID-19 pandemic caused by the SARS-CoV-2 virus. RT-qPCR is the gold standard test, and comparison of methodologies and reagents, utilizing patient samples, is important to establish reliable diagnostic pipelines.

METHODS

Here, we assessed indirect methods that require RNA extraction with direct RT-qPCR on patient samples. Four different RNA extraction kits (Qiagen, Invitrogen, BGI and Norgen Biotek) were compared. For detection, we assessed two recently developed Taqman-based modules (BGI and Norgen Biotek), a SYBR green-based approach (NEB Luna Universal One-Step Kit) with published and newly-developed primers, and clinical results (Seegene STARMag RNA extraction system and Allplex 2019-nCoV RT-qPCR assay). We also tested and optimized direct, extraction-free detection using these RT-qPCR systems and performed a cost analysis of the different methods evaluated here.

RESULTS

Most RNA isolation procedures performed similarly, and while all RT-qPCR modules effectively detected purified viral RNA, the BGI system provided overall superior performance (lower detection limit, lower Ct values and higher sensitivity), generating comparable results to original clinical diagnostic data, and identifying samples ranging from 65 copies to 2.1 × 105 copies of viral genome/μl. However, the BGI detection system is more expensive than other options tested here. With direct RT-qPCR, simply adding an RNase inhibitor greatly improved detection, without the need for any other treatments (e.g. lysis buffers or boiling). The best direct methods detected ~ 10 fold less virus than indirect methods, but this simplified approach reduced sample handling, as well as assay time and cost.

CONCLUSIONS

With extracted RNA, the BGI RT-qPCR detection system exhibited superior performance over the Norgen system, matching initial clinical diagnosis with the Seegene Allplex assay. The BGI system was also suitable for direct, extraction-free analysis, providing 78.4% sensitivity. The Norgen system, however, still accurately detected samples with a clinical Ct < 33 from extracted RNA, provided significant cost savings, and was superior to SYBR green assays that exhibited reduced specificity.

A multiplexed, next generation sequencing platform for high-throughput detection of SARS-CoV-2

Population scale sweeps of viral pathogens, such as SARS-CoV-2, require high intensity testing for effective management. Here, we describe "Systematic Parallel Analysis of RNA coupled to Sequencing for Covid-19 screening" (C19-SPAR-Seq), a multiplexed, scalable, readily automated platform for SARS-CoV-2 detection that is capable of analyzing tens of thousands of patient samples in a single run. To address strict requirements for control of assay parameters and output demanded by clinical diagnostics, we employ a control-based Precision-Recall and Receiver Operator Characteristics (coPR) analysis to assign run-specific quality control metrics. C19-SPAR-Seq coupled to coPR on a trial cohort of several hundred patients performs with a specificity of 100% and sensitivity of 91% on samples with low viral loads, and a sensitivity of >95% on high viral loads associated with disease onset and peak transmissibility. This study establishes the feasibility of employing C19-SPAR-Seq for the large-scale monitoring of SARS-CoV-2 and other pathogens.

An endogenous PI3K interactome promoting astrocyte-mediated neuroprotection identifies a novel association with RNA-binding protein ZC3H14

Astrocytes can support neuronal survival through a range of secreted signals that protect against neurotoxicity, oxidative stress, and apoptotic cascades. Thus, analyzing the effects of the astrocyte secretome may provide valuable insight into these neuroprotective mechanisms. Previously, we characterized a potent neuroprotective activity mediated by retinal astrocyte conditioned media (ACM) on retinal and cortical neurons in metabolic stress models. However, the molecular mechanism underlying this complex activity in neuronal cells has remained unclear. Here, a chemical genetics screen of kinase inhibitors revealed phosphoinositide 3-kinase (PI3K) as a central player transducing ACM-mediated neuroprotection. To identify additional proteins contributing to the protective cascade, endogenous PI3K was immunoprecipitated from neuronal cells exposed to ACM or control media, followed by MS/MS proteomic analyses. These data pointed toward a relatively small number of proteins that coimmunoprecipitated with PI3K, and surprisingly only five were regulated by the ACM signal. These hits included expected PI3K interactors, such as the platelet-derived growth factor receptor A (PDGFRA), as well as novel RNA-binding protein interactors ZC3H14 (zinc finger CCCH-type containing 14) and THOC1 (THO complex protein 1). In particular, ZC3H14 has recently emerged as an important RNA-binding protein with multiple roles in posttranscriptional regulation. In validation studies, we show that PI3K recruitment of ZC3H14 is necessary for PDGF-induced neuroprotection and that this interaction is present in primary retinal ganglion cells. Thus, we identified a novel non-cell autonomous neuroprotective signaling cascade mediated through PI3K that requires recruitment of ZC3H14 and may present a promising strategy to promote astrocyte-secreted prosurvival signals.

Persistence of serum and saliva antibody responses to SARS-CoV-2 spike antigens in COVID-19 patients

While the antibody response to SARS-CoV-2 has been extensively studied in blood, relatively little is known about the antibody response in saliva and its relationship to systemic antibody levels. Here, we profiled by enzyme-linked immunosorbent assays (ELISAs) IgG, IgA and IgM responses to the SARS-CoV-2 spike protein (full length trimer) and its receptor-binding domain (RBD) in serum and saliva of acute and convalescent patients with laboratory-diagnosed COVID-19 ranging from 3-115 days post-symptom onset (PSO), compared to negative controls. Anti-SARS-CoV-2 antibody responses were readily detected in serum and saliva, with peak IgG levels attained by 16-30 days PSO. Longitudinal analysis revealed that anti-SARS-CoV-2 IgA and IgM antibodies rapidly decayed, while IgG antibodies remained relatively stable up to 105 days PSO in both biofluids. Lastly, IgG, IgM and to a lesser extent IgA responses to spike and RBD in the serum positively correlated with matched saliva samples. This study confirms that serum and saliva IgG antibodies to SARS-CoV-2 are maintained in the majority of COVID-19 patients for at least 3 months PSO. IgG responses in saliva may serve as a surrogate measure of systemic immunity to SARS-CoV-2 based on their correlation with serum IgG responses.

Persistence of serum and saliva antibody responses to SARS-CoV-2 spike antigens in COVID-19 patients

While the antibody response to SARS-CoV-2 has been extensively studied in blood, relatively little is known about the antibody response in saliva and its relationship to systemic antibody levels. Here, we profiled by enzyme-linked immunosorbent assays (ELISAs) IgG, IgA and IgM responses to the SARS-CoV-2 spike protein (full length trimer) and its receptor-binding domain (RBD) in serum and saliva of acute and convalescent patients with laboratory-diagnosed COVID-19 ranging from 3-115 days post-symptom onset (PSO), compared to negative controls. Anti-SARS-CoV-2 antibody responses were readily detected in serum and saliva, with peak IgG levels attained by 16-30 days PSO. Longitudinal analysis revealed that anti-SARS-CoV-2 IgA and IgM antibodies rapidly decayed, while IgG antibodies remained relatively stable up to 105 days PSO in both biofluids. Lastly, IgG, IgM and to a lesser extent IgA responses to spike and RBD in the serum positively correlated with matched saliva samples. This study confirms that serum and saliva IgG antibodies to SARS-CoV-2 are maintained in the majority of COVID-19 patients for at least 3 months PSO. IgG responses in saliva may serve as a surrogate measure of systemic immunity to SARS-CoV-2 based on their correlation with serum IgG responses.

Modeling the Control of TGF-β/Smad Nuclear Accumulation by the Hippo Pathway Effectors, Taz/Yap

Integration of transforming growth factor β (TGF-β) signals with those of other pathways allows for precise temporal and spatial control of gene expression patterns that drive development and homeostasis. The Hippo pathway nuclear effectors, Taz/Yap, interact with the TGF-β transcriptional mediators, Smads, to control Smad activity. Key to TGF-β signaling is the nuclear localization of Smads. Thus, to investigate the role of Taz/Yap in Smad nuclear accumulation, we developed mathematical models of Hippo and TGF-β cross talk. The models were based on experimental measurements of TGF-β-induced changes in Taz/Yap and Smad subcellular localization obtained using high-throughput immunofluorescence (IF) imaging in the mouse mammary epithelial cell line, EpH4. Bayesian MCMC DREAM parameter estimation was used to quantify the uncertainty in estimates of the kinetic parameters. Variation of the model parameters and statistical analysis show that our modeling predicts that Taz/Yap can alter TGF-β receptor activity and directly or indirectly act as nuclear retention factors.

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Taz/Yap modulate TGF-β-induced nuclear accumulation of Smad2/3 and Smad4

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TGF-β does not affect Taz/Yap localization when Hippo activity is constant

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Taz/Yap loss may alter activity of both Receptor and Smad nuclear retention factors

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The mediator complex regulates Smad nuclear accumulation

Overexpression of the Severe Acute Respiratory Syndrome Coronavirus-2 Receptor, Angiotensin-Converting Enzyme 2, in Diabetic Kidney Disease: Implications for Kidney Injury in Novel Coronavirus Disease 2019

Objectives

Diabetes is associated with adverse outcomes, including death, after coronavirus disease 19 (COVID-19) infection. Beyond the lungs, Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), the etiologic agent of the COVID-19 pandemic, can infect a range of other tissues, including the kidney, potentially contributing to acute kidney injury in those with severe disease. We hypothesized that the renal abundance of angiotensin-converting enzyme (ACE) 2, the cell surface receptor for SARS-CoV-2, may be modulated by diabetes and agents that block the renin-angiotensin-aldosterone system (RAAS).

Methods

The expression of ACE 2 was examined in 49 archival kidney biopsies from patients with diabetic kidney disease and from 12 healthy, potential living allograft donors using next-generation sequencing technology (RNA Seq).

Results

Mean ACE 2 messenger RNA was increased approximately 2-fold in diabetes when compared with healthy control subjects (mean ± SD, 13.2±7.9 vs 7.7±3.6 reads per million reads, respectively; p=0.001). No difference in transcript abundance was noted between recipients and nonrecipients of agents that block the RAAS (12.2±6.7 vs 16.2±10.7 reads per million reads, respectively; p=0.25).

Conclusions

Increased ACE 2 messenger RNA in the diabetic kidney may increase the risk and/or severity of kidney infection with SARS-CoV-2 in the setting of COVID-19 disease. Further studies are needed to ascertain whether this diabetes-related overexpression is generalizable to other tissues, most notably the lungs.

Robust production of uniform human cerebral organoids from pluripotent stem cells

Human cerebral organoid (hCO) models offer the opportunity to understand fundamental processes underlying human-specific cortical development and pathophysiology in an experimentally tractable system. Although diverse methods to generate brain organoids have been developed, a major challenge has been the production of organoids with reproducible cell type heterogeneity and macroscopic morphology. Here, we have directly addressed this problem by establishing a robust production pipeline to generate morphologically consistent hCOs and achieve a success rate of >80%. These hCOs include both a radial glial stem cell compartment and electrophysiologically competent mature neurons. Moreover, we show using immunofluorescence microscopy and single-cell profiling that individual organoids display reproducible cell type compositions that are conserved upon extended culture. We expect that application of this method will provide new insights into brain development and disease processes.

Gaining Insights into the Function of Post-Translational Protein Modification Using Genome Engineering and Molecular Cell Biology

Modifications by kinases are a fast and reversible mechanism to diversify the function of the targeted proteins. The OCT4 transcription factor is essential for preimplantation development and pluripotency of embryonic stem cells (ESC), and its activity is tightly regulated by post-transcriptional modifications. Several phosphorylation sites have been identified by systemic approaches and their functions proposed. Here, we combined molecular and cellular biology with CRISPR/Cas9-mediated genome engineering to pinpoint the function of serine 12 of OCT4 in ESCs. Using chemical inhibitors and an antibody specific to OCT4 phosphorylated on S12, we identified cyclin-dependent kinase (CDK) 7 as upstream kinase. Surprisingly, generation of isogenic mESCs that endogenously ablate S12 revealed no effects on pluripotency and self-renewal, potentially due to compensation by other phosphorylation events. Our approach reveals that modification of distinct amino acids by precise genome engineering can help to clarify the functions of post-translational modifications on proteins encoded by essential gene in an endogenous context.

Atypical function of a centrosomal module in WNT signalling drives contextual cancer cell motility

Centrosomes control cell motility, polarity and migration that is thought to be mediated by their microtubule-organizing capacity. Here we demonstrate that WNT signalling drives a distinct form of non-directional cell motility that requires a key centrosome module, but not microtubules or centrosomes. Upon exosome mobilization of PCP-proteins, we show that DVL2 orchestrates recruitment of a CEP192-PLK4/AURKB complex to the cell cortex where PLK4/AURKB act redundantly to drive protrusive activity and cell motility. This is mediated by coordination of formin-dependent actin remodelling through displacement of cortically localized DAAM1 for DAAM2. Furthermore, abnormal expression of PLK4, AURKB and DAAM1 is associated with poor outcomes in breast and bladder cancers. Thus, a centrosomal module plays an atypical function in WNT signalling and actin nucleation that is critical for cancer cell motility and is associated with more aggressive cancers. These studies have broad implications in how contextual signalling controls distinct modes of cell migration.

Centrosomes function in cell migration by organizing microtubules. Here, Luo et al. surprisingly show that centrosome proteins also control migration after recruitment by Wnt-PCP proteins to the cell cortex, leading to actin remodelling and protrusive activity relevant to aggressive cancer motility.

Single-cell transcriptomes of the regenerating intestine reveal a revival stem cell

The turnover of the intestinal epithelium is driven by multipotent LGR5⁺ crypt-base columnar cells (CBCs) located at the bottom of crypt zones¹. However, CBCs are lost following injury, such as irradiation², but the intestinal epithelium is nevertheless able to recover³. Thus, a second population of quiescent '+4' cells, or reserve stem cells (RSCs), has previously been proposed to regenerate the damaged intestine^4-7. Although CBCs and RSCs were thought to be mutually exclusive^4,8, subsequent studies have found that LGR5⁺ CBCs express RSC markers⁹ and that RSCs were dispensable-whereas LGR5⁺ cells were essential-for repair of the damaged intestine³. In addition, progenitors of absorptive enterocytes¹⁰, secretory cells^11-15 and slow cycling LGR5⁺ cells¹⁶ have been shown to contribute to regeneration whereas the transcriptional regulator YAP1, which is important for intestinal regeneration, was suggested to induce a pro-survival phenotype in LGR5⁺ cells¹⁷. Thus, whether cellular plasticity or distinct cell populations are critical for intestinal regeneration remains unknown. Here we applied single-cell RNA sequencing to profile the regenerating mouse intestine and identified a distinct, damage-induced quiescent cell type that we term the revival stem cell (revSC). revSCs are marked by high clusterin expression and are extremely rare under homoeostatic conditions, yet give rise-in a temporal hierarchy-to all the major cell types of the intestine, including LGR5⁺ CBCs. After intestinal damage by irradiation, targeted ablation of LGR5⁺ CBCs, or treatment with dextran sodium sulfate, revSCs undergo a YAP1-dependent transient expansion, reconstitute the LGR5⁺ CBC compartment and are required to regenerate a functional intestine. These studies thus define a unique stem cell that is mobilized by damage to revive the homoeostatic stem cell compartment and regenerate the intestinal epithelium.

Cell competition during reprogramming gives rise to dominant clones

The ability to generate induced pluripotent stem cells from differentiated cell types has enabled researchers to engineer cell states. Although studies have identified molecular networks that reprogram cells to pluripotency, the cellular dynamics of these processes remain poorly understood. Here, by combining cellular barcoding, mathematical modeling, and lineage tracing approaches, we demonstrate that reprogramming dynamics in heterogeneous populations are driven by dominant “elite” clones. Clones arise a priori from a population of poised mouse embryonic fibroblasts derived from Wnt1-expressing cells that may represent a neural crest–derived population. This work highlights the importance of cellular dynamics in fate programming outcomes and uncovers cell competition as a mechanism by which cells with eliteness emerge to occupy and dominate the reprogramming niche.

A feed forward loop enforces YAP/TAZ signaling during tumorigenesis

In most solid tumors, the Hippo pathway is inactivated through poorly understood mechanisms that result in the activation of the transcriptional regulators, YAP and TAZ. Here, we identify NUAK2 as a YAP/TAZ activator that directly inhibits LATS-mediated phosphorylation of YAP/TAZ and show that NUAK2 induction by YAP/TAZ and AP-1 is required for robust YAP/TAZ signaling. Pharmacological inhibition or loss of NUAK2 reduces the growth of cultured cancer cells and mammary tumors in mice. Moreover, in human patient samples, we show that NUAK2 expression is elevated in aggressive, high-grade bladder cancer and strongly correlates with a YAP/TAZ gene signature. These findings identify a positive feed forward loop in the Hippo pathway that establishes a key role for NUAK2 in enforcing the tumor-promoting activities of YAP/TAZ. Our results thus introduce a new opportunity for cancer therapeutics by delineating NUAK2 as a potential target for re-engaging the Hippo pathway.

The Hippo pathway is frequently dysregulated in cancer. Here, the authors identify NUAK2 as negative regulator of the Hippo pathway from a siRNA kinome screen and show that NUAK2 promotes YAP/TAZ nuclear localisation while NUAK2 is a transcriptional target of YAP/TAZ, thus providing a feed forward loop to promote tumorigenesis.

Measurement of Fibrinogen Concentrations in Suspensions of Washed Rabbit and Human Platelets by Radioimmunoassays

Although fibrinogen is a cofactor in platelet aggregation, washed rabbit platelets aggregate when stimulated with ADP even when no fibrinogen is added to the platelet suspension. Washed human platelets usually do not aggregate to a significant extent when stimulated with ADP unless fibrinogen is added. To study this phenomenon, radioimmunoassays for rabbit and human fibrinogens have been developed and used to measure fibrinogen concentrations in suspensions of washed platelets. The fibrinogen concentration in the suspending medium of rabbit platelets was 2.5 ± 0.9 μg/109 platelets, and upon stimulation with 9 μM ADP it increased to 10.7 ± 2.9 μg/109 platelets. The loss of fibrinogen from the platelets was significantly greater than the loss of 14C-serotonin (11% vs 2%). The presence of prostaglandin E1 reduced the fibrinogen concentration to approximately 1 μg/109 platelets and prevented aggregation and loss of fibrinogen when the platelets were stimulated with ADP. With human platelets, the extracellular concentrations of fibrinogen and β-thromboglobulin, expressed as percentages of the amount in the platelets, were similar, and the increase in fibrinogen concentration upon ADP stimulation (approximately 2%) was much lower than with rabbit platelets. We conclude that rabbit platelets may release fibrinogen from their α-granules when stimulated with ADP, and that a portion of the released fibrinogen becomes available to support aggregation. Smaller amounts of fibrinogen would become available in the case of human platelets.

Exosomes Mediate Mobilization of Autocrine Wnt10b to Promote Axonal Regeneration in the Injured CNS

Developing strategies that promote axonal regeneration within the injured CNS is a major therapeutic challenge, as axonal outgrowth is potently inhibited by myelin and the glial scar. Although regeneration can be achieved using the genetic deletion of PTEN, a negative regulator of the mTOR pathway, this requires inactivation prior to nerve injury, thus precluding therapeutic application. Here, we show that, remarkably, fibroblast-derived exosomes (FD exosomes) enable neurite growth on CNS inhibitory proteins. Moreover, we demonstrate that, upon treatment with FD exosomes, Wnt10b is recruited toward lipid rafts and activates mTOR via GSK3β and TSC2. Application of FD exosomes shortly after optic nerve injury promoted robust axonal regeneration, which was strongly reduced in Wnt10b-deleted animals. This work uncovers an intercellular signaling pathway whereby FD exosomes mobilize an autocrine Wnt10b-mTOR pathway, thereby awakening the intrinsic capacity of neurons for regeneration, an important step toward healing the injured CNS.

Multilayered Control of Alternative Splicing Regulatory Networks by Transcription Factors

Networks of coordinated alternative splicing (AS) events play critical roles in development and disease. However, a comprehensive knowledge of the factors that regulate these networks is lacking. We describe a high-throughput system for systematically linking trans-acting factors to endogenous RNA regulatory events. Using this system, we identify hundreds of factors associated with diverse regulatory layers that positively or negatively control AS events linked to cell fate. Remarkably, more than one-third of the regulators are transcription factors. Further analyses of the zinc finger protein Zfp871 and BTB/POZ domain transcription factor Nacc1, which regulate neural and stem cell AS programs, respectively, reveal roles in controlling the expression of specific splicing regulators. Surprisingly, these proteins also appear to regulate target AS programs via binding RNA. Our results thus uncover a large "missing cache" of splicing regulators among annotated transcription factors, some of which dually regulate AS through direct and indirect mechanisms.

TGF-β Family Signaling in Embryonic and Somatic Stem-Cell Renewal and Differentiation

Soon after the discovery of transforming growth factor-β (TGF-β), seminal work in vertebrate and invertebrate models revealed the TGF-β family to be central regulators of tissue morphogenesis. Members of the TGF-β family direct some of the earliest cell-fate decisions in animal development, coordinate complex organogenesis, and contribute to tissue homeostasis in the adult. Here, we focus on the role of the TGF-β family in mammalian stem-cell biology and discuss its wide and varied activities both in the regulation of pluripotency and in cell-fate commitment.

Recent advances in understanding contextual TGFβ signaling

The appearance of the first animal species on earth coincides with the emergence of transforming growth factor β (TGFβ) pathways. The evolution of these animals into more complex organisms coincides with a progressively increased TGFβ repertoire through gene duplications and divergence, making secreted TGFβ molecules the largest family of morphogenetic proteins in humans. It is therefore not surprising that TGFβ pathways govern numerous aspects of human biology from early embryonic development to regeneration, hematopoiesis, neurogenesis, and immunity. Such heavy reliance on these pathways is reflected in the susceptibility to minor perturbations in pathway components that can lead to dysregulated signaling and a diverse range of human pathologies such as cancer, fibrosis, and developmental disorders. Attempts to comprehensively resolve these signaling cascades are complicated by the long-recognized paradoxical role the pathway plays in cell biology. Recently, several groups have probed examples of the disparate aspects of TGFβ biology in a variety of animal models and uncovered novel context-dependent regulatory mechanisms. Here, we briefly review recent advancements and discuss their overall impact in directing future TGFβ research.

LUMIER: A Discovery Tool for Mammalian Protein Interaction Networks

Protein-protein interactions (PPIs) play an essential role in all biological processes. In vivo, PPIs occur dynamically and depend on extracellular cues. To discover novel protein-protein interactions in mammalian cells, we developed a high-throughput automated technology called LUMIER (LUminescence-based Mammalian IntERactome). In this approach, we co-express a Luciferase (LUC)-tagged fusion protein along with a Flag-tagged protein in an efficiently transfectable cell line such as HEK-293T cells. The interaction between the two proteins is determined by co-immunoprecipitation using an anti-Flag antibody, and the presence of the LUC-tagged interactor in the complex is subsequently detected via its luciferase activity. LUMIER can easily detect transmembrane protein partners, interactions that are signaling- or splice isoform-dependent, as well as those that may occur only in the presence of posttranslational modifications. Using various collections of Flag-tagged proteins, we have generated protein interaction networks for several TGF-β family receptors, Wnt pathway members, and have systematically analyzed the effect of neural-specific alternative splicing on protein interaction networks. The results have provided important insights into the physiological and functional relevance of some of the novel interactions found. LUMIER is highly scalable and can be used for both low- and high-throughput strategies. LUMIER is thus a valuable tool for the identification and characterization of dynamically regulated PPIs in mammalian systems. Here, we describe a manual version of LUMIER in a 96-well format that can be easily implemented in any laboratory.

Reciprocal stabilization of ABL and TAZ regulates osteoblastogenesis through transcription factor RUNX2

Cellular identity in metazoan organisms is frequently established through lineage-specifying transcription factors, which control their own expression through transcriptional positive feedback, while antagonizing the developmental networks of competing lineages. Here, we have uncovered a distinct positive feedback loop that arises from the reciprocal stabilization of the tyrosine kinase ABL and the transcriptional coactivator TAZ. Moreover, we determined that this loop is required for osteoblast differentiation and embryonic skeletal formation. ABL potentiated the assembly and activation of the RUNX2-TAZ master transcription factor complex that is required for osteoblastogenesis, while antagonizing PPARγ-mediated adipogenesis. ABL also enhanced TAZ nuclear localization and the formation of the TAZ-TEAD complex that is required for osteoblast expansion. Last, we have provided genetic data showing that regulation of the ABL-TAZ amplification loop lies downstream of the adaptor protein 3BP2, which is mutated in the craniofacial dysmorphia syndrome cherubism. Our study demonstrates an interplay between ABL and TAZ that controls the mesenchymal maturation program toward the osteoblast lineage and is mechanistically distinct from the established model of lineage-specific maturation.

Regulation of Rho GTPases from the lateral sides of migrating cells

Migratory polarity and epithelial polarity share many common regulatory mechanisms. Rho GTPases play a key role in modulating cell polarity, which in migrating cells has been conventionally studied along the solitary front-rear axis. In recent work, we discovered that Prickle1 (Pk1), a core com-ponent of planar cell polarity (PCP) signaling, mediates a novel lateral signaling pathway that coordinates multi-axial protrusive activities from the lateral cortex of migrating cancer cells. We identified that Arhgap21 and 23 are essential effectors of Pk1, and that lateral signaling regulates RhoA, actomyosin and focal adhesion dynamics. Interestingly, we showed that lateral signaling coordinates shape dynamics that are critical during cell migration and function orthogonally to front-rear directional polarity.

KATapulting toward Pluripotency and Cancer

Development is generally regarded as a unidirectional process that results in the acquisition of specialized cell fates. During this process, cellular identity is precisely defined by signaling cues that tailor the chromatin landscape for cell-specific gene expression programs. Once established, these pathways and cell states are typically resistant to disruption. However, loss of cell identity occurs during tumor initiation and upon injury response. Moreover, terminally differentiated cells can be experimentally provoked to become pluripotent. Chromatin reorganization is key to the establishment of new gene expression signatures and thus new cell identity. Here, we explore an emerging concept that lysine acetyltransferase (KAT) enzymes drive cellular plasticity in the context of somatic cell reprogramming and tumorigenesis.

The RNF146 and tankyrase pathway maintains the junctional Crumbs complex through regulation of angiomotin

The Crumbs complex is an important determinant of epithelial apical-basal polarity that functions in regulation of tight junctions, resistance to epithelial-to-mesenchymal transitions and as a tumour suppressor. Although the functional role of the Crumbs complex is being elucidated, its regulation is poorly understood. Here, we show that suppression of RNF146, an E3 ubiquitin ligase that recognizes ADP-ribosylated substrates, and tankyrase, a poly(ADP-ribose) polymerase, disrupts the junctional Crumbs complex and disturbs the function of tight junctions. We show that RNF146 binds a number of polarity-associated proteins, in particular members of the angiomotin (AMOT) family. Accordingly, AMOT proteins are ADP-ribosylated by TNKS2, which drives ubiquitylation by RNF146 and subsequent degradation. Ablation of RNF146 or tankyrase, as well as overexpression of AMOT, led to the relocation of PALS1 (a Crumbs complex component) from the apical membrane to internal puncta, a phenotype that is rescued by AMOTL2 knockdown. We thus reveal a new function of RNF146 and tankyrase in stabilizing the Crumbs complex through downregulation of AMOT proteins at the apical membrane.

Multiple roles for the hippo effector yap in gut regeneration and cancer initiation

The Hippo signaling effector Yes-associated protein (Yap) is known for its potent control of tissue growth. Our recent work now shows that Yap promotes regeneration in the intestine by reprogramming intestinal stem cells and blocking their terminal differentiation. Similarly, in tumor-initiating cells Yap regenerative signaling synergizes with Wnt activation to drive adenoma formation.

A lateral signalling pathway coordinates shape volatility during cell migration

Cell migration is fundamental for both physiological and pathological processes. Migrating cells usually display high dynamics in morphology, which is orchestrated by an integrative array of signalling pathways. Here we identify a novel pathway, we term lateral signalling, comprised of the planar cell polarity (PCP) protein Pk1 and the RhoGAPs, Arhgap21/23. We show that the Pk1–Arhgap21/23 complex inhibits RhoA, is localized on the non-protrusive lateral membrane cortex and its disruption leads to the disorganization of the actomyosin network and altered focal adhesion dynamics. Pk1-mediated lateral signalling confines protrusive activity and is regulated by Smurf2, an E3 ubiquitin ligase in the PCP pathway. Furthermore, we demonstrate that dynamic interplay between lateral and protrusive signalling generates cyclical fluctuations in cell shape that we quantify here as shape volatility, which strongly correlates with migration speed. These studies uncover a previously unrecognized lateral signalling pathway that coordinates shape volatility during productive cell migration.

Migrating cells display dynamic morphologies that are coordinated by signalling pathways. Here the authors identify a lateral signalling pathway, comprised of the planar cell polarity protein Pk1 and Arhgap21/23, that regulates fluctuations in cell shape during productive cell migration.

Seeing is believing: Wnt3 localization in the gut epithelium

Wnt morphogens are notoriously elusive proteins. Thanks to a recent study published in Nature, Clevers and colleagues give us a first glimpse of a mammalian Wnt in action in the gut epithelium.

Disulfiram when Combined with Copper Enhances the Therapeutic Effects of Temozolomide for the Treatment of Glioblastoma

PURPOSE

Glioblastoma is one of the most lethal cancers in humans, and with existing therapy, survival remains at 14.6 months. Current barriers to successful treatment include their infiltrative behavior, extensive tumor heterogeneity, and the presence of a stem-like population of cells, termed brain tumor-initiating cells (BTIC) that confer resistance to conventional therapies.

EXPERIMENTAL DESIGN

To develop therapeutic strategies that target BTICs, we focused on a repurposing approach that explored already-marketed (clinically approved) drugs for therapeutic potential against patient-derived BTICs that encompass the genetic and phenotypic heterogeneity of glioblastoma observed clinically.

RESULTS

Using a high-throughput in vitro drug screen, we found that montelukast, clioquinol, and disulfiram (DSF) were cytotoxic against a large panel of patient-derived BTICs. Of these compounds, disulfiram, an off-patent drug previously used to treat alcoholism, in the presence of a copper supplement, showed low nanomolar efficacy in BTICs including those resistant to temozolomide and the highly infiltrative quiescent stem-like population. Low dose DSF-Cu significantly augmented temozolomide activity in vitro, and importantly, prolonged in vivo survival in patient-derived BTIC models established from both newly diagnosed and recurrent tumors. Moreover, we found that in addition to acting as a potent proteasome inhibitor, DSF-Cu functionally impairs DNA repair pathways and enhances the effects of DNA alkylating agents and radiation. These observations suggest that DSF-Cu inhibits proteasome activity and augments the therapeutic effects of DNA-damaging agents (temozolomide and radiation).

CONCLUSIONS

DSF-Cu should be considered as an adjuvant therapy for the treatment of patients with glioblastoma in both newly diagnosed and recurrent settings. Clin Cancer Res; 22(15); 3860-75. ©2016 AACR.

YAP/TAZ Are Mechanoregulators of TGF-β-Smad Signaling and Renal Fibrogenesis

Like many organs, the kidney stiffens after injury, a process that is increasingly recognized as an important driver of fibrogenesis. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are related mechanosensory proteins that bind to Smad transcription factors, the canonical mediators of profibrotic TGF-β responses. Here, we investigated the role of YAP/TAZ in the matrix stiffness dependence of fibroblast responses to TGF-β In contrast to growth on a stiff surface, fibroblast growth on a soft matrix led to YAP/TAZ sequestration in the cytosol and impaired TGF-β-induced Smad2/3 nuclear accumulation and transcriptional activity. YAP knockdown or treatment with verteporfin, a drug that was recently identified as a potent YAP inhibitor, elicited similar changes. Furthermore, verteporfin reduced YAP/TAZ levels and decreased the total cellular levels of Smad2/3 after TGF-β stimulation. Verteporfin treatment of mice subjected to unilateral ureteral obstruction similarly reduced YAP/TAZ levels and nuclear Smad accumulation in the kidney, and attenuated renal fibrosis. Our data suggest that organ stiffening cooperates with TGF-β to induce fibrosis in a YAP/TAZ- and Smad2/3-dependent manner. Interference with this YAP/TAZ and TGF-β/Smad crosstalk likely underlies the antifibrotic activity of verteporfin. Finally, through repurposing of a clinically used drug, we illustrate the therapeutic potential of a novel mechanointerference strategy that blocks TGF-β signaling and renal fibrogenesis.