Biology subjects

Wang, R.

Publications and source records attributed to Wang, R..

At least 433 records · Page 24Linked to original sources

bioRxiv2021

Stiffness Regulates Intestinal Stem Cell Fate

Does fibrotic gut stiffening caused by inflammatory bowel diseases (IBD) direct the fate of intestinal stem cells (ISCs)? To address this question we first developed a novel long-term culture of quasi-3D gut organoids plated on hydrogel matrix of varying stiffness. Stiffening from 0.6kPa to 9.6kPa significantly reduces Lgr5high ISCs and Ki67+ progenitor cells while promoting their differentiation towards goblet cells. These stiffness-driven events are attributable to YAP nuclear translocation. Matrix stiffening also extends the expression of the stemness marker Olfactomedin 4 (Olfm4) into villus-like regions, mediated by cytoplasmic YAP. We next used single-cell RNA sequencing to generate for the first time the stiffness-regulated transcriptional signatures of ISCs and their differentiated counterparts. These signatures confirm the impact of stiffening on ISC fate and additionally suggest a stiffening-induced switch in metabolic phenotype, from oxidative phosphorylation to glycolysis. Finally, we used colon samples from IBD patients as well as chronic colitis murine models to confirm the in vivo stiffening-induced epithelial deterioration similar to that observed in vitro. Together, these results demonstrate stiffness-dependent ISC reprograming wherein YAP nuclear translocation diminishes ISCs and Ki67+ progenitors and drives their differentiation towards goblet cells, suggesting stiffening as potential target to mitigate gut epithelial deterioration during IBD.

cell biology↗

bioRxiv2021

Bacteriophage inhibits murine norovirus replication after co-incubation in RAW 264.7 cells

Bacteriophages (phages) are viruses of bacteria. Despite the growing progress in research on phage interactions with eukaryotic cells, our understanding of the roles of phages and their potential implications remains incomplete. The objective of this study was to investigate the effects of the Staphylococcus aureus phage vB_SauM_JS25 on murine norovirus (MNV) replication. Experiments were performed using the RAW 264.7 cell line. After phage treatment, MNV multiplication was significantly inhibited, as indicated by real-time quantitative PCR (RT-qPCR) analysis, western blot, and immunofluorescence assay. Furthermore, we demonstrated the transcriptional changes in phage-MNV co-incubated RAW 264.7 cells through RNA sequencing (RNA-Seq) and bioinformatic analysis. Our subsequent analyses revealed that the innate immune response may play an important role in the restriction of MNV replication, such as the cellular response to IFN-{gamma} and response to IFN-{gamma}. In addition, the gene expression of IL-10, Arg-1, Ccl22, GBP2, GBP3, GBP5, and GBP7 was proven to increase significantly by RT-qPCR, showing a strong correlation between RT-qPCR and RNA-Seq results. Furthermore, phage treatment activated guanylate binding proteins (GBPs), as revealed by RT-qPCR analysis, western blotting, and confocal microscopy. Taken together, these data suggest that the phage affects the innate response (such as the IFN-inducible GTPases and GBPs), reflecting their direct antimicrobial effect on the membrane structure of the MNV replication complexes, and therefore, exerts an antiviral effect in vitro. Collectively, our findings provide insights into the interactions of immune cells and phages, which improve our understanding of the actual role and potential of phages.

microbiology↗

bioRxiv2021

In vitro rapid inactivation of SARS-CoV-2 by visible light photocatalysis using boron-doped bismuth oxybromide

Inactivation of SARS-CoV-2 in wastewater and on surfaces is critical to prevent the fecal-oral and fomite transmission, respectively. We hypothesized that visible light active photocatalysts could dramatically enhance the rate or extent of virus inactivation and enable the use of visible light rather than shorter wavelength ultraviolet light. A novel visible light active photocatalyst, boron-doped bismuth oxybromide (B-BiOBr), was synthesized and tested for its SARS-CoV-2 inactivation towards Vero E6 cell lines in dark and under irradiation at 426 nm by a light emitting diode (LED) in water. SARS-CoV-2 inactivation in the presence of B-BiOBr (0.8 g/L) under LED irradiation reached 5.32-log in 5 min, which was 400 to 10,000 times higher than those achieved with conventional photocatalysts of tungsten or titanium oxide nanomaterials, respectively. Even without LED irradiation, B-BiOBr inactivated 3.32-log of SARS-CoV-2 in the dark due to the ability of bismuth ions interfering with the SARS-CoV-2 helicase function. LED irradiation at 426 nm alone, without the photocatalyst, contributed to 10% of the observed inactivation and was attributed to production of reactive oxygen species due to blue-light photoexcitation of molecules in the culture media, which opens further modes of action to engineer disinfection strategies. The visible light active B-BiOBr photocatalyst, with its rapid SARS-CoV-2 inactivation in the presence and absence of light, holds tremendous opportunities to build a healthy environment by preventing the fecal-oral and fomite transmission of emerging pathogens.

bioengineering↗

bioRxiv2021

Spike mutations in SARS-CoV-2 variants confer resistance to antibody neutralization

New SARS-CoV-2 variants continue to emerge from the current global pandemic, some of which can replicate faster and with greater transmissibility and pathogenicity. In particular, UK501Y.V1 identified in UK, SA501Y.V2 in South Africa, and BR501Y.V3 in Brazil are raising serious concerns as they spread quickly and contain spike protein mutations that may facilitate escape from current antibody therapies and vaccine protection. Here, we constructed a panel of 28 SARS-CoV-2 pseudoviruses bearing single or combined mutations found in the spike protein of these three variants, as well as additional nine mutations that within or close by the major antigenic sites in the spike protein identified in the GISAID database. These pseudoviruses were tested against a panel of monoclonal antibodies (mAbs), including some approved for emergency use to treat SARS-CoV-2 infection, and convalescent patient plasma collected early in the pandemic. SA501Y.V2 pseudovirus was the most resistant, in magnitude and breadth, against mAbs and convalescent plasma, followed by BR501Y.V3, and then UK501Y.V1. This resistance hierarchy corresponds with Y144del and 242-244del mutations in the N-terminal domain as well as K417N/T, E484K and N501Y mutations in the receptor binding domain (RBD). Crystal structural analysis of RBD carrying triple K417N-E484K-N501Y mutations found in SA501Y.V2 bound with mAb P2C-1F11 revealed a molecular basis for antibody neutralization and escape. SA501Y.V2 and BR501Y.V3 also acquired substantial ability to use mouse and mink ACE2 for entry. Taken together, our results clearly demonstrate major antigenic shifts and potentially broadening the host range of SA501Y.V2 and BR501Y.V3, which pose serious challenges to our current antibody therapies and vaccine protection.

immunology↗

bioRxiv2021

Cinnamoyl-CoA Reductase 1 (CCR1) and CCR2 Function Divergently in Tissue Lignification, Flux Control and Cross-talk with Glucosinolate Pathway in Brassica napus

Cinnamoyl-CoA reductase (CCR) is the entry point of lignin pathway and a crucial locus in dissection and manipulation of associated traits, but its functional dissection in Brassicaceae plants is largely lagged behind though Arabidopsis thaliana CCR1 has been characterized to certain extent. Here, 16 CCR genes are identified from Brassica napus and its parental species B. rapa and B. oleracea. Brassicaceae CCR genes are divided into CCR1 subfamily and CCR2 subfamily with divergent organ-specificity, yellow-seed trait participation and stresses responsiveness. CCR1 is preferential in G- and H-lignins biosynthesis and vascular development, while CCR2 has a deviation to S-lignin biosynthesis and interfascicular fiber development. CCR1 has stronger effects on lignification-related development, lodging resistance, phenylpropanoid flux control and seed coat pigmentation, whereas CCR2 controls sinapates levels. CCR1 upregulation could delay bolting and flowering time, while CCR2 upregulation weakens vascular system in leaf due to suppressed G lignin accumulation. Besides, CCR1 and CCR2 are deeply but almost oppositely linked with glucosinolates metabolism through inter-pathway crosstalk. Strangely, upregulation of both CCR1 and CCR2 could not enhance resistance to UV-B and S. sclerotiorum though CCR2 is sharply induced by them. These results provide systemic dissection on Brassica CCRs and CCR1-CCR2 divergence in Brassicaceae. HighlightBrassicaceae contains two types of Cinnamoyl-CoA reductase. As revealed in Brassica napus, they are divergently involved in lignin monomer biosynthesis, tissue lignification, phenylpropanoid flux control, and inter-pathway crosstalk with glucosinolates.

plant biology↗

bioRxiv2021

Apoptotic Extracellular Vesicles (ApoEVs) Safeguard Liver Homeostasis and Regeneration via Assembling an ApoEV-Golgi Organelle

Apoptosis is an integral physiological cell death process that occurs frequently and generates a huge number of apoptotic extracellular vesicles (apoEVs). However, whether apoEVs are necessary for maintaining organ homeostasis remains unclear. Here, we show that circulatory apoEVs engraft in liver and undergo specialized internalization by hepatocytes (HCs) based on surface signature of galactose and N-acetylgalactosamine. Furthermore, apoEVs rescue liver injury in apoptotic-deficient Fas mutant and Caspase-3 knockout mice, which is exerted by restoring the featured hepatic ploidy homeostasis. Surprisingly, apoEVs form a chimeric organelle complex with recipient Golgi apparatus via SNARE-mediated membrane interaction, which consequently facilitates microtubule organization and HC cytokinesis. Notably, through Golgi recovery and ploidy transition, apoEVs contribute to liver regeneration and protect against acute hepatic failure. Collectively, these results identify a previously unrecognized role for apoEVs and the specific mechanisms by which they safeguard liver homeostasis, and suggest the potential of apoEV-based therapy for liver disorders.

cell biology↗

bioRxiv2021

SENP1 in the retrosplenial agranular cortex regulates core autistic-like symptoms in mice

Autism spectrum disorder (ASD) is a highly heritable neurodevelopmental disorder, in which core symptoms are defects of social interaction and evidently repetitive behaviors. Although around 50-70 % of ASD patients have comorbidity of intellectual disabilities (ID) or developmental delay (DD), there are some ASD patients who exhibit only core symptoms but without ID/DD, raising the question whether there are genetic components and neural circuits specific for core symptoms of ASD. Here, by focusing on ASD patients who do not show compound ID or DD, we identified a de novo heterozygous gene-truncating mutation of the Sentrin-specific peptidase1 (SENP1) gene, coding the small ubiquitin-like modifiers (SUMO) deconjugating enzyme, as a potentially new candidate gene for ASD. We found that Senp1 haploinsufficient mice exhibited core symptoms of autism such as deficits in social interaction and repetitive behaviors, but normal learning and memory ability. Moreover, we found that the inhibitory and excitatory synaptic functions were severely affected in the retrosplenial agranular (RSA) cortex of Senp1 haploinsufficient mice. Lack of Senp1 led to over SUMOylation and degradation of fragile X mental retardation protein (FMRP) proteins, which is coded by the FMR1 gene, also implicated in syndromic ASD. Importantly, re-introducing SENP1 or FMRP specifically in RSA fully rescued the defects of synaptic functions and core autistic-like symptoms of Senp1 haploinsufficient mice. Together, these results demonstrated that disruption of the SENP1-FMRP regulatory axis in the RSA may cause core autistic symptoms, which provide a candidate brain region of ASD for potential therapeutic intervene by neural modulation approaches.

neuroscience↗

bioRxiv2021

Ubiquitination and degradation of NF90 by Tim-3 inhibits antiviral innate immunity

Nuclear Factor 90 (NF90) is a novel virus sensor that serves to initiate antiviral innate immunity by triggering the stress granules (SGs) formation. However, the regulation of the NF90-SGs pathway remain largely unclear. We found that Tim-3, an immune checkpoint inhibitor, promotes the ubiquitination and degradation of NF90 and inhibits NF90-SGs mediated antiviral immunity. Vesicular Stomatitis Virus (VSV) infection induces the up-regulation and activation of Tim-3 in macrophages which in turn recruited the E3 ubiquitin ligase TRIM47 to the zinc finger domain of NF90 and initiated a proteasome-dependent degradation of the NF90 via K48-linked ubiquitination at Lys297. Targeted inactivation of the Tim-3 enhances the NF90 downstream SGs formation by selectively increasing the phosphorylation of PKR and eIF2a, the expression of SGs markers G3BP1 and TIA-1, and protected mice from lethal VSV challenge. These findings provide insights into the crosstalk between Tim-3 and other receptors in antiviral innate immunity and its related clinical significance.

immunology↗

bioRxiv2021

Natural variations in the P-type ATPase heavy metal transporter ZmCd1 controlling cadmium accumulation in maize grains

Cadmium (Cd) accumulation in maize grains is detrimental to human health. Developing maize varieties with low-Cd contents via marker-assisted selection is important for ensuring the production of maize grains safe for consumption. However, the key gene controlling maize grain Cd accumulation has not been cloned. In this study, we identified two major loci for maize grain Cd accumulation (qCd1 and qCd2) on chromosome 2 during a genome-wide association study (GWAS). The qCd1 locus was analyzed by bulked segregant RNA-seq and fine mapping with a biparental segregating population of Jing724 (low-Cd line) and Mo17 (high-Cd line). The ZmCd1 candidate gene in the qCd1 locus encodes a vacuolar membrane-localized heavy metal P-type ATPase transporter, ZmHMA3, which is orthologous to the tonoplast Cd transporter OsHMA3. Genomic DNA sequence and transcript analyses suggested that a transposon in intron 1 of ZmCd1 is responsible for the abnormal amino acid sequence in Mo17. An EMS mutant analysis and an allelism test confirmed ZmCd1 influences maize grain Cd accumulation. The natural variations in ZmCd1 were used to develop four PCR-based molecular markers, which revealed five ZmCd1 haplotypes in the GWAS population. The molecular markers were also used to predict the grain Cd contents in commonly cultivated maize germplasms in China. The predicted Cd contents for 36 inbred lines and 13 hybrids were consistent with the measured Cd contents. Furthermore, several low-Cd elite inbred lines and hybrids were identified, including Jing2416, MC01, Jingnonke728, and Jingke968. Therefore, the molecular markers developed in this study are applicable for molecular breeding and developing maize varieties with low grain Cd contents.

plant biology↗

bioRxiv2021

Role of the mobilome in the global dissemination of the carbapenem resistance gene blaNDM

The mobile resistance gene blaNDM encodes the NDM enzyme which hydrolyses carbapenems, a class of antibiotics used to treat some of the most severe bacterial infections. blaNDM is globally distributed across a variety of Gram-negative bacteria on multiple plasmids, typically located within a highly recombining and transposon-rich genomic region. This complexity means the dynamics underlying the dissemination of blaNDM remain poorly resolved. In this work, we compile a dataset of over 6000 bacterial genomes harbouring the blaNDM gene including 104 newly generated PacBio hybrid assemblies from clinical and livestock associated isolates across China. We develop a novel computational approach to track structural variants surrounding blaNDM in bacterial genomes. This allows us to identify the prevalent genomic contexts of blaNDM and reconstruct the key mobile genetic elements and events in its global spread. We estimate that blaNDM emerged on a Tn125 transposon before 1985 but only reached a global prevalence around a decade after its first recorded observation in 2005. We find that the Tn125 transposon played an important role in early plasmid-mediated jumps of blaNDM but was overtaken by other elements in recent years including IS26-flanked pseudo-composite transposons and Tn3000. Lastly, we observe a notable correlation between plasmid backbones bearing blaNDM and the sampling location of isolates. This observation suggests that the dissemination of resistance genes is mainly driven by successive between-plasmid transposon jumps, with plasmid exchange much more restricted due to the adaptation of plasmids to specific bacterial hosts.

microbiology↗

bioRxiv2020

Human Polyomavirus-Encoded Circular RNAs

Circular RNAs (circRNAs) are a conserved class of RNAs with diverse functions. A subset of circRNAs are translated into peptides. Here we describe circular RNAs encoded by human polyomaviruses (HPyVs), including circular forms of RNAs encoding variants of the previously described alternative large T antigen open reading frame (ALTO) gene. Circular ALTO RNAs (circALTOs) can be detected in virus positive Merkel cell carcinoma (VP-MCC) cell lines and tumor samples. CircALTOs are stable, predominantly located in the cytoplasm, and N6-methyladenosine (m6A) modified. MCPyV circALTOs produce ALTO protein in cultured cells. MCPyV ALTO promotes the transcription of co-transfected reporter genes. MCPyV circALTOs are enriched in exosomes derived from VP-MCC lines and circALTO-transfected 293T cells, and purified exosomes can mediate ALTO expression and transcriptional activation. The related trichodysplasia spinulosa polyomavirus (TSPyV) also expresses a circALTO that can be detected in infected tissues and produces ALTO protein in cultured cells. Thus, human polyomavirus circRNAs are expressed in human tumors and tissues, encode for proteins, and may contribute to the infectious and tumorigenic properties of these viruses.

molecular biology↗

bioRxiv2020

Precise Regulation and Site-specifically Covalent Labeling of NSUN2 Enable by Genetic Encoding Expansion

RNA plays a critical role in gene expression regulation, cell migration, differentiation, cell death in living organism. 5-Methylcytosine is a post transcriptional RNA modification identified across wide ranges of RNA species including message RNAs. It is reported the addition of m5C to RNA cytosines is enabled by use of NSUN family enzyme, NSUN2 is identified as a critical RNA methyltransferase for adding m5C to mRNA. We demonstrated here that natural lysines modified with special groups were synthesized via chemical synthesis. Through two rounds of positive screening and one round of negative screening, MbPylRS-tRNAcua unnatural lysine substitution system which can specifically recognize lysine with defined group was evaluated and identified. Non-natural lysine substitution at C271 of NSUN2 active site and subsequently fluorescent labeling was realized via so-called click reaction. The function of NSUN2 mutant and its upregulated CDK1 gene and its effect on cell proliferation were also evaluated.

molecular biology↗

bioRxiv2020

Integrating thermodynamic and enzymatic constraints into genome-scale metabolic models

Stoichiometric genome-scale metabolic network models (GEMs) have been widely used to predict metabolic phenotypes. In addition to stoichiometric ratios, other constraints such as enzyme availability and thermodynamic feasibility can also limit the phenotype solution space. Extended GEM models considering either enzymatic or thermodynamic constraints have been shown to improve prediction accuracy. In this paper, we propose a novel method that integrates both enzymatic and thermodynamic constraints in a single Pyomo modeling framework (ETGEMs). We applied this method to construct the EcoETM, the E. coli metabolic model iML1515 with enzymatic and thermodynamic constraints. Using this model, we calculated the optimal pathways for cellular growth and the production of 22 metabolites. When comparing the results with those of iML1515 and models with one of the two constraints, we observed that many thermodynamically unfavorable and/or high enzyme cost pathways were excluded from EcoETM. For example, the synthesis pathway of carbamoyl-phosphate (Cbp) from iML1515 is both thermodynamically unfavorable and enzymatically costly. After introducing the new constraints, the production pathways and yields of several Cbp-derived products (e.g. L-arginine, orotate) calculated using EcoETM were more realistic. The results of this study demonstrate the great application potential of metabolic models with multiple constraints for pathway analysis and phenotype predication.

bioinformatics↗

bioRxiv2020

High throughput functional screening for next generation cancer immunotherapy using droplet-based microfluidics

Currently high throughput approaches are lagged for isolation of antibodies whose function goes beyond simple binding, which have prevented the next generation cancer immunotherapeutics, such as bispecific T cell engager antibodies or agonist antibody of costimulatory receptor, from reaching their full potential. Here we developed a highly efficient droplet-based microfluidics platform combining with lentivirus transduction system that enables functional screening of millions of antibodies. To showcase the capacity of the system, functional antibodies for CD40 agonism with low frequency (<0.02%) were identified with 2 rounds of screening. To demonstrate its versatility, an anti-Her2/anti-CD3 bispecific antibody library was established using bispecific T cell Engager (BiTE) platform and functional screening enabled efficient identification of potent anti-Her2/anti-CD3 BiTE antibodies. The platform could revolutionize the next generation cancer immunotherapy drug development and research world.

cancer biology↗

bioRxiv2020

Cancer cells are sensitive to wild-type IDH1 inhibition under nutrient limitation

Pancreatic cancer cells alter their metabolism to survive cancer-associated stress (1-4). For example, cancer cells must adapt to steep nutrient gradients that characterize the natural tumor microenvironment (TME) (5-7). In the absence of adaptive strategies, harsh metabolic conditions promote the generation of free radicals (8) and impair energy production in tumor cells. Towards this end, wild-type isocitrate dehydrogenase 1 (IDH1) activity is a metabolic requirement for cancer cells living in a harsh metabolic milieu. The cytosolic enzyme interconverts isocitrate and alpha-ketoglutarate, and uses NADP(H) as a cofactor. We show that under low nutrient conditions, the enzymatic reaction favors oxidative decarboxylation to yield NADPH and alpha-ketoglutarate. Metabolic studies showed that the IDH1 products directly support antioxidant defense and mitochondrial function in stressed cancer cells. Genetic IDH1 suppression reduced growth of pancreatic cancer cells in vitro under low nutrient conditions and in mouse models of pancreatic cancer. Surprisingly, allosteric inhibitors of mutant IDH1 proved to be potent wild-type IDH1 inhibitors under conditions specific to the TME, highlighting a natural therapeutic window. The presence of low magnesium enhanced allosteric inhibition by the drug, and ambient low glucose levels enhanced cancer cells dependence on wild-type IDH1. Thus, intrinsic TME conditions sensitized wild-type IDH1 to FDA-approved AG-120 (ivosidenib), and revealed the drug to be a potent single-agent therapeutic in cell culture and diverse in vivo cancer models. This work identified a potentially new repertoire of safe cancer therapies, including a clinically available compound, for the treatment of multiple wild-type IDH1 cancers (e.g., pancreatic).

cancer biology↗

bioRxiv2020

Developing a broadly applicable pyrF-based genetic manipulation system in Acinetobacter baumannii

Acinetobacter baumannii is an emergency pathogenic bacterium for its multidrug-resistance and high mortality rates after infection. In-depth genetic analysis of A. baumannii virulence and drug-resistant genes is highly desirable. Existing methods for genetic manipulation of A. baumannii mainly rely on the use of antibiotic as the selectable marker, and the sacB/sucrose as the counter-selectable marker, which is inconvenient and inappropriate for all research of A. baumannii. Based on the highly conserved pyrF gene and its conserved 500bp-flanking sequence, we quickly and easily generated the pyrF-deleted mutants as the uracil auxotrophic host strain in three model strains and 11 clinical strains. The pyrF-carried vectors constructed for gene editing with pyrF/5-FOA as the counter-selection were conveniently and time-saving in these pyrF-deleted mutants. Utilizing the pyrF-based genetic manipulation system, we easily and efficiently modified the cas gene and CRISPR sequence of I-F CRISPR-Cas system in A. baumannii AYE, and detected the CRISPR interference and adaptation in these mutants. In summary, the pyrF-based genetic manipulation system could be broadly applicable used for efficiently maker-less gene editing in most A. baumannii strains.

microbiology↗

bioRxiv2020

The epithelial-mesenchymal transcription factor SNAI1 represses transcription of the tumor suppressor miRNA let-7 in cancer

We aimed to determine the mechanism of epithelial-mesenchymal transition (EMT)-induced stemness in cancer cells. Cancer relapse and metastasis are caused by rare stem-like cells within tumors. Studies of stem cell reprogramming have linked let-7 repression and acquisition of stemness with the EMT factor, SNAI1. The mechanisms for the loss of let-7 in cancer cells are incompletely understood. In four carcinoma cell lines from breast cancer, pancreatic cancer and ovarian cancer and in ovarian cancer patient-derived cells, we analyzed stem cell phenotype and tumor growth via mRNA, miRNA, and protein expression, spheroid formation, and growth in patient-derived xenografts. We show that treatment with EMT-promoting growth factors or SNAI1 overexpression increased stemness and reduced let-7 expression, while SNAI1 knockdown reduced stemness and restored let-7 expression. Rescue experiments demonstrate that the pro-stemness effects of SNAI1 are mediated via let-7. In vivo, nanoparticle-delivered siRNA successfully knocked down SNAI1 in orthotopic patient-derived xenografts, accompanied by reduced stemness and increased let-7 expression, and reduced tumor burden. Chromatin immunoprecipitation demonstrated that SNAI1 binds the promoters of various let-7 family members, and luciferase assays revealed that SNAI1 represses let-7 transcription. In conclusion, the SNAI1/let-7 axis is an important component of stemness pathways in cancer cells, and this study provides a rationale for future work examining this axis as a potential target for cancer stem cell-specific therapies. Novelty and ImpactThis study provides new insight into molecular mechanisms by which EMT transcription factor SNAI1 exerts its pro-stemness effects in cancer cells, demonstrating its potential as a stem cell-directed target for therapy. In vitro and in vivo, mesoporous silica nanoparticle-mediated SNAI1 knockdown resulted in restoration of let-7 miRNA, inhibiting stemness and reducing tumor burden. Our studies validate in vivo nanoparticle-delivered RNAi targeting the SNAI1/let-7 axis as a clinically relevant approach.

cancer biology↗

bioRxiv2020

In vivo optical metabolic imaging of long-chain fatty acid uptake in orthotopic models of triple negative breast cancer

Targeting a tumors metabolic dependencies is a clinically actionable therapeutic approach, but identifying subtypes of tumors likely to respond remains difficult. The use of lipids as a nutrient source is of particular importance, especially in breast cancer. Imaging techniques offer the opportunity to quantify nutrient use in preclinical models to aid in the development of new drugs to restrict uptake or utilization of these nutrients. We describe a fast and dynamic approach to image fatty acid uptake in vivo, a tool relevant to study tumor metabolic reprogramming or for studying the effectiveness of drugs targeting lipid metabolism spanning beyond breast cancer and optical imaging alone. Specifically, we developed a quantitative optical approach to spatially and longitudinally map the kinetics of long-chain fatty acid uptake in in vivo murine models of breast cancer using a fluorescently labeled palmitate molecule, Bodipy FL c16. We chose intra-vital microscopy of mammary tumor windows to validate our approach in two orthotopic breast cancer models: a MYC-overexpressing transgenic triple-negative breast cancer (TNBC) model and a murine model of the 4T1 family. Following injection, Bodipy FL c16 fluorescence increased and reached its maximum after approximately 30 minutes, with the signal remaining stable during the 30-80-minute post-injection period. We used the fluorescence at 60 minutes (Bodipy60), the mid-point in the plateau region, as a summary parameter to quantify Bodipy FL c16 fluorescence in subsequent experiments. Using our imaging platform, we observed a two- to four-fold decrease in fatty acid uptake in response to the downregulation of the MYC oncogene consistent with findings from in vitro metabolic assays. In contrast, our imaging studies report an increase in fatty acid uptake with tumor aggressiveness (6NR, 4T07, and 4T1), and uptake was significantly decreased after treatment with a fatty acid transport inhibitor, perphenazine, in both normal mammary pads and in the most aggressive 4T1 tumor model. Our approach fills an important gap between in vitro assays, which provide rich metabolic information but at static time points, and imaging approaches that can visualize metabolism in whole organs, but which suffer from poor resolution.

bioengineering↗