Interaction between MED12 and ΔNp63 activates basal identity in pancreatic ductal adenocarcinoma.

The presence of basal lineage characteristics signifies hyperaggressive human adenocarcinomas of the breast, bladder and pancreas. However, the biochemical mechanisms that maintain this aberrant cell state are poorly understood. Here we performed marker-based genetic screens in search of factors needed to maintain basal identity in pancreatic ductal adenocarcinoma (PDAC). This approach revealed MED12 as a powerful regulator of the basal cell state in this disease. Using biochemical reconstitution and epigenomics, we show that MED12 carries out this function by bridging the transcription factor ΔNp63, a known master regulator of the basal lineage, with the Mediator complex to activate lineage-specific enhancer elements. Consistent with this finding, the growth of basal-like PDAC is hypersensitive to MED12 loss when compared to PDAC cells lacking basal characteristics. Taken together, our genetic screens have revealed a biochemical interaction that sustains basal identity in human cancer, which could serve as a target for tumor lineage-directed therapeutics.

Chronic stress increases metastasis via neutrophil-mediated changes to the microenvironment.

Chronic stress is associated with increased risk of metastasis and poor survival in cancer patients, yet the reasons are unclear. We show that chronic stress increases lung metastasis from disseminated cancer cells 2- to 4-fold in mice. Chronic stress significantly alters the lung microenvironment, with fibronectin accumulation, reduced T cell infiltration, and increased neutrophil infiltration. Depleting neutrophils abolishes stress-induced metastasis. Chronic stress shifts normal circadian rhythm of neutrophils and causes increased neutrophil extracellular trap (NET) formation via glucocorticoid release. In mice with neutrophil-specific glucocorticoid receptor deletion, chronic stress fails to increase NETs and metastasis. Furthermore, digesting NETs with DNase I prevents chronic stress-induced metastasis. Together, our data show that glucocorticoids released during chronic stress cause NET formation and establish a metastasis-promoting microenvironment. Therefore, NETs could be targets for preventing metastatic recurrence in cancer patients, many of whom will experience chronic stress due to their disease.

A sub-set of guanine- and cytosine-rich genes are actively transcribed at the nuclear Lamin B1 region.

Chromatin organization in the mammalian cell nucleus plays a vital role in the regulation of gene expression. The lamina-associated domain at the inner nuclear membrane has been proposed to harbor heterochromatin, while the nuclear interior has been shown to contain most of the euchromatin. Here, we show that a sub-set of actively transcribing genes, marked by RNA Pol II pSer2, are associated with Lamin B1 at the inner nuclear envelop in mESCs and the number of genes proportionally increases upon in vitro differentiation of mESC to olfactory precursor cells. These nuclear periphery-associated actively transcribing genes primarily represent housekeeping genes, and their gene bodies are significantly enriched with guanine and cytosine compared to genes actively transcribed at the nuclear interior. We found the promoters of these genes to also be significantly enriched with guanine and to be predominantly regulated by zinc finger protein transcription factors. We provide evidence supporting the emerging notion that the Lamin B1 region is not solely transcriptionally silent.

Identification of glioblastoma stem cell-associated lncRNAs using single-cell RNA sequencing datasets.

Glioblastoma multiforme (GBM) is an aggressive, heterogeneous brain tumor in which glioblastoma stem cells (GSCs) are known culprits of therapy resistance. Long non-coding RNAs (lncRNAs) have been shown to play a critical role in both cancer and normal biology. A few studies have suggested that aberrant expression of lncRNAs is associated with GSCs. However, a comprehensive single-cell analysis of the GSC-associated lncRNA transcriptome has not been carried out. Here, we analyzed recently published single-cell RNA sequencing datasets of adult GBM tumors, GBM organoids, GSC-enriched GBM tumors, and developing human brain samples to identify lncRNAs highly expressed in GSCs. We further revealed that the GSC-specific lncRNAs GIHCG and LINC01563 promote proliferation, migration, and stemness in the GSC population. Together, this study identified a panel of uncharacterized GSC-enriched lncRNAs and set the stage for future in-depth studies to examine their role in GBM pathology and their potential as biomarkers and/or therapeutic targets in GBM.

Allele pairing at Sun1-enriched domains at the nuclear periphery via T1A3 tandem DNA repeats.

Spatiotemporal gene regulation is fundamental to the biology of diploid cells. Therefore, effective communication between two alleles and their geometry in the nucleus is important. However, the mechanism that fine-tunes the expression from each of the two alleles of an autosome is enigmatic. Establishing an allele-specific gene expression visualization system in living cells, we show that alleles of biallelically expressed Cth and Ttc4 genes are paired prior to acquiring monoallelic expression. We found that active alleles of monoallelic genes are preferentially localized at Sun1-enriched domains at the nuclear periphery. These peripherally localized active DNA loci are enriched with adenine-thymidine-rich tandem repeats that interact with Hnrnpd and reside in a Hi-C-defined A compartment within the B compartment. Our results demonstrate the biological significance of T 1 A 3 tandem repeat sequences in genome organization and how the regulation of gene expression, at the level of individual alleles, relates to their spatial arrangement.

Neutrophil extracellular traps formed during chemotherapy confer treatment resistance via TGF-ß activation.

Metastasis is the major cause of cancer death, and the development of therapy resistance is common. The tumor microenvironment can confer chemotherapy resistance (chemoresistance), but little is known about how specific host cells influence therapy outcome. We show that chemotherapy induces neutrophil recruitment and neutrophil extracellular trap (NET) formation, which reduces therapy response in mouse models of breast cancer lung metastasis. We reveal that chemotherapy-treated cancer cells secrete IL-1ß, which in turn triggers NET formation. Two NET-associated proteins are required to induce chemoresistance: integrin-αvß1, which traps latent TGF-ß, and matrix metalloproteinase 9, which cleaves and activates the trapped latent TGF-ß. TGF-ß activation causes cancer cells to undergo epithelial-to-mesenchymal transition and correlates with chemoresistance. Our work demonstrates that NETs regulate the activities of neighboring cells by trapping and activating cytokines and suggests that chemoresistance in the metastatic setting can be reduced or prevented by targeting the IL-1ß-NET-TGF-ß axis.

Establishment and Culture of Patient-Derived Breast Organoids.

Breast cancer is a complex disease that has been classified into several different histological and molecular subtypes. Patient-derived breast tumor organoids developed in our laboratory consist of a mix of multiple tumor-derived cell populations, and thus represent a better approximation of tumor cell diversity and milieu than the established 2D cancer cell lines. Organoids serve as an ideal in vitro model, allowing for cell-extracellular matrix interactions, known to play an important role in cell-cell interactions and cancer progression. Patient-derived organoids also have advantages over mouse models as they are of human origin. Furthermore, they have been shown to recapitulate the genomic, transcriptomic as well as metabolic heterogeneity of patient tumors; thus, they are capable of representing tumor complexity as well as patient diversity. As a result, they are poised to provide more accurate insights into target discovery and validation and drug sensitivity assays. In this protocol, we provide a detailed demonstration of how patient-derived breast organoids are established from resected breast tumors (cancer organoids) or reductive mammoplasty-derived breast tissue (normal organoids). This is followed by a comprehensive account of 3D organoid culture, expansion, passaging, freezing, as well as thawing of patient-derived breast organoid cultures.

Identification of glioblastoma stem cell-associated lncRNAs using single-cell RNA-sequencing datasets.

Glioblastoma multiforme (GBM) is an aggressive, heterogeneous grade IV brain tumor. Glioblastoma stem cells (GSCs) initiate the tumor and are known culprits of therapy resistance. Mounting evidence has demonstrated a regulatory role of long non-coding RNAs (lncRNAs) in various biological processes, including pluripotency, differentiation, and tumorigenesis. A few studies have suggested that aberrant expression of lncRNAs is associated with GSCs. However, a comprehensive single-cell analysis of the GSC-associated lncRNA transcriptome has not been carried out. Here, we analyzed recently published single-cell RNA-sequencing datasets of adult human GBM tumors, GBM organoids, GSC-enriched GBM tumors, and developing human brains to identify lncRNAs highly expressed in GBM. To categorize GSC populations in the GBM tumors, we used the GSC marker genes SOX2, PROM1, FUT4, and L1CAM. We found three major GSC population clusters: radial glia, oligodendrocyte progenitor cells, and neurons. We found 10â€"100 lncRNAs significantly enriched in different GSC populations. We also validated the level of expression and localization of several GSC-enriched lncRNAs using qRT-PCR, single-molecule RNA FISH, and sub-cellular fractionation. We found that the radial glia GSC-enriched lncRNA PANTR1 is highly expressed in GSC lines and is localized to both the cytoplasmic and nuclear fractions. In contrast, the neuronal GSC-enriched lncRNAs LINC01563 and MALAT1 are highly enriched in the nuclear fraction of GSCs. Together, this study identified a panel of uncharacterized GSC-specific lncRNAs. These findings set the stage for future in-depth studies to examine their role in GBM pathology and their potential as biomarkers and/or therapeutic targets in GBM.

Long non-coding RNAs: definitions, functions, challenges and recommendations.

Genes specifying long non-coding RNAs (lncRNAs) occupy a large fraction of the genomes of complex organisms. The term 'lncRNAs' encompasses RNA polymerase I (Pol I), Pol II and Pol III transcribed RNAs, and RNAs from processed introns. The various functions of lncRNAs and their many isoforms and interleaved relationships with other genes make lncRNA classification and annotation difficult. Most lncRNAs evolve more rapidly than protein-coding sequences, are cell type specific and regulate many aspects of cell differentiation and development and other physiological processes. Many lncRNAs associate with chromatin-modifying complexes, are transcribed from enhancers and nucleate phase separation of nuclear condensates and domains, indicating an intimate link between lncRNA expression and the spatial control of gene expression during development. lncRNAs also have important roles in the cytoplasm and beyond, including in the regulation of translation, metabolism and signalling. lncRNAs often have a modular structure and are rich in repeats, which are increasingly being shown to be relevant to their function. In this Consensus Statement, we address the definition and nomenclature of lncRNAs and their conservation, expression, phenotypic visibility, structure and functions. We also discuss research challenges and provide recommendations to advance the understanding of the roles of lncRNAs in development, cell biology and disease.

Testing for Phylogenetic Signal in Single-Cell RNA-Seq Data.

Phylogenetic methods are emerging as a useful tool to understand cancer evolutionary dynamics, including tumor structure, heterogeneity, and progression. Most currently used approaches utilize either bulk whole genome sequencing or single-cell DNA sequencing and are based on calling copy number alterations and single nucleotide variants (SNVs). Single-cell RNA sequencing (scRNA-seq) is commonly applied to explore differential gene expression of cancer cells throughout tumor progression. The method exacerbates the single-cell sequencing problem of low yield per cell with uneven expression levels. This accounts for low and uneven sequencing coverage and makes SNV detection and phylogenetic analysis challenging. In this article, we demonstrate for the first time that scRNA-seq data contain sufficient evolutionary signal and can also be utilized in phylogenetic analyses. We explore and compare results of such analyses based on both expression levels and SNVs called from scRNA-seq data. Both techniques are shown to be useful for reconstructing phylogenetic relationships between cells, reflecting the clonal composition of a tumor. Both standardized expression values and SNVs appear to be equally capable of reconstructing a similar pattern of phylogenetic relationship. This pattern is stable even when phylogenetic uncertainty is taken in account. Our results open up a new direction of somatic phylogenetics based on scRNA-seq data. Further research is required to refine and improve these approaches to capture the full picture of somatic evolutionary dynamics in cancer.

Platr4 is an early embryonic lncRNA that exerts its function downstream on cardiogenic mesodermal lineage commitment.

The mammalian genome encodes thousands of long non-coding RNAs (lncRNAs), many of which are developmentally regulated and differentially expressed across tissues, suggesting their potential roles in cellular differentiation. Despite this expression pattern, little is known about how lncRNAs influence lineage commitment at the molecular level. Here, we demonstrate that perturbation of an embryonic stem cell/early embryonic lncRNA, pluripotency-associated transcript 4 (Platr4), directly influences the specification of cardiac-mesoderm-lineage differentiation. We show that Platr4 acts as a molecular scaffold or chaperone interacting with the Hippo-signaling pathway molecules Yap and Tead4 to regulate the expression of a downstream target gene, Ctgf, which is crucial to the cardiac-lineage program. Importantly, Platr4 knockout mice exhibit myocardial atrophy and valve mucinous degeneration, which are both associated with reduced cardiac output and sudden heart failure. Together, our findings provide evidence that Platr4 is required in cardiac-lineage specification and adult heart function in mice.

Simultaneous visualization of RNA transcripts and proteins in whole-mount mouse preimplantation embryos using single-molecule fluorescence in situ hybridization and immunofluorescence microscopy.

Whole-mount single-molecule RNA fluorescence in situ hybridization (smRNA FISH) in combination with immunofluorescence (IF) offers great potential to study long non-coding RNAs (lncRNAs): their subcellular localization, their interactions with proteins, and their function. Here, we describe a step-by-step, optimized, and robust protocol that allows detection of multiple RNA transcripts and protein molecules in whole-mount preimplantation mouse embryos. Moreover, to simultaneously detect protein and enable RNA probe penetration for the combined IF/smRNA FISH technique, we performed IF before smRNA FISH. We removed the zona pellucida, used Triton X-100 to permeabilize the embryos, and did not use a proteinase digestion step so as to preserve the antigens. In addition, we modified the IF technique by using RNase-free reagents to prevent RNA degradation during the IF procedure. Using this modified sequential IF/smRNA FISH technique, we have simultaneously detected protein, lncRNA, and mRNA in whole-mount preimplantation embryos. This reliable and robust protocol will contribute to the developmental biology and RNA biology fields by providing information regarding 3D expression patterns of RNA transcripts and proteins, shedding light on their biological function.

Allele-specific differential regulation of monoallelically expressed autosomal genes in the cardiac lineage.

Each mammalian autosomal gene is represented by two alleles in diploid cells. To our knowledge, no insights have been made in regard to allele-specific regulatory mechanisms of autosomes. Here we use allele-specific single cell transcriptomic analysis to elucidate the establishment of monoallelic gene expression in the cardiac lineage. We find that monoallelically expressed autosomal genes in mESCs and mouse blastocyst cells are differentially regulated based on the genetic background of the parental alleles. However, the genetic background of the allele does not affect the establishment of monoallelic genes in differentiated cardiomyocytes. Additionally, we observe epigenetic differences between deterministic and random autosomal monoallelic genes. Moreover, we also find a greater contribution of the maternal versus paternal allele to the development and homeostasis of cardiac tissue and in cardiac health, highlighting the importance of maternal influence in male cardiac tissue homeostasis. Our findings emphasize the significance of allele-specific insights into gene regulation in development, homeostasis and disease.

Patient-Derived Triple-Negative Breast Cancer Organoids Provide Robust Model Systems That Recapitulate Tumor Intrinsic Characteristics.

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer with poor patient outcomes, highlighting the unmet clinical need for targeted therapies and better model systems. Here, we developed and comprehensively characterized a diverse biobank of normal and breast cancer patient-derived organoids (PDO) with a focus on TNBCs. PDOs recapitulated patient tumor intrinsic properties and a subset of PDOs can be propagated for long-term culture (LT-TNBC). Single cell profiling of PDOs identified cell types and gene candidates affiliated with different aspects of cancer progression. The LT-TNBC organoids exhibit signatures of aggressive MYC-driven, basal-like breast cancers and are largely comprised of luminal progenitor (LP)-like cells. The TNBC LP-like cells are distinct from normal LPs and exhibit hyperactivation of NOTCH and MYC signaling. Overall, this study validates TNBC PDOs as robust models for understanding breast cancer biology and progression, paving the way for personalized medicine and tailored treatment options. SIGNIFICANCE: A comprehensive analysis of patient-derived organoids of TNBC provides insights into cellular heterogeneity and mechanisms of tumorigenesis at the single-cell level.

Single Oligonucleotide Capture of RNA And Temperature Elution Series ( SOCRATES ) for Identification of RNA-binding Proteins.

The importance of studying the mechanistic aspects of long non-coding RNAs is being increasingly emphasized as more and more regulatory RNAs are being discovered. Non-coding RNA sequences directly associate with generic RNA-binding proteins as well as specific proteins, which cooperate in the downstream functions of the RNA and can also be dysregulated in various physiologic states and/or diseases. While current methods exist for identifying RNA-protein interactions, these methods require high quantities of input cells or use pooled capture reagents that may increase non-specific binding. We have developed a method to efficiently capture specific RNAs using less than one million input cells. One single oligonucleotide is used to pull down the target RNA of choice and oligonucleotide selection is driven by sequence accessibility. We perform thermal elution to specifically elute the target RNA and its associated proteins, which are identified by mass spectrometry. Ultimately, two target and control oligonucleotides are used to create an enrichment map of interacting proteins of interest. This protocol was validated in: eLife (2021), DOI: 10.7554/eLife.68263.

Noncoding RNAs: biology and applications-a Keystone Symposia report.

The human transcriptome contains many types of noncoding RNAs, which rival the number of protein-coding species. From long noncoding RNAs (lncRNAs) that are over 200 nucleotides long to piwi-interacting RNAs (piRNAs) of only 20 nucleotides, noncoding RNAs play important roles in regulating transcription, epigenetic modifications, translation, and cell signaling. Roles for noncoding RNAs in disease mechanisms are also being uncovered, and several species have been identified as potential drug targets. On May 11-14, 2021, the Keystone eSymposium "Noncoding RNAs: Biology and Applications" brought together researchers working in RNA biology, structure, and technologies to accelerate both the understanding of RNA basic biology and the translation of those findings into clinical applications.

Activating a collaborative innate-adaptive immune response to control metastasis.

Tumor-associated macrophages (TAMs) promote metastasis and inhibit T cells, but macrophages can be polarized to kill cancer cells. Macrophage polarization could thus be a strategy for controlling cancer. We show that macrophages from metastatic pleural effusions of breast cancer patients can be polarized to kill cancer cells with monophosphoryl lipid A (MPLA) and interferon (IFN) γ. MPLA + IFNγ injected intratumorally or intraperitoneally reduces primary tumor growth and metastasis in breast cancer mouse models, suppresses metastasis, and enhances chemotherapy response in an ovarian cancer model. Both macrophages and T cells are critical for the treatment's anti-metastatic effects. MPLA + IFNγ stimulates type I IFN signaling, reprograms CD206+ TAMs to inducible NO synthase (iNOS)+ macrophages, and activates cytotoxic T cells through macrophage-secreted interleukin-12 (IL-12) and tumor necrosis factor alpha (TNFα). MPLA and IFNγ are used individually in clinical practice and together represent a previously unexplored approach for engaging a systemic anti-tumor immune response.

PHAROH lncRNA regulates Myc translation in hepatocellular carcinoma via sequestering TIAR.

Hepatocellular carcinoma, the most common type of liver malignancy, is one of the most lethal forms of cancer. We identified a long non-coding RNA, Gm19705, that is overexpressed in hepatocellular carcinoma and mouse embryonic stem cells. We named this RNA Pluripotency and Hepatocyte Associated RNA Overexpressed in HCC, or PHAROH. Depletion of PHAROH impacts cell proliferation and migration, which can be rescued by ectopic expression of PHAROH. RNA-seq analysis of PHAROH knockouts revealed that a large number of genes with decreased expression contain a Myc motif in their promoter. MYC is decreased in knockout cells at the protein level, but not the mRNA level. RNA-antisense pulldown identified nucleolysin TIAR, a translational repressor, to bind to a 71-nt hairpin within PHAROH, sequestration of which increases MYC translation. In summary, our data suggest that PHAROH regulates MYC translation by sequestering TIAR and as such represents a potentially exciting diagnostic or therapeutic target in hepatocellular carcinoma.

MaTAR25: a long non-coding RNA involved in breast cancer progression.

We recently reported on the role of Mammary Tumor Associated RNA 25 (MaTAR25) in mammary tumor cell proliferation, migration, and invasion. MaTAR25 interacts with transcriptional activator protein Pur-beta (Purb) to regulate its downstream targets such as Tensin1 in trans. The human ortholog of MaTAR25, LINC01271, is upregulated with human breast cancer stage and metastasis.

MaTAR25 lncRNA regulates the Tensin1 gene to impact breast cancer progression.

Misregulation of long non-coding RNA (lncRNA) genes has been linked to a wide variety of cancer types. Here we report on Mammary Tumor Associated RNA 25 (MaTAR25), a nuclear enriched and chromatin associated lncRNA that plays a role in mammary tumor cell proliferation, migration, and invasion, both in vitro and in vivo. MaTAR25 functions by interacting with purine rich element binding protein B (PURB), and associating with a major downstream target gene Tensin1 (Tns1) to regulate its expression in trans. The Tns1 protein product is a critical component of focal adhesions linking signaling between the extracellular matrix and the actin cytoskeleton. Knockout of MaTAR25 results in down-regulation of Tns1 leading to a reorganization of the actin cytoskeleton, and a reduction of focal adhesions and microvilli. We identify LINC01271 as the human ortholog of MaTAR25, and importantly, increased expression of LINC01271 is associated with poor patient prognosis and metastasis. Our findings demonstrate that LINC01271 represents a potential therapeutic target to alter breast cancer progression.