Mature miRNAs Research Articles

Selective arm-usage of pre-miR-1307 dysregulates angiogenesis and affects breast cancer aggressiveness

BackgroundBreast cancer is the leading cause of cancer-related mortality in women. Deregulation of miRNAs is frequently observed in breast cancer and affects tumor biology. A pre-miRNA, such as pre-miR-1307, gives rise to several mature miRNA molecules with distinct functions. However, the impact of global deregulation of pre-miR-1307 and its individual mature miRNAs in breast cancer has not been investigated in breast cancer, yet.ResultsHere, we found significant upregulation of three mature miRNA species derived from pre-miR-1307 in human breast cancer tissue. Surprisingly, the overexpression of pre-miR-1307 in breast cancer cell lines resulted in reduced xenograft growth and impaired angiogenesis. Mechanistically, overexpression of miR-1307-5p altered the secretome of breast cancer cells and reduced endothelial cell sprouting. Consistently, expression of miR-1307-5p was inversely correlated with endothelial cell fractions in human breast tumors pointing at an anti-angiogenic role of miR-1307-5p. Importantly, the arm usage of miR-1307 and other miRNAs was highly correlated, which suggests an undefined common regulatory mechanism.ConclusionsIn summary, miR-1307-5p reduces angiogenesis in breast cancer, thereby antagonizing the oncogenic effects of miR-1307-3p. Our results emphasize the importance of future research on the regulation of miRNA arm selection in cancer. The underlying mechanisms might inspire new therapeutic strategies aimed at shifting the balance towards tumor-suppressive miRNA species.Graphical

Promising Biotechnological Applications of the Artificial Derivatives Designed and Constructed from Plant microRNA Genes

MicroRNAs (miRNAs) are small regulatory RNAs that are expressed in a tissue-specific manner during the development of plants and animals. The genes of miRNAs have been found to produce the following two products: (i) primary transcripts of these genes (pri-miRNA) are processed to give rise to mature miRNA, and (ii) in some cases, the pri-miRNA molecules can be translated to form small peptides, named as miPEPs. Gene silencing by artificial microRNAs (amiRNAs) is one of the potential crucial methods for the regulation of desired genes to improve horticultural plants. Likewise, external application of chemically synthesized miPEPs may help plants to resist biotic/abiotic stresses and grow faster. These potent and reliable derivatives of miRNA genes can be applied for improving useful traits in crop plants. This review summarizes the progress in research on the artificial gene derivatives involved in regulating plant development, virus and pest diseases, and abiotic stress resistance pathways. We also briefly discuss the molecular mechanisms of relevant target genes for future research on breeding in plants. In general, this review may be useful to researchers who are implementing amiRNA and miPEP for accelerating breeding programs and developmental studies in crop plants.

Targeting the Hh and Hippo pathways by miR-7 suppresses the development of insect wings.

Wings are important organs of insects involved in flight, mating, and other behaviors, and are therefore prime targets for pest control. The formation of insect wings is a complex process that is regulated by multiple pathways. The Hedgehog (Hh) pathway regulates the distribution of wing veins, while the Hippo pathway modulates wing size. Any interventions that can manipulate these pathways have the potential to disrupt wing development and could be used for pest control. In this study, we find that overexpression of miR-7 in Drosophila results in smaller wings with disordered veins. Mechanistically, miR-7 directly targets both ci and yki via different mature miRNAs (miR-7-5p and miR-7-3p), thereby disrupting the Hh and Hippo pathways. Importantly, this regulatory mechanism is also observed in another insect species, Helicoverpa armigera. Finally, by utilizing a nanocarrier delivery system, we show that introducing miR-7 via star polycation (SPc) leads to wing defects in H.armigera. In conclusion, these findings uncover that miR-7 inhibits wing formation by targeting both the Hippo and Hh pathways, indicating its potential for use in pest control strategies.

Hsa-miR-548d-3p: a potential microRNA to target nucleocapsid and/or capsid genes in multiple members of the Flaviviridae family.

Flaviviridae comprise a group of enveloped, positive-stranded RNA viruses that are mainly transmitted through either mosquitoes or tick bites and/or contaminated blood, blood products, or other body secretions. These viruses cause diseases ranging from mild to severe and are considered important human pathogens. MicroRNAs (miRNAs) are non-coding molecules involved in growth, development, cell proliferation, protein synthesis, apoptosis, and pathogenesis. These small molecules are even being used as gene suppressors in antiviral therapeutics, inhibiting viral replication. In the current study, we used bioinformatic tools to predict a possible miRNA sequence that could be complementary to the nucleocapsid (NP) and/or capsid (CP) gene of the Flaviviridae family and provide an inhibitory solution. Bioinformatics is a field of science that includes tremendous computational analysis, logarithms, and sequence alignments. To predict the right alignments between miRNA and viral mRNA genomes, we used computational databases such as miRBase, NCBI, and Basic Alignment Search Tool-nucleotides (BLAST-n). Of the 2,600 mature miRNAs, hsa-miR-548d-3p revealed complementary sequences with the flavivirus capsid gene and bovine viral diarrhea virus (BVDV) capsid gene and was selected as a possible candidate to inhibit flaviviruses. Although more detailed in vitro and in vivo studies are required to test the possible inhibitory effects of hsa-miR-548d-3p against flaviviruses, this computational study may be the first step to study further, developing a novel therapeutic for lethal viruses within the Flaviviridae family using suggested candidate miRNAs.

PmiRScan: a LightGBM based method for prediction of animal pre-miRNAs.

MicroRNAs (miRNA) are categorized as short endogenous non-coding RNAs, which have a significant role in post-transcriptional gene regulation. Identifying new animal precursor miRNA (pre-miRNA) and miRNA is crucial to understand the role of miRNAs in various biological processes including the development of diseases. The present study focuses on the development of a Light Gradient Boost (LGB) based method for the classification of animal pre-miRNAs using various sequence and secondary structural features. In various pre-miRNA families, distinct k-mer repeat signatures with a length of three nucleotides have been identified. Out of nine different classifiers that have been trained and tested in the present study, LGB has an overall better performance with an AUROC of 0.959. In comparison with the existing methods, our method 'pmiRScan' has an overall better performance with accuracy of 0.93, sensitivity of 0.86, specificity of 0.95 and F-score of 0.82. Moreover, pmiRScan effectively classifies pre-miRNAs from four distinct taxonomic groups: mammals, nematodes, molluscs and arthropods. We have used our classifier to predict genome-wide pre-miRNAs in human. We find a total of 313 pre-miRNA candidates using pmiRScan. A total of 180 potential mature miRNAs belonging to 60 distinct miRNA families are extracted from predicted pre-miRNAs; of which 128 were novel and are note reported in miRBase. These discoveries may enhance our current understanding of miRNAs and their targets in human. pmiRScan is freely available at http://www.csb.iitkgp.ac.in/applications/pmiRScan/index.php .

MiR-1233-3p Inhibits Angiopoietin-1-Induced Endothelial Cell Survival, Migration, and Differentiation.

Angiopoietin-1 (Ang-1) and its receptor Tie-2 promote vascular integrity and angiogenesis. MicroRNAs (miRNAs) are involved in the regulation of many cellular functions, including endothelial cell (EC) survival, proliferation, and differentiation. Several reports indicate that these effects of miRNAs on EC functions are mediated through the modulation of angiogenesis factor signaling including that of vascular endothelial growth factor (VEGF). To date, very little is known about the roles played by miRNAs in the signaling and angiogenesis promoted by the Ang-1-Tie-2 receptor axis. Our high-throughput screening of miRNAs regulated by Ang-1 exposure in human umbilical vein endothelial cells (HUVECs) has identified miR-1233-3p as a mature miRNA whose cellular levels are significantly downregulated in response to Ang-1 exposure. The expression of miR-1233-3p in these cells is also downregulated by other angiogenesis factors including VEGF, fibroblast growth factor 2 (FGF-2), transforming growth factor β (TGFβ), and angiopoietin-2 (Ang-2). The overexpression of miR-1233-3p in HUVECs using specific mimics significantly attenuated cell survival, migration, and capillary-like tube formation, and promoted apoptosis. Moreover, miR-1233-3p overexpression resulted in reversal of the anti-apoptotic, pro-migration, and pro-differentiation effects of Ang-1. Biotinylated miRNA pull-down assays showed that p53 and DNA damage-regulated 1 (PDRG1) is a direct target of miR-1233-3p in HUVECs. The exposure of HUVECs to Ang-1, angiopoietin-2 (Ang-2), fibroblast growth factor 2 (FGF2), vascular endothelial growth factor (VEGF), or transforming growth factor β (TGFβ) triggers the regulation of PDRG1 expression. This study highlights that miR-1233-3p exerts inhibitory effects on Ang-1-induced survival, migration, and the differentiation of cultured ECs.

An intron-split microRNA mediates cleavage of the mRNA encoded by low phosphate root in Solanaceae

Main conclusionA microRNA with a non-canonical precursor structure harbours an intron in between its miRNA-5p and miRNA-3p relevant for its biogenesis, is conserved across Solanaceae, and targets the mRNA of low phosphate root.Hundreds of miRNAs have been identified in plants and great advances have been accomplished in the understanding of plant miRNA biogenesis, mechanisms and functions. Still, many miRNAs, particularly those with less conventional features, remain to be discovered. Likewise, additional layers of regulation from miRNA generation to action and turnover are still being revealed. The current study describes a microRNA not previously identified given its unusual intron-split stem-loop structure, that has been previously observed only within the monocot-specific miRNA444 family. It shows its conservation across a branch of Solanales including agriculturally relevant Solanaceae family, where its transcripts had already been predicted in several species within sequence databases. The miRNA is absent in Arabidopsis thaliana but present in Solanum lycopersicum, Nicotiana benthamiana, Petunia axillaris, and Ipomoea nil. It proves that at least two different pri-miRNA variants are produced from this miRNA gene, one spliced and the other one retaining the intron. It demonstrates the dual function of its intron in the miRNA biogenesis. On the one hand, its presence in the pri-miRNA positively influences mature miRNA accumulation, but on the other hand, it needs to be removed from the pri-miRNA for efficient mature miRNA production. Finally, it sets low phosphate root as one of its targets, a protein known to be involved in root growth regulation under phosphate starvation in other plant species.

In silico identification of chilli genome encoded MicroRNAs targeting the 16S rRNA and secA genes of "Candidatus phytoplasma trifolii".

Phytoplasma, a potentially hazardous pathogen associated with witches' broom, is an economically harmful disease-producing bacteria that damages chilli cultivation. Phytoplasma-infected plants display various symptoms that indicate significant disruptions in normal plant physiology and behaviour. Diseases caused by phytoplasma are widespread and have a major economic impact on crop quality and yield. This work focuses on identifying and examining chilli microRNAs (miRNAs) as potential targets against the 16S rRNA and secA gene of "Candidatus Phytoplasma trifolii" ("Ca. P. trifolii") through plant miRNA prediction algorithms. Mature chilli miRNAs (CA-miRNAs) were collected and used to hybridise the 16S rRNA and secA genes. A total of four common CA-miRNAs were picked according to genetic consensus. Three algorithms applied in the present study suggested that the physiologically relevant, top-ranked miR169b_2 has a possibly specific site at nucleotide position 1,006 for targeting the 'Ca. P. trifolii' 16S rRNA gene. The circos algorithm was then utilised to create the miRNA-mRNA regulatory network. The free energy between the miRNA:mRNA duplex was also computed, and the best value of -17.46 kcal/mol was obtained for CA-miR166c_2. Currently, there are no suitable commercial 'Ca. P. trifolii'-resistant chilli crops. As a result, the expected biological data provide useful evidence for developing 'Ca. P. trifolii'-resistant chilli plants.

New anti-ovarian cancer quinolone derivatives acting by modulating microRNA processing machinery.

MicroRNAs (miRNAs) play a crucial role in ovarian cancer (OC) pathogenesis and miRNA processing can be the object of pharmacological intervention. By exploiting our in-house quinolone library, we combined a cell-based screening with medicinal chemistry efforts, ultimately leading to derivative 33 with anti-OC activity against distinct cell lines (GI50 values 13.52-31.04 μM) and CC50 Wi-38 = 142.9 μM. Compound 33 retained anticancer activity against additional cancer cells and demonstrated a synergistic effect with cisplatin against cisplatin-resistant A2780 cells. Compound 33 bound TRBP by SPR (K D = 4.09 μM) and thermal shift assays and its activity was TRBP-dependent, leading to modulation of siRNA and miRNA maturation. Derivative 33 exhibited augmented potency against OC cells and a stronger binding affinity for TRBP compared to enoxacin, the sole quinolone identified as a modulator of miRNA maturation. Consequently, 33 represents a promising template for developing novel anti-OC agents with a distinctive mechanism of action.

Validation of miR-21, miR-31, miR-34A, and miR-203 Changes by Quantitative Polymerase Chain Reaction in Isolated Keratinocytes.

MiRNAs play integral roles in diverse cellular functions, and their dysregulation is central to various pathological processes. Thyroid hormone (TH) is indispensable for numerous physiological processes, and it has been shown that multiple miRNAs regulate TH signaling in various tissues.This chapter describes a method for validating changes in miRNA observed through RNAseq. The method involves measuring the expression of mature miRNA levels in keratinocytes using the stem-loop real-time PCR. This method utilizes stem-loop RT primers to create cDNA for specific miRNAs in a single RT reaction. The keratinocytes used are derived from the total skin of four-day-old wild-type controls and double thyroid receptors knock-out mice (dTRKO).

Evolutionary conservation of salinity responsive miRNAs from Indian wheat (Triticum aestivum) landrace, Kharchia Local

Being temporal, majority of abiotic stresses induces responses in plants that needs to be regulated in energy efficient manner. These regulations are carried out by many regulatory molecules including microRNAs and transcription factors. Like protein coding genes, miRNAs are also conserved across the plant species to exhibit their conserved function during growth, development and response to biotic or abiotic stresses. The present study was carried out during 2020 and 2021 at National phytotron facility, ICAR-Indian Agricultural Research Institute, New Delhi. Control and salinity treated plants of Kharchia Local, a highly salt tolerant landrace of wheat (Triticum aestivum L.) from India, were grown in hydroponics and after sequencing and analysis of small RNA data, salinity responsive mature miRNA sequences from Kharchia Local were analyzed for their evolutionary relationship with sequences from the public databases. The phylogenetic study, sequence similarity (identity scores) and multiple sequence comparison was used for evolutionary conservation analysis. The study revealed that, miRNA sequences from Kharchia Local are diverse and did not group with the salinity responsive miRNAs from the database except miR1551. Interestingly, a total of 25 known or conserved miRNA families were identified as salinity responsive across the plant species. The miRNAs from Kharchia Local appears to play regulatory role in novel mechanisms of salinity tolerance.

The biogenesis and regulation of animal microRNAs.

MicroRNAs (miRNAs) are small, yet profoundly influential, non-coding RNAs that base-pair with mRNAs to induce RNA silencing. Although the basic principles of miRNA biogenesis and function have been established, recent breakthroughs have yielded important new insights into the molecular mechanisms of miRNA biogenesis. In this Review, we discuss the metazoan miRNA biogenesis pathway step-by-step, focusing on the key biogenesis machinery, including the Drosha-DGCR8 complex (Microprocessor), exportin-5, Dicer and Argonaute. We also highlight newly identified cis-acting elements and their impact on miRNA maturation, informed by advanced high-throughput and structural studies, and discuss recently discovered mechanisms of clustered miRNAprocessing, target recognition and target-directed miRNA decay (TDMD). Lastly, we explore multiple regulatory layers of miRNA biogenesis, mediated by RNA-protein interactions, miRNA tailing (uridylation or adenylation) and RNA modifications.

MiR472 Deficiency Enhances Arabidopsis thaliana Defense Without Reducing Seed Production.

After having co-existed in plant genomes for at least 200 million years, the products of microRNA (miRNA) and nucleotide-binding leucine-rich repeat protein (NLR) genes formed a regulatory relationship in the common ancestor of modern gymnosperms and angiosperms. From then on, DNA polymorphisms occurring at miRNA target sequences within NLR transcripts must have been compensated by mutations in the corresponding mature miRNA sequence. The potential evolutionary advantage of such regulation remains largely unknown and might be related to two nonexclusive scenarios: (i) miRNA-dependent regulation of NLR levels might prevent defense mis-activation with negative effects on plant growth and reproduction or (ii) reduction of active miRNA levels in response to pathogen-derived molecules (pathogen-associated molecular patterns [PAMPs] and silencing suppressors) might rapidly release otherwise silent NLR transcripts for rapid translation and thereby enhance defense. Here, we used Arabidopsis thaliana plants deficient for miR472 function to study the impact of releasing its NLR targets on plant growth and reproduction and on defense against the fungal pathogen Plectosphaerella cucumerina. We show that miR472 regulation has a dual role, participating both in the tight regulation of plant defense and growth. MIM472 lines, with reduced active miR472, are more resistant to pathogens and, correlatively, have reduced relative growth compared with wild-type plants, although the end of their reproductive phase is delayed, exhibiting higher adult biomass and similar seed yield as the wild-type. Our study highlights how negative consequences of defense activation might be compensated by changes in phenology and that miR472 reduction is an integral part of plant defense responses. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Advantage looping: Gene regulatory circuits between microRNAs and their target transcription factors in plants.

The 20 to 24 nucleotide microRNAs (miRNAs) and their target transcription factors (TF) have emerged as key regulators of diverse processes in plants, including organ development and environmental resilience. In several instances, the mature miRNAs degrade the TF-encoding transcripts, while their protein products in turn bind to the promoters of the respective miRNA-encoding genes and regulate their expression, thus forming feedback loops (FBLs) or feedforward loops (FFLs). Computational analysis suggested that such miRNA-TF loops are recurrent motifs in gene regulatory networks (GRNs) in plants as well as animals. In recent years, modeling and experimental studies have suggested that plant miRNA-TF loops in GRNs play critical roles in driving organ development and abiotic stress responses. Here, we discuss the miRNA-TF FBLs and FFLs that have been identified and studied in plants over the past decade. We then provide some insights into the possible roles of such motifs within GRNs. Lastly, we provide perspectives on future directions for dissecting the functions of miRNA-centric GRNs in plants.

Molecular Characterization of miRNAs in Myzus persicae Carrying Brassica Yellows Virus.

microRNAs (miRNAs) influence many biological processes at the post-transcriptional level. However, the molecular characterization of miRNAs in the Myzus persicae response to Brassica yellows virus (BrYV) stress remains unclear. In this study, we present the results of miRNA profiling in Myzus persicae under two different treatments: treatment one (raised on turnip plants), and treatment two (raised on Arabidopsis thaliana). A total of 72 known and 113 novel mature miRNAs were identified in both non-viruliferous and viruliferous aphids, under treatment one. In treatment two, 72 known and 112 novel mature miRNAs were identified in BrYV-free aphids; meanwhile, 71 known and 115 novel miRNAs were identified in BrYV-carrying aphids. Moreover, eight upregulated and four downregulated miRNAs were identified in viruliferous aphids under treatment two, whereas only two miRNAs were differentially expressed under treatment one. These results indicated the relative BrYV level could influence miRNA expression in aphids. KEGG enrichment analysis showed the predicted genes targeted by differentially expressed miRNAs were primarily involved in Peroxisome, neuroactive ligand-receptor interaction, and metabolism of xenobiotics by cytochrome P450 pathways. Taken together, these findings reveal the effect of BrYV on miRNAs in Myzus persicae and provide key clues for further studies on the molecular mechanisms of BrYV transmission via aphids.

Behavioural phenotypes of Dicer knockout in the mouse SCN

AbstractThe suprachiasmatic nucleus (SCN) is the master clock that directly dictates behavioural rhythms to anticipate the earth's light/dark cycles. Although post‐transcriptional regulators called microRNAs have been implicated in physiological SCN function, how the absence of the entire mature miRNome impacts SCN output has not yet been explored. To study the behavioural consequences of miRNA depletion in the SCN, we first generated a mouse model in which Dicer is inactivated in the SCN by crossing Syt10Cre mice with Dicerflox mice to study behavioural consequences of miRNA depletion in the SCN. Loss of all mature miRNAs in the SCN shortened the circadian period length by ~37 minutes at the tissue level and by ~45 minutes at the locomotor activity level. Moreover, knockout animals exhibited a reduction in the precision of the circadian rhythm with more variable activity onsets under both LD 12:12 and DD conditions. We also observed that knockouts with higher onset variations were inclined to develop ultradian rhythms under constant light. In a second mouse model, recombination of Dicerflox via Cre delivery specifically in the SCN resulted in loss of behavioural rhythms in some animals depending on the injection efficiency. Together, our observations highlight the importance of microRNAs for a physiological SCN function and their pivotal role in robust circadian oscillations.

Abstract A039: A sensitive tool for the detection of RNA modifications in blood samples

Abstract The epitranscriptome is the set of chemical modifications applied naturally to RNA to regulate seemingly all aspects of its function, including splicing, translation initiation and fidelity, trafficking, RNA folding and stability, and transcript lifetime. Detecting RNA in blood reliably continues to be a challenge due to its labile nature, and detecting RNA modifications is an even greater challenge. For this reason, current liquid biopsy approaches concentrate on determining the mutational burden in cell-free DNA and do not harness the potential of cfRNA. In contrast to cfDNA, cfRNA is a biomarker for dynamic events that are known to occur at early stages of carcinogenesis, such as alterations to transcriptional profiles and other aspects of the regulatory state of cells. In many RNA species, the modification state is linked to the RNA lifecycle, thus providing important insights into cell state. For example, pre-miRNA is modified before miRNA maturation, tRNA cleavage is initiated by changes to the modification pattern and mRNA is decapped for storage in stress granules. AlidaBio is introducing the EpiPlex platform, an assay platform with an integrated bioinformatics solution that is designed for ultra-low RNA input and has been tested with blood samples. In addition to its sensitivity, the EpiPlex platform has the advantage of detecting multiple RNA modifications in the same reaction, enabling users to elucidate how RNA modifications act in concert to fine-tune RNA function. The approach uses targeted, multiplexed barcoding to reveal co-localization of modifications on the same molecule and to provide semi-quantitative data on mod abundance. This sensitive, multiplexed target detection has the potential to advance the field of RNA liquid biopsy with new biomarker discovery. Citation Format: Andrew Price, Zachary Miles, Byron Purse, Gudrun Stengel. A sensitive tool for the detection of RNA modifications in blood samples [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr A039.

MicroRNAome profiling of breast cancer unveils hsa-miR-5683 as a tumor suppressor microRNA predicting favorable clinical outcome

BackgroundBreast cancer is a heterogeneous disease with diverse molecular subtypes, underscoring a better understanding of its molecular features and underlying regulatory mechanisms. Therefore, identifying novel prognostic biomarkers and therapeutic targets is crucial for advancing the current standard of care for breast cancer patients.MethodsNinety-six formalin-fixed paraffin-embedded (FFPE) breast cancer samples underwent miRNAome profiling using QIAseq microRNA library kit and sequencing on Illumina platform. Mature miRNA quantification was conducted using CLC Genomics Workbench v21.0.5, while Relapse-free survival (RFS) analysis was conducted using RStudio 2023.09.1. Gain-of-function studies were conducted using miRNA mimics, while the effects of miRNA exogenous expression on cancer hallmark were assessed using 2-dimentional (2D) proliferation assay, three-dimensional (3D) organotypic culture, and live-dead staining. TargetScan database and Ingenuity Pathway Analysis (IPA) were used for miRNA target identification.ResultsHierarchical clustering based on miRNA expression revealed distinct patterns in relation to PAM50 classification and identified miRNAs panels associated with luminal, HER2, and basal subtypes. hsa-miR-5683 emerged as a potential prognostic biomarker, showing a favorable correlation with RFS and suppressing tumorigenicity under 2D and 3D conditions in triple-negative breast cancer (TNBC) models. Findings were further extended to the MCF7 hormone receptor positive (HR+) model. Transcriptomic profiling of hsa-miR-5683 overexpressing TNBC cells revealed its potential role in key oncogenic pathways. Integration of downregulated genes and CRISPR-Cas9 perturbational effects identified ACLY, RACGAP1, AK4, MRPL51, CYB5B, MKRN1, TMEM230, NUP54, ANAPC13, PGAM1, and SOD1 as bona fide gene targets for hsa-miR-5683.ConclusionsOur data provides comprehensive miRNA expression atlas in breast cancer subtypes and underscores the prognostic and therapeutic significance of numerous miRNAs, including hsa-miR-5683 in TNBC. The identified gene targets unravel the intricate regulatory network in TNBC progression, suggesting promising avenues for further research and targeted therapeutic interventions.

Rapid downregulation of DICER is a hallmark of adipose tissue upon high-fat diet feeding

Adipose tissue regulates whole-body energy balance and is crucial for metabolic health. With energy surplus, adipose tissue expands, which may lead to local areas of hypoxia and inflammation, and consequently impair whole-body insulin sensitivity. We report that DICER, a key enzyme for miRNA maturation, is significantly lower in abdominal subcutaneous white adipose tissue of men with obesity compared with men with a lean phenotype. Furthermore, DICER is profoundly downregulated in mouse adipose tissue and liver within the first week on a high-fat diet (HFD), and remains low after prolonged HFD feeding. Downregulation of DICER in mice occurs in both mature adipocytes and stromal vascular cells. Mechanistically, chemically induced hypoxia in vitro shows DICER degradation via interaction with hypoxia-inducible factor 1-α (HIF1α). Moreover, DICER and HIF1α interact in brown adipose tissue post-HFD which may signal for DICER degradation. Finally, RNA sequencing reveals a striking time-dependent downregulation of total miRNA content in mouse subcutaneous adipose tissue after HFD feeding. Collectively, HFD in mice reduces adipose tissue DICER, likely due to hypoxia-induced interaction with HIF1α during tissue expansion, and this significantly impacts miRNA content.

EPCO-09. DICER1-MUTANT PRIMARY INTRACRANIAL SARCOMA: ASSESSING THE ONCOGENIC ROLE OF MIRNA DYSREGULATION

Abstract Cross-cancer profiling has shown that mutations in human DICER1 are recurrent in diverse cancers including intracranial sarcoma. Due to the rarity of these tumors, treatment options for these patients remain poorly defined. DICER1 encodes an endoribonuclease that processes the hairpin precursor microRNAs (miRNAs) into functionally mature miRNAs. In particular, hotspot mutations in the RNase IIIb domain of DICER1 are predicted to confer an oncogenic role although the precise mechanism is unknown. In a case of a 28-year-old male who presented with multicentric right frontal dural and parenchymal enhancing masses and underwent partial resection, pathology showed a DICER1-mutant primary intracranial sarcoma with a hotspot E1813G mutation in the RNase IIIb domain. Additionally, due to a family history of an unknown fatal brain tumor in his mother, the patient had additional molecular testing which revealed a germline BRCA2 mutation. After surgery, the patient received intensity-modulated radiation therapy followed by 6 cycles of ICE (ifosfamide, carboplatin, etoposide) chemotherapy with significant radiographic response and clinical improvement. He remains progression-free on radiological surveillance for 13 months since diagnosis. The treatment was well tolerated with clinically manageable myelosuppression (including grade 3 thrombocytopenia). This is the first reported case of an adult DICER1-mutant primary intracranial sarcoma patient with a germline BRCA2 mutation although the interaction between these oncogenic mechanisms is unclear. Based on the role of DICER1 in miRNA processing and to test the hypothesize that DICER1 mutations drive primary intracranial sarcoma through dysregulation of miRNA function, we have established a multi-institutional collaboration that is collecting and profiling DICER 1 mutant primary intracranial sarcoma cases from across the United States preliminary results of which will be presented. Identification of a miRNA-driven oncogenic mechanism in these tumors may yield novel targeted approaches beyond intensive chemotherapy for these patients.