Repression Pathway Research Articles

Research progress on the function and regulatory pathways of amino acid permeases in fungi.

Nitrogen sources are pivotal for the formation of fungal mycelia and the biosynthesis of metabolites, playing a crucial role in the growth and development of fungi. Amino acids are integral to protein construction, constitute an essential nitrogen source for fungi. Fungi actively uptake amino acids from their surroundings, a process that necessitates the involvement of amino acid permeases (AAPs) located on the plasma membrane. By sensing the intracellular demand for amino acids and their extracellular availability, fungi activate or suppress relevant pathways to precisely regulate the genes encoding these transporters. This review aims to illustrate the function of fungal AAPs on uptake of amino acids and the effect of AAPs on fungal growth, development and virulence. Additionally, the complex mechanisms to regulate expression of aaps are elucidated in mainly Saccharomyces cerevisiae, including the Ssy1-Ptr3-Ssy5 (SPS) pathway, the Nitrogen Catabolite Repression (NCR) pathway, and the General Amino Acid Control (GAAC) pathway. However, the physiological roles of AAPs and their regulatory mechanisms in other species, particularly pathogenic fungi, merit further exploration. Gaining insights into these aspects could reveal how AAPs facilitate fungal adaptation and survival under diverse stress conditions, shedding light on their potential impact on fungal biology and pathogenicity.

CsPHRs-CsJAZ3 incorporates phosphate signaling and jasmonate pathway to regulate catechin biosynthesis in Camellia sinensis.

Catechins constitute abundant metabolites in tea and have potential health benefits and high economic value. Intensive study has shown that the biosynthesis of tea catechins is regulated by environmental factors and hormonal signals. However, little is known about the coordination of phosphate (Pi) signaling and the jasmonic acid (JA) pathway on biosynthesis of tea catechins. We found that Pi deficiency caused changes in the content of catechins and modulated the expression levels of genes involved in catechin biosynthesis. Herein, we identified two transcription factors of phosphate signaling in tea, named CsPHR1 and CsPHR2, respectively. Both regulated catechin biosynthesis by activating the transcription of CsANR1 and CsMYB5c. We further demonstrated CsSPX1, a Pi pathway repressor, suppressing the activation by CsPHR1/2 of CsANR1 and CsMYB5c. JA, one of the endogenous plant hormones, has been reported to be involved in the regulation of secondary metabolism. Our work demonstrated that the JA signaling repressor CsJAZ3 negatively regulated catechin biosynthesis via physical interaction with CsPHR1 and CsPHR2. Thus, the CsPHRs-CsJAZ3 module bridges the nutrition and hormone signals, contributing to targeted cultivation of high-quality tea cultivars with high fertilizer efficiency.

Rewiring of a KNOXI regulatory network mediated by UFO underlies the compound leaf development in Medicago truncatula

Class I KNOTTED-like homeobox (KNOXI) genes are parts of the regulatory network that control the evolutionary diversification of leaf morphology. Their specific spatiotemporal expression patterns in developing leaves correlate with the degrees of leaf complexity between simple-leafed and compound-leafed species. However, KNOXI genes are not involved in compound leaf formation in several legume species. Here, we identify a pathway for dual repression of MtKNOXI function in Medicago truncatula. PINNATE-LIKE PENTAFOLIATA1 (PINNA1) represses the expression of MtKNOXI, while PINNA1 interacts with MtKNOXI and sequesters it to the cytoplasm. Further investigations reveal that UNUSUAL FLORAL ORGANS (MtUFO) is the direct target of MtKNOXI, and mediates the transition from trifoliate to pinnate-like pentafoliate leaves. These data suggest a new layer of regulation for morphological diversity in compound-leafed species, in which the conserved regulators of floral development, MtUFO, and leaf development, MtKNOXI, are involved in variation of pinnate-like compound leaves in M. truncatula.

Abstract 5550: Crosstalk of estrogen receptor Β with tumor microenvironment signaling explains tumor suppressor actions in TNBC

Abstract Triple Negative Breast Cancer (TNBC) is a subtype of breast cancer lacking molecular targets, possessing one of the poorest prognoses of all breast cancers. Recent studies using breast tumor samples show an association between the expression of estrogen receptor β (ERβ) and improved survival of patients with TNBC. ERβ - whose function largely opposes that of oncogenic ERα - is involved in the regulation of many tumor repressive pathways and has lately been observed to partake in immune modulation, thus presenting a promising target for TNBC. Discovering selective ERβ agonists is critical to understanding the potential of activating the receptor as a therapy approach for TNBC. It enables us to elicit estrogen signaling response specific to the tumor suppressive function of the β receptor subtype. We have set out a screening process to test and identify ligands that display the greatest activation and specificity for ERβ as determined by reporter assays and changes in downstream target gene expression. We selected to study in vitro and in vivo the compounds with optimal biological activity to delineate tumor-intrinsic and -extrinsic effects and validate the mechanism of action employing human and mouse cell models that reflect the heterogeneity of the disease. We propose that activation of ERβ decreases the proliferative and metastatic ability of breast cancer cells by altering cellular pathways and crosstalk with immune cells. The results of these studies help lay the groundwork for further research on the clinical potential of ERβ especially in the realm of immunotherapy and treatment of TNBC. Citation Format: Kristina Diana A. Zambo, Harika Nagandla, Kim Cuong Cap, Aireana Phillips, Fotis Nikolos, Wei Qian, Jianying Zhou, Jenny Chang, Christoforos Thomas. Crosstalk of estrogen receptor Β with tumor microenvironment signaling explains tumor suppressor actions in TNBC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5550.

Quality and flavor development of solid-state fermented surimi with Actinomucor elegans: A perspective on the impacts of carbon and nitrogen sources

The influence of four carbon and nitrogen substrates on the quality and flavor of a novel surimi-based product fermented with Actinomucor elegans (A. elegans) was investigated, with a focus on carbon and nitrogen catabolite repression. The results showed that the substrate significantly affected mycelial growth, enzyme activities, and the metabolites of A. elegans. Although glucose significantly promoted A. elegans growth by 116.69%, it decreased enzyme secretion by 69.79% for α-amylase and 59.80% for protease, most likely by triggering the carbon catabolite repression pathway. Starch, soy protein, and wheat gluten substantially affected the textural properties of the fermented surimi. Furthermore, wheat gluten significantly promoted the protease activity (102.70%) and increased protein degradation during surimi fermentation. The fishy odor of surimi was alleviated through fermentation, and a correlation between the volatile compounds and A. elegans metabolism was observed. These results explore fermentation substrates in filamentous fungi metabolism from a catabolite repression perspective.

Jasmonic acid signaling pathway repressor JAZ3 integrates light and temperature signaling in Arabidopsis.

Jasmonic acid signaling pathway repressor JAZ3 integrates light and temperature signaling in Arabidopsis.

Lignin biosynthesis pathway repressors in gymnosperms: differential repressor domains as compared to angiosperms.

Lignin is a polyphenolic polymer present in the cell walls of specialized plant cell types in vascular plants that provides structural support and plays a major role in plant protection. The lignin biosynthesis pathway is regulated by transcription factors from the MYB (myeloblastosis) family. While several MYB members positively regulate lignin synthesis, only a few negatively regulate lignin synthesis. These lignin suppressors are well characterized in model plant species; however, their role has not been fully explored in gymnosperms. Lignin forms one of the major hurdles for the forest-based industry e.g. paper, pulp, and biofuel production. Therefore, the detailed mechanisms involved in the regulation of lignin synthesis are valuable, especially in conifers that form the major source of softwood for timber and paper production. In this review, the potential and differential domains present in the MYB suppressors in gymnosperms are discussed, along with their phylogenetic analysis. Sequence analysis revealed that the N-terminal regions of the MYB suppressor members were found to be conserved among the gymnosperms and angiosperms containing the R2, R3, and bHLH domains, while the C-terminal regions were found to be highly variable. The typical repressor motifs like the LxLxL-type EAR motif and the TLLLFR motif were absent from the C-terminal regions of MYB suppressors from most gymnosperms. However, although the gymnosperms lacked the characteristic repressor domains, a R2R3-type MYB member from Ginkgo was reported to repress the lignin biosynthetic pathway. It is proposed that gymnosperms possess unique kinds of repressors that need further functional validation.

Root branching under high salinity requires auxin-independent modulation of LATERAL ORGAN BOUNDARY DOMAIN 16 function.

Salinity stress constrains lateral root (LR) growth and severely affects plant growth. Auxin signaling regulates LR formation, but the molecular mechanism by which salinity affects root auxin signaling and whether salt induces other pathways that regulate LR development remains unknown. In Arabidopsis thaliana, the auxin-regulated transcription factor LATERAL ORGAN BOUNDARY DOMAIN 16 (LBD16) is an essential player in LR development under control conditions. Here, we show that under high-salt conditions, an alternative pathway regulates LBD16 expression. Salt represses auxin signaling but, in parallel, activates ZINC FINGER OF ARABIDOPSIS THALIANA 6 (ZAT6), a transcriptional activator of LBD16. ZAT6 activates LBD16 expression, thus contributing to downstream cell wall remodeling and promoting LR development under high-salt conditions. Our study thus shows that the integration of auxin-dependent repressive and salt-activated auxin-independent pathways converging on LBD16 modulates root branching under high-salt conditions.

Abscisic acid biosynthesis is necessary for full auxin effects on hypocotyl elongation.

In concert with other phytohormones, auxin regulates plant growth and development. However, how auxin and other phytohormones coordinately regulate distinct processes is not fully understood. In this work, we uncover an auxin-abscisic acid (ABA) interaction module in Arabidopsis that is specific to coordinating activities of these hormones in the hypocotyl. From our forward genetics screen, we determine that ABA biosynthesis is required for the full effects of auxin on hypocotyl elongation. Our data also suggest that ABA biosynthesis is not required for the inhibitory effects of auxin treatment on root elongation. Our transcriptome analysis identified distinct auxin-responsive genes in root and shoot tissues, which is consistent with differential regulation of growth in these tissues. Further, our data suggest that many gene targets repressed upon auxin treatment require an intact ABA pathway for full repression. Our results support a model in which auxin stimulates ABA biosynthesis to fully regulate hypocotyl elongation.

Evidence of a conserved mammalian immunosuppression mechanism in Lutzomyia longipalpis upon infection with Leishmania.

Sand flies (Diptera: Phlebotominae) belonging to the Lutzomyia genus transmit Leishmania infantum parasites. To understand the complex interaction between the vector and the parasite, we have been investigating the sand fly immune responses during the Leishmania infection. Our previous studies showed that genes involved in the IMD, Toll, and Jak-STAT immunity pathways are regulated upon Leishmania and bacterial challenges. Nevertheless, the parasite can thrive in the vectors' gut, indicating the existence of mechanisms capable of modulating the vector defenses, as was already seen in mammalian Leishmania infections. In this study, we investigated the expression of Lutzomyia longipalpis genes involved in regulating the Toll pathway under parasitic infection. Leishmania infantum infection upregulated the expression of two L. longipalpis genes coding for the putative repressors cactus and protein tyrosine phosphatase SHP. These findings suggest that the parasite can modulate the vectors' immune response. In mammalian infections, the Leishmania surface glycoprotein GP63 is one of the inducers of host immune depression, and one of the known effectors is SHP. In L. longipalpis we found a similar effect: a genetically modified strain of Leishmania amazonensis over-expressing the metalloprotease GP63 induced a higher expression of the sand fly SHP indicating that the L. longipalpis SHP and parasite GP63 increased expressions are connected. Immuno-stained microscopy of L. longipalpis LL5 embryonic cells cultured with Leishmania strains or parasite conditioned medium showed cells internalization of parasite GP63. A similar internalization of GP63 was observed in the sand fly gut tissue after feeding on parasites, parasite exosomes, or parasite conditioned medium, indicating that GP63 can travel through cells in vitro or in vivo. When the sand fly SHP gene was silenced by RNAi and females infected by L. infantum, parasite loads decreased in the early phase of infection as expected, although no significant differences were seen in late infections of the stomodeal valve. Our findings show the possible role of a pathway repressor involved in regulating the L. longipalpis immune response during Leishmania infections inside the insect. In addition, they point out a conserved immunosuppressive effect of GP63 between mammals and sand flies in the early stage of parasite infection.

Adaptation to sorbic acid in low sugar promotes resistance of yeast to the preservative

The weak acid sorbic acid is a common preservative used in soft drink beverages to control microbial spoilage. Consumers and industry are increasingly transitioning to low-sugar food formulations, but potential impacts of reduced sugar on sorbic acid efficacy are barely characterised. In this study, we report enhanced sorbic acid resistance of yeast in low-glucose conditions. We had anticipated that low glucose would induce respiratory metabolism, which was shown previously to be targeted by sorbic acid. However, a shift from respiratory to fermentative metabolism upon sorbic acid exposure of Saccharomyces cerevisiae was correlated with relative resistance to sorbic acid in low glucose. Fermentation-negative yeast species did not show the low-glucose resistance phenotype. Phenotypes observed for certain yeast deletion strains suggested roles for glucose signalling and repression pathways in the sorbic acid resistance at low glucose. This low-glucose induced sorbic acid resistance was reversed by supplementing yeast cultures with succinic acid, a metabolic intermediate of respiratory metabolism (and a food-safe additive) that promoted respiration. The results indicate that metabolic adaptation of yeast can promote sorbic acid resistance at low glucose, a consideration for the preservation of foodstuffs as both food producers and consumers move towards a reduced sugar landscape.

Spatial heterogeneity in biofilm metabolism elicited by local control of phenazine methylation.

Within biofilms, gradients of electron acceptors such as oxygen stimulate the formation of physiological subpopulations. This heterogeneity can enable cross-feeding and promote drug resilience, features of the multicellular lifestyle that make biofilm-based infections difficult to treat. The pathogenic bacterium Pseudomonas aeruginosa produces pigments called phenazines that can support metabolic activity in hypoxic/anoxic biofilm subzones, but these compounds also include methylated derivatives that are toxic to their producer under some conditions. In this study, we uncover roles for the global regulators RpoS and Hfq/Crc in controlling the beneficial and detrimental effects of methylated phenazines in biofilms. Our results indicate that RpoS controls phenazine methylation by modulating activity of the carbon catabolite repression pathway, in which the Hfq/Crc complex inhibits translation of the phenazine methyltransferase PhzM. We find that RpoS indirectly inhibits expression of CrcZ, a small RNA that binds to and sequesters Hfq/Crc, specifically in the oxic subzone of P. aeruginosa biofilms. Deletion of rpoS or crc therefore leads to overproduction of methylated phenazines, which we show leads to increased metabolic activity-an apparent beneficial effect-in hypoxic/anoxic subpopulations within biofilms. However, we also find that under specific conditions, biofilms lacking RpoS and/or Crc show increased sensitivity to phenazines indicating that the increased metabolic activity in these mutants comes at a cost. Together, these results suggest that complex regulation of PhzM allows P. aeruginosa to simultaneously exploit the benefits and limit the toxic effects of methylated phenazines.

PAI-1 Regulation of p53 Expression and Senescence in Type II Alveolar Epithelial Cells.

Cellular senescence contributes importantly to aging and aging-related diseases, including idiopathic pulmonary fibrosis (IPF). Alveolar epithelial type II (ATII) cells are progenitors of alveolar epithelium, and ATII cell senescence is evident in IPF. Previous studies from this lab have shown that increased expression of plasminogen activator inhibitor 1 (PAI-1), a serine protease inhibitor, promotes ATII cell senescence through inducing p53, a master cell cycle repressor, and activating p53-p21-pRb cell cycle repression pathway. In this study, we further show that PAI-1 binds to proteasome components and inhibits proteasome activity and p53 degradation in human lung epithelial A549 cells and primary mouse ATII cells. This is associated with a senescence phenotype of these cells, manifested as increased p53 and p21 expression, decreased phosphorylated retinoblastoma protein (pRb), and increased senescence-associated beta-galactose (SA-β-gal) activity. Moreover, we find that, although overexpression of wild-type PAI-1 (wtPAI-1) or a secretion-deficient, mature form of PAI-1 (sdPAI-1) alone induces ATII cell senescence (increases SA-β-gal activity), only wtPAI-1 induces p53, suggesting that the premature form of PAI-1 is required for the interaction with the proteasome. In summary, our data indicate that PAI-1 can bind to proteasome components and thus inhibit proteasome activity and p53 degradation in ATII cells. As p53 is a master cell cycle repressor and PAI-1 expression is increased in many senescent cells, the results from this study will have a significant impact not only on ATII cell senescence/lung fibrosis but also on the senescence of other types of cells in different diseases.

Glucose-enhanced oxidative stress resistance-A protective anticipatory response that enhances the fitness of Candida albicans during systemic infection.

Most microbes have developed responses that protect them against stresses relevant to their niches. Some that inhabit reasonably predictable environments have evolved anticipatory responses that protect against impending stresses that are likely to be encountered in their niches-termed "adaptive prediction". Unlike yeasts such as Saccharomyces cerevisiae, Kluyveromyces lactis and Yarrowia lipolytica and other pathogenic Candida species we examined, the major fungal pathogen of humans, Candida albicans, activates an oxidative stress response following exposure to physiological glucose levels before an oxidative stress is even encountered. Why? Using competition assays with isogenic barcoded strains, we show that "glucose-enhanced oxidative stress resistance" phenotype enhances the fitness of C. albicans during neutrophil attack and during systemic infection in mice. This anticipatory response is dependent on glucose signalling rather than glucose metabolism. Our analysis of C. albicans signalling mutants reveals that the phenotype is not dependent on the sugar receptor repressor pathway, but is modulated by the glucose repression pathway and down-regulated by the cyclic AMP-protein kinase A pathway. Changes in catalase or glutathione levels do not correlate with the phenotype, but resistance to hydrogen peroxide is dependent on glucose-enhanced trehalose accumulation. The data suggest that the evolution of this anticipatory response has involved the recruitment of conserved signalling pathways and downstream cellular responses, and that this phenotype protects C. albicans from innate immune killing, thereby promoting the fitness of C. albicans in host niches.

Linking microbial slime community structure with abiotic factors and antifouling strategy in hydroelectric cooling systems.

Microfouling can have significant economic impacts for hydroelectric power plants. However, knowledge concerning the composition and metabolism of microbial biofilm in cooling systems remains scarce. We examined the metagenome present in a cooling system, comprising a filter (F) and heat exchanger (HE), in the Nova Ponte hydroelectric power plant in Brazil, to identify bacteria and pathways that could be targeted to monitor and control biofilm formation. Our data revealed that the microfouling sample from heat exchanger 1 (HEM1), with porous consistency, presented enriched bacterial members not frequently described as biofilm formers in cooling systems, besides it has been shown to be an autoinducer repression pathway. Furthermore, the microfouling sample from heat exchanger 2 (HEM2), with gelatinous consistency, seemed to be an established biofilm, containing enriched bacterial groups such as Desulfotomaculum and Crenothrix and autoinducers, with biotechnological relevance in industrial biofilms. The results demonstrate that biofilm composition will vary depending on different abiotic conditions and the antifouling strategy used, including type of compound, concentration, and frequency of use. Therefore, all these variables must be evaluated when a power plant is affected by microbial slime in the cooling system. Our findings could help to define strategies for efficient and ecofriendly measures to contain microfouling in power plants.

MAP4K3 inhibits Sirtuin-1 to repress the LKB1-AMPK pathway to promote amino acid-dependent activation of the mTORC1 complex.

mTORC1 is the key rheostat controlling the cellular metabolic state. Of the various inputs to mTORC1, the most potent effector of intracellular nutrient status is amino acid supply. Despite an established role for MAP4K3 in promoting mTORC1 activation in the presence of amino acids, the signaling pathway by which MAP4K3 controls mTORC1 activation remains unknown. Here, we examined the process of MAP4K3 regulation of mTORC1 and found that MAP4K3 represses the LKB1-AMPK pathway to achieve robust mTORC1 activation. When we sought the regulatory link between MAP4K3 and LKB1 inhibition, we discovered that MAP4K3 physically interacts with the master nutrient regulatory factor sirtuin-1 (SIRT1) and phosphorylates SIRT1 to repress LKB1 activation. Our results reveal the existence of a novel signaling pathway linking amino acid satiety with MAP4K3-dependent suppression of SIRT1 to inactivate the repressive LKB1-AMPK pathway and thereby potently activate the mTORC1 complex to dictate the metabolic disposition of the cell.

MTOR pathway: Insights into an established pathway for brain mosaicism in epilepsy

The mechanistic target of rapamycin (mTOR) signaling pathway is an essential regulator of numerous cellular activities such as metabolism, growth, proliferation, and survival. The mTOR cascade recently emerged as a critical player in the pathogenesis of focal epilepsies and cortical malformations. The 'mTORopathies' comprise a spectrum of cortical malformations that range from whole brain (megalencephaly) and hemispheric (hemimegalencephaly) abnormalities to focal abnormalities, such as focal cortical dysplasia type II (FCDII), which manifest with drug-resistant epilepsies. The spectrum of cortical dysplasia results from somatic brain mutations in the mTOR pathway activators AKT3, MTOR, PIK3CA, and RHEB and from germline and somatic mutations in mTOR pathway repressors, DEPDC5, NPRL2, NPRL3, TSC1 and TSC2. The mTORopathies are characterized by excessive mTOR pathway activation, leading to a broad range of structural and functional impairments. Here, we provide a comprehensive literature review of somatic mTOR-activating mutations linked to epilepsy and cortical malformations in 292 patients and discuss the perspectives of targeted therapeutics for personalized medicine.

The Anti-Viral Activity of Stem Cells: A Rational Explanation for their Use in Clinical Application.

It is well established the importance of stem cells (SCs) in tissue growth, regeneration and repair, given their ability to self-renew and differentiate into mature cells. Stem cells are present in all individuals and are potentially active to the end of life. However, less is known about their unique function within the immune system as immune regulators and their important task in viral protection. Antiviral resistance is a common mechanism in all cells though stem cells utilize an antiviral RNA interference (RNAi) mechanism, while adult cells react by using the interferondependent repression pathway via interferon-associated protein-based response to induce an antiviral response. Therefore, the idea behind this review is to highlight the mechanisms of viral evasion of host defense, which would then allow us to highlight the rationale use of autologous stem cells and their biochemical and immunological ability to reset the subverted immune responses. Recently, scientists have highlighted their use in the field of immune-therapy, establishing the possibilities of using them outside the conventional protocol with the advancement in manipulating these cells in such a way that specific body activity can be restored. This paper describes the remarkable SCs profile and discusses some ideas regarding their promising use in vivo.

Impact of the cAMP-cAMP Receptor Protein Regulatory Complex on Lipopolysaccharide Modifications and Polymyxin B Resistance in Escherichia coli.

Gram-negative bacteria have a unique cell surface that can be modified to maintain bacterial fitness in diverse environments. A well-defined example is the modification of the lipid A component of lipopolysaccharide (LPS), which promotes resistance to polymyxin antibiotics and antimicrobial peptides. In many organisms, such modifications include the addition of the amine-containing constituents 4-amino-4-deoxy-l-arabinose (l-Ara4N) and phosphoethanolamine (pEtN). Addition of pEtN is catalyzed by EptA, which uses phosphatidylethanolamine (PE) as its substrate donor, resulting in production of diacylglycerol (DAG). DAG is then quickly recycled into glycerophospholipid (GPL) synthesis by the DAG kinase A (DgkA) to produce phosphatidic acid, the major GPL precursor. Previously, we hypothesized that loss of DgkA recycling would be detrimental to the cell when LPS is heavily modified. Instead, we found that DAG accumulation inhibits EptA activity, preventing further degradation of PE, the predominant GPL of the cell. However, DAG inhibition of pEtN addition results in complete loss of polymyxin resistance. Here, we selected for suppressors to find a mechanism of resistance independent of DAG recycling or pEtN modification. Disrupting the gene encoding the adenylate cyclase, cyaA, fully restored antibiotic resistance without restoring DAG recycling or pEtN modification. Supporting this, disruptions of genes that reduce CyaA-derived cAMP formation (e.g., ptsI) or disruption of the cAMP receptor protein, Crp, also restored resistance. We found that loss of the cAMP-CRP regulatory complex was necessary for suppression and that resistance arises from a substantial increase in l-Ara4N-modified LPS, bypassing the need for pEtN modification. IMPORTANCE Gram-negative bacteria can alter the structure of their LPS to promote resistance to cationic antimicrobial peptides, including polymyxin antibiotics. Polymyxins are considered last-resort antibiotics for treatment against multidrug-resistant Gram-negative organisms. Here, we explore how changes in general metabolism and carbon catabolite repression pathways can alter LPS structure and influence polymyxin resistance.

Abstract 2355: Transcription factor EB modulates fibrotic response in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC), which comprises 85% of all the pancreatic cancers, is one of the most aggressive and deadly tumor that exists today with less than 8% of survival 5 years after diagnosis. It is predicted to become the second cause of cancer death by 2030. A typical characteristic of this tumor is the presence of prominent stroma component mainly produced by Pancreatic Stellate Cells (PSCs) in response to soluble factors released by cancer cells. PSCs activation and differentiation into CAF (Cancer-associated fibroblasts) is a reversible process, which impacts on both tumor progression and drug resistance. Transcription factor EB (TFEB) is mostly known as a master regulator of autophagy and lysosomal biogenesis. A recent study demonstrated that TFEB inhibits epithelial-to-mesenchymal transition (EMT) and myofibroblast differentiation in epicardial cells by upregulating TGIF1, a TGFβ pathway repressor. Based on this observation, we investigated if TFEB might have an inhibitory role in PSCs activation, taking into consideration the crucial role of TGFβ signaling in this process. The TFEB expression, measured by immunostaining, was significantly downregulated in CAFs in human PDAC samples compared to PSCs in healthy pancreas. In PSCs, co-cultured with PDAC cell lines, CAF markers were upregulated while TFEB expression was downregulated. The overexpression of TFEB in PSCs suppressed CAF markers upregulation induced by co-culture with PDAC cells at both mRNA and protein levels. The bulk RNAseq analysis showed the differential expression of genes required for extracellular matrix production, fibrotic response and inflammation in PSCs co-cultured with PDAC cell lines versus PSCs alone, with and without TFEB overexpression. These in vitro data suggest a role for TFEB in PSCs activation and stroma formation which will be further investigated in PDAC mouse models. Citation Format: Alejandra Diaz Alcalde, Edoardo Vallariello, Elena Astanina, Emanuele Middonti, Federico Bussolino. Transcription factor EB modulates fibrotic response in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2355.