Explore the vast range of titles available.

Regulation of all-trans retinoic acid (ATRA) signaling is crucial to early embryonic development. Embryonic stem (ES) cell-derived gastruloids mimic normal development in response to the Wnt/β-catenin agonist CHIR9901, and this study has examined the importance of the activities of RAR (retinoic acid receptor) α and γ to gastruloid development. Expression of retinoic acid receptor (RAR)γ within developing gastruloids was spatially restricted to primitive cells that co-expressed ES cell and early progenitor cell markers, i.e., Nanog, Sox2, and Oct4. In contrast, RARα expression was ubiquitous. mRNAs for the key enzymes involved in ATRA synthesis (Aldh1a2) and degradation (Cyp26a1) were not seen in cells that expressed RARγ. Treatment of ES cell-derived gastruloids with physiologically relevant (10 nm) levels of ATRA or with a highly selective RARγ agonist blocked normal developmental processes, preventing symmetry-breaking and axial elongation. This was not seen following treatments with an RARα agonist, where there was a tendency for enhanced axial elongation. Brachyury (TBXT) immuno-positive cells localized in the posterior end of elongated gastruloids in control- and RARα agonist-treated cultures, with Sox2 immuno-positive cells seen more widely, whilst both TBXT and Sox2 immuno-positive cells were randomly distributed throughout ATRA- and RARγ agonist-treated gastruloids. Concurrent treatment of gastruloids with 10 nm ATRA and 100 nm of an RARγ antagonist partially abrogated the ATRA-mediated block to axial elongation. Conversely, 10 nm RARγ antagonist treatments were associated with the formation of multi-axis gastruloid elongations, with comparatively little effect seen after treatments with an RARα antagonist. These findings reveal that RARγ plays a crucial role in the development of embryonic tissues.

Oculo-auriculo-vertebral spectrum (OAVS) is a developmental disorder characterized by hemifacial microsomia associated with ear, eyes and vertebrae malformations showing highly variable expressivity. Recently, MYT1, encoding the myelin transcription factor 1, was reported as the first gene involved in OAVS, within the retinoic acid (RA) pathway. Fifty-seven OAVS patients originating from Brazil were screened for MYT1 variants. A novel de novo missense variant affecting function, c.323C>T (p.(Ser108Leu)), was identified in MYT1, in a patient presenting with a severe form of OAVS. Functional studies showed that MYT1 overexpression downregulated all RA receptors genes (RARA, RARB, RARG), involved in RA-mediated transcription, whereas no effect was observed on CYP26A1 expression, the major enzyme involved in RA degradation, Moreover, MYT1 variants impacted significantly the expression of these genes, further supporting their pathogenicity. In conclusion, a third variant affecting function in MYT1 was identified as a cause of OAVS. Furthermore, we confirmed MYT1 connection to RA signaling pathway.

Background Acute myeloid leukemia (AML) remains a challenging disease with a poor prognosis, necessitating more personalized therapeutic strategies. Retinoic acid receptor (RAR) activation is crucial for myeloid differentiation, but non-APL AML cells resist differentiation induced by the pan-RAR agonist all-trans retinoic acid (ATRA). Am80 (tamibarotene), a specific RARA agonist, has been reported to partially overcome this resistance in AML with high RARA expression. However, its effects on myeloid differentiation, especially in comparison to ATRA, remain understudied. Methods In this study we compared the effects of Am80 and ATRA in non-APL AML samples, focusing on subsets with high RARA and/or RARG expression, using molecular and phenotypic differentiation assessments. Results In contrast to previous findings, Am80 showed no advantage over ATRA in inducing differentiation in AML cell lines or primary samples, regardless of RARA and RARG expression levels. Cotreatment with inhibitors of the epigenetic modifiers LSD1 and GCN5, which facilitates retinoid-induced myeloid differentiation, enhanced the effects of both Am80 and ATRA to the same extent, with more pronounced responses observed in RARA-high samples. Gene expression analysis revealed identical molecular responses to Am80 and ATRA. Conclusions The study provides evidence that ATRA can be substituted by the more stable Am80 in retinoid-based AML therapies. It also identifies elevated RARA expression as a potential marker for sensitivity to combination therapy with retinoids and epigenetic inhibitors in AML.

Pregnancy critically depends on the transformation of the human endometrium into a decidual matrix that controls embryo implantation and placenta formation, a process driven foremost by differentiation and polarization of endometrial stromal cells into mature and senescent decidual cells. Perturbations in the decidual process underpin a spectrum of prevalent reproductive disorders, including implantation failure and early pregnancy loss, emphasizing the need for new therapeutic interventions. Resveratrol is a naturally occurring polyphenol, widely used for its antioxidant and anti-inflammatory properties. Using primary human endometrial stromal cell (HESC) cultures, we demonstrate that resveratrol has anti-deciduogenic properties, repressing not only the induction of the decidual marker genes PRL and IGFBP1 but also abrogating decidual senescence. Knockdown of Sirtuin 1, a histone deacetylase activated by resveratrol, restored the expression of IGFBP1 but not the induction of PRL or senescence markers in decidualizing HESCs, suggesting involvement of other pathways. We demonstrate that resveratrol interferes with the reprogramming of the retinoic acid signaling pathway in decidualizing HESCs by accelerating down-regulation of cellular retinoic acid-binding protein 2 (CRABP2) and retinoic acid receptor (RAR). Notably, knockdown of CRABP2 or RAR in HESCs was sufficient to recapitulate the anti-deciduogenic effects of resveratrol. Thus, while resveratrol has been advanced as a potential fertility drug, our results indicate it may have detrimental effects on embryo implantation by interfering with decidual remodeling of the endometrium.

CDK4/6 inhibitors (CDK4/6i) have shown striking clinical potential in hormone receptor-positive breast cancers (BC) and endometrial cancers (EC), whereas resistance hinders their clinical utilization. The role of epigenetic alterations in CDK4/6i resistance remains poorly elucidated. Herein, through a comprehensive analysis of transcriptomic and chromatin profiles in 16 EC tissues and cell-based resistance models, we delineate the super-enhancer (SE) landscape and identify aldehyde dehydrogenase 1 family member A1 ( ALDH1A1 ) as a SE-driven gene closely associated with CDK4/6i resistance. ALDH1A1 inhibition increases susceptibility to CDK4/6i in multiple EC and BC models. Mechanistically, we demonstrate that ALDH1A1 promotes vitamin A (vitA) metabolism and induces the accumulation of its downstream metabolite, retinoic acid (RA), in resistant cells. In return, the elevated RA potentiates the interaction between retinoic acid receptor alpha (RARα) and estrogen receptor alpha (ERα) in the nucleus and facilitates RARα/ERα-occupied SE-driven transcriptional activation of ALDH1A1 , establishing a positive feedback loop that promotes CDK4/6i resistance. These findings highlight the crucial role of vitA metabolism in the epigenetic transcriptional program associated with CDK4/6i resistance, suggesting that avoiding high vitA intake or inhibiting the ALDH1A1-RA axis may be effective strategies to overcome this challenge. CDK4/6 inhibitors response is limited by frequent resistance in hormone receptor– positive cancers. Here, the authors show that a super enhancer driven increase in aldehyde dehydrogenase creates a vitamin A/retinoic acid feedback loop that promotes resistance in breast and endometrial cancer.

Chaperone-mediated autophagy activity, essential in the cellular defense against proteotoxicity, declines with age, and preventing this decline in experimental genetic models has proven beneficial. Here, we have identified the mechanism of action of selective chaperone-mediated autophagy activators previously developed by our group and have leveraged that information to generate orally bioavailable chaperone-mediated autophagy activators with favorable brain exposure. Chaperone-mediated autophagy activating molecules stabilize the interaction between retinoic acid receptor alpha - a known endogenous inhibitor of chaperone-mediated autophagy - and its co-repressor, nuclear receptor corepressor 1, resulting in changes of a discrete subset of the retinoic acid receptor alpha transcriptional program that leads to selective chaperone-mediated autophagy activation. Chaperone-mediated autophagy activators molecules activate this pathway in vivo and ameliorate retinal degeneration in a retinitis pigmentosa mouse model. Our findings reveal a mechanism for pharmacological targeting of chaperone-mediated autophagy activation and suggest a therapeutic strategy for retinal degeneration. Gomez-Sintes et al. have developed small molecules that selectively activate chaperone-mediated autophagy by stabilizing the interaction between retinoic acid receptor alpha and its co-repressor N-CoR1. They demonstrate the protective effect of boosting chaperone-mediated autophagy against retinal degeneration.

Half of estrogen receptor-positive breast cancers contain a subpopulation of cytokeratin 5 (CK5)-expressing cells that are therapy resistant and exhibit increased cancer stem cell (CSC) properties. We and others have demonstrated that progesterone (P4) increases CK5+ breast cancer cells. We previously discovered that retinoids block P4 induction of CK5+ cells. Here we investigated the mechanisms by which progesterone receptors (PR) and retinoic acid receptors (RAR) regulate CK5 expression and breast CSC activity. After P4 treatment, sorted CK5+ compared to CK5− cells were more tumorigenic in vivo . In vitro , P4-treated breast cancer cells formed larger mammospheres and silencing of CK5 using small hairpin RNA abolished this P4-dependent increase in mammosphere size. Retinoic acid (RA) treatment blocked the P4 increase in CK5+ cells and prevented the P4 increase in mammosphere size. Dual small interfering RNA (siRNA) silencing of RARα and RARγ reversed RA blockade of P4-induced CK5. Using promoter deletion analysis, we identified a region 1.1 kb upstream of the CK5 transcriptional start site that is necessary for P4 activation and contains a putative progesterone response element (PRE). We confirmed by chromatin immunoprecipitation that P4 recruits PR to the CK5 promoter near the −1.1 kb essential PRE, and also to a proximal region near −130 bp that contains PRE half-sites and a RA response element (RARE). RA induced loss of PR binding only at the proximal site. Interestingly, RARα was recruited to the −1.1 kb PRE and the −130 bp PRE/RARE regions with P4, but not RA alone or RA plus P4. Treatment of breast cancer xenografts in vivo with the retinoid fenretinide reduced the accumulation of CK5+ cells during estrogen depletion. This reduction, together with the inhibition of CK5+ cell expansion through RAR/PR cross talk, may explain the efficacy of retinoids in prevention of some breast cancer recurrences.

HNF4α, a member of the nuclear receptor superfamily, regulates the genes involved in lipid and glucose metabolism. The expression of the RARβ gene in the liver of HNF4α knock-out mice was higher versus wildtype controls, whereas oppositely, RARβ promoter activity was 50% reduced by the overexpression of HNF4α in HepG2 cells, and treatment with retinoic acid (RA), a major metabolite of vitamin A, increased RARβ promoter activity 15-fold. The human RARβ2 promoter contains two DR5 and one DR8 binding motifs, as RA response elements (RARE) proximal to the transcription start site. While DR5 RARE1 was previously reported to be responsive to RARs but not to other nuclear receptors, we show here that mutation in DR5 RARE2 suppresses the promoter response to HNF4α and RARα/RXRα. Mutational analysis of ligand-binding pocket amino acids shown to be critical for fatty acid (FA) binding indicated that RA may interfere with interactions of FA carboxylic acid headgroups with side chains of S190 and R235, and the aliphatic group with I355. These results could explain the partial suppression of HNF4α transcriptional activation toward gene promoters that lack RARE, including APOC3 and CYP2C9, while conversely, HNF4α may bind to RARE sequences in the promoter of the genes such as CYP26A1 and RARβ, activating these genes in the presence of RA. Thus, RA could act as either an antagonist towards HNF4α in genes lacking RAREs, or as an agonist for RARE-containing genes. Overall, RA may interfere with the function of HNF4α and deregulate HNF4α targets genes, including the genes important for lipid and glucose metabolism.

ProMyelocyticLeukemia (PML) protein can polymerize into a mega-Dalton nuclear assembly of 0.1–2 μm in diameter. The mechanism of PML nuclear body biogenesis remains elusive. Here, PML RBCC is successfully purified. The gel filtration and ultracentrifugation analysis suggest a previously unrecognized sequential oligomerization mechanism via PML monomer, dimer, tetramer and N-mer. Consistently, PML B1-box structure (2.0 Å) and SAXS characterization reveal an unexpected networking by W157-, F158- and SD1-interfaces. Structure-based perturbations in these B1 interfaces not only impair oligomerization in vitro but also abolish PML sumoylation and nuclear body biogenesis in HeLa Pml -/- cell. More importantly, as demonstrated by in vivo study using transgenic mice, PML-RARα (PR) F158E precludes leukemogenesis. In addition, single cell RNA sequencing analysis shows that B1 oligomerization is an important regulator in PML-RARα-driven transactivation. Altogether, these results not only define a previously unrecognized B1-box oligomerization in PML, but also highlight oligomerization as an important factor in carcinogenesis. Promyelocytic leukemia protein (PML) is the scaffolding protein that organizes PML nuclear bodies. Here the authors determine the crystal structure of a PML B1-box multimer and characterise the oligomerisation behaviour of the PML RBCC construct and show that disrupting B1-B1 interactions precludes promyelocytic leukemia leukemogenesis in transgenic mice.

Cutaneous T-cell lymphoma (CTCL) is a heterogeneous non-Hodgkin lymphoma originating in the skin and invading the systemic hematopoietic system. Current treatments, including chemotherapy and monoclonal antibodies yielded limited responses with high incidence of side effects, highlighting the need for targeted therapy. Screening with small inhibitors library, herein we identify cyclin dependent kinase 9 (CDK9) as a driver of CTCL growth. Single-cell RNA-seq analysis reveals a CDK9 high malignant T cell cluster with a unique actively proliferating feature. Inhibition, depletion or proteolysis targeting chimera (PROTAC)-mediated degradation of CDK9 significantly reduces CTCL cell growth in vitro and in murine models. CDK9 also promotes degradation of retinoic acid receptor α (RARα) via recruiting the E3 ligase HUWE1. Co-administration of CDK9-PROTAC (GT-02897) with all-trans retinoic acid (ATRA) leads to synergistic attenuation of tumor growth in vitro and in xenograft models, providing a potential translational treatment for complete eradication of CTCL. Cutaneous T-cell lymphoma (CTCL) is a rare type of non-Hodgkin lymphoma that affects the skin. Here authors show that CDK9 degradation of retinoic acid receptor α is a vulnerability for CTCL and develop a degrader targeting CDK9 that synergizes with all-trans retinoic acid to reduce CTCL tumor growth.