All-trans Retinoic Acid Research Articles

All-Trans Retinoic Acid-Induced Cell Surface Heat Shock Protein 90 Mediates Tau Protein Internalization and Degradation in Human Microglia.

This study investigates the role of all-trans retinoic acid (ATRA) in modulating the expression of heat shock protein 90 (Hsp90) and its influence on the uptake and degradation of tau proteins in immortalized human microglia cells. We demonstrate that ATRA significantly upregulates Hsp90 expression in a concentration-dependent manner, enhancing both extracellular and intracellular Hsp90 levels. Our results show that ATRA-treated cells exhibit increased tau protein uptake via caveolae/raft-dependent endocytosis pathways. This uptake is mediated by surface Hsp90, as evidenced by the inhibition of tau internalization using an extracellular Hsp90-selective inhibitor. Further, we establish that the exogenously added full-sized monomeric tau proteins bind to Hsp90. The study also reveals that ATRA-enhanced tau uptake is followed by effective degradation through both lysosomal and proteasomal pathways. We observed a significant reduction in intracellular tau levels in ATRA-treated cells, which was reversed by lysosome or proteasome inhibitors, suggesting the involvement of both degradation pathways. Our findings highlight the potential therapeutic role of ATRA in Alzheimer's disease and related tauopathies. By enhancing Hsp90 expression and facilitating tau degradation, ATRA could contribute to the clearance of pathological tau proteins, offering a promising strategy for mitigating neurodegeneration. This research underscores the need for further exploration into the molecular mechanisms of tau protein internalization and degradation, which could provide valuable insights into the treatment of neurodegenerative diseases.

Molecular Interactions of Selective Agonists and Antagonists with the Retinoic Acid Receptor γ.

All-trans retinoic acid (ATRA), the major active metabolite of all-trans retinol (vitamin A), is a key hormonal signaling molecule. In the adult organism, ATRA has a widespread influence on processes that are crucial to the growth and differentiation of cells and, in turn, the acquisition of mature cell functions. Therefore, there is considerable potential in the use of retinoids to treat diseases. ATRA binds to the retinoic acid receptors (RAR) which, as activated by ATRA, selectively regulate gene expression. There are three main RAR isoforms, RARα, RARβ, and RARγ. They each have a distinct role, for example, RARα and RARγ regulate myeloid progenitor cell differentiation and hematopoietic stem cell maintenance, respectively. Hence, targeting an isoform is crucial to developing retinoid-based therapeutics. In principle, this is exemplified when ATRA is used to treat acute promyelocytic leukemia (PML) and target RARα within PML-RARα oncogenic fusion protein. ATRA with arsenic trioxide has provided a cure for the once highly fatal leukemia. Recent in vitro and in vivo studies of RARγ have revealed the potential use of agonists and antagonists to treat diseases as diverse as cancer, heterotopic ossification, psoriasis, and acne. During the final drug development there may be a need to design newer compounds with added modifications to improve solubility, pharmacokinetics, or potency. At the same time, it is important to retain isotype specificity and activity. Examination of the molecular interactions between RARγ agonists and the ligand binding domain of RARγ has revealed aspects to ligand binding that are crucial to RARγ selectivity and compound activity and key to designing newer compounds.

Nano-fenretinide demonstrates remarkable activity in acute promyeloid leukemia cells

Acute promyelocytic leukemia (APL) is characterized by rearrangements of the retinoic acid receptor, RARα, which makes all-trans retinoic acid (ATRA) highly effective in the treatment of this disease, inducing promyelocytes differentiation. Current therapy, based on ATRA in combination with arsenic trioxide, with or without chemotherapy, provides high rates of event-free survival and overall survival. However, a decline in the drug activity, due to increased ATRA metabolism and RARα mutations, is often observed over long-term treatments. Furthermore, dedifferentiation can occur providing relapse of the disease. In this study we evaluated fenretinide, a semisynthetic ATRA derivative, encapsulated in nanomicelles (nano-fenretinide) as an alternative treatment to ATRA in APL. Nano-fenretinide was prepared by fenretinide encapsulation in a self-assembling phospholipid mixture. Physico-chemical characterization was carried out by dinamic light scattering and spectrophotometry. The biological activity was evaluated by MTT assay, flow cytometry and confocal laser-scanning fluorescence microscopy. Nano-fenretinide induced apoptosis in acute promyelocytic leukemia cells (HL60) by an early increase of reactive oxygen species and a mitochondrial potential decrease. The fenretinide concentration that induced 90–100% decrease in cell viability was about 2.0 µM at 24 h, a concentration easily achievable in vivo when nano-fenretinide is administered by oral or intravenous route, as demonstrated in previous studies. Nano-fenretinide was effective, albeit at slightly higher concentrations, also in doxorubicin-resistant HL60 cells, while a comparison with TK6 lymphoblasts indicated a lack of toxicity on normal cells. The results indicate that nano-fenretinide can be considered an alternative therapy to ATRA in acute promyelocytic leukemia when decreased efficacy, resistance or recurrence of disease emerge after protracted treatments with ATRA.

Negative expression of CD117 predicted inferior OS and PFS in acute promyelocytic leukemia.

In recent years, the correlation between CD117 antigen and the prognosis of hematological malignancies has been demonstrated. However, there is limited literature on the clinical significance of CD117 antigen in acute promyelocytic leukemia (APL). The aim of this study was to retrospectively analyze the clinical features and prognostic significance of CD117 in APL. In this study, we retrospectively investigated the clinicopathological characteristics, outcome, and prognostic impact of negative CD117 expression (CD117-) in 169 APL patients treated with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) containing regimen. The median follow-up period was 63.0 months. CD117- was detected in 13 APL patients (7.7%). No significant differences were found in baseline characteristics between CD117+ and CD117- subgroups. However, compared to CD117+ APL, the incidence of early death (ED) was significantly higher in CD117- APL (p = 0.023). By multivariate analysis, CD117- was an independent adverse prognostic factor for overall survival (OS) and progression-free survival (PFS) (p = 0.022 and p = 0.014, respectively). To sum up, CD117- is associated with greater risk of ED and has the statistical power to predict inferior OS and PFS, this marker may be considered to build prognostic scores for risk-adapted therapeutic strategies in APL management.

Acute promyelocytic leukemia in children cancer hospital Egypt

BackgroundPediatric acute promyelocytic leukemia (APL) accounts for 5 to 15% of all myelocytic leukemia. A retrospective analysis of pediatric patients diagnosed and treated with APL was conducted at CCHE from July 2012 to the end of December 2019, to report the prevalence, clinical characteristics, results, and risk factors associated with induction failure and early death.ResultSixty-two patients were reported, with an age greater than ten, an initial poor coagulation profile, and a total leukocyte count (TLC) greater than 30 103/mm3 influencing 5-year overall (OS) and event-free survival (EFS), as well as a high promyelocyte count affecting 5-year EFS. Patients received a regimen based on the COG AAML0631 protocol. High-risk patients with an initial TLC > 10 × 103/mm3 and an initial promyelocytic count of 30% or more with a substantial P-value are prognostic markers for early death during induction. In females, wild FLT3 increases the risk of differentiation syndrome (DS). Receiving steroids with all-trans retinoic acid (ATRA) induction may reduce the occurrence of DS. Relapse alters the outcome. In the current study, 45 patients are alive in complete remission, with a 5-year OS of 72.5% and a 5-year EFS of 69.4%, respectively.ConclusionPediatric APL outcomes are influenced by age above 10, an initial poor coagulation profile, and a promyelocyte count of more than 10%. An initial leukocyte count of more than 10 × 103/mm and an initial promyelocytic count of more than 30% increase the risk of early death. Receiving steroids with ATRA may reduce the occurrence of DS.

Functional multiomics reveals genetic and pharmacologic regulation of surface CD38 in multiple myeloma

AbstractCD38 is a surface ectoenzyme expressed at high levels on myeloma plasma cells and is the target for the monoclonal antibodies (mAbs) daratumumab and isatuximab. Pretreatment CD38 density on tumor cells is an important determinant of mAb efficacy. Several small molecules have been found to increase tumor surface CD38, with the goal of boosting mAb efficacy in a cotreatment strategy. Numerous other CD38-targeting therapeutics are currently in preclinical or clinical development. Here, we sought to extend our currently limited insight into CD38 surface expression by using a multiomics approach. Genome-wide CRISPR interference screens integrated with patient–centered epigenetic analysis confirmed known regulators of CD38, such as RARA, while revealing XBP1 and SPI1 as other key transcription factors governing surface CD38 levels. CD38 knockdown followed by cell surface proteomics demonstrated no significant remodeling of the myeloma “surfaceome” after genetically induced loss of this antigen. Integrated transcriptome and surface proteome data confirmed high specificity of all-trans retinoic acid in upregulating CD38, in contrast to the broader effects of azacytidine and panobinostat. Finally, unbiased phosphoproteomics identified inhibition of MAP kinase pathway signaling in tumor cells after daratumumab treatment. Our work provides a resource to design strategies to enhance efficacy of CD38-targeting immunotherapies in myeloma.

Gasdermin D deficiency aborts myeloid calcium influx to drive granulopoiesis in lupus nephritis

Gasdermin D (GSDMD) is emerging as an important player in autoimmune diseases, but its exact role in lupus nephritis (LN) remains controversial. Here, we identified markedly elevated GSDMD in human and mouse LN kidneys, predominantly in CD11b+ myeloid cells. Global or myeloid-conditional deletion of GSDMD was shown to exacerbate systemic autoimmunity and renal injury in lupus mice with both chronic graft-versus-host (cGVH) disease and nephrotoxic serum (NTS) nephritis. Interestingly, RNA sequencing and flow cytometry revealed that myeloid GSDMD deficiency enhanced granulopoiesis at the hematopoietic sites in LN mice, exhibiting remarkable enrichment of neutrophil-related genes, significant increases in total and immature neutrophils as well as granulocyte/macrophage progenitors (GMPs). GSDMD-deficient GMPs and all-trans-retinoic acid (ATRA)-stimulated human promyelocytes NB4 were further demonstrated to possess enhanced clonogenic and differentiation abilities compared with controls. Mechanistically, GSDMD knockdown promoted self-renewal and granulocyte differentiation by restricting calcium influx, contributing to granulopoiesis. Functionally, GSDMD deficiency led to increased pathogenic neutrophil extracellular traps (NETs) in lupus peripheral blood and bone marrow-derived neutrophils. Taken together, our data establish that GSDMD deletion accelerates LN development by promoting granulopoiesis in a calcium influx-regulated manner, unraveling its unrecognized critical role in LN pathogenesis.

A prospective study of all-trans retinoic acid plus venetoclax and azacitidine in newly diagnosed acute myeloid leukemia.

6545 Background: Over the decade, anthracycline and cytarabine-based intensive chemotherapy remains the standard of care for acute myeloid leukemia (AML) but is hampered by serious toxicities like myelosuppression, increased transfusion requirement and disappointing clinical outcomes among the so-called poor-prognosis AML subsets. BCL-2 inhibitor plus azacitidine (AZA) has become a preferred treatment for AML, but the remission rate and overall survival (OS) are suboptimal. Apart from hematologic toxicities, 70.0% of patients were RBC transfusion dependent and 58.6% were platelet transfusion dependent. At present, all-trans retinoic acid (ATRA) is used as a differentiation drug, and there is no combination regimen with BCL-2 inhibitor. This study aimed to assess the efficacy and safety of ATRA plus venetoclax and AZA for newly diagnosed AML. Methods: This study enrolled 35 patients (≥18 years) with newly diagnosed AML between 2022 and 2023. For induction, patients received AZA (75 mg/m²) from Day 1 to 7, venetoclax at a target dose of 400 mg/d from Day 2 to 10, and ATRA (45 mg/m²/d) from Day 12 to 28 of each 28-day cycle for up to 2 cycles or until disease progression. Patients who achieved complete remission (CR) after two cycles of induction therapy received bone marrow transplantation or consolidation at their own discretion. For consolidation, patients received ATRA (45 mg/m²/d) from Day 1 to 21 and AZA (75 mg/m²) from Day 1 to 7 of each 28-day cycle for up to 4 cycles or until disease progression. For maintenance, patients received ATRA (45 mg/m²/d) for 21 days per cycle plus AZA (75 mg/m²). Maintenance therapy was given every 3 months until disease progression and ATRA was provided during intermissions. The primary endpoint was the composite CR rate (CR and CR with incomplete hematologic recovery) at the end of cycle 1 of inductive therapy. Results: As of now, the composite CR rate reached 74% (26/35) and the objective response rate reached 91% (32/35). The composite CR was 73% (11/15) in the adverse risk group and 75% (15/20) in the favorable-intermediate risk group at the end of cycle 1. Thirty-three patients entered cycle 2. The cumulative composite CR rate reached 91%(30/33) after 2 cycles of induction therapy. The median event-free survival was 390 days, and the median OS was 573 days. Platelet transfusion independence occurred in 17% (6/35) patients in cycle 1 and 73% (24/33) in cycle 2. Furthermore, 20% (7/35) and 73% (24/33) patients were RBC transfusion independent in cycle 1 and 2, respectively. Any-grade infections occurred in 74% (26/35) patients, including 12 before admission. Conclusions: The treatment regimen achieved a high composite CR rate and was well tolerated, with reduced hematologic toxicities in cycle 2 of induction therapy. Both adverse risk and favorable-intermediate risk patients benefited from the regimen, which holds promise for treating AML in adult patients. Clinical trial information: NCT05654194 .

WITHDRAWN: ATRA regulates myoblast differentiation and fusion through the RARα/Pitx2 signaling pathway, causing abnormal development of PFMs in ARM fetal rats.

Anorectal malformation (ARM) is the most common congenital digestive tract anomaly in newborns, and children with ARM often have varying degrees of underdevelopment of the pelvic floor muscles (PFMs). To explore the effects of RARα and Pitx2 on the development of rat PFMs, we constructed a rat ARM animal model using all-trans retinoic acid (ATRA), and verified the expression of RARα and Pitx2 in the PFMs of fetal rats. Additionally, we used rat myoblasts (L6 cells) to investigate the regulatory roles of RARα and Pitx2 in skeletal muscle myoblast differentiation and their interactions. The results indicated a significant decrease in the expression of RARα and Pitx2 in the PFMs of fetal rats with ARM. ATRA can also decrease the expression of RARα and Pitx2 in the L6 cells, while affecting the differentiation and fusion of L6 cells. Knocking down RARα in L6 cells reduced the expression of Pitx2, MYOD1, MYMK, and decreased myogenic activity in L6 cells. When RARα is activated, the decreased expression of Pitx2, MYOD1, and MYMK and myogenic differentiation can be restored to different extents. At the same time, increasing or inhibiting the expression of Pitx2 can counteract the effects of knocking down RARα and activating RARα respectively. These results indicate that Pitx2 may be downstream of the transcription factor RARα, mediating the effects of ATRA on the development of fetal rat PFMs.

Triplet combination treatments with pembrolizumab (pembro) for anti–PD-(L)1–refractory advanced melanoma: Preliminary results of the phase 1/2 KEYMAKER-U02A study.

9506 Background: Anti–PD-(L)1–refractory melanoma is a major challenge, and immunotherapy combination treatment may be useful in this patient population. The phase 1/2 KEYMAKER-U02A (NCT04305041) is a multi-arm, open-label, adaptive umbrella study designed to evaluate pembro + investigational agents for the treatment of anti–PD-(L)1–refractory melanoma. We report results from arm 1 (pembro + quavonlimab [qmab] (anti-CTLA4) + vibostolimab [vibo] (anti-TIGIT)), arm 2 [pembro + qmab + lenvatinib [len] (TKI)), and arm 3 (pembro + ATRA [all-trans retinoic acid]) of KEYMAKER-U02A. Methods: In all arms, adults had stage III/IV melanoma, ≥1 measurable lesion per RECIST v1.1, an Eastern Cooperative Oncology Group performance status score of 0 or 1, and disease progression on anti–PD-(L)1 therapy alone or in combination. Pts were randomized equally to open arms. In arm 1, pts received pembro 200 mg IV Q3W + qmab 25 mg IV Q6W + vibo 200 mg IV Q3W. In arm 2, pts received pembro 400 mg IV Q6W + qmab 25 mg IV Q6W + len 20 mg PO QD. In arm 3, pts received pembro 400 mg IV Q6W + ATRA 150 mg/m2/day PO for 3 days Q3W. Pts received treatment for up to 2 y or until intolerable toxicity, disease progression, or pt withdrawal. Primary end points were safety and ORR per RECIST v1.1 by blinded independent central review (BICR). DOR per RECIST v1.1 by BICR was the secondary end point. PFS per RECIST v1.1 by BICR and OS were exploratory end points. Enrollment was planned for a maximum of 20 pts in each arm and enrollment could continue to up to 40 pts if an ORR of > 20% (5/20) was observed. Enrollment would then continue up to 100 pts if an ORR of ≥35% (14/40) was observed. Results: At data cutoff (Oct 18, 2022), 40 pts had been assigned to arms 1 and 2 and 20 pts to arm 3. Median (range) follow-up was 18.4 (1.7-24.5) mo in arm 1, 18.5 mo (1.6-25.4) in arm 2, and 2.7 mo (0.8-3.5) in arm 3. Efficacy is reported in the table. Treatment-related adverse events (TRAEs) occurred in 35 pts (88%) in arm 1, 38 pts (95%) in arm 2, and 15 pts (75%) in arm 3. Grade 3-5 TRAEs occurred in 11 pts (28%) in arm 1, 23 pts (58%) in arm 2, and 3 pts (15%) in arm 3; 1 pt in arm 2 died from a grade 5 TRAE (immune-mediated nephritis). Conclusions: Although objective responses were observed in some pts with anti–PD-(L)1–refractory melanoma, protocol-prespecified criteria for enrollment expansion were not met in any arm. The safety profile was manageable. Additional arms will be reported for this pt population with a high unmet need. Clinical trial information: NCT04305041 . [Table: see text]

Development and validation of CYP26A1 inhibition assay for high-throughput screening.

All-trans retinoic acid (atRA) is an endogenous ligand of the retinoic acid receptors, which heterodimerize with retinoid X receptors. AtRA is generated in tissues from vitamin A (retinol) metabolism to form a paracrine signal and is locally degraded by cytochrome P450 family 26 (CYP26) enzymes. The CYP26 family consists of three subtypes: A1, B1, and C1, which are differentially expressed during development. This study aims to develop and validate a high throughput screening assay to identify CYP26A1 inhibitors in a cell-free system using a luminescent P450-Glo assay technology. The assay performed well with a signal to background ratio of 25.7, a coefficient of variation of 8.9%, and a Z-factor of 0.7. To validate the assay, we tested a subset of 39 compounds that included known CYP26 inhibitors and retinoids, as well as positive and negative control compounds selected from the literature and/or the ToxCast/Tox21 portfolio. Known CYP26A1 inhibitors were confirmed, and predicted CYP26A1 inhibitors, such as chlorothalonil, prochloraz, and SSR126768, were identified, demonstrating the reliability and robustness of the assay. Given the general importance of atRA as a morphogenetic signal and the localized expression of Cyp26a1 in embryonic tissues, a validated CYP26A1 assay has important implications for evaluating the potential developmental toxicity of chemicals.

Exploratory phase I study of HF1K16 for the treatment of patients with refractory/recurrent advanced glioma: Preliminary efficacy and mechanism as a monotherapy.

e14030 Background: The absence of I.O success in advanced glioma treatment suggests that a deeper understanding of the brain tumor and the immune microenvironment is critical. It is well-documented that refractory/recurrent glioma has an immunosuppressive nature. One frequent observation is the high level of circulating myeloid-derived suppressor cells (MDSCs). We conducted a exploratory study to assess an immunomodulatory approach for relieving immune suppression employing HF1K16, a liposome all-trans retinoic acid (ATRA) suspension. Methods: This Phase I study (NCT05388487) comprise a conventional 3+3 dose escalation plus an advanced glioma-specific expansion arm. Eligible patients had prior confirmed advanced solid tumor and failed standard treatment. HF1K16 infusions were administered in 21-day cycles (q.o.d days 1-14). Prior to and during treatment, peripheral blood mononuclear cells were collected and analyzed with flow cytometry to monitor the changes in myeloid cell phenotype and T cell composition. Survival data were calculated as it is difficult to determine the timing of progression for immunotherapies owing to pseudoprogression. Results: As of Feb 2th, 2024, 14 recurrent/refractory glioma patients including 6 males and 8 females had been enrolled in this study. 2 of them withdrew before finished 1st cycle. 7 had received treatment for at least 3 cycles and 1 had achieved CR after 15 cycles. For the 8 primary diagnosed grade IV glioma patients, the mOS is 7.8m, and 6 (75%) are alive. The mOS for the primary dignosed grade II/III is 13.7m and 100% patients are alive (n=4). There is 1 recurrent GBM patent who had received 5 cycles of treatment. MRI showed an enlargement of tumor lesion while KPS score remained >90. A surgical resection was performed and we subsequently studied the posttreatment tumor specimens (window of opportunity). IHC and flow cytometry analysis revealed prominent perivascular and intratumoral inflammatory infiltrate, containing CD8+CTL cells and HLA-DR expressing cells. Conclusions: While the interpretation of our data is limited by the small sample size, the results provide an encouraging signal and warrants further assessment. Patient recruitment continues with anticipated completion in 2024. Clinical trial information: NCT05388487 . [Table: see text]

Clinical networking results in continuous improvement of the outcome of patients with acute promyelocytic leukemia

AbstractThe introduction of all-trans retinoic acid combined with anthracyclines has significantly improved the outcomes for patients diagnosed with acute promyelocytic leukemia (APL), and this strategy remains the standard of care in countries in which arsenic trioxide is not affordable. However, data from national registries and real-world databases indicate that low- and middle-income countries (LMIC) still face disappointing results, mainly because of high induction mortality and suboptimal management of complications. The American Society of Hematology established the International Consortium on Acute Leukemias (ICAL) to address this challenge through international clinical networking. Here, we present the findings from the International Consortium on Acute Promyelocytic Leukemia study involving 806 patients with APL recruited from 2005 to 2020 in Brazil, Chile, Paraguay, Peru, and Uruguay. The induction mortality rate has notably decreased to 14.6% compared with the pre-ICAL rate of 32%. Multivariable logistic regression analysis revealed as factors associated with induction death: age of ≥40 years, Eastern Cooperative Oncology Group performance status score of 3, high-risk status based on the Programa Español de Tratamiento en Hematologia/Gruppo Italiano Malattie EMatologiche dell'Adulto classification, albumin level of ≤3.5 g/dL, bcr3 PML/RARA isoform, the interval between presenting symptoms to diagnosis exceeding 48 hours, and the occurrence of central nervous system and pulmonary bleeding. With a median follow-up of 53 months, the estimated 4-year overall survival rate is 81%, the 4-year disease-free survival rate is 80%, and the 4-year cumulative incidence of relapse rate is 15%. These results parallel those observed in studies conducted in high-income countries, highlighting the long-term effectiveness of developing clinical networks to improve clinical care and infrastructure in LMIC.

ZMYND8 Is a Regulator of Sonic Hedgehog Signaling in ATRA-Mediated Differentiation of Neuroblastoma Cells.

Zinc Finger MYND (Myeloid, Nervy, and DEAF-1) type containing 8 (ZMYND8) is a crucial epigenetic regulator that plays a multifaceted role in governing a spectrum of vital cellular processes, encompassing proliferation, apoptosis, migration, tumor suppression, and differentiation. It has emerged as a key player in neuronal differentiation by orchestrating the expression of neuronal lineage-committed genes. The present study uncovers the role of ZMYND8 in regulating the Sonic Hedgehog (SHH) signaling axis, which is crucial for neuronal differentiation. Genetic deletion of ZMYND8 leads to a significant reduction in SHH pathway genes, GLI1, and PTCH1 expression during all-trans-retinoic acid (ATRA)-induced differentiation. ZMYND8 and RNA pol II S5P are found to co-occupy the GLI1 and PTCH1 gene promoters, positively impacting their gene transcription upon ATRA treatment. Interestingly, ZMYND8 is found to counteract the inhibitory effects of Cyclopamine that block the upstream SHH pathway protein SMO, resulting in enhanced neurite formation in neuroblastoma cells following their treatment with ATRA. These results indicate that ZMYND8 is an epigenetic regulator of the SHH signaling pathway and has tremendous therapeutic potential in ATRA-mediated differentiation of neuroblastoma.

All-trans retinoic acid pretreatment of mesenchymal stem cells enhances the therapeutic effect on acute kidney injury.

A promising new therapy option for acute kidney injury (AKI) is mesenchymal stem cells (MSCs). However, there are several limitations to the use of MSCs, such as low rates of survival, limited homing capacity, and unclear differentiation. In search of better therapeutic strategies, we explored all-trans retinoic acid (ATRA) pretreatment of MSCs to observe whether it could improve the therapeutic efficacy of AKI. We established a renal ischemia/reperfusion injury model and treated mice with ATRA-pretreated MSCs via tail vein injection. We found that AKI mice treated with ATRA-MSCs significantly improved renal function compared with DMSO-MSCs treatment. RNA sequencing screened that hyaluronic acid (HA) production from MSCs promoted by ATRA. Further validation by chromatin immunoprecipitation experiments verified that retinoic acid receptor RARα/RXRγ was a potential transcription factor for hyaluronic acid synthase 2. Additionally, an in vitro hypoxia/reoxygenation model was established using human proximal tubular epithelial cells (HK-2). After co-culturing HK-2 cells with ATRA-pretreated MSCs, we observed that HA binds to cluster determinant 44 (CD44) and activates the PI3K/AKT pathway, which enhances the anti-inflammatory, anti-apoptotic, and proliferative repair effects of MSCs in AKI. Inhibition of the HA/CD44 axis effectively reverses the renal repair effect of ATRA-pretreated MSCs. Taken together, our study suggests that ATRA pretreatment promotes HA production by MSCs and activates the PI3K/AKT pathway in renal tubular epithelial cells, thereby enhancing the efficacy of MSCs against AKI.

A rare incidence of severe dermatological toxicities triggered by concomitant administration of all-trans retinoic acid and triazole antifungal in patients with acute promyelocytic leukemia: a case series and review of the literature

BackgroundAll-trans retinoic acid (ATRA) is an indispensable part of the treatment of acute promyelocytic leukemia (APL). Although, mild cutaneous toxicities like mucocutaneous xerosis, rash, and pruritus are well reported, ATRA associated severe dermatological toxicities are extremely rare. ATRA is primary metabolized by cytochrome P450 (CYP450) enzyme system, and triazole antifungals are notorious for their strong inhibitory effect on CYP450.Case presentationThree Asian APL patients experienced rare ATRA-induced severe dermatological toxicities: exfoliative dermatitis (ED) in cases 1 and 2, and necrotic scrotal ulceration in case 3. Both case 1 (33-year-old female), and case 2 (28-year-old male) landed in emergency department with dehydration, generalized skin erythema and xerosis during their induction chemotherapy. Both of these patients also developed invasive aspergillosis and required concomitant triazole antifungals during their chemotherapy. For ED, intravenous fluids and broad-spectrum antibiotics were started along with application of local emollients to prevent transdermal water loss. Although their general condition improved but skin exfoliation continued with complete desquamation of palms and soles. Dermatology was consulted, and clinical diagnosis of ED was established. Discontinuation of ATRA resulted in complete resolution of ED. Case 3 (15-year-old boy) reported two blackish mildly tender scrotal lesions during induction chemotherapy. He also had mucocutaneous candidiasis at presentation and was kept on triazole antifungal. Local bacterial & fungal cultures, and serological testing for herpes simplex virus were reported negative. Despite adequate local care and optimal antibiotic support, his lesions persisted, and improved only after temporary discontinuation of ATRA. After a thorough literature review and considering the temporal association of cutaneous toxicities with triazole antifungals, we speculate that the concomitant use of triazole antifungals inhibited the hepatic metabolism of ATRA, resulting in higher serum ATRA concentration, and markedly accentuated cutaneous toxicities in our patients.ConclusionBy highlighting this crucial pharmacokinetic interaction, we want to caution the fellow oncologists to be mindful of the inhibitory effect of triazole antifungals on CYP450. We propose using a non-myelosuppressive combination of ATRA and arsenic trioxide for management of APL hence, obliterating the need of prophylactic antifungals. However, in the event of invasive fungal infection (IFI), we suggest using alternative class of antifungals.

Association of the retinol to all-trans retinoic acid pathway with autism spectrum disorder.

Autism spectrum disorder (ASD) is a complex group of neurodevelopmental disorders. Research has highlighted a close association between the retinoic acid (RA) signaling pathway and ASD. This study investigates alterations in the vitamin A (VA, retinol) to RA metabolic pathway in children with ASD and speculates on the underlying reasons for these changes. We propose a subtype characterized by downregulated RA signaling in ASD, laying the groundwork for precise diagnosis and treatment research. We included 489 children with ASD and 280 typically developing (TD) children. Those with ASD underwent evaluations of core symptoms and neuro-developmental levels, which were conducted by professional developmental behavior physicians using assessment scales. Serum VA and all-trans RA (atRA) levels were determined by high-performance liquid chromatography and ultra-high-performance liquid chromatography-tandem mass spectrometry. The expression levels and concentrations of enzyme molecules such as retinol dehydrogenase 10 were assessed using quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Children with ASD exhibited reduced serum atRA, accompanied by a downregulation of atRA synthesis enzymes. The reduction in serum atRA levels was linked not only to VA levels but also to the aberrant expression of metabolic enzymes responsible for atRA. Furthermore, the serum atRA levels in children with ASD were more strongly correlated with core symptoms and neurodevelopmental levels than VA levels. Children with ASD exhibited a dual regulation of reduced serum atRA levels, influenced by both VA levels and abnormal expression of atRA metabolic enzymes.

#2339 All-trans retinoic acid enhances the efficacy of mesenchymal stem cells in acute kidney injury

Abstract Background and Aims Mesenchymal stem cells (MSCs) have emerged as a promising therapeutic strategy for acute kidney injury (AKI), but still suffer from the drawbacks of low survival rate, low homing rate, and uncertain differentiation. In search of better therapeutic strategies, we explored all-trans retinoic acid (ATRA) pretreatment of MSCs to observe whether it could improve the therapeutic efficacy on AKI. Method We established a renal ischemia/reperfusion (I/R) injury model induced by clamping of left renal artery for 30 minutes and contralateral nephrectomy. C57BL/6 mice were randomly divided into 4 groups: sham group, IRI group, MSCs group, and ATRA-MSCs group. MSCs or ATRA-pretreated MSCs were injected via tail vein. GFR was measured by transcutaneous monitoring the clearance of FITC-sinistrin. These mice were sacrificed 3 days after surgery, and the serum creatinine (SCr) and blood urea nitrogen (BUN) levels were measured. The renal pathological changes were examined by Periodic Acid-Schiff staining (PAS). The in vitro hypoxia/reoxygenation (H/R) model was established using human proximal tubular epithelial cells (HK-2 cells). Co-culturing HK-2 cells with MSCs or ATRA-pretreated MSCs. Western blot, quantitative real time-PCR (qRT-PCR), and immunohistochemistry were used to detect mRNA or protein expression. We performed RNA sequencing (RNA-seq) analysis in ATRA-pretreated MSCs. The content of hyaluronic acid (HA) in the supernatant of ATRA-pretreated MSCs culture was detected by ELISA. Hyaluronan synthase mRNA expression level in ATRA-pretreated MSCs assessed by qRT-PCR analysis. The HAS2 promoter-binding transcription factors were forecasted by the JASPAR Transcription Factor Binding Site database. Western blot was used to detect whether P13K/AKT pathway was activated by ATRA-pretreated MSCs. Whether this nephroprotective effect could be reversed were explored by silencing HAS2 or CD44 antibodies. Results The AKI mice showed a significant decrease in GFR and even complete loss of renal function. Administration of MSCs significantly increased GFR, and MSCs pretreated with ATRA further increased GFR. Mice injected with ATRA-pretreated MSCs had significantly lower levels of SCr, BUN and ATN scores compared with untreated MSCs. Western blot, quantitative real-time PCR (qRT-PCR), and immunohistochemistry showed that ATRA pretreated MSCs were more effective in reducing AKI inflammation and apoptosis and promoting proliferative repair than untreated MSCs. GO enrichment analysis demonstrated that the hyaluronan biosynthetic process may be a significantly expressed. HAS2 expression and HA content of MSCS were significantly increased after the addition of ATRA. Analysis for potential transcription factor binding sites revealed that the HAS2 promoter region has multiple potential binding sites for the retinoic acid receptor. Based on the predictions from the JASPAR database, the RXR-RAR heterodimer had the highest prediction score. We then performed ChIP analysis to experimentally verify the binding of RXR-RAR heterodimer transcription factor to HAS2 promoters. We further found that ATRA-pretreated MSCs activated the PI3K/AKT signaling pathway in AKI. As expected, we found that ATRA-pretreated MSCs anti-inflammatory, anti-apoptosis, and pro-proliferation effects were substantially reversed by silencing HAS2 or blocking CD44. Conclusion ATRA promotes HA secretion from MSCs and activates the PI3K/AKT pathway, which in turn enhances the therapeutic efficacy of MSCs on AKI.

Identification and Evaluation of Olive Phenolics in the Context of Amine Oxidase Enzyme Inhibition and Depression: In Silico Modelling and In Vitro Validation.

The Mediterranean diet well known for its beneficial health effects, including mood enhancement, is characterised by the relatively high consumption of extra virgin olive oil (EVOO), which is rich in bioactive phenolic compounds. Over 200 phenolic compounds have been associated with Olea europaea, and of these, only a relatively small fraction have been characterised. Utilising the OliveNetTM library, phenolic compounds were investigated as potential inhibitors of the epigenetic modifier lysine-specific demethylase 1 (LSD1). Furthermore, the compounds were screened for inhibition of the structurally similar monoamine oxidases (MAOs) which are directly implicated in the pathophysiology of depression. Molecular docking highlighted that olive phenolics interact with the active site of LSD1 and MAOs. Protein-peptide docking was also performed to evaluate the interaction of the histone H3 peptide with LSD1, in the presence of ligands bound to the substrate-binding cavity. To validate the in silico studies, the inhibitory activity of phenolic compounds was compared to the clinically approved inhibitor tranylcypromine. Our findings indicate that olive phenolics inhibit LSD1 and the MAOs in vitro. Using a cell culture model system with corticosteroid-stimulated human BJ fibroblast cells, the results demonstrate the attenuation of dexamethasone- and hydrocortisone-induced MAO activity by phenolic compounds. The findings were further corroborated using human embryonic stem cell (hESC)-derived neurons stimulated with all-trans retinoic acid. Overall, the results indicate the inhibition of flavin adenine dinucleotide (FAD)-dependent amine oxidases by olive phenolics. More generally, our findings further support at least a partial mechanism accounting for the antidepressant effects associated with EVOO and the Mediterranean diet.

All-trans-retinoic acid modulates glycolysis via H19 and telomerase: the role of mir-let-7a in estrogen receptor-positive breast cancer cells

BackgroundBreast cancer (BC) is the most commonly diagnosed cancer in women. Treatment approaches that differ between estrogen-positive (ER+) and triple-negative BC cells (TNBCs) and may subsequently affect cancer biomarkers, such as H19 and telomerase, are an emanating delight in BC research. For instance, all-trans-Retinoic acid (ATRA) could represent a potent regulator of these oncogenes, regulating microRNAs, mostly let-7a microRNA (miR-let-7a), which targets the glycolysis pathway, mainly pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA) enzymes. Here, we investigated the potential role of ATRA in H19, telomerase, miR-let-7a, and glycolytic enzymes modulation in ER + and TNBC cells.MethodsMCF-7 and MDA-MB-231 cells were treated with 5 µM ATRA and/or 100 nM fulvestrant. Then, ATRA-treated or control MCF-7 cells were transfected with either H19 or hTERT siRNA. Afterward, ATRA-treated or untreated MDA-MB-231 cells were transfected with estrogen receptor alpha ER(α) or beta ER(β) expression plasmids. RNA expression was evaluated by RT‒qPCR, and proteins were assessed by Western blot. PKM2 activity was measured using an NADH/LDH coupled enzymatic assay, and telomerase activity was evaluated with a quantitative telomeric repeat amplification protocol assay. Student’s t-test or one-way ANOVA was used to analyze data from replicates.ResultsOur results showed that MCF-7 cells were more responsive to ATRA than MDA-MB-231 cells. In MCF-7 cells, ATRA and/or fulvestrant decreased ER(α), H19, telomerase, PKM2, and LDHA, whereas ER(β) and miR-let-7a increased. H19 or hTERT knockdown with or without ATRA treatment showed similar results to those obtained after ATRA treatment, and a potential interconnection between H19 and hTERT was found. However, in MDA-MB-231 cells, RNA expression of the aforementioned genes was modulated after ATRA and/or fulvestrant, with no significant effect on protein and activity levels. Overexpression of ER(α) or ER(β) in MDA-MB-231 cells induced telomerase activity, PKM2 and LDHA expression, in which ATRA treatment combined with plasmid transfection decreased glycolytic enzyme expression.ConclusionsTo the best of our knowledge, our study is the first to elucidate a new potential interaction between the estrogen receptor and glycolytic enzymes in ER + BC cells through miR-let-7a.