Engineered liposomes targeting hepatic stellate cells overcome pathological barriers and reverse liver fibrosis

Dual pathological barriers, including capillarized liver sinusoidal endothelial cells (LSECs) and deposited extracellular matrix (ECM), result in insufficient drug delivery, significantly compromising the anti-fibrosis efficacy. Additionally, excessive reactive oxygen species (ROS) in the hepatic microenvironment are crucial factors contributing to the progression of liver fibrosis. Hence, hyaluronic acid (HA) modified liposomes co-delivering all-trans retinoic acid (RA) and L-arginine (L-arg) were constructed to reverse hepatic fibrosis. By exhibiting exceptional responsiveness to the fibrotic microenvironment, our cleverly constructed liposomes efficiently disrupted the hepatic sinus pathological barrier, leading to enhanced accumulation of liposomes in activated hepatic stellate cells (HSCs) and subsequent induction of HSCs quiescence. Specially, excessive ROS in liver fibrosis promotes the conversion of loaded L-arg to nitric oxide (NO). The ensuing NO serves to reestablish the fenestrae structure of capillarized LSECs, thereby augmenting the likelihood of liposomes reaching the hepatic sinus space. Furthermore, subsequent oxidation of NO by ROS into peroxynitrite activates pro-matrix metalloproteinases into matrix metalloproteinases, which further disrupts the deposited ECM barrier. Consequently, this NO-induced cascade process greatly amplifies the accumulation of liposomes within activated HSCs. More importantly, the released RA could induce quiescence of activated HSCs by significantly downregulating the expression of myosin light chain-2, thereby effectively mitigating excessive collagen synthesis and ultimately leading to the reversal of liver fibrosis. Overall, this integrated systemic strategy has taken a significant step forward in advancing the treatment of liver fibrosis.

All-trans retinoic acid alleviates transmissible gastroenteritis virus-induced intestinal inflammation and barrier dysfunction in weaned piglets

BACKGROUND

Transmissible gastroenteritis virus (TGEV) is one of the main pathogens causing severe diarrhea of piglets. The pathogenesis of TGEV is closely related to intestinal inflammation. All-trans retinoic acid (ATRA) is the main active metabolite of vitamin A, which has immunomodulatory and anti-inflammatory properties. However, it is unclear whether ATRA can alleviate TGEV-induced intestinal inflammation and barrier dysfunction in piglets. This study aimed to investigate the effects of ATRA on growth performance, diarrhea, intestinal inflammation and intestinal barrier integrity of TGEV-challenged piglets.

METHODS

In a 19-d study, 32 weaned piglets were randomly divided into 4 treatments: Control group (basal diet), TGEV group (basal diet + TGEV challenge), TGEV + ATRA5 group (basal diet + 5 mg/d ATRA + TGEV challenge) and TGEV + ATRA15 group (basal diet + 15 mg/d ATRA + TGEV challenge). On d 14, piglets were orally administered TGEV or the sterile medium.

RESULTS

Feeding piglets with 5 and 15 mg/d ATRA alleviated the growth inhibition and diarrhea induced by TGEV (P < 0.05). Feeding piglets with 5 and 15 mg/d ATRA also inhibited the increase of serum diamine oxidase (DAO) activity and the decrease of occludin and claudin-1 protein levels in jejunal mucosa induced by TGEV, and maintained intestinal barrier integrity (P < 0.05). Meanwhile, 5 mg/d ATRA feeding increased the sucrase activity and the expressions of nutrient transporter related genes (GLUT2 and SLC7A1) in jejunal mucosa of TGEV-challenged piglets (P < 0.05). Furthermore, 5 mg/d ATRA feeding attenuated TGEV-induced intestinal inflammatory response by inhibiting the release of interleukin (IL)-1β, IL-8 and tumor necrosis factor-α (TNF-α), and promoting the secretion of IL-10 and secretory immunoglobulin A (sIgA) (P < 0.05). Feeding 5 mg/d ATRA also down-regulated the expressions of Toll-like receptors and RIG-I like receptors signaling pathway related genes (TLR3, TLR4, RIG-I, MyD88, TRIF and MAVS) and the phosphorylation level of nuclear factor-κB-p65 (NF-κB p65), and up-regulated the inhibitor kappa B alpha (IκBα) protein level in jejunal mucosa of TGEV-challenged piglets (P < 0.05).

CONCLUSIONS

ATRA alleviated TGEV-induced intestinal barrier damage by inhibiting inflammatory response, thus improving the growth performance and inhibiting diarrhea of piglets. The mechanism was associated with the inhibition of NF-κB signaling pathway mediated by TLR3, TLR4 and RIG-I.

Outcome of Patients With Relapsed Acute Promyelocytic Leukemia

BACKGROUND

The outcome of patients with acute promyelocytic leukemia (APL) has improved significantly since the introduction of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) as APL therapies. The optimal therapy for APL relapse is believed to require autologous or allogeneic stem cell transplantation (SCT) based on historical experience.

STUDY AIMS

To evaluate the outcome of patients with relapsed APL before and after the era of ATRA-ATO.

PATIENTS AND METHODS

We reviewed 61 patients with relapsed APL treated from November 1991 to June 2023; 31 patients (51%) received modern therapy with the combination of ATRA and ATO with and without idarubicin and gemtuzumab ozogamicin (GO).

RESULTS

Overall, 56 patients (92%) achieved CR after the first salvage therapy; 20 patients received SCT (10 autologous SCT;10 allogeneic SCT). With a median follow-up time of 138 months, the median survival durations were 32 months and 164 months with historical therapy vs. modern (ATRA-ATO) therapy (P = .035); the 5-year survival rates were 44% vs. 71%. With a 10-month landmark analysis, the median survival durations were 102 months vs. not reached, and the 5-year survival rates were 57% and 70% without SCT vs. with SCT (P = .193). The survival benefit with SCT was more prominent in the historical therapy era. However, patients who received the modern combination therapy of ATRA-ATO with and without idarubicin and GO had similar outcomes without vs. with SCT (P = .848).

CONCLUSION

The combination of ATRA-ATO (+/- GO and idarubicin) is a highly effective salvage therapy in relapsed APL. The use of SCT may not be needed after first relapse-second remission but may be considered in subsequent relapses.

Fucosylation inhibitor 6-alkynylfucose enhances the ATRA-induced differentiation effect on acute promyelocytic leukemia cells

For acute promyelocytic leukemia (APL), differentiation therapy with all-trans retinoic acid (ATRA) is well established. However, the narrow application and tolerance development of ATRA remain to be improved. In this study, we investigated the effects of combinations of glycosylation inhibitors with ATRA to achieve better efficiency than ATRA alone. We found that the combination of fucosylation inhibitor 6-alkynylfucose (6AF) and ATRA had an additional effect on cell differentiation, as revealed by expression changes in two differentiation markers, CD11b and CD11c, and significant morphological changes in NB4 APL and HL-60 acute myeloid leukemia (AML) cells. In AAL lectin blot analyses, ATRA or 6AF alone could decrease fucosylation, while their combination decreased fucosylation more efficiently. To clarify the molecular mechanism for the 6AF effect on ATRA-induced differentiation, we performed microarray analyses using NB4 cells. In a pathway analysis using DAVID software, we found that the C-type lectin receptor (CLR) signaling pathway was enriched with high significance. In real-time PCR analyses using NB4 and HL-60 cells, FcεRIγ, CLEC6A, CLEC7A, CASP1, IL-1β, and EGR3, as components of the CLR pathway, as well as CD45 and AKT3 were upregulated by 6AF in ATRA-induced differentiation. Taken together, the present findings suggest that the CLR signaling pathway is involved in the 6AF effect on ATRA-induced differentiation.

Combination of Ethacrynic Acid and ATRA Triggers Differentiation and/or Apoptosis of Acute Myeloid Leukemia Cells through ROS

BACKGROUND AND OBJECTIVE

All-trans retinoic acid (ATRA), an effective differentiation inducer, has been applied clinically to treat acute promyelocytic leukemia (APL). Unfortunately, it is not as potent in other kinds of acute myeloid leukemia (AML). Ethacrynic acid (EA), a classical powerful diuretic, can increase reactive oxygen species (ROS) contents, which can assist ATRA in inducing differentiation in AML cells. Here, we investigated the effect of EA combined with ATRA (EA+RA) on some AML cells except APL.

METHODS

Apoptosis and differentiation were determined by morphology, cell viability, Annexin-V assay and CD11c expression. Western blot analysis and the detection of ROS and mitochondrial transmembrane potentials (MMP) were used to investigate the mechanisms.

RESULTS

AML cells exhibited differentiation and/or apoptosis after EA+RA treatment. EA+RA increased the intracellular ROS contents. EA+RA-induced apoptosis was accompanied by MMP attenuation and caspase-3/7 activation. EA+RA-induced differentiation was along with MEK/ERK and Akt activation and increased expression of PU.1, CCAAT/enhancer-binding protein β (C/EBPβ) and C/EBPε. N-acetyl-L-cysteine (NAC), an antioxidant, thoroughly reduced EA+RA-increased ROS, and also inhibited MMP attenuation, the activation of caspase- 3/7, MEK/ERK and Akt pathways, the elevation of PU.1 and C/EBPs, and apoptosis and differentiation. However, MEK or PI3K specific inhibitors only suppressed EA+RA-triggered differentiation and the elevation of PU.1 and C/EBPs, but not ROS levels.

CONCLUSION

EA+ATRA induced cell apoptosis through ROS dependent MMP attenuation and caspase 3/7 activation while inducing differentiation by ROS-MEK/ERK-PU.1/C/EBPs and ROS-Akt-PU.1/C/EBPs pathways. In summary, it may provide innovative ATRA-based combination therapy strategies for AML patients via ROS.

Photothermal hyaluronic acid composite hydrogel targeting cancer stem cells for inhibiting recurrence and metastasis of breast cancer

Recurrence and metastasis have been recognized as a great challenge in cancer treatment. Cancer stem cells (CSCs), as a small subset of cancer cells, are closely associated with tumor metastasis and recurrence due to their resistance and multi-differentiation characteristics. Herein, we developed a local injectable hyaluronic acid (HA) composite hydrogel (HAAG) that targets CSCs, which can continuously release all-trans retinoic acid (ATRA) and gold nanoparticles (AuNPs) at tumor sites. The composite hydrogel was endowed with the ability to target CSCs through the specific binding of HA to CD44. ATRA was loaded into HA micelles to induce CSCs to differentiate into normal cancer cells, while AuNPs was incorporated into the hydrogel for photothermal therapy (PTT). HAAG exhibited good injectability, photothermal properties and CSCs targeting ability. HAAG not only significantly inhibited the growth of 4T1 mouse breast cancer cells and 4T1-CSCs in vitro, but also effectively inhibited tumor recurrence and metastasis in a 4T1-CSC mouse model in vivo. Our study provides a novel strategy of local differentiation combined with PTT for inhibiting the recurrence and metastasis of breast cancer.

Associations between the proliferation of palatal mesenchymal cells, Tgfβ2 promoter methylation, Meg3 expression, and Smad signaling in atRA-induced cleft palate

All-trans retinoic acid (atRA) is a teratogen that can induce cleft palate formation. During palatal development, murine embryonic palate mesenchymal (MEPM) cell proliferation is required for the appropriate development of the palatal frame, with Meg3 serving as a key regulator of the proliferative activity of these cells and the associated epithelial-mesenchymal transition process. DNA methylation and signaling via the TGFβ/Smad pathway are key in regulating embryonic development. Here, the impact of atRA on MEPM cell proliferation and associations between Tgfβ2 promoter methylation, Meg3, and signaling via the Smad pathway were explored using C57BL/6 N mice treated with atRA (100 mg/kg) to induce fetal cleft palate formation. Immunohistochemistry and BrdU assays were used to detect MEPM proliferation and DNA methylation assays were performed to detect Tgfβ2 promoter expression. These analyses revealed that atRA suppressed MEPM cell proliferation, promoted the upregulation of Meg3, and reduced the levels of Smad2 and Tgfβ2 expression phosphorylation, whereas Tgfβ2 promoter methylation was unaffected. RNA immunoprecipitation experiments indicated that the TgfβI receptor is directly targeted by Meg3, suggesting that the ability of atRA to induce cleft palate may be mediated through the Tgfβ/Smad signaling pathway.

Pharmacological EZH2 inhibition combined with retinoic acid treatment promotes differentiation and apoptosis in rhabdomyosarcoma cells

BACKGROUND

Rhabdomyosarcomas (RMS) are predominantly paediatric sarcomas thought to originate from muscle precursor cells due to impaired myogenic differentiation. Despite intensive treatment, 5-year survival for patients with advanced disease remains low (< 30%), highlighting a need for novel therapies to improve outcomes. Differentiation therapeutics are agents that induce differentiation of cancer cells from malignant to benign. The histone methyltransferase, Enhancer of Zeste Homolog 2 (EZH2) suppresses normal skeletal muscle differentiation and is highly expressed in RMS tumours.

RESULTS

We demonstrate combining inhibition of the epigenetic modulator EZH2 with the differentiating agent retinoic acid (RA) is more effective at reducing cell proliferation in RMS cell lines than single agents alone. In PAX3-FOXO1 positive RMS cells this is due to an RA-driven induction of the interferon pathway resulting in apoptosis. In fusion negative RMS, combination therapy led to an EZH2i-driven upregulation of myogenic signalling resulting in differentiation. In both subtypes, EZH2 is significantly associated with enrichment of trimethylated lysine 27 on histone 3 (H3K27me3) in genes that are downregulated in untreated RMS cells and upregulated with EZH2 inhibitor treatment. These results provide insight into the mechanism that drives the anti-cancer effect of the EZH2/RA single agent and combination treatment and indicate that the reduction of EZH2 activity combined with the induction of RA signalling represents a potential novel therapeutic strategy to treat both subtypes of RMS.

CONCLUSIONS

The results of this study demonstrate the potential utility of combining EZH2 inhibitors with differentiation agents for the treatment of paediatric rhabdomyosarcomas. As EZH2 inhibitors are currently undergoing clinical trials for adult and paediatric solid tumours and retinoic acid differentiation agents are already in clinical use this presents a readily translatable potential therapeutic strategy. Moreover, as inhibition of EZH2 in the poor prognosis FPRMS subtype results in an inflammatory response, it is conceivable that this strategy may also synergise with immunotherapies for a more effective treatment in these patients.

Nano transdermal system combining mitochondria-targeting cerium oxide nanoparticles with all-trans retinoic acid for psoriasis

Psoriasis is an inflammatory skin disease that is intricately linked to oxidative stress. Antioxidation and inhibition of abnormal proliferation of keratinocytes are pivotal strategies for psoriasis. Delivering drugs with these effects to the site of skin lesions is a challenge that needs to be solved. Herein, we reported a nanotransdermal delivery system composed of all-trans retinoic acid (TRA), triphenylphosphine (TPP)-modified cerium oxide (CeO2) nanoparticles, flexible nanoliposomes and gels (TCeO2-TRA-FNL-Gel). The results revealed that TCeO2 synthesized by the anti-micelle method, with a size of approximately 5 nm, possessed excellent mitochondrial targeting ability and valence conversion capability related to scavenging reactive oxygen species (ROS). TCeO2-TRA-FNL prepared by the film dispersion method, with a size of approximately 70 nm, showed high drug encapsulation efficiency (>96%). TCeO2-TRA-FNL-Gel further showed sustained drug release behaviors, great transdermal permeation ability, and greater skin retention than the free TRA. The results of in vitro EGF-induced and H2O2-induced models suggested that TCeO2-TRA-FNL effectively reduced the level of inflammation and alleviated oxidative stress in HaCat cells. The results of in vivo imiquimod (IMQ)-induced model indicated that TCeO2-TRA-FNL-Gel could greatly alleviate the psoriasis symptoms. In summary, the transdermal drug delivery system designed in this study has shown excellent therapeutic effects on psoriasis and is prospective for the safe and accurate therapy of psoriasis.

Nervous system development related gene expression regulation in the zebrafish embryo after exposure to valproic acid and retinoic acid: A genome wide approach

The evaluation of chemical and pharmaceutical safety for humans is moving from animal studies to New Approach Methodologies (NAM), reducing animal use and focusing on mechanism of action, whilst enhancing human relevance. In developmental toxicology, the mechanistic approach is facilitated by the assessment of predictive biomarkers, which allow mechanistic pathways perturbation monitoring at the basis of human hazard assessment. In our search for biomarkers of maldevelopment, we focused on chemically-induced perturbation of the retinoic acid signaling pathway (RA-SP), a major pathway implicated in a plethora of developmental processes. A genome-wide expression screening was performed on zebrafish embryos treated with two teratogens, all-trans retinoic acid (ATRA) and valproic acid (VPA), and a non-teratogen reference compound, folic acid (FA). Each compound was found to have a specific mRNA expression profile with 248 genes commonly dysregulated by both teratogenic compounds but not by FA. These genes were implicated in several developmental processes (e.g., the circulatory and nervous system). Given the prominent response of neurodevelopmental gene sets, and the crucial need to better understand developmental neurotoxicity, our study then focused on nervous system development. We found 62 genes that are potential early neurodevelopmental toxicity biomarker candidates. These results advance NAM-based safety assessment evaluation by highlighting the usefulness of the RA-SP in providing early toxicity biomarker candidates.

The mechanisms governing mouse embryonic palate mesenchymal cells' proliferation associated with atRA-induced cleft palate in mice: insights from integrated transcriptomic and metabolomic analyses

While exposure to high levels of all-trans retinoic acid (atRA) during pregnancy is known to suppress murine embryonic palate mesenchymal (MEPM) cells proliferation and to result in cleft palate (CP) development, the underlying mechanisms are poorly understood. Accordingly, this study was designed with the goal of clarifying the etiological basis for atRA-induced CP. A murine model of CP was established via the oral administration of atRA to pregnant mice on gestational day (GD) 10.5, after which transcriptomic and metabolomic analyses were performed with the goal of clarifying the critical genes and metabolites associated with CP development through an integrated multi-omics approach. MEPM cells proliferation was altered by atRA exposure as expected, contributing to CP incidence. In total, 110 genes were differentially expressed in the atRA treatment groups, suggesting that atRA may influence key biological processes including stimulus, adhesion, and signaling-related activities. In addition, 133 differentially abundant metabolites were identified including molecules associated with ABC transporters, protein digestion and absorption, mTOR signaling pathway, and the TCA cycle, suggesting a link between these mechanisms and CP. Overall, combined analyses of these transcriptomic and metabolomic results suggested that the MAPK, calcium, PI3K-Akt, Wnt, and mTOR signaling pathways are particularly important pathways enriched in the palatal cleft under conditions of atRA exposure. Together, these integrated transcriptomic and metabolomic approaches provided new evidence with respect to the mechanisms underlying altered MEPM cells proliferation and signal transduction associated with atRA-induced CP, revealing a possible link between oxidative stress and these pathological changes.

CD71-mediated liposomal arsenic-nickel complex combined with all-trans retinoic acid for the efficacy of acute promyelocytic leukemia

Clinically, arsenic trioxide (ATO) was applied to the treatment of acute promyelocytic leukemia (APL) as a reliable and effective frontline drug. However, the administration regimen of AsⅢ was limited due to its fast clearance, short therapeutic window and toxicity as well. Based on CD71 overexpressed on APL cells, in present study, a transferrin (Tf)-modified liposome (LP) was established firstly to encapsulate AsⅢ in arsenic-nickel complex by nickel acetate gradient method. The AsⅢ-loaded liposomes (AsLP) exhibited the feature of acid-sensitive release in vitro. Tf-modified AsLP (Tf-AsLP) were specifically taken up by APL cells and the acidic intracellular environment triggered liposome to release AsⅢ which stimulated reactive oxygen species level and caspase-3 activity. Tf-AsLP prolonged half-life of AsⅢ in blood circulation, lowered systemic toxicity, and promoted apoptosis and induced cell differentiation at lesion site in vivo. Considering that ATO combined with RA is usually applied as the first choice in clinic for APL treatment to improve the therapeutic effect, accordingly, a Tf-modified RA liposome (Tf-RALP) was designed to reduce the severe side effects of free RA and assist Tf-AsLP for better efficacy. As expected, the tumor inhibition rate of Tf-AsLP was improved significantly with the combination of Tf-RALP on subcutaneous tumor model. Furthermore, APL orthotopic NOD/SCID mice model was established by 60CO irradiation and HL-60 cells intravenously injection. The effect of co-administration (Tf-AsLP + Tf-RALP) was also confirmed to conspicuous decrease the number of leukemia cells in the circulatory system and prolong the survival time of APL mice by promoting the APL cells' apoptosis and differentiation in peripheral blood and bone marrow. Collectively, Tf-modified acid-sensitive AsLP could greatly reduce the systemic toxicity of free drug. Moreover, Tf-AsLP combined with Tf-RALP could achieve better efficacy. Thus, transferrin-modified AsⅢ liposome would be a novel clinical strategy to improve patient compliance, with promising translation prospects.

ATRA ameliorates fibrosis by suppressing the pro-fibrotic molecule Fra2/AP-1 in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune connective tissue disease that leads to irreversible fibrosis of the skin and the internal organs. The etiology of SSc is complex, its pathophysiology is poorly understood, and clinical therapeutic options are restricted. Thus, research into medications and targets for treating fibrosis is essential and urgent. Fos-related antigen 2 (Fra2) is a transcription factor that is a member of the activator protein-1 family. Fra2 transgenic mice were shown to have spontaneous fibrosis. All-trans retinoic acid (ATRA) is a vitamin A intermediate metabolite and ligand for the retinoic acid receptor (RAR), which possesses anti-inflammatory and anti-proliferative properties. Recent research has demonstrated that ATRA also has an anti-fibrotic effect. However, the exact mechanism is not fully understood. Interestingly, we identified potential binding sites for the transcription factor RARα to the promoter region of the FRA2 gene through JASPAR and PROMO databases. In this study, the pro-fibrotic effect of Fra2 in SSc is confirmed. SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc animals exhibit increased levels of Fra2. Inhibition of Fra2 expression in SSc dermal fibroblasts with Fra2 siRNA markedly decreased collagen I expression. ATRA reduced the expressions of Fra2, collagen I, and α-smooth muscle actin(α-SMA) in SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc mice. In addition, chromatin immunoprecipitation and dual-luciferase assays demonstrated that retinoic acid receptor RARα binds to the FRA2 promoter and modulates its transcriptional activity. ATRA decreases collagen I expression both in vivo and in vitro via the reduction of Fra2 expression. This work establishes the rationale for expanding the use of ATRA in the treatment of SSc and indicates that Fra2 can be used as an anti-fibrotic target.

All-trans retinoic acid added to treatment of primary immune thrombocytopenia: a systematic review and meta-analysis

All-trans retinoic acid (ATRA) application is a novel treatment approach for primary immune thrombocytopenia (ITP). This study aimed to evaluate the efficacy and safety of ATRA in the treatment of ITP. The databases of PubMed (MEDLINE), EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and China National Knowledge Internet were searched on August 5, 2022, to find randomized controlled trials (RCTs) and observational studies. Five observational studies and four RCTs from China were included, and 760 Chinese patients were analyzed. In the five observational studies, the pooled overall response rate (ORR) and complete response rate (CRR) were 59.5% (95% confidence interval [CI], 52.4-66.4%) and 20.6% (95% CI, 14.3-27.6%), respectively. In the selected four RCTs, the pooled odds ratios for sustained response rate, ORR, and CRR were 3.00 (95% CI, 1.97-4.57; P < 0.01), 3.21 (95% CI, 2.15-4.78; P < 0.01), and 2.12 (95% CI, 1.17-3.86; P = 0.01), respectively. ATRA was associated with a reduction in relapse rate and salvage treatment rate (odds ratio, 0.30; 95% CI, 0.18-0.50; P < 0.01; 0.36; 95% CI, 0.23-0.56; P < 0.01, respectively). The pooled odds ratios for grade 1-2 dry skin, headache (or dizziness), and rash acneiform were 49.99 (95% CI, 16.05-155.67; P < 0.01), 1.75 (95% CI, 0.98-3.12; P = 0.06), and 0.37 (95% CI, 0.10-1.34; P = 0.13), respectively. This study suggests that ATRA may significantly improve the initial and long-term response of patients with ITP.

Detection and characterization of free oxygen radicals induced protein adduct formation in differentiating macrophages

Reactive oxygen species play a key role in cellular homeostasis and redox signaling at physiological levels, where excessive production affects the function and integrity of macromolecules, specifically proteins. Therefore, it is important to define radical-mediated proteotoxic stress in macrophages and identify target protein to prevent tissue dysfunction. A well employed, THP-1 cell line was utilized as in vitro model to study immune response and herein we employ immuno-spin trapping technique to investigate radical-mediated protein oxidation in macrophages. Hydroxyl radical formation along macrophage differentiation was confirmed by electron paramagnetic resonance along with confocal laser scanning microscopy using hydroxyphenyl fluorescein. Lipid peroxidation product, malondialdehyde, generated under experimental conditions as detected using swallow-tailed perylene derivative fluorescence observed by confocal laser scanning microscopy and high-performance liquid chromatography, respectively. The results obtained from this study warrant further corroboration and study of specific proteins involved in the macrophage activation and their role in inflammations.

Liver fibrosis therapy based on biomimetic nanoparticles which deplete activated hepatic stellate cells

Liver fibrosis is one of the most common liver diseases with substantial morbidity and mortality. However, effective therapy for liver fibrosis is still lacking. Considering the key fibrogenic role of activated hepatic stellate cells (aHSCs), here we reported a strategy to deplete aHSCs by inducing apoptosis as well as quiescence. Therefore, we engineered biomimetic all-trans retinoic acid (ATRA) loaded PLGA nanoparticles (NPs). HSC (LX2 cells) membranes, presenting the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), were coated on the surface of the nanoparticles, while the clinically approved agent ATRA with anti-fibrosis ability was encapsulated in the inner core. The biomimetic coating of TRAIL-expressing HSC membranes does not only provide homologous targeting to HSCs, but also effectively triggers apoptosis of aHSCs. ATRA could induce quiescence of activated fibroblasts. While TM-NPs (i.e. membrane coated NPs without ATRA) and ATRA/NPs (i.e. non-coated NPs loaded with ATRA) only showed the ability to induce apoptosis and decrease the α-SMA expression in aHSCs, respectively, TM-ATRA/NPs induced both apoptosis and quiescence in aHSCs, ultimately leading to improved fibrosis amelioration in both carbon tetrachloride-induced and methionine and choline deficient L-amino acid diet induced liver fibrosis mouse models. We conclude that biomimetic TM-ATRA/NPs may provide a novel strategy for effective antifibrosis therapy.

Short communication: In ovo injection of all-trans retinoic acid causes adipocyte hypertrophy in embryos but lost its effect in posthatch chickens

The regulation of adipose deposition in broiler chickens is an important factor for production efficiency to poultry producers and health concerns to customers. Although vitamin A and its metabolite [all-trans retinoic acid (atRA)] have been used for studies on adipogenesis in mammals and avian, effects of embryonic atRA on adipose development in embryonic (E) and posthatch (D) ages in broiler chickens have not been studied yet. Different concentrations of atRA (0 M-2 μM) were injected in broiler eggs at E10, and adipose tissues were sampled at E16. Percentages of adipose tissues in chicken embryos were significantly increased in the group injected with 500 nM of atRA compared to the 0 M group (P < 0.05). In addition, the adipocyte cross-sectional area (CSA) was significantly greater by in ovo injection of 500 nM atRA compared to the injection of 0 M (P < 0.01). Moreover, in ovo atRA-injected embryos were hatched and BWs were measured at D0, D7, and D14. BWs were not different from those of the 0 M group. Percentages of adipose tissues and CSA of the in ovo atRA-injected group (500 nM) were not different from those of the 0 M group at D14. Taken together, the current study clearly showed that in ovo injection of atRA promoted adipose deposition with hypertrophy during embryonic development, but its effects were not maintained in early posthatch age in broiler chickens, implying that embryonic atRA has an important role in the regulation of adipose development in chicken embryos.

All-Trans Retinoic Acid Promotes M2 Macrophage Polarization in Vitro by Activating the p38MAPK/STAT6 Signaling Pathway

BACKGROUND

M2-type macrophages are inflammation-suppressing cells that are differentiated after induction by cytokines such as IL-4 or IL-13, which play an important regulatory role in inflammation and influence the regression of inflammation-related diseases. All-trans retinoic acid (ATRA) has an important role in suppressing immune-mediated inflammatory responses but the effect and underlying mechanism of ATRA on the polarization of M2 macrophages remains unclear.

METHODS

Macrophages were isolated from peritoneal wash fluid, and IL-4 (20 ng/mL) was used to construct a m2-type macrophage polarization model. The model was incubated with different concentrations of ATRA (15 µg/ml, 30 µg/ml, 45 µg/ml) for 24 h, and pretreated macrophages with p38MAPKα inhibitor SB202190 (20 μM). MTT, Trypan blue staining, Annexin V-PE/7-AAD staining, flow cytometry, real-time PCR and western blotting were used to investigate the effect and mechanism of ATRA on the polarization of M2 macrophages.

RESULTS

Compared with the IL-4 group, the proportion of F4/80⁺CD206⁺ M2-type macrophages was significantly higher in the ATRA group (P < 0.01). mRNA and protein expression levels of Arg-1, IL-10 and TGF-β1 were as significantly higher (P < 0.01) in the ATRA group as phosphorylation levels of STAT6 and p38MAPK (P < 0.01). After pretreatment with the addition of the inhibitor SB202190, M2-type macrophages proportion and their associated factors expression were significantly (P < 0.01) reduced, as compared with those in the ATRA group, but they were comparable (P > 0.05) with the IL-4 group.

CONCLUSION

The combination of ATRA and IL-4 activated the p38MAPK/STAT6-signaling pathway to promote polarization of M2 macrophages.

Efficacy and safety of treatments in newly diagnosed adult primary immune thrombocytopenia: A systematic review and network meta-analysis

BACKGROUND

Immune thrombocytopenia is an autoimmune disease characterised by decreased platelet count. In recent years, novel therapeutic regimens have been investigated in randomised controlled trials (RCTs). We aimed to compare the efficacy and safety of different treatments in newly diagnosed adult primary immune thrombocytopenia.

METHODS

We did a systematic review and network meta-analysis of RCTs involving treatments for newly diagnosed primary immune thrombocytopenia. PubMed, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov databases were searched up to April 31, 2022. The primary outcomes were 6-month sustained response and early response. Secondary outcome was grade 3 or higher adverse events. This study is registered with PROSPERO (CRD42022296179).

FINDINGS

Eighteen RCTs (n = 1944) were included in this study. Pairwise meta-analysis showed that the percentage of patients achieving early response was higher in the dexamethasone-containing doublet group than in the dexamethasone group (79.7% vs 68.7%, odds ratio [OR] 1.82, 95% CI 1.10-3.02). The difference was more profound for sustained response (60.5% vs 37.4%, OR 2.57, 95% CI 1.95-3.40). Network meta-analysis showed that dexamethasone plus recombinant human thrombopoietin ranked first for early response, followed by dexamethasone plus oseltamivir or tacrolimus. Rituximab plus prednisolone achieved highest sustained response, followed by dexamethasone plus all-trans retinoic acid or rituximab. Rituximab plus dexamethasone showed 15.3% of grade 3 or higher adverse events, followed by prednis(ol)one (4.8%) and all-trans retinoic acid plus dexamethasone (4.7%).

INTERPRETATION

Our findings suggested that compared with monotherapy dexamethasone or prednis(ol)one, the combined regimens had better early and sustained responses. rhTPO plus dexamethasone ranked top in early response, while rituximab plus corticosteroids obtained the best sustained response, but with more adverse events. Adding oseltamivir, all-trans retinoic acid or tacrolimus to dexamethasone reached equally encouraging sustained response, without compromising safety profile. Although this network meta-analysis compared all the therapeutic regimens up to date, more head-to-head RCTs with larger sample size are warranted to make direct comparison among these strategies.

FUNDING

National Natural Science Foundation of China, Major Research Plan of National Natural Science Foundation of China, Shandong Provincial Natural Science Foundation and Young Taishan Scholar Foundation of Shandong Province.

Combined Application of Salinomycin and ATRA Induces Apoptosis and Differentiation of Acute Myeloid Leukemia Cells by Inhibiting WNT/β-catenin Pathway

BACKGROUND AND OBJECTIVE

All-trans retinoic acid (ATRA) is only effective in acute promyelocytic leukemia (APL), but not in other subtype of acute myeloid leukemia (AML). Salinomycin targets tumor cells rather than non-tumorigenic cells, and WNT/β-catenin pathway inhibition is one of the mechanisms of its anti-tumor activity. There is a crosstalk between RA and WNT/β-catenin pathway. Here, we investigate the effect of the combination of salinomycin and ATRA (S+RA) in non-APL AML cells.

METHODS

Apoptosis was evaluated by cell viability and Annexin-V assay. Cell differentiation was analyzed by CD11c expression and morphology. To explore the underlying mechanisms, Western blot analysis and mitochondrial transmembrane potentials (Δ ψ m) were used.

RESULTS & DISCUSSION

S+RA induced differentiation and apoptosis in AML cell lines and AML primary cells. S+RA inhibited the β-catenin signal pathway as determined by the decreased protein levels of β-catenin, the low-density lipoprotein receptor-related proteins 6 (LRP6), and its downstream proteins such as survivin, c-Myc, caspase-3/7, cdc25A and cyclinD1 and reduced phosphorylation level of GSK3β S9. S+RA also increased the protein levels of CCAAT/enhancer-binding proteins (C/EBPs) and PU.1 and collapsed Δ ψ m. The above molecular and cellular changes induced by S+RA were inhibited by β-catenin specific activator and promoted by β-catenin specific inhibitor.

CONCLUSION

S+RA induced differentiation by β-catenin-inhibition-mediated up-regulation of C/EBPs and PU.1 and suppression of c-Myc. S+RA triggered apoptosis through β-catenin-inhibition-regulated Δ ψ m collapse and caspase-3/7 activation. Taken together, our findings may provide novel therapeutic strategies for AML patients by targeting the WNT/β-catenin pathway.

[Acute promyelocytic leukemia with asymptomatic cerebral hemorrhage]

A 43-year-old man presenting with oral bleeding was diagnosed with acute promyelocytic leukemia (APL). Induction chemotherapy consisting of all-trans retinoic acid and idarubicin was initiated, and disseminated intravascular coagulation (DIC) was treated with fresh frozen plasma and recombinant thrombomodulin infusions. The patient was free from neurological symptoms throughout the clinical course. However, cerebral hemorrhagic lesions were detected incidentally on magnetic resonance imaging performed to screen for leukemic central nervous system invasion at 2 weeks after treatment initiation. Imaging findings suggested subacute or later-phase cerebral hemorrhage. Platelet transfusions and other supportive care was provided. Serial imaging evaluations confirmed reduction of the hemorrhagic lesions. Hematological remission was achieved after induction chemotherapy, and no symptoms due to cerebral hemorrhage developed during the subsequent consolidation therapy. As patients with APL characteristically experience hemorrhagic events due to bleeding tendency caused by DIC, physicians should be aware of the possibility of asymptomatic cerebral hemorrhage in these patients.

[Successful treatment of acute promyelocytic leukemia with all-trans retinoic acid on hemodialysis for acute renal failure]

All-trans retinoic acid (ATRA) is used as standard induction therapy for acute promyelocytic leukemia (APL), but it is contraindicated for patients on hemodialysis. We present a case of a patient with APL on hemodialysis, intubated, and with marked disseminated intravascular coagulation (DIC) who was successfully treated with ATRA. A 49-year-old man was transferred to our hospital and admitted into the intensive care unit due to renal dysfunction, DIC, and pneumonia. Promyelocytes were noted in the peripheral blood, and he was diagnosed with APL after bone-marrow examination. Because of renal dysfunction, only Ara-C was used but with a reduced dose. The patient's condition improved, and he was extubated and withdrawn from dialysis on the 5^th day of hospitalization. The patient suffered from APL syndrome during induction therapy, which necessitated ATRA withdrawal and steroid administration. Remission was achieved after induction therapy, and the patient is currently on maintenance therapy. There are few cases of patients with APL on hemodialysis who were treated with ATRA; hence, it is necessary to review the treatment plan for these patients.

Long-term retrospective study of retinoic acid combined with arsenic and chemotherapy for acute promyelocytic leukemia

Chemotherapy, all-trans retinoic acid (ATRA), and arsenic are effective options for acute promyelocytic leukemia (APL). We conducted a 20-year retrospective analysis of newly diagnosed (ND) APL patients treated with arsenic, ATRA and mitoxantrone. After achieving complete remission (CR), patients received 3-5 cycles of chemotherapy followed by AS4S4 maintenance for 3 years. Eighty-eight ND APL patients were treated with either oral AS4S4 (n = 42) or arsenic trioxide (ATO) (n = 46). The 8-year overall survival (OS) rate was 100% in the AS4S4 group and 90% in the ATO group. The disease-free survival (DFS) rates were 100% and 87.1% (p = 0.027), respectively. Patients in the ATO group had more side effects. A subsequent cohort of 33 ND APL patients received triple therapy with oral AS4S4, ATRA, and chemotherapy. The 13-year OS and DFS rates were 100% and 90.9%. Our long-term analyses show that APL patients with oral AS4S4 had better outcomes compared to ATO, with no need for hospitalization.

[The characteristics of neutrophil extracellular traps produced by all-trans retinoic acid-induced dHL-60 under PMA stimulation]

Extracellular traps released by neutrophils (neutrophil extracellular traps, NETs) are a double-edged sword, and understanding the mechanism of NET formation is of great significance for disease treatment. However, the short lifespan, the large individual differences, and the inability to perform gene editing render it difficult to decipher NET formation using neutrophils. It is necessary to find a model cell to replace neutrophils to study the mechanism of NET formation. In this study, we used different concentrations (0, 0.1, 1, and 10 μmol/L) of all-trans retinoic acid (ATRA) to differentiate HL-60 cells for different days (1, 3, 5, and 7 days). By detecting the cell viability and nuclear morphology of cells, we confirmed that HL-60 cells were differentiated to neutrophil-like cells (dHL-60) after treated with ATRA for at least 5 days. Using immunofluorescence staining to detect the formation of NETs, we demonstrated that dHL-60 cells differentiated for 5 days with 1 μmol/L ATRA could generate NETs comparable to those produced by neutrophils upon phorbol 12-myristate 13-acetate (PMA) stimulation, without histone H3 citrullination. Furthermore, the formation of NETs by dHL-60 cells were NADPH-dependent and PAD4-independent, consistent with neutrophils. Taken together, these observations suggest that dHL-60 cells differentiated with 1 μmol/L ATRA for 5 days can be used as a model cell for neutrophils to study the mechanism of NET formation.

All-trans retinoic acid-mediated miR-30a up-regulation suppresses autophagy and sensitizes gastric cancer cells to cisplatin

AIMS

The potential of all-trans retinoic acid (ATRA) in regulating some microRNAs (miRNAs) involved in multiple cancer-related pathways, including resistance to chemotherapeutics, may be a valuable idea for overcoming the CDDP resistance of GC cells.

MAIN METHODS

Treatment of gastric AGS and MKN-45 cells with CDDP enriched the CDDP surviving cells (CDDP-SCs). The abilities of chemoresistance to CDDP drug, migration, either apoptosis or cell cycle distribution, spheroid body formation and changes at miRNA and protein levels were evaluated in vitro by MTT assay, colony formation assay, flow cytometry, tumor spheres culture, qRT-PCR and western blot assay in CDDP-SCs and ATRA-treated CDDP-SCs cells, respectively.

KEY FINDINGS

CDDP-based chemotherapy significantly reduced microRNA-30a (miR-30a) levels in GC cells. We also observed elevated autophagy activity in cancer cells that possess stem cell-like properties with overexpressed specific stem cell markers. Our extended study suggested that the reduction of miR-30a by CDDP treatment, is the possible underlying mechanism of enhanced autophagic activity, as demonstrated by enhancing autophagy-related protein beclin 1 and LC3-II/LC-I ratio. The addition of ATRA in the culture medium of GC cells increased the expression of miR-30a, and disturbed characteristic CSC-like properties. Additional studies revealed that the increased expression of miR-30a declined the expression level of its target gene, beclin 1, and beclin 1-mediated autophagy. This leads to promoted CDDP-induced GC cell apoptosis and G2/M cell cycle arrest.

SIGNIFICANCE

Overall, miR-30a/autophagy signaling has a critical role in regulating the chemoresistance of GC cells that ATRA could modulate.

All-trans retinoic acid modulates pigmentation, neuroretinal maturation, and corneal transparency in human multiocular organoids

BACKGROUND

All-trans retinoic acid (ATRA) plays an essential role during human eye development, being temporally and spatially adjusted to create gradient concentrations that guide embryonic anterior and posterior axis formation of the eye. Perturbations in ATRA signaling can result in severe ocular developmental diseases. Although it is known that ATRA is essential for correct eye formation, how ATRA influences the different ocular tissues during the embryonic development of the human eye is still not well studied. Here, we investigated the effects of ATRA on the differentiation and the maturation of human ocular tissues using an in vitro model of human-induced pluripotent stem cells-derived multiocular organoids.

METHODS

Multiocular organoids, consisting of the retina, retinal pigment epithelium (RPE), and cornea, were cultured in a medium containing low (500 nM) or high (10 µM) ATRA concentrations for 60 or 90 days. Furthermore, retinal organoids were cultured with taurine and T3 to further study photoreceptor modulation during maturation. Histology, immunochemistry, qPCR, and western blot were used to study gene and protein differential expression between groups.

RESULTS

High ATRA levels promote the transparency of corneal organoids and the neuroretinal development in retinal organoids. However, the same high ATRA levels decreased the pigmentation levels of RPE organoids and, in long-term cultures, inhibited the maturation of photoreceptors. By contrast, low ATRA levels enhanced the pigmentation of RPE organoids, induced the opacity of corneal organoids-due to an increase in collagen type IV in the stroma- and allowed the maturation of photoreceptors in retinal organoids. Moreover, T3 promoted rod photoreceptor maturation, whereas taurine promoted red/green cone photoreceptors.

CONCLUSION

ATRA can modulate corneal epithelial integrity and transparency, photoreceptor development and maturation, and the pigmentation of RPE cells in a dose-dependent manner. These experiments revealed the high relevance of ATRA during ocular tissue development and its use as a potential new strategy to better modulate the development and maturation of ocular tissue through temporal and spatial control of ATRA signaling.

Combination of midostaurin and ATRA exerts dose-dependent dual effects on acute myeloid leukemia cells with wild type FLT3

Background

Midostaurin combined with chemotherapy is currently used to treat newly diagnosed acute myeloid leukemia (AML) patients with FMS-like tyrosine kinase 3 (FLT3)-mutations. However, midostaurin acts as an antagonist to some chemotherapeutic agents in leukemia cell lines without FLT3 mutations. All-trans retinoic acid (ATRA) induces apoptosis when used in combination with midostaurin in FLT3-mutated AML cells. This combination has been shown to be safe in AML patients. However, the effect of this combination has not been investigated in AML without FLT3 mutations.

Methods

Cell proliferation was assessed by a cell counting assay. Cell death was evaluated by cell viability and Annexin-V assays. Cell differentiation was assessed by CD11b expression profiling and morphological analysis. To explore the underlying mechanisms, we studied the role of caspase3/7, Lyn, Fgr, Hck, RAF, MEK, ERK, AKT, PU.1, CCAAT/enhancer binding protein β (C/EBPβ) and C/EBPε by Western blot analysis and immunoprecipitation assays. Antitumor activity was also confirmed in mouse xenograft models established with AML cells.

Results

In this study, 0.1 − 0.25 μM midostaurin (mido(L)) combined with ATRA induced differentiation while 0.25 − 0.5 μM midostaurin (mido(H)) combined with ATRA triggered apoptosis in some AML cell lines without FLT3-mutations. Midostaurin combined with ATRA (mido-ATRA) also exhibited antitumor activity in mouse xenograft models established with AML cells. Mechanistically, mido(H)-ATRA-induced apoptosis was dependent on caspase-3/7. Mido(L)-ATRA inhibited Akt activation which was associated with decreased activity of Lyn/Fgr/Hck, resulted in dephosphorylation of RAF S259, activated RAF/MEK/ERK, along with upregulating the protein levels of C/EBPβ, C/EBPε and PU.1. A MEK specific inhibitor was observed to suppress mido(L)-ATRA-induced increases in the protein levels of C/EBPs and PU.1 and mido(L)-ATRA-induced differentiation. Furthermore, inhibition of Akt activity promoted mido(L)-ATRA-induced downregulation of RAF S259 phosphorylation and mido(L)-ATRA-induced differentiation. Therefore, Lyn/Fgr/Hck-associated Akt inhibition activated RAF/MEK/ERK and controlled mido(L)-ATRA-induced differentiation by upregulation of C/EBPs and PU.1. Mido(L)-ATRA also promoted assembly of the signalosome, which may facilitate RAF activation.

Conclusions

Midostaurin combined with ATRA exerts antitumor activity against AML with wild-type FLT3 mutations in vitro and in vivo. These findings may provide novel therapeutic strategies for some AML patients without FLT3 mutations and imply a new target of midostaurin.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09828-2.

Expanding anti-CD38 immunotherapy for lymphoid malignancies

BACKGROUND

Lymphoid neoplasms, including multiple myeloma (MM), non-Hodgkin lymphoma (NHL), and NK/T cell neoplasms, are a major cause of blood cancer morbidity and mortality. CD38 (cyclic ADP ribose hydrolase) is a transmembrane glycoprotein expressed on the surface of plasma cells and MM cells. The high expression of CD38 across MM and other lymphoid malignancies and its restricted expression in normal tissues make CD38 an attractive target for immunotherapy. CD38-targeting antibodies, like daratumumab, have been approved for the treatment of MM and tested against lymphoma and leukemia in multiple clinical trials.

METHODS

We generated chimeric antigen receptor (CAR) T cells targeting CD38 and tested its cytotoxicity against multiple CD38^high and CD38^low lymphoid cancer cells. We evaluated the synergistic effects of all-trans retinoic acid (ATRA) and CAR T cells or daratumumab against cancer cells and xenograft tumors.

RESULTS

CD38-CAR T cells dramatically inhibited the growth of CD38^high MM, mantle cell lymphoma (MCL), Waldenstrom's macroglobulinemia (WM), T-cell acute lymphoblastic leukemia (T-ALL), and NK/T-cell lymphoma (NKTCL) in vitro and in mouse xenografts. ATRA elevated CD38 expression in multiple CD38^low cancer cells and enhanced the anti-tumor activity of daratumumab and CD38-CAR T cells in xenograft tumors.

CONCLUSIONS

These findings may expand anti-CD38 immunotherapy to a broad spectrum of lymphoid malignancies and call for the incorporation of ATRA into daratumumab or other anti-CD38 immunological agents for cancer therapy.

All-trans retinoic acid inhibits HCV replication by downregulating core levels via E6AP-mediated proteasomal degradation

Here, we found that all-trans retinoic acid (ATRA), the most biologically active metabolite of vitamin A, strengthens the anti-viral defense mechanism of E6-associated protein (E6AP) that downregulates hepatitis C virus (HCV) Core levels via ubiquitin-dependent proteasomal degradation. For this effect, ATRA downregulated both protein and enzyme activity levels of DNA methyltransferase 1 and 3b and activated E6AP expression via promoter hypomethylation in HepG2 cells but not in Hep3B cells, in which p53 was absent. Ectopic p53 expression but not E6AP overexpression restored the ability of ATRA to downregulate HCV Core levels in Hep3B cells, suggesting a direct role of p53 in the E6AP-mediated ubiquitination of HCV Core. ATRA also downregulated HCV Core levels during HCV infection in Huh7D cells to inhibit virus replication, providing theoretical basis for the clinical application of ATRA against HCV infection.

The effect of all-trans retinoic acid on the mitochondrial function and survival of cardiomyoblasts exposed to local photodamage

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All-Trans Retinoic Acid-Preconditioned Mesenchymal Stem Cells Improve Motor Function and Alleviate Tissue Damage After Spinal Cord Injury by Inhibition of HMGB1/NF-κB/NLRP3 Pathway Through Autophagy Activation

Spinal cord injury (SCI) is a significant public health issue that imposes numerous burdens on patients and society. Uncontrolled excessive inflammation in the second pathological phase of SCI can aggravate the injury. In this paper, we hypothesized that suppressing inflammatory pathways via autophagy could aid functional recovery, and prevent spinal cord tissue degeneration following SCI. To this end, we examined the effects of intrathecal injection of all-trans retinoic acid (ATRA)-preconditioned bone marrow mesenchymal stem cells (BM-MSCs) (ATRA-MSCs) on autophagy activity and the HMGB1/NF-κB/NLRP3 inflammatory pathway in an SCI rat model. This study demonstrated that SCI increased the expression of Beclin-1 (an autophagy-related gene) and NLRP3 inflammasome components such as NLRP3, ASC, Caspase-1, and pro-inflammatory cytokines IL-1β, IL-18, IL-6, and TNF-α. Additionally, following SCI, the protein levels of key autophagy factors (Beclin-1 and LC3-II) and HMGB1/NF-κB/NLRP3 pathway factors (HMGB1, p-NF-κB, NLRP3, IL-1β, and TNF-α) increased. Our findings indicated that ATRA-MSCs enhanced Beclin-1 and LC3-II levels, regulated the HMGB1/NF-κB/NLRP3 pathway, and inhibited pro-inflammatory cytokines. These factors improved hind limb motor activity and aided in the survival of neurons. Furthermore, ATRA-MSCs demonstrated greater beneficial effects than MSCs in treating spinal cord injury. Overall, ATRA-MSC treatment revealed beneficial effects on the damaged spinal cord by suppressing excessive inflammation and activating autophagy. Further research and investigation of the pathways involved in SCI and the use of amplified stem cells may be beneficial for future clinical use.

[Acute promyelocytic leukemia complicated with central nervous system involvement successfully treated with all-trans retinoic acid via nasogastric tube]

At initial diagnosis, central nervous system (CNS) involvement in acute promyelocytic leukemia (APL) is rare. Here, we report a case of newly diagnosed APL with CNS involvement that was successfully treated with all-trans retinoic acid (ATRA)-combined chemotherapy. A 64-year-old woman was referred to our hospital to evaluate a bleeding tendency, and she was diagnosed with APL. Induction chemotherapy with ATRA via a nasogastric tube was initiated under mechanical ventilation because of respiratory failure and disturbance of consciousness. Although her respiratory condition improved a few days after initiating treatment, the disturbance of consciousness remained. Brain magnetic resonance imaging showed mixed signals of tumor infiltration and acute cerebral infarction with a focus on the right cerebellum. The patient was diagnosed with CNS involvement of APL and acute cerebral infarction. Three months after the initiation of induction therapy, her consciousness improved along with the reduction in CNS involvement, and complete molecular remission was achieved. Thus, patients with APL can have CNS involvement at initial diagnosis. Administering ATRA via nasogastric tube can be a good therapeutic option in patients with difficulty swallowing due to disturbance of consciousness.

Distinct Characteristics of Sweet's Syndrome of the Scrotum Caused by All-trans Retinoic Acid in a Patient with Acute Promyelocytic Leukemia

Induction therapy with all-trans retinoic acid (ATRA) is effective for acute promyelocytic leukemia (APL). ATRA induces neutrophil differentiation and its associated side effects. The differentiation syndrome is the most characterized ATRA-induced adverse effect. Sweet's syndrome, also known as neutrophilic dermatosis, is another form of ATRA-associated disease characterized by neutrophil infiltrating erythema that develops with fever. This is a case of a 34-year-old Japanese man diagnosed with APL. At the onset, the patient did not have skin involvement of APL cells. He was treated with ATRA and induction chemotherapy with idarubicin and cytarabine. Scrotal skin rash occurred at day 14, which developed into scrotal ulceration up to day 28 even after eliminating APL cells in his peripheral blood. Sweet's syndrome is a pathological diagnosis of scrotal skin ulceration representing neutrophil infiltration. The infiltrating neutrophils showed PML-RARα rearrangement. The patient was diagnosed with ATRA-associated Sweet's syndrome with skin ulcer. His cutaneous lesion did not respond to intravenous prednisolone therapy; thereby, ATRA was discontinued. After the cessation of ATRA, the skin lesion improved in the next week. We confirmed he achieved a complete response after induction chemotherapy. In our observation, ATRA-associated Sweet's syndrome is characterized by the following clinical manifestations: preferable occurrence in the scrota, tend to progress into skin ulcer, and pathogenicity associated with PML-RARα-positive matured neutrophils. The etiology, pathogenesis, and risk factors of ATRA-associated scrotal ulceration were discussed in the literature review.

Phospholipid/zein hybrid nanoparticles as promising carriers for the protection and delivery of all-trans retinoic acid

A totally biodegradable mixed system made up of phospholipids and zein was developed in order to effectively improve the photostability of all-trans retinoic acid (ATRA) preserving its pharmacological properties. Photon correlation spectroscopy showed that the formulation obtained using phospholipon 85G and zein at a ratio of 7:3 w/w was characterized by an average diameter of less than 200 nm, a narrow size distribution and a significant time- and temperature-dependent stability. The use of specific cryoprotectants such as mannose and glucose favoured the long-term storage of the nanocarriers after the freeze-drying procedure. The nanoparticles increased the stability of the ATRA against photochemical degradation with respect to the free drug and its antitumor effect was preserved as a consequence of the cell uptake of the colloidal systems. The results demonstrate the potential of the proposed hybrid nanosystems to provide a high level of stabilization for sensitive and labile antitumor compounds.

Risk factors for early in-hospital death in patients who developed coagulopathy during induction therapy for acute promyelocytic leukemia: a nationwide analysis in Japan

To prevent early death, management of coagulopathy is important in patients with untreated acute promyelocytic leukemia (APL). This study aimed to clarify factors associated with in-hospital death in patients with coagulopathy during induction therapy for APL. We retrospectively identified patients with newly diagnosed APL who received induction therapy including all-trans retinoic acid (ATRA) and developed coagulopathy, using a nationwide inpatient database in Japan. Of 1115 eligible patients, 175 (15%) died at a median of 13 days (interquartile range, 7-30) after admission. In the multivariable analysis, compared with younger patients (aged < 40 years), the occurrence of in-hospital death was significantly more common among older patients (aged ≥ 40 and < 60 years: odds ratio = 2.58 [95% confidence interval: 1.29-5.19]; aged ≥ 60 and < 80 years: 7.66 [3.89-15.10]; aged ≥ 80 years: 16.83 [7.41-38.21]). Delayed initiation of ATRA and no conventional chemotherapy were significantly associated with in-hospital death (1.79 [1.16-2.76] and 2.40 [1.47-3.92], respectively). A total of 699 patients (63%) received anticoagulant therapies, but none of these was significantly associated with lower mortality. Although the present study was constrained by a lack of laboratory findings because of database limitations, the results showed that untreated patients with APL, especially the elderly, had a poor prognosis. Immediate administration of ATRA may reduce in-hospital mortality.

Myeloid sarcoma of the colon as initial presentation in acute promyelocytic leukemia: A case report and review of the literature

BACKGROUND

Myeloid sarcoma (MS) rarely occurs in acute promyelocytic leukemia (APL) at onset, but it can develop in relapse cases, especially after APL treated with all-trans retinoic acid (ATRA). Therefore little is known about the clinical features and suitable treatment for APL related MS due to the rarity of the disease, although this may be different from the treatment and prognosis of MS in the relapse stage. To our best knowledge, this is the second case report of APL initial presentation as colon MS.

CASE SUMMARY

A 77-year-old woman complained of intermittent right lower abdominal pain, black stool, and difficult defecation for 2 mo. Physical examination showed diffuse tenderness during deep palpation and an anemic appearance. Laboratory findings showed positivity for fecal occult blood testing; white blood cell count: 3.84 × 10⁹/L; hemoglobin: 105 g/L; platelet count: 174 × 10⁹/L; and negativity for tumor markers. Abdominal enhanced computed tomography showed a space occupying lesion in the colon (1.9 cm). Fibrocolonoscopy revealed a polypoid and ulcerated mass measuring 2.5 cm. The tumor was removed. To our surprise, MS was confirmed by immunohistochemistry. PML/RARα fusion gene was detected in colon specimens by fluorescent in situ hybridization and real-time reverse transcription polymerase chain reaction, which was consistent with the bone marrow. She was diagnosed as having APL related MS. A smooth and unobstructed intestinal wall was found by fibrocolonoscopy, and continuous molecular remission was confirmed in both the bone marrow and colon after four courses of ATRA + arsenic trioxide (ATO). ATRA + ATO showed a favorable therapeutic response for both APL and MS.

CONCLUSION

Early use of ATRA can benefit APL patients, regardless of whether MS is the first or recurrent manifestation.

All-trans-retinoic acid suppresses rat embryo hindlimb bud mesenchymal chondrogenesis by modulating HoxD9 expression

In vertebrates, 5ʹ-Hoxd genes (Hoxd9), which are expressed in the hindlimb bud mesenchyme, participate in limb growth and patterning in early embryonic development. In the present study, We investigated the mechanisms by which ATRA regulates cultured E12.5 rat embryo hindlimb bud mesenchymal cells (rEHBMCs). Following exposure to ATRA over 24 h, mRNA and protein expression levels of HoxD9 were evaluated by reverse transcription-polymerase chain reaction (RT-PCR), quantitative real-time PCR (qPCR), and western blotting. Flow cytometry was used to detect apoptosis. ATRA inhibited the condensation and proliferation, and promoted the apoptosis rate of the rEHBMCs in a dose-dependent manner. Sox9 and Col2a1 in rEHBMCs were downregulated by ATRA in a dose-dependent manner at both mRNA and protein levels. Similarly, HoxD9 was downregulated by ATRA in a dose-dependent manner, in parallel with the cartilage-specific molecules Sox9 and Col2a1. Both qPCR and western blotting showed that both Shh and Gli3 were downregulated. Overexpression of HoxD9 reversed the effects of ATRA. These results demonstrate that ATRA suppresses chondrogenesis in rEHBMCs by inhibiting the expression of HoxD9 and its downstream protein targets, including Sox9 and Col2a1. This effect may also be correlated with inhibition of the Shh-Gli3 signaling pathway.

Polymeric micelles of a copolymer composed of all-trans retinoic acid, methoxy-poly(ethylene glycol), and b-poly(N-(2 hydroxypropyl) methacrylamide) as a doxorubicin-delivery platform and for combination chemotherapy in breast cancer

Delivery of combination chemotherapeutic agents to the tumor via nanovesicles has the potential for superior tumor suppression and reduced toxicity. Herein, we prepare a block copolymer (mPH-RA) composed of methoxy-poly(ethylene glycol) (mPEG), b-poly(N-(2 hydroxypropyl) methacrylamide) (pHPMA), and all-trans retinoic acid (ATRA) by conjugating ATRA to the pre-formed copolymer, mPEG-b-pHPMA(mP-b-pH). Doxorubicin-loaded micelles, Dox@mP-b-pH, and Dox@mPH-RA were characterized by determining particle size, zeta potential, % DL, EE, Dox release, hemolysis study, and by DSC. The Dox@mPH-RA micelles (mPH-RA: Dox ratios of 10:0.5-2) displayed nano-size (36-45 nm), EE. 26-74%, and DL. 2.9-5.6%. Dox@mPH-RA micelles displayed the highest penetrability and cytotoxicity than free Dox and Dox@mP-b-pH micelles in breast cancer cell lines. Dox@mPH-RA exhibited the highest induction of apoptosis (94.1 ± 3%) than Dox (52.1 ± 4.5%), and Dox@mP-b-pH (81.7 ± 3%), and arrested cells in the highest population in G2 and S phase. Dox@mPH-RA increased the t_1/2 and C_max of Dox and demonstrated improved therapeutic efficacy and highest Dox distribution to the tumor. The Dox@mPH-RA increased the levels of apoptosis markers, caspase 3, 7, Ki-67, and caused the highest DNA fragmentation. The presence of RA improved the micelles' physicochemical properties, Dox-loading ability, and the therapeutic potential in Dox@mPH-RA via the combination therapeutic strategy.

Advances in the management of coagulopathy in acute promyelocytic leukemia

Since the introduction of all-trans retinoic acid and, more recently, arsenic trioxide into the therapy of acute promyelocytic leukemia (APL), significant improvements in patient outcomes have been achieved, and this disease has become the most curable subtype of acute myeloid leukemia. However, while primary leukemia resistance has virtually disappeared, a sizable fraction of APL patients still die before or during induction therapy. Hemorrhagic death still remains the major problem during this early phase of treatment and, to a lesser extent, deaths due to infection, differentiation syndrome and other causes. Patients with APL typically present with a range of laboratory abnormalities consistent with the diagnosis of disseminated intravascular coagulation and hyperfibrinolysis. This APL-associated coagulopathy, as a result of a dysregulation of the hemostatic system due to the imbalance between procoagulant, anticoagulant and profibrinolytic mechanisms, may show a variety of clinical manifestations, ranging from minimal bleeding or localized thrombosis to lethal or life-threatening hemorrhages or thrombotic events that sometimes occur concomitantly. Hemorrhagic events are the most common cause of death associated with APL coagulopathy, but thrombosis, a less recognized and probably underestimated life-threatening manifestation of the thrombo-hemorrhagic syndrome, is also a non-negligible cause of morbidity and mortality in patients with APL. In this article, we aim to discuss recent advances in the knowledge of pathogenesis, predictors of thrombo-hemorrhagic events, management of coagulopathy associated with APL and the controversial issues that still persist.

AXL receptor tyrosine kinase: a possible therapeutic target in acute promyelocytic leukemia

BACKGROUND

Acute promyelocytic leukemia (APL) is a subset of acute myeloid leukemia (AML) which is characterized by the fusion of promyelocytic leukemia PML and retinoic acid receptor- alpha (RAR-alpha) genes. All-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO) have resulted in durable cytogenetic and molecular remissions in most APL patients and have altered the natural history of the disease. Most APL patients treated with ATRA and/or ATO are now anticipated to have a nearly normal life expectancy. Unfortunately, relapse and resistance to the current treatment occur in APL patients and the outcome remains dismal in these refractory patients. AXL receptor tyrosine kinase (AXL-RTK) has been shown to increase tumour burden, provide resistance to therapy and is critical to maintain cancer stem cells (CSCs) in chronic myeloid leukemia (CML) by stabilizing β-catenin in the Wnt/β-catenin signalling pathway. However, the role of AXL-RTK has not been explored in PML/RARα-positive APL. This study aimed to explore the role of AXL-RTK receptor in PML/RARα-positive APL.

METHODS AND RESULTS

By using biochemical and pharmacological approaches, here we report that targeting of AXL-RTK is related to the down-regulation of β-catenin target genes including c-myc (p < 0.001), AXIN2 (p < 0.001), and HIF1α (p < 0.01) and induction of apoptosis in PML/RARα-positive APL cell line. Resistance to all-trans retinoic acid (ATRA) was also overcomed by targeting AXL-RTK with R428 in APL (p < 0.05).

CONCLUSION

Our results provide clear evidence of the involvement of AXL-RTK in leukemogenic potential of PML/RARα-positive APL and suggest targeting of AXL-RTK in the treatment of therapy resistant APL patients.

Downregulation of fibronectin 1 attenuates ATRA-induced inhibition of cell migration and invasion in neuroblastoma cells

Neuroblastoma (NB) is the most common malignant extra cranial solid tumors in children. It has been well established that retinoic acid (RA) inhibits proliferation of neuroblastoma (NB) by blocking cells at G1 phase of the cell cycle. Clinically, RA has been successfully used to treat NB patients. However, the precise mechanism underlying the potent action of RA-treated NB is not fully explored. In this work, we carried out a gene expression profiling by RNA sequencing on all-trans retinoic acid (ATRA)-treated NB cells. Cancer-related pathway enrichment and subsequent protein-protein interaction (PPI) network analysis identified fibronectin 1 (FN1) as one of the central molecules in the network, which was significantly upregulated during ATRA treatment. In addition, we found that although downregulation of FN1 had no significant effects on either cell proliferation or cell cycle distributions in the presence or absence of ATRA, it increased cell migration and invasion in NB cells and partially blocked ATRA-induced inhibition of cell migration and invasion in SY5Y NB cells. Consistent with this finding, FN1 expression levels in NB patients positively correlate with their overall survivals. Taken together, our data suggest that FN1 is a potential target for effective ATRA treatment on NB patients, likely by facilitating ATRA-induced inhibition of cell migration and invasion.

Fabrication of All-Trans Retinoic Acid loaded Chitosan/Tripolyphosphate Lipid Hybrid Nanoparticles as a Novel Oral Delivery Approach for Management of Diabetic Nephropathy in Rats

The present study aims to formulate all-trans retinoic acid (ATRA) loaded chitosan/tripolyphosphate lipid hybrid nanoparticles (CTLHNs) for enhancing its solubility and oral delivery. This is to improve ATRA therapeutic effect on diabetic nephropathy (DN). CTLHNs were prepared by o/w homogenization, employing stearic acid, to form lipid nanoparticles coated with chitosan that is stabilized against acidic pH via sodium tripolyphosphate crosslinking. Chitosan coated (F7) and naked lipid nanoparticles (F6) were also prepared for comparison with CTLHNs. In vitro characterization for the prepared formulations was performed comprising entrapment efficiency, particle size, zeta potential, transmission electron microscopy, FT-IR spectroscopy and x-ray diffraction. Stability of chitosan coat in GI fluid revealed that CTLHNs were more stable than F7. In vitro release indicated an enhanced release of ATRA from the developed formulations. In vitro mucoadhesion study proved a notable mucoadhesive property for CTLHNs. In DN rat model, serum levels of creatinine and urea were elevated, over expression of tumor necrosis factor alpha (TNF-α), granulocyte macrophage colony-stimulating factor (GM-CSF), vascular endothelial growth factor (VEGF) and intercellular adhesion molecule-1 (ICAM-1) were observed. In addition, adenosine monophosphate activated protein kinase (AMPK) and liver kinase B1 (LKB1) expressions were decreased in DN rats. Treatment with free ATRA and the selected formulations led to a significant amelioration of DN by reducing of creatinine, urea, TNF-α, ICAM-1, GM-CSF, VEGF levels as well as elevating AMPK and LKB1 levels. The order of activity was: CTLHNs > F7 > F6 > free ATRA, as proved by histopathological examination.

Treatment of progressive multiple sclerosis with high-dose all-trans retinoic acid - no clear evidence of positive disease modifying effects

BACKGROUND

All-trans retinoic acid (ATRA) is an acid derivative of vitamin A which is discussed as a promising candidate to ameliorate the disease course of multiple sclerosis (MS) by immunomodulation or even by promoting regeneration in progressive MS. Here we report a patient who significantly improved for MS related disability following administration of chemotherapy including ATRA for mitoxantrone-related acute promyelocytic leukemia and assess the effect of high-dose ATRA in three additional patients with progressive MS.

METHODS

Patients with progressive MS who had failed previous therapies were treated with high-dose ATRA. Patients underwent clinical and routine laboratory monitoring. Additionally, PBMCs were analyzed by flow cytometry for lymphocyte subsets.

RESULTS

ATRA was well tolerated and no pathological laboratory abnormalities were observed. After initial mild (not statistically significant) improvement of EDSS and mean MSFC z-score, ongoing disease progression was observed. One patient subacutely experienced severe cognitive and motor worsening. Cerebral MRI revealed persistent gadolinium-enhancing lesions. Flow cytometric alterations of peripheral blood naïve, central memory and effector memory CD4 and CD8 T cells, B lymphocytes, plasma cells, memory B cells, plasmablasts and natural killer (NK) cells did not reach statistical significance.

CONCLUSIONS

Stand-alone therapy with ATRA did not ameliorate progressive MS in our limited cohort and we did not observe consistent alterations of T and B cell subsets. Intriguingly, application of ATRA may have caused marked disease exacerbation in one patient.

Targeting of myeloid-derived suppressor cells by all-trans retinoic acid as host-directed therapy for human tuberculosis

Conventional anti-tuberculosis (TB) therapies comprise lengthy antibiotic treatment regimens, exacerbated by multi-drug resistant and extensively drug resistant mycobacterial strains. We assessed the ability of all-trans retinoic acid (ATRA), as repurposed compound serving as host-directed therapy (HDT), to counteract the suppressive effects of myeloid-derived suppressor cells (MDSCs) obtained from active TB cases (untreated or during week one of treatment) on T-cell responsiveness. We show for the first time that MDSCs suppress non-specific T-cell activation and production of interleukin (IL)-2, IL-4, IL-13 and GM-CSF via contact-dependent mechanisms. ATRA treatment decreases MDSC frequency, but fails to mature MDSCs to non-suppressive, terminally differentiated myeloid cells and does not restore T-cell function or cytokine production in the presence of MDSCs. The impact of ATRA treatment on improved immunity, using the concentration tested here, is likely to be minimal, but further identification and development of MDSC-targeting TB host-directed therapies are warranted.

Oral delivery of all-trans retinoic acid mediated by liposome carriers

All-trans retinoic acid (ATRA) is a molecule that finds wide applications in medicine. Connection between cancer cell proliferation and ATRA is a well-established item. Driven by the potential applications of liposomes in stabilizing and protecting therapeutic compounds thus enabling effective delivery of encapsulated compounds, recent research efforts have been directed to understanding mechanisms of oral delivery through the gastrointestinal tract. The surface charge of the liposome bilayers can modify the interactions between the aggregates and the gastrointestinal fluids. Here, we investigated the ability of cationic and anionic liposomes to encapsulate, protect and deliver ATRA in an in-vitro digestion process as a different oral administration route. Stability and encapsulation efficiency of ATRA in negatively and positively charged liposomes enriched with α-tocopherol were investigated by means of UV-vis spectroscopy, dynamic light scattering and ζ-potential. The applicability of the carriers was tested by means of an in-vitro digestion procedure allowing for the measurement of the bioavailability of ATRA. From this study evidence was provided that the water insoluble molecules, ATRA and α-tocopherol are intercalated in liposome membranes regardless of the surface charge of the vesicle bilayers. Comparisons between cationic and anionic liposomes incorporating retinoic acid show differences in bioavailability. The cationic vesicles are preferable for a larger amount of ATRA bioavailability, which can be understood from electrostatic interactions. Thus ATRA is ionized in a wide range of pHs but protonated in anionic vesicles.

Ellagic acid and its fermentative derivative urolithin A show reverse effects on the gp91-phox gene expression, resulting in opposite alterations in all-trans retinoic acid-induced superoxide generating activity of U937 cells

Ellagitannins (esters composed of glucose and ellagic acid) are hydrolyzed to generate ellagic acid in gut followed by conversion of ellagic acid to urolithins such as urolithin A by intestinal bacteria. Since urolithins are absorbed by gut easier than ellagitannins and ellagic acid, and show various physiological activities (e.g. anti-cancer, anti-cardiovascular disease, anti-diabetes mellitus, anti-obesity and anti-Alzheimer disease activities), they are expected as excellent health-promoting phytochemicals. Here, using human monoblast U937 cells, we investigated the effect of ellagic acid and urolithin A on the superoxide anion (O₂⁻)-generating system of phagocytes, which is consisted of five specific protein factors (membrane proteins: p22-phox and gp91-phox, cytosolic proteins: p40-phox, p47-phox and p67-phox). Twenty micromolar of urolithin A enhanced the all-trans retinoic acid (ATRA)-induced O₂⁻-generating activity (to ~175%) while 20 μM ellagic acid inhibited the ATRA-induced O₂⁻-generating activity (to ~70%). Semiquantitative RT-PCR showed that transcription level of gp91-phox was certainly decreased (to ~70%) in ATRA plus ellagic acid-treated cells, while that of gp91-phox was significantly increased (to ~160%) in ATRA plus urolithin A-treated cells. Chromatin immunoprecipitation assay suggested that urolithin A enhanced acetylations of Lys-9 residues of histone H3 within chromatin surrounding the promoter region of gp91-phox gene, but ellagic acid suppressed the acetylations. Immunoblotting also revealed that ATRA plus urolithin A-treatment up-regulated protein levels of p22-phox (to ~160%) and gp91-phox (to ~170%) although ATRA plus ellagic acid-treatment down-regulated protein levels of p22-phox (to ~70%) and gp91-phox (to ~60%). These results suggested that conversion of ellagic acid to urolithin A in gut may bring about reverse effects on the gp91-phox gene expression, resulting in opposite alterations in O₂⁻-generating activity of intestinal macrophages.

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Ellagic acid down-regulated the ATRA-induced O₂⁻-generating activity.

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Ellagic acid significantly suppressed transcription of gp91-phox gene.

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Urolithin An up-regulated the ATRA-induced O₂⁻-generating activity.

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Urolithin A significantly enhanced transcription of gp91-phox gene.

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Production of urolithin A by gut bacteria may affect the intestinal macrophages.

[Effect of endoplasmic reticulum stress induced by all-trans retinoic acid on apoptosis of FLT3-ITD mutated leukemia cells by activating autophagy in FLT3-ITD mutated protein]

Objective: Endoplasmic reticulum stress(ERS)was used as the research emphasis to further investigate the mechanisms of apoptosis of FLT3-ITD-mutated leukemia cells and decreased expression of FLT3-ITD mutated protein induced by all-trans retinoic acid(ATRA). Methods: FLT3-ITD-mutated leukemia cell lines(MV4-11 and MOLM13)were treated with ATRA. Flow cytometry was conducted to assess cell apoptosis. Real-time fluorescent quantitative PCR(RT-qPCR)and Western blot were used to detect the expression of ERS-related and autophagy-related genes and protein, respectively. Results: A low-dose ATRA further increased FLT3-ITD cells and ERS levels. ATRA acted on the ERS-related PERK/eif2ɑ signaling pathway and continued to increase the ERS of FLT3-ITD cells, resulting in an upregulation of apoptotic gene CHOP expression. After the treatment with ATRA, FLT3-ITD protein in FLT3-ITD cells was decreased. Of the two main ERS-related protein degradation pathways, ER-associated degradation(ERAD)and ER-activated autophagy(ERAA), the expression of ERAD-related protein ATF6 in FLT3-ITD cells was not significantly changed on ATRA, whereas the expression of ERAA-related proteins Atg7 and Atg5 were significantly increased. Conclusions: ATRA further raises the ERS level of FLT3-ITD cells continuously by activating the ERS-related PERK/eif2ɑ signal pathway and induces FLT3-ITD protein autophagy degradation through ERAA pathway, which induces apoptosis of FLT3-ITD-mutated leukemia cells. These results provide preliminary evidence on the use of ATRA in the treatment of refractory leukemia with FLT3-ITD.

[Acute promyelocytic leukemia recurrence diagnosed due to granulocytic sarcoma of the external auditory canal]

A 47-year-old man was diagnosed with acute promyelocytic leukemia (APL) accompanied by pancytopenia and left forearm swelling. Complete remission was achieved with remission induction therapy using all-trans retinoic acid (ATRA), and consolidation therapy was completed. Three months after the treatment, left ear closure was observed, and a mass lesion was found in the left external auditory canal. An initial tumor biopsy only revealed inflammatory cell infiltration. Moreover, the tumor's rebiopsy performed 3 months later revealed MPO-positive and CD68-positive granulocyte infiltration. Furthermore, the rebiopsy revealed 4.9×10⁵ copies/µgRNA of PML/RARα, the patient was diagnosed with locally recurrent APL. A bone marrow examination 2 weeks later confirmed an increase in myeloblasts and promyelocytes for the first time since the confirmation of remission. Therefore, it was diagnosed as bone marrow recurrence. Reinduction therapy using ATRA and arsenic trioxide again led to complete remission, after which autologous peripheral blood stem cell transplantation was performed. Currently, complete remission is being maintained. In this case, the recurrence of the external auditory canal lesion preceded the bone marrow recurrence. Therefore, it is important to note the nonspecific leukemia recurrence patterns of the external auditory canal.

[Therapies for newly diagnosed acute promyelocytic leukemia]

All-trans retinoic acid (ATRA) in combination with chemotherapies had been the standard therapy for newly diagnosed acute promyelocytic leukemia (APL). In Japan, APL204 study using ATRA+chemotherapy showed favorable outcomes, in which 7-year event-free and overall survival rates were 79% and 87%, respectively. Recently, a combination of ATRA and arsenic trioxide (ATO) has emerged as a promising therapy for newly diagnosed APL. Specifically, for patients with standard-risk APL with an initial white blood cell count (WBC) of <10,000/µl, two randomized controlled trials showed superior outcomes using ATRA+ATO to ATRA+chemotherapy, with long-term survival rates above 90%. Now ATRA+ATO is considered as an established standard therapy for newly diagnosed patients with standard-risk APL. Some prospective studies have also showed the efficacies of ATRA+ATO in patients with high-risk APL with an initial WBC of >10,000/µl although the administration of gemtuzumab ozogamicin or idarubicin was required in addition to ATRA+ATO during induction therapy. This review briefly summarizes the findings of ATRA+chemotherapy, focusing on the APL204 study, and introduces trials of ATRA+ATO for newly diagnosed APL. Furthermore, it describes the management of complications, including disseminated coagulation and differentiation syndrome.