Search

Cellular retinoic acid binding protein 2 (CRABP2) transports retinoic acid from the cytoplasm to the nucleus where it then transfers its cargo to retinoic acid receptor-containing complexes leading to activation of gene transcription. We demonstrate using purified proteins that CRABP2 is also a cyclin D3-specific binding protein and that the CRABP2 cyclin D3 binding site and the proposed CRABP2 nuclear localization sequence overlap. Both sequences are within the helix-loop-helix motif that forms a lid to the retinoic acid binding pocket. Mutations within this sequence that block both cyclin D3 and retinoic acid binding promote formation of a CRABP2 structure in which the retinoic acid binding pocket is occupied by an alternative lid conformation. Structural and functional analysis of CRABP2 and cyclin D3 mutants combined with AlphaFold models of the ternary CDK4/6-cyclin D3-CRABP2 complex supports the identification of an α-helical protein binding site on the cyclin D3 C-terminal cyclin box fold. [Display omitted] • CRABP2 binds selectively to CDK4/6-cyclin D3 and not to CDK4/6 or CDK4/6-cyclin D1 • The CRABP2 nuclear localization sequence and cyclin D3 binding site overlap • CRABP2 mutants adopt alternative monomeric CRABP2 conformations • Cyclin D3 mutants identify a protein binding site on the C-terminal cyclin box fold Using purified proteins, Pastok et al. confirm CRABP2 binding to cyclin D3. Their mutational study, supported by crystal structures of CRABP2 mutants and AlphaFold modeling, identifies a protein-protein interaction interface between the cyclin D3 C-terminal cyclin box fold and the CRABP2 helical cap. [ABSTRACT FROM AUTHOR]

Summary: All‐trans‐retinoic acid (ATRA) and arsenic trioxide (ATO) represent the standard of care for low‐intermediate risk acute promyelocytic leukaemia (APL). Leucocytosis during induction with ATRA‐ATO represents a common complication with an incidence of up to 60%. To identify predictive factors for this complication, we studied a cohort of 65 low‐intermediate risk APL patients treated with ATRA‐ATO in three highly specialized Italian centres. Overall, 39/65 (60%) patients developed leucocytosis, with a peak in leucocyte count being most frequent in the second week from diagnosis. All cases were successfully managed with hydroxyurea. Predictive factors for leucocytosis in univariate analysis were lower platelet counts (odds ratio [OR] 0.98, 0.97–1.00, p = 0.018), lower fibrinogen levels (OR 0.36, 0.17–0.66, p = 0.003), higher bone marrow blast infiltration (OR 1.03, 1.01–1.07, p = 0.021) and CD117 expression by flow (OR 1.04, 1.01–1.08, p = 0.012). Multivariate analysis confirmed lower levels of fibrinogen at diagnosis as the strongest predictive factor for the development of leucocytosis (OR 0.36, 0.15–0.72, p = 0.009). Differentiation syndrome (DS) occurred only in patients developing leucocytosis showing a strict correlation with rising leucocytes counts (16/39 vs. 0/26, p < 0.001). In addition, other treatment‐related complications including QTc prolongation, cardiac events, liver, and haematological toxicities were significantly more frequent in patients experiencing leucocytosis (22/39 vs. 3/26, p < 0.001). In conclusion, APL patients undergoing ATRA‐ATO therapy with lower fibrinogen levels and platelet counts at diagnosis and with a massive bone marrow blast infiltrate should be carefully monitored for the development of leucocytosis during induction. DS and other treatment‐related complications seem to occur almost exclusively in patients developing leucocytosis, who should necessarily receive DS prophylaxis and more intensive monitoring and supportive therapy to prevent treatment complications. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) is a debilitating and the second most common neurodegenerative disorder with a high prevalence. PD has a multifaceted etiology characterized by an altered redox state and an excessive inflammatory response. Extensive research has consistently demonstrated the role of the nuclear factor E2-related factor (Nrf2) and inflammasomes, notably NLRP3 in neurodegenerative diseases. In this study, our focus was on exploring the potential neuroprotective properties of carveol in Parkinson's disease. Our findings suggest that carveol may exhibit these effects through Nrf2 and by suppressing pyroptosis. Male albino mice were treated with carveol, and the animal PD model was induced through a single intranigral dose of 2 µg/2µl lipopolysaccharide (LPS). To further demonstrate the essential role of the Nrf2 pathway, we utilized all-trans retinoic acid (ATRA) to inhibit the Nrf2. Our finding showed the induction of pyroptosis as evidenced by increased levels of NLRP3 and other inflammatory mediators, including IL-1β, iNOS, p-NFKB, and apoptotic cell death indicated by positive fluoro Jade B (FJB) staining. Moreover, increased levels of lipid peroxides and reactive oxygen species indicated a significant rise in oxidative stress due to LPS. The administration of carveol mitigates oxidative stress and suppresses inflammatory pathways through the augmentation of intrinsic antioxidant defenses, primarily via the activation of the Nrf2. Conversely, ATRA reversed carveol protective effects by increasing FJB-positive cells, inflammatory and oxidative biomarkers. Taken together, our findings suggest that carveol mitigated LPS-induced Parkinson-like symptoms, partially through the activation of the Nrf2 and downregulation of pyroptosis notably NLRP3. [ABSTRACT FROM AUTHOR]

Glial scar formation is a major obstacle to nerve regeneration following spinal cord injury (SCI). Pin1 and the PI3K/AKT/CDK2 signaling pathway play crucial roles in neuronal regulation, but research on their involvement in glial scarring remains limited. In this study, we have for the first time observed that Pin1, PI3K, AKT, and CDK2 are upregulated and interact with each other following SCI. Further experiments revealed that Pin1 contributes to the development of glial scars by promoting astrocyte proliferation, inhibiting apoptosis, and activating the PI3K/AKT/CDK2 pathway. Additionally, all‐trans retinoic acid (ATRA), a specific chemical inhibitor of Pin1, effectively suppresses Pin1 expression. However, its clinical application is limited by its short half‐life and susceptibility to inactivation. To address these issues, we have developed a thermosensitive sodium beta‐glycerophosphate (β‐GP)/chitosan (CS) hydrogel loaded with ATRA (β‐GP/CS@ATRA). This hydrogel exhibits favorable morphology and biocompatibility. Compared to free ATRA, the β‐GP/CS@ATRA hydrogel significantly enhances functional motor recovery after SCI and protects spinal cord tissue, thereby inhibiting glial scar formation. Mechanistically, ATRA administration blocks the development of glial scars and the activation of the PI3K/AKT/CDK2 pathway by inhibiting Pin1 expression. This study suggests that combining ATRA with a hydrogel to target Pin1 expression may be a promising strategy for treating glial scar formation following SCI. [ABSTRACT FROM AUTHOR]

ABSTRACT In a randomized phase II trial (AMLSG 14‐09, NCT00867672) of elderly, newly diagnosed AML patients, ATRA combined with decitabine (DEC) significantly improved the overall response rate (ORR) and survival also in patients with adverse‐risk genetics, without adding toxicity. We performed a post hoc analysis to determine the predictive impact of TP53 status. Despite a nominally higher ORR, the clinically meaningful survival benefit when adding ATRA to DEC was diminished, but not completely negated, in TP53‐mutated patients. Indeed, 2 out of 14 TP53‐mutated patients (14%) randomized to a DEC + ATRA‐containing regimen lived for > 36 months. Further studies of ATRA combined with hypomethylating agents appear warranted in non‐M3 AML patients ineligible for HMA/venetoclax therapy.Trial Registration: ClinicalTrials.gov identifier: NCT00867672 [ABSTRACT FROM AUTHOR]

Objectives: To study the effects of all-trans retinoic acid (ATRA) on TGF-β2-induced effects of human retinal pigment epithelium cells under normoxia and hypoxia conditions. Methods: Two-dimensionally (2D) and three-dimensionally (3D) cultured ARPE19 cells were subjected to cellular functional analyses by transepithelial electrical resistance (TEER) and an extracellular flux assay (2D), measurement of levels of reactive oxygen species (ROS), gene expression analyses of COL1, αSMA, Zo-1, HIF1α, and PGC1α (2D), and physical property analyses (3D). Results: Under a normoxia condition, treatment with 100 nM ATRA substantially decreased barrier function regardless of the presence of 5 ng/mL TGF-β2 in 2D ARPE19 monolayer cells. Under a hypoxia condition, treatment with ATRA conversely increased barrier function, but the effect was masked by a marked increase in effects induced by TGF-β2. Although ATRA alone did not affect cellular metabolism and ROS levels in 2D ARPE cells, treatment with ATRA under a hypoxia condition did not affect ROS levels but shifted cellular metabolism from mitochondrial respiration to glycolysis. The changes of cellular metabolism and ROS levels were more pronounced with treatment of both ATRA and TGF-β2 independently of oxygen conditions. Changes in mRNA expressions of some of the above genes suggested the involvement of synergistical regulation of cellular functions by TGF-β2 and hypoxia. In 3D ARPE spheroids, the size was decreased and the stiffness was increased by either treatment with TGF-β2 or ATRA, but these changes were unexpectedly modulated by both ATRA and TGF-β2 treatment regardless of oxygen conditions. Conclusions: The findings reported herein indicate that TGF-β2 and hypoxia synergistically and differentially induce effects in 2D and 3D cultured ARPE19 cells and that their cellular properties are significantly altered by the presence of ATRA. [ABSTRACT FROM AUTHOR]

Improvements in clinical assessment have occurred since the last published recommendations on the diagnosis and treatment of acute promyelocytic leukemia in 2013. Here, a committee of specialists of the Brazilian Association of Hematology, Hemotherapy and Cellular Therapy presents a comprehensive review on the current knowledge, focusing on the advances in diagnosis, risk assessment, and frontline and salvage therapy. The concept of urgent diagnosis is explored as well as the management of critical situations such as coagulopathy and differentiation syndrome. Recent adjustments in risk stratification based on white blood cell counts only are presented together with the incorporation of chemo-free regimens for non-high-risk patients. Special conditions such as acute promyelocytic leukemia in children, the elderly and pregnant women are discussed. Finally, acute promyelocytic leukemia is presented as a highly curable disease because of the real possibility of targeted therapy towards differentiation, and, paradoxically, as a serious and urgent condition that deserves prompt recognition and management to avoid early mortality.

Background: Ovarian cancer is a malignant tumor of the female reproductive system, and its mortality rate is as high as 70%. Estrogen receptor α (ERα)-positive ovarian cancer accounted for most of all ovarian cancer patients. ERα can promote the growth and proliferation of tumors. Methods: The combined effect of All-trans retinoic acid (ATRA) and tamoxifen was obtained by the combination screening of tamoxifen and compound library by MTS. In addition, colony formation assay, flow cytometry analysis, immunofluorescence staining, quantitative real-time polymerase chain reaction (PCR), western blot, and tumor xenotransplantation models were used to further evaluate the efficacy of tamoxifen and ATRA in vitro and in vivo for ER-α-positive ovarian cancer. Results: In our study, we found that All-trans retinoic acid (ATRA) can cooperate with tamoxifen to cause cell cycle arrest and apoptosis and inhibit ERα-positive ovarian cancer in vivo and in vitro. Further exploration of the mechanism found that ATRA can Inhibit genes related to the ERα signaling pathway, enhance the sensitivity of ERα-positive ovarian cancer cells to tamoxifen, and ascertain the effectiveness of tamoxifen and ATRA as treatments for ovarian cancer with an ERα-positive status. Conclusion: Combination of ATRA and tamoxifen is a new way for the treatment of ERα-positive ovarian cancer. [ABSTRACT FROM AUTHOR]

Background: Cholangiocarcinoma (CCA), a primary hepatobiliary malignancy, is characterized by a poor prognosis and a lack of effective treatments. Therefore, the need to explore novel therapeutic approaches is urgent. While the role of Peptidylprolyl Cis/Trans Isomerase, NIMA-Interacting 1 (PIN1) has been extensively studied in various tumor types, its involvement in CCA remains poorly understood. Methods: In this study, we employed tissue microarray (TMA), reverse transcription-polymerase chain reaction (RT-PCR), and The Cancer Genome Atlas (TCGA) database to assess the expression of PIN1. Through in vitro and in vivo functional experiments, we investigated the impact of PIN1 on the adhesion and metastasis of CCA. Additionally, we explored downstream molecular pathways using RNA-seq, western blotting, co-immunoprecipitation, immunofluorescence, and mass spectrometry techniques. Results: Our findings revealed a negative correlation between PIN1 overexpression and prognosis in CCA tissues. Furthermore, high PIN1 expression promoted CCA cell proliferation and migration. Mechanistically, PIN1 functioned as an oncogene by regulating ANXA2 phosphorylation, thereby promoting CCA adhesion. Notably, the interaction between PIN1 and ANXA2 was facilitated by RACK1. Importantly, pharmacological inhibition of PIN1 using the FDA-approved drug all-trans retinoic acid (ATRA) effectively suppressed the metastatic potential of CCA cells in a nude mouse lung metastasis model. Conclusion: Overall, our study emphasizes the critical role of the PIN1/RACK1/ANXA2 complex in CCA growth and functionality, highlighting the potential of targeting PIN1 as a promising therapeutic strategy for CCA. [ABSTRACT FROM AUTHOR]

The present study described an extremely rare case of acute promyelocytic leukemia (APL) characterized by a complex three‑way (15;22;17)(q22;q11.2;q21) translocation. Acute promyelocytic leukemia (APL) is a specific subtype of acute myeloid leukemia with distinctive clinical and therapeutic characteristics. Besides being characterized by the t(15;17)(q22;q12) translocation, this subtype is also notable for its response to all-trans-retinoic acid (ATRA) treatment. APL is highly responsive to a combination of ATRA and chemotherapeutic agents, achieving over 90 % complete remission rates and over 80 % long-term remission rates. In this case, a 79-year-old male patient presented with complaints of weakness, fatigue, and petechial rash, with no other significant medical history except for diabetes mellitus and hypertension. Conventional cytogenetic methods, dual-color dual-fusion, and dual-color break-apart fluorescent in situ hybridization techniques together identified the t(15;22;17) translocation. RT-PCR analysis was performed for expression of PML/RARA fusion transcripts. The patient, diagnosed with APL, exhibited a complete response to all-trans retinoic acid (ATRA) and idarubicin treatment. In this paper, we present the second documented case of t(15;22;17) and explore the remarkable remission observed following treatment with All-Trans Retinoic Acid (ATRA). [ABSTRACT FROM AUTHOR]

Objective: To investigate the protective effect of all-trans retinoic acid （ATRA） on the function of NK cells dam-aged by oxidative stress in liver fibrosis. Methods: Mouse model with liver injury was established by carbon tetrachloride （CCl4）， biochemical and pathological assays were used to evaluate the degree of liver injury and fibrosis in mice， and changes of NK cells and oxidative stress injury in liver tissue of mice were observed. In vitro， NK92 cell lines damaged by H2O2 oxidative stress were evaluated the protective effect of ATRA. Results: Liver inflammation and fibrosis were suppressed and liver function was improved in CCl4 model mice by ATRA treatment. ATRA could increase SOD activity and GSH content in liver tissue， which promoted the proportion and num-ber of hepatic NK cells. ATRA could protect NK cells from oxidative damage and apoptosis induced by H2O2 in vitro. Conclusion: ATRA can ameliorate liver injury and fibrosis induced by CCl4， which may be related to the inhibition of oxidative stress on NK cells. [ABSTRACT FROM AUTHOR]

The objective of this study is to explore the possibility of treating APL patients fully as outpatients. A total of 21 consecutive APL patients were identified over 30 years in the Centro de Hematología y Medicina Interna de Puebla, at Clínica Ruiz, but only 17 were studied, treated as outpatients, and followed for at least 1 month; they were observed for median of 95 months, their median age was 27 years and all were treated with ATRA, prednisone, and adriamycin as outpatients. Treatment was completed on an outpatient basis in 15/17 cases. Molecular remission was achieved in 16/17 patients. The median follow-up was 95 months (IQR 19 - 360). The median OS and LFS were not reached, and the 12-month LFS was 94%. We have confirmed that APL can be treated entirely on an outpatient basis: this observation is of utmost relevance in a resource-limited setting, such as those prevailing in low- and middle-income countries.

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. [ABSTRACT FROM AUTHOR]

The limited availability of molecularly targeted low‐molecular‐weight imaging agents for monitoring multiple myeloma (MM)‐targeted therapies has been a significant challenge in the field. In response, a first‐in‐class peptide‐based radiotracer, [68Ga]Ga‐AJ206, is developed that can be seamlessly integrated into the standard clinical workflow and is specifically designed to noninvasively quantify CD38 levels and pharmacodynamics by positron emission tomography (PET). A bicyclic peptide, AJ206, is synthesized and exhibits high affinity to CD38 (KD: 19.1 ± 0.99 × 10−9m) by surface plasmon resonance. Further, [68Ga]Ga‐AJ206‐PET shows high contrast within 60 min and suitable absorbed dose estimates for clinical use. Additionally, [68Ga]Ga‐AJ206 detects CD38 expression in cell line‐derived xenografts, patient‐derived xenografts (PDXs), and disseminated disease models in a manner consistent with flow cytometry and immunohistochemistry findings. Moreover, [68Ga]Ga‐AJ206‐PET successfully quantifies CD38 pharmacodynamics in PDXs, revealing increased CD38 expression in the tumor following all‐trans retinoic acid (ATRA) therapy. In conclusion, [68Ga]Ga‐AJ206 exhibits the salient features required for clinical translation, providing CD38‐specific high‐contrast images in multiple models of MM. [68Ga]Ga‐AJ206‐PET could be useful for quantifying total CD38 levels and pharmacodynamics during therapy to evaluate approved and new therapies in MM and other diseases with CD38 involvement. [ABSTRACT FROM AUTHOR]

Light‐mediated processes have received significant attention, since they have re‐surfaced unconventional reactivity platforms, complementary to conventional polar chemistry. γ‐Lactones and cyclopropanes are prevalent moieties, found in numerous natural products and pharmaceuticals. Among various methods for their synthesis, light‐mediated protocols are coming to the spotlight, although these are contingent upon the use of photoorgano‐ or metal‐based catalysts. Herein, we introduce a novel photochemical activation of iodo‐reagents via the use of cheap sodium ascorbate or ascorbic acid to enable their homolytic scission and addition onto double bonds. The developed protocol was applied successfully to the formal [3+2] cycloaddition for the synthesis of γ‐lactones, traditional atom transfer radical addition (ATRA) reactions and the one‐pot two‐step conversion of alkenes to cyclopropanes. In all cases, the desired products were obtained in good to high yields, while the reaction mechanism was thoroughly investigated. Depending on the nature of the iodo‐reagent, a halogen or a hydrogen‐bonded complex is formed, which initiates the process. [ABSTRACT FROM AUTHOR]

Background: Acute myeloid leukemia (AML) with Fms-like tyrosine kinase 3 gene internal tandem duplication (FLT3-ITD) mutations has a poor prognosis. The combination of arsenic trioxide (ATO) and all-trans retinoic acid (ATRA) has a synergistic killing effect on leukemia cells with FLT3-ITD mutation. However, the mechanism, especially the changes of gene expression and metabolic activity remain unclear. Here we explore the transcriptome and metabolomics changes of FLT3-ITD AML cells treated with ATO/ATRA. Methods: RNA-seq was used to identify differential expressed genes (DEGs), and ultra-high performance liquid chromatography-quadrupole electrostatic field orbital trap mass spectrometry (UHPLC-QE-MS) nontargeted metabolomics method was used to screen out the differential metabolites in FLT3-ITD mutant cell lines treated with ATRA and ATO. KEGG pathway database was utilized for pathway exploration and Seahorse XF24 was used to detect extracellular acidification rate (ECAR). Metabolic polymerase chain reaction (PCR) array and real-time quantitative PCR (RT-qPCR) were used to detect mRNA levels of key metabolic genes of glycolysis and fatty acid after drug treatment. Results: A total of 3873 DEGs were identified and enriched in 281 Gene Ontology (GO) terms, among which 210 were related to biological processes, 43 were related to cellular components, and 28 were related to molecular functions. Besides, 1794 and 927 differential metabolites were screened in positive and negative ion mode separately, and 59 different metabolic pathways were involved, including alanine-aspartate-glutamate metabolic pathway, arginine, and proline metabolic pathway, glycerophospholipid metabolic pathways, etc. According to KEGG Pathway analysis of transcriptome combined with metabolome, glycolysis/gluconeogenesis pathway and fatty acid metabolism pathway were significantly founded enriched. ATRA + ATO may inhibit the glycolysis of FLT3-ITD AML cells by inhibiting FLT3 and its downstream AKT/HK2-VDAC1 signaling pathway. Conclusions: The gene transcription profile and metabolites of FLT3-ITD mutant cells changes significantly after treatment, which might be related to the anti-FLT3-ITD AML effect. The screened DEGs, differential metabolites pathway are helpful in studying the mechanism of anti-leukemia effects and drug targets. [ABSTRACT FROM AUTHOR]

Abstract The limited availability of molecularly targeted low‐molecular‐weight imaging agents for monitoring multiple myeloma (MM)‐targeted therapies has been a significant challenge in the field. In response, a first‐in‐class peptide‐based radiotracer, [68Ga]Ga‐AJ206, is developed that can be seamlessly integrated into the standard clinical workflow and is specifically designed to noninvasively quantify CD38 levels and pharmacodynamics by positron emission tomography (PET). A bicyclic peptide, AJ206, is synthesized and exhibits high affinity to CD38 (KD: 19.1 ± 0.99 × 10−9 m) by surface plasmon resonance. Further, [68Ga]Ga‐AJ206‐PET shows high contrast within 60 min and suitable absorbed dose estimates for clinical use. Additionally, [68Ga]Ga‐AJ206 detects CD38 expression in cell line‐derived xenografts, patient‐derived xenografts (PDXs), and disseminated disease models in a manner consistent with flow cytometry and immunohistochemistry findings. Moreover, [68Ga]Ga‐AJ206‐PET successfully quantifies CD38 pharmacodynamics in PDXs, revealing increased CD38 expression in the tumor following all‐trans retinoic acid (ATRA) therapy. In conclusion, [68Ga]Ga‐AJ206 exhibits the salient features required for clinical translation, providing CD38‐specific high‐contrast images in multiple models of MM. [68Ga]Ga‐AJ206‐PET could be useful for quantifying total CD38 levels and pharmacodynamics during therapy to evaluate approved and new therapies in MM and other diseases with CD38 involvement.

Abstract One of the defining features of acute myeloid leukemia (AML) is an arrest of myeloid differentiation whose molecular determinants are still poorly defined. Pharmacological removal of the differentiation block contributes to the cure of acute promyelocytic leukemia (APL) in the absence of cytotoxic chemotherapy, but this approach has not yet been translated to non‐APL AMLs. Here, by investigating the function of hypoxia‐inducible transcription factors HIF1α and HIF2α, we found that both genes exert oncogenic functions in AML and that HIF2α is a novel regulator of the AML differentiation block. Mechanistically, we found that HIF2α promotes the expression of transcriptional repressors that have been implicated in suppressing AML myeloid differentiation programs. Importantly, we positioned HIF2α under direct transcriptional control by the prodifferentiation agent all‐trans retinoic acid (ATRA) and demonstrated that HIF2α blockade cooperates with ATRA to trigger AML cell differentiation. In conclusion, we propose that HIF2α inhibition may open new therapeutic avenues for AML treatment by licensing blasts maturation and leukemia debulking.

Objectives: To study the effects of all-trans retinoic acid (ATRA) on TGF-β2-induced effects of human retinal pigment epithelium cells under normoxia and hypoxia conditions. Methods: Two-dimensionally (2D) and three-dimensionally (3D) cultured ARPE19 cells were subjected to cellular functional analyses by transepithelial electrical resistance (TEER) and an extracellular flux assay (2D), measurement of levels of reactive oxygen species (ROS), gene expression analyses of COL1, αSMA, Zo-1, HIF1α, and PGC1α (2D), and physical property analyses (3D). Results: Under a normoxia condition, treatment with 100 nM ATRA substantially decreased barrier function regardless of the presence of 5 ng/mL TGF-β2 in 2D ARPE19 monolayer cells. Under a hypoxia condition, treatment with ATRA conversely increased barrier function, but the effect was masked by a marked increase in effects induced by TGF-β2. Although ATRA alone did not affect cellular metabolism and ROS levels in 2D ARPE cells, treatment with ATRA under a hypoxia condition did not affect ROS levels but shifted cellular metabolism from mitochondrial respiration to glycolysis. The changes of cellular metabolism and ROS levels were more pronounced with treatment of both ATRA and TGF-β2 independently of oxygen conditions. Changes in mRNA expressions of some of the above genes suggested the involvement of synergistical regulation of cellular functions by TGF-β2 and hypoxia. In 3D ARPE spheroids, the size was decreased and the stiffness was increased by either treatment with TGF-β2 or ATRA, but these changes were unexpectedly modulated by both ATRA and TGF-β2 treatment regardless of oxygen conditions. Conclusions: The findings reported herein indicate that TGF-β2 and hypoxia synergistically and differentially induce effects in 2D and 3D cultured ARPE19 cells and that their cellular properties are significantly altered by the presence of ATRA.

Abstract Background Sorafenib resistance greatly reduces the efficacy of treatments in advanced hepatocellular carcinoma (HCC) patients, but the underlying mechanisms are not thoroughly understood. All-trans retinoic acid (ATRA), an anti-leukaemia agent, has attracted considerable attention due to its role in sensitizing cells to other anticancer treatments. We aimed to investigate the combined effect of ATRA and Sorafenib on HCC and the underlying mechanisms. Methods CCK-8, cell sphere formation, trans-well migration, and wound-healing assays were used to analyse the biological behaviours of HCC cells in vitro. Western blotting and qRT-PCR analysis were conducted to measure the expression of p21 activated kinase 1 (PAK1) and phospho-p21 activated kinase 1 (pPAK1). Xenograft models were established to confirm the synergistic effects of ATRA and Sorafenib in vivo. TUNEL assays and immunohistochemistry were utilized to determine apoptosis, proliferation, PAK1 and pPAK1 levels in tumour tissues. Results We observed that PAK1 was overexpressed in HCC, and its expression was negatively correlated with the survival of patients. PAK1 promoted the proliferation, self-renewal and epithelial-mesenchymal transition of HCC cells. Correlation analysis indicated that the IC50 of Sorafenib was positively correlated with the level of pPAK1 in HCC cell lines. ATRA inhibited the progression of HCC and sensitized HCC response to Sorafenib by downregulation of PAK1, as shown by the calculated coefficient of drug interaction and the data obtained from xenograft models. Conclusions Our findings indicated that instead of treatment with Sorafenib alone, the combination of ATRA and Sorafenib provides a more effective treatment for HCC patients. Video Abstract

Resistance of tumor cells to retinoic acid (RA), a promising therapeutic agent, is the major factor limiting the use of RA in clinical practice. The mechanisms of resistance to RA are still poorly understood. Cellular Retinoic Acid Binding Proteins, CRABP1 and CRABP2, are essential mediators of RA signaling, but role of the two CRABP homologs in regulating cellular sensitivity to RA has not been well studied. In addition, the effects of CRABP1 and CRABP2 on cell proliferation have not been compared. Here, using a broad panel of breast cancer cell lines with different levels of RA sensitivity/resistance, we show for the first time that in the RA-sensitive cells, CRABP1 expression is restricted by methylation, and protein levels are highly variable. In the moderately-RA-resistant cell lines, high level of CRABP1 is observed both at the mRNA and protein levels, unchanged by inhibition of DNA methylation. The cell lines with maximum resistance to RA are characterized by complete repression of CRABP1 expression realized at transcriptional and posttranscriptional levels, and exogenous expression of each of the CRABP homologs has no effect on the studied characteristics. CRABP1 and CRABP2 proteins have opposing effects on proliferation and sensitivity to RA. In particular, CRABP1 stimulates and CRABP2 reduces proliferation and resistance to RA in the initially RA-sensitive cells, while in the more resistant cells the role of each homolog in both of these parameters is reversed. Overall, we have shown for the first time that CRABP proteins exert different effects on the growth and sensitivity to RA of breast cancer cells (stimulation, suppression, or no effect) depending on the baseline level of RA-sensitivity, with the effects of CRABP1 and CRABP2 homologs on the studied properties always being opposite. [ABSTRACT FROM AUTHOR]

to review the current diagnostic and therapeutic landscape of AML in Latin America as a reflection of other low- and middle-income countries and regions of the world. Encompassing both acute promyelocytic and non-promyelocytic disease types. We reviewed the literature and study registries concerning epidemiological features of patients with AML/APL treated in Latin America, as well as evaluated diagnostic and genetic stratification and patient fitness assessment challenges, the importance of early mortality and supportive care capacity, intensive and non-intensive chemotherapy alternatives, consolidation, and maintenance strategies including novel agents and hematopoietic stem cell transplantation. Although most of the current technologies and treatment options are available in the region, a significant fraction of patients have only limited access to them. In addition, mortality in the first weeks from diagnosis is higher in the region compared to developed countries. Disparities in access to technologies, supportive care capacity, and availability of novel agents and HSCT hinder results in our region, reflecting barriers common to other LMICs. Recent developments in the diagnosis and treatment of this disease must be implemented through education, collaborative clinical research, and advocacy to improve outcomes. [ABSTRACT FROM AUTHOR]

Background: Single-target inhibitors have not been successful in cancer treatment due to the development of drug resistance. Nevertheless, therapeutic agents capable of simultaneously inhibiting multiple targets have revealed encouraging results in inducing apoptosis and overcoming drug resistance in cancerous cells. Here, we designed a composite liposomal nano-carrier co-loading 5-Fluorouracil (5-FU) with all-trans retinoic acid (ATRA) to assess anticancer efficacy of the combined drugs in colorectal cancer (CRC). Methods: A PEGylated liposomal nano-carrier with phospholipid/cholesterol/DSPE-PEG (2000) was synthesized by the thin film hydration technique for co-delivery of ATRA and 5-FU. After characterizing, the role of 5-FU and ATRA co-loaded liposomal nano-carrier in proliferation, epithelial-mesenchymal transition (EMT), apoptosis, and cancer stem cells (CSCs) were investigated by using colony forming and MTT assay, RT-qPCR and Annexin V/PI kit. Results: The average size of liposomes (LPs) was < 150 nm with uniform size distribution. Drug release analyses indicated that both ATRA and 5-FU could simultaneously release from LPs in a sustained release manner. The synergistic inhibitory effects of ATRA and 5-FU loaded in LPs were verified with a combination index of 0.43. Dual drug LPs showed the highest cytotoxicity, enhanced inhibition of cell proliferation, increased apoptotic potential, decreased CSCs, and attenuated EMT-associated biomarkers. Also, dual drug LPs decreased β-catenin gene expression more than other liposomal formulations. Conclusion: These findings suggest that using LPs to achieve a synergistic effect of ATRA and 5-FU is an effectual approach to increase the therapeutic effect of 5-FU toward CRC cells. [ABSTRACT FROM AUTHOR]

Introduction: Acute promyelocytic leukemia (APL) is a rare myeloid leukemia subtype affecting adult and pediatric populations. APL constitutes 15-20% of all childhood AML in Latin America, compared to 7% in the non-Latino population. This leukemia has unique characteristics, such as its association with chromosomal translocations involving the retinoid acid receptor a (RARA) gene on chromosome 17. In addition, APL is also distinct from other AML subtypes due to its response to all-trans-retinoic acid (ATRA), which induces terminal granulocytic differentiation of blasts. Overall 5-year survival rates are generally reported to be greater than 80%. Materials and methods: A study was conducted from January 2008 to December 2022 applying the IC-APL 2006 treatment protocol. This case series reports the clinical results of 22 children with APL. In all cases, the diagnosis was made by bone marrow aspiration and evaluation of the t(15:17) or t(11:17) transcripts. Results: We identified 22 patients with APL, of whom 10 were female and 12 were male. Twelve patients debuted with coagulation abnormalities. The doses of anthracyclines varied according to the risk, with an average of 496.8 mgm2. The cardiological assessment was performed before and after chemotherapy, finding 2/22 patients with moderate sisto-diastolic dysfunction and one with mild pulmonary insufficiency at the end of treatment. There were 6/22 patients with complications related to ATRA treatment, the most frequent being pseudotumor cerebri. All complications were transitory and treated immediately without complications. In this series of cases, an overall survival of 90.6% and a relapse-free survival of 90.6% were recorded. The follow-up mean was 9.1 ± 3.8 years. Conclusion: APL is a highly curable disease when combined with ATRA and anthracyclines. In this series of cases, good long-term results were observed with the IC-APL 2006 protocol. However, in Latin America, the availability of drugs such as arsenic trioxide as the first line of treatment is an unresolved challenge. [ABSTRACT FROM AUTHOR]

One of the defining features of acute myeloid leukemia (AML) is an arrest of myeloid differentiation whose molecular determinants are still poorly defined. Pharmacological removal of the differentiation block contributes to the cure of acute promyelocytic leukemia (APL) in the absence of cytotoxic chemotherapy, but this approach has not yet been translated to non‐APL AMLs. Here, by investigating the function of hypoxia‐inducible transcription factors HIF1α and HIF2α, we found that both genes exert oncogenic functions in AML and that HIF2α is a novel regulator of the AML differentiation block. Mechanistically, we found that HIF2α promotes the expression of transcriptional repressors that have been implicated in suppressing AML myeloid differentiation programs. Importantly, we positioned HIF2α under direct transcriptional control by the prodifferentiation agent all‐trans retinoic acid (ATRA) and demonstrated that HIF2α blockade cooperates with ATRA to trigger AML cell differentiation. In conclusion, we propose that HIF2α inhibition may open new therapeutic avenues for AML treatment by licensing blasts maturation and leukemia debulking. Synopsis: Hypoxia‐inducible transcription factor HIF2α contributes to acute myeloid leukemia (AML) pathogenesis by taking part to the molecular network that suppresses differentiation of leukemic blasts along the myeloid lineage. Hypoxia‐inducible factors HIF1α and HIF2α promote leukemia progression in cell and patient‐derived models of established AML.In AML cells, HIF2α regulates a novel gene signature that contains Runx2 and BCL11A and transcriptional repressors implicated in suppressing AML myeloid differentiation programs.HIF2α targeting via gene silencing or pharmacological inhibition triggers a myeloid differentiation program and promotes leukemia debulking.All‐trans retinoid acid induces HIF2α expression via direct activity of RAR proteins.Targeting HIF2α cooperates with ATRA to promote myeloid differentiation. [ABSTRACT FROM AUTHOR]

Background: Hepatocellular carcinoma (HCC) is a highly heterogeneous cancer with major challenges in both prevention and therapy. Metformin, adenosine monophosphate‐activated protein kinase (AMPK) activator, has been suggested to reduce the incidence of HCC when used for patients with diabetes in preclinical and clinical studies. However, the possible effects of metformin and their mechanisms of action in non‐diabetic HCC have not been adequately investigated. Methods: Fah−/− mice were used to construct a liver‐injury‐induced non‐diabetic HCC model for exploring hepatocarcinogenesis and therapeutic potential of metformin. Changes in relevant tumour and biochemical indicators were measured. Bulk and single‐cell RNA‐sequencing analyses were performed to validate the crucial role of proinflammatory/pro‐tumour CD8+ T cells. In vitro and in vivo experiments were performed to confirm Cyp26a1‐related antitumour mechanisms of metformin. Results: RNA‐sequencing analysis showed that chronic liver injury led to significant changes in AMPK‐, glucose‐ and retinol metabolism‐related pathways in Fah−/− mice. Metformin prevented the formation of non‐diabetic HCC in Fah−/− mice with chronic liver injury. Cyp26a1 ddexpression in hepatocytes was significantly suppressed after metformin treatment. Moreover, downregulation of Cyp26a1 occurred in conjunction with increased levels of all‐trans‐retinoic acid (atRA), which is involved in the activation of metformin‐suppressed hepatocarcinogenesis in Fah−/− mice. In contrast, both CD8+ T‐cell infiltration and proinflammatory/pro‐tumour cytokines in the liver were significantly upregulated in Fah−/− mice during chronic liver injury, which was notably reversed by either metformin or atRA treatment. Regarding mechanisms, metformin regulated the decrease in Cyp26a1 enzyme expression and increased atRA expression via the AMPK/STAT3/Gadd45β/JNK/c‐Jun pathway. Conclusions: Metformin inhibits non‐diabetic HCC by upregulating atRA levels and downregulating CD8+ T cells. This is the first reporting that the traditional drug metformin regulates the metabolite atRA via the Cyp26a1‐involved pathway. The present study provides a potential application of metformin and atRA in non‐diabetic HCC. [ABSTRACT FROM AUTHOR]

Simple Summary: Differentiation syndrome (DS) is a frequent clinical complication of treatment with all-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO), and is typically characterized by non-infectious related fever, dyspnea, hypotension, weight gain > 5 kg, pleural or pericardial effusions, and acute renal failure. DS was initially observed in patients with acute promyelocytic leukemia (APL) treated with ATRA and ATO but was later recognized with other targeted therapies for acute myeloid leukemia (AML). In this review, we discuss the pathogenesis, clinical manifestations, radiological findings, diagnosis, and treatment of DS in patients with APL treated with ATRA and ATO, as well as discuss DS in patients with AML treated with novel therapeutics. Differentiation syndrome (DS) is a frequent and potentially life-threatening clinical syndrome first recognized with the advent of targeted therapeutics for acute promyelocytic leukemia (APL). DS was subsequently observed more broadly with targeted therapeutics for acute myeloid leukemia (AML). DS is typically characterized by fever, dyspnea, hypotension, weight gain, pleural or pericardial effusions, and acute renal failure. The incidence in patients with APL ranges from 2 to 37%, with the wide variation likely attributed to different diagnostic criteria, use of prophylactic treatment, and different treatment regimens. Treatment with corticosteroids +/- cytoreductive therapy should commence as soon as DS is suspected to reduce DS-related morbidity and mortality. The targeted anti-leukemic therapy should be discontinued in patients with severe DS. Here, we discuss the pathogenesis of DS, clinical presentations, diagnostic criteria, management strategies, and implementation of prospective tracking on clinical trials. [ABSTRACT FROM AUTHOR]

Significant variations exist related to the end of induction practices in the management of Acute Promyelocytic Leukemia (APL). These variations include all-trans retinoic acid (ATRA)-arsenic trioxide (ATO) in fixed doses versus continuation until hematologic complete remission (CR) and performance versus omission of post-induction bone marrow biopsy to confirm morphological CR. A retrospective chart review was conducted of 61 patients (42 low/intermediate-risk and 19 high-risk) aged ≥ 18 years with newly diagnosed APL treated with fixed duration ATRA-ATO +/- cytoreduction at a tertiary medical center from December 2012 through March 2020. Of the 54 patients with post-induction bone marrow biopsy results, 52 (96%) demonstrated no morphologic evidence of APL while the remaining were equivocal. After 2.6 years median follow-up, no relapses occurred. The estimated 2-year overall survival rate of 95% suggests excellent outcomes with a fixed ATO induction regimen and safe omission of post-induction bone marrow biopsy irrespective of hematologic parameters. [ABSTRACT FROM AUTHOR]

ABSTRACTObjective to review the current diagnostic and therapeutic landscape of AML in Latin America as a reflection of other low- and middle-income countries and regions of the world. Encompassing both acute promyelocytic and non-promyelocytic disease types.Methods We reviewed the literature and study registries concerning epidemiological features of patients with AML/APL treated in Latin America, as well as evaluated diagnostic and genetic stratification and patient fitness assessment challenges, the importance of early mortality and supportive care capacity, intensive and non-intensive chemotherapy alternatives, consolidation, and maintenance strategies including novel agents and hematopoietic stem cell transplantation.Results Although most of the current technologies and treatment options are available in the region, a significant fraction of patients have only limited access to them. In addition, mortality in the first weeks from diagnosis is higher in the region compared to developed countries.Conclusions Disparities in access to technologies, supportive care capacity, and availability of novel agents and HSCT hinder results in our region, reflecting barriers common to other LMICs. Recent developments in the diagnosis and treatment of this disease must be implemented through education, collaborative clinical research, and advocacy to improve outcomes.

Abstract Background Hepatocellular carcinoma (HCC) is a highly heterogeneous cancer with major challenges in both prevention and therapy. Metformin, adenosine monophosphate‐activated protein kinase (AMPK) activator, has been suggested to reduce the incidence of HCC when used for patients with diabetes in preclinical and clinical studies. However, the possible effects of metformin and their mechanisms of action in non‐diabetic HCC have not been adequately investigated. Methods Fah−/− mice were used to construct a liver‐injury‐induced non‐diabetic HCC model for exploring hepatocarcinogenesis and therapeutic potential of metformin. Changes in relevant tumour and biochemical indicators were measured. Bulk and single‐cell RNA‐sequencing analyses were performed to validate the crucial role of proinflammatory/pro‐tumour CD8+ T cells. In vitro and in vivo experiments were performed to confirm Cyp26a1‐related antitumour mechanisms of metformin. Results RNA‐sequencing analysis showed that chronic liver injury led to significant changes in AMPK‐, glucose‐ and retinol metabolism‐related pathways in Fah−/− mice. Metformin prevented the formation of non‐diabetic HCC in Fah−/− mice with chronic liver injury. Cyp26a1 ddexpression in hepatocytes was significantly suppressed after metformin treatment. Moreover, downregulation of Cyp26a1 occurred in conjunction with increased levels of all‐trans‐retinoic acid (atRA), which is involved in the activation of metformin‐suppressed hepatocarcinogenesis in Fah−/− mice. In contrast, both CD8+ T‐cell infiltration and proinflammatory/pro‐tumour cytokines in the liver were significantly upregulated in Fah−/− mice during chronic liver injury, which was notably reversed by either metformin or atRA treatment. Regarding mechanisms, metformin regulated the decrease in Cyp26a1 enzyme expression and increased atRA expression via the AMPK/STAT3/Gadd45β/JNK/c‐Jun pathway. Conclusions Metformin inhibits non‐diabetic HCC by upregulating atRA levels and downregulating CD8+ T cells. This is the first reporting that the traditional drug metformin regulates the metabolite atRA via the Cyp26a1‐involved pathway. The present study provides a potential application of metformin and atRA in non‐diabetic HCC.

IntroductionAcute promyelocytic leukemia (APL) is a rare myeloid leukemia subtype affecting adult and pediatric populations. APL constitutes 15-20% of all childhood AML in Latin America, compared to 7% in the non-Latino population. This leukemia has unique characteristics, such as its association with chromosomal translocations involving the retinoid acid receptor α (RARA) gene on chromosome 17. In addition, APL is also distinct from other AML subtypes due to its response to all-trans-retinoic acid (ATRA), which induces terminal granulocytic differentiation of blasts. Overall 5-year survival rates are generally reported to be greater than 80%.Materials and methodsA study was conducted from January 2008 to December 2022 applying the IC-APL 2006 treatment protocol. This case series reports the clinical results of 22 children with APL. In all cases, the diagnosis was made by bone marrow aspiration and evaluation of the t(15:17) or t(11:17) transcripts.ResultsWe identified 22 patients with APL, of whom 10 were female and 12 were male. Twelve patients debuted with coagulation abnormalities. The doses of anthracyclines varied according to the risk, with an average of 496.8 mgm2. The cardiological assessment was performed before and after chemotherapy, finding 2/22 patients with moderate sisto-diastolic dysfunction and one with mild pulmonary insufficiency at the end of treatment. There were 6/22 patients with complications related to ATRA treatment, the most frequent being pseudotumor cerebri. All complications were transitory and treated immediately without complications. In this series of cases, an overall survival of 90.6% and a relapse-free survival of 90.6% were recorded. The follow-up mean was 9.1 ± 3.8 years.ConclusionAPL is a highly curable disease when combined with ATRA and anthracyclines. In this series of cases, good long-term results were observed with the IC-APL 2006 protocol. However, in Latin America, the availability of drugs such as arsenic trioxide as the first line of treatment is an unresolved challenge.

Simple Summary: Proper development of the fetal lung is vital to the survival and healthy growth of pigs after birth, but many factors can disturb the normal growth of the fetal pig lung. In the previous study, we found that the Hoxa1 mutation of g.50111251 G > TC resulted in the congestion and edema of fetal lungs, and all neonatal Hoxa1−/− piglets died of respiratory failure during the suckling period. The results of this study showed that supplementing all-trans retinoic acid (ATRA) to pregnant sows alleviated the dyspnea of neonatal Hoxa1−/− piglets by increasing the IFN-γ concentration (p < 0.05), airspace area (p < 0.01) and pulmonary microvessel density (p < 0.01); increasing the expression of VEGFD (p < 0.01), PDGFD (p < 0.01), KDR (p < 0.01), ID1 (p < 0.01), and NEDD4 (p < 0.01); and decreasing the septal wall thickness (p < 0.01) and the expression of SFTPC (p < 0.01) and FOXO3 (p < 0.01). Neonatal Hoxa1−/− piglets were characterized by dyspnea owing to the Hoxa1 mutation, and maternal administration with ATRA alleviated the dyspnea of neonatal Hoxa1−/− piglets. The purpose of this experiment was to explore how maternal ATRA administration rescued the abnormal fetal lungs of Hoxa1−/− piglets. Samples of the lungs were collected from neonatal Hoxa1−/− and non-Hoxa1−/− piglets delivered by sows in the control group, and from neonatal Hoxa1−/− piglets born by sows administered with ATRA at 4 mg/kg body weight on dpc 12, 13, or 14, respectively. These were used for the analysis of ELISA, histological morphology, immunofluorescence staining, immunohistochemistry staining, and quantitative real-time PCR. The results indicate that the Hoxa1 mutation had adverse impacts on the development of the alveoli and pulmonary microvessels of Hoxa1−/− piglets. Maternal administration with ATRA at 4 mg/kg body weight on dpc 14 rescued the abnormal lung development of Hoxa1−/− piglets by increasing the IFN-γ concentration (p < 0.05), airspace area (p < 0.01) and pulmonary microvessel density (p < 0.01); increasing the expression of VEGFD (p < 0.01), PDGFD (p < 0.01), KDR (p < 0.01), ID1 (p < 0.01), and NEDD4 (p < 0.01); and decreasing the septal wall thickness (p < 0.01) and the expression of SFTPC (p < 0.01) and FOXO3 (p < 0.01). Maternal administration with ATRA plays a vital role in rescuing the abnormal development of lung of Hoxa1−/− fetal piglets. [ABSTRACT FROM AUTHOR]

Background: Sorafenib resistance greatly reduces the efficacy of treatments in advanced hepatocellular carcinoma (HCC) patients, but the underlying mechanisms are not thoroughly understood. All-trans retinoic acid (ATRA), an anti-leukaemia agent, has attracted considerable attention due to its role in sensitizing cells to other anticancer treatments. We aimed to investigate the combined effect of ATRA and Sorafenib on HCC and the underlying mechanisms. Methods: CCK-8, cell sphere formation, trans-well migration, and wound-healing assays were used to analyse the biological behaviours of HCC cells in vitro. Western blotting and qRT-PCR analysis were conducted to measure the expression of p21 activated kinase 1 (PAK1) and phospho-p21 activated kinase 1 (pPAK1). Xenograft models were established to confirm the synergistic effects of ATRA and Sorafenib in vivo. TUNEL assays and immunohistochemistry were utilized to determine apoptosis, proliferation, PAK1 and pPAK1 levels in tumour tissues. Results: We observed that PAK1 was overexpressed in HCC, and its expression was negatively correlated with the survival of patients. PAK1 promoted the proliferation, self-renewal and epithelial-mesenchymal transition of HCC cells. Correlation analysis indicated that the IC50 of Sorafenib was positively correlated with the level of pPAK1 in HCC cell lines. ATRA inhibited the progression of HCC and sensitized HCC response to Sorafenib by downregulation of PAK1, as shown by the calculated coefficient of drug interaction and the data obtained from xenograft models. Conclusions: Our findings indicated that instead of treatment with Sorafenib alone, the combination of ATRA and Sorafenib provides a more effective treatment for HCC patients. 2_mPhFeBDQdvWNSurq11yx Video Abstract [ABSTRACT FROM AUTHOR]

Simple Summary: In the realm of cancer treatment and prevention, the application of retinoids has led to unparalleled successes and humbling disappointments; all-trans retinoic acid (ATRA) has transformed APL (acute promyelocytic leukemia) into an eminently curable disease but has demonstrated little efficacy in acute myeloid leukemia (AML) more broadly. As a cancer prevention strategy, vitamin A supplementation was ineffective and appeared to increase lung cancer incidence, underscoring the complex relationship between retinoic acid signaling and carcinogenesis. This review aims to provide a survey of our current understanding of retinoic acid homeostasis and signaling, to reflect on prior successes and failures to deploy retinoids in the treatment and prevention of cancer, and to explore the unfulfilled potential of retinoids in cancer. New biological insights relating to the regulation of retinoid homeostasis and the discovery of biomarkers of retinoid sensitivity in subsets of non-APL AML have revived enthusiasm for the therapeutic potential of synthetic retinoids, and thus warrant a reacquaintance with retinoid biology. Since the introduction of all-trans retinoic acid (ATRA), acute promyelocytic leukemia (APL) has become a highly curable malignancy, especially in combination with arsenic trioxide (ATO). ATRA's success has deepened our understanding of the role of the RARα pathway in normal hematopoiesis and leukemogenesis, and it has influenced a generation of cancer drug development. Retinoids have also demonstrated some efficacy in a handful of other disease entities, including as a maintenance therapy for neuroblastoma and in the treatment of cutaneous T-cell lymphomas; nevertheless, the promise of retinoids as a differentiating therapy in acute myeloid leukemia (AML) more broadly, and as a cancer preventative, have largely gone unfulfilled. Recent research into the mechanisms of ATRA resistance and the biomarkers of RARα pathway dysregulation in AML have reinvigorated efforts to successfully deploy retinoid therapy in a broader subset of myeloid malignancies. Recent studies have demonstrated that the bone marrow environment is highly protected from exogenous ATRA via local homeostasis controlled by stromal cells expressing CYP26, a key enzyme responsible for ATRA inactivation. Synthetic CYP26-resistant retinoids such as tamibarotene bypass this stromal protection and have shown superior anti-leukemic effects. Furthermore, recent super-enhancer (SE) analysis has identified a novel AML subgroup characterized by high expression of RARα through strong SE levels in the gene locus and increased sensitivity to tamibarotene. Combined with a hypomethylating agent, synthetic retinoids have shown synergistic anti-leukemic effects in non-APL AML preclinical models and are now being studied in phase II and III clinical trials. [ABSTRACT FROM AUTHOR]

AtrA belongs to the TetR family and has been well characterized for its roles in antibiotic biosynthesis regulation. Here, we identified an AtrA homolog (AtrA-lin) in Streptomyces lincolnensis. Disruption of atrA-lin resulted in reduced lincomycin production, whereas the complement restored the lincomycin production level to that of the wild-type. In addition, atrA-lin disruption did not affect cell growth and morphological differentiation. Furthermore, atrA-lin disruption hindered the transcription of regulatory gene lmbU, structural genes lmbA and lmbW inside the lincomycin biosynthesis gene cluster, and 2 other regulatory genes, adpA and bldA. Completement of atrA-lin restored the transcription of these genes to varying degrees. Notably, we found that AtrA-lin directly binds to the promoter region of lmbU. Collectively, AtrA-lin positively modulated lincomycin production via both pathway-specific and global regulators. This study offers further insights into the functional diversity of AtrA homologs and the mechanism of lincomycin biosynthesis regulation. [ABSTRACT FROM AUTHOR]

Background: Acute promyelocytic leukemia (APL) comprises approximately 10% of acute myeloid leukemia (AML) cases. Material and Methods: Both options of treatment (ATRA-ATO and ATRA-chemotherapy) were discussed with patients with low- and intermediate-risk APL, pros and cons explained in details, and treatment regimen selected after getting informed written consent. Results: Total 71 patients were included in the study; among these patients, 3 were negative for both FISH for t (15,17) and RT-PCR for promyelocytic leukemia retinoic acid receptor alpha, and 36 patients with APL had white blood cell count at diagnosis >10 × 109/l. Total 30 patients with newly diagnosed as low- and intermediate-risk-APL fulfilled all inclusion criteria, treated and followed for a minimum period of 2 years up to June, 2016. Fifteen patients liked to be treated with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), while rest of the 15 patients preferred treatment with ATRA and chemotherapy. Conclusion: Combination of ATRA and ATO is equally effective, less toxic, and more feasible in comparison to ATRA and chemotherapy for patients with low- and intermediate-risk APL and is a viable option for this subset of patients, especially in countries with limited resources. [ABSTRACT FROM AUTHOR]

Background Retinol concentrations in serum are significantly higher in patients on hemodialysis (HD) compared to healthy controls. Its lower concentrations have been reported to be an independent predictor of mortality. ATRA – all-trans retinoic acid – is an important compound related to retinol. The objective was to determine ATRA concentrations in serum and to find their association with the prognosis of patients on long-term HD.Methods ATRA was determined by high-performance liquid chromatography in a group of 247 HD patients (follow-up five years) and 54 healthy controls.Results Although serum retinol concentrations were higher in the studied cohort of HD patients, ATRA was lower – median 1.13 (interquartile range 0.90–1.60) ng/mL in HD patients versus 1.42 (1.08–1.63) ng/mL in healthy controls, p = 0.02. Lower ATRA was significantly related to overall mortality of HD patients (HR (95%CI) 0.63 (0.47–0.85) per interquartile range, p = 0.003). The best prognosis was observed in patients with concentrations of both ATRA and retinol above the median (p = 0.003).Conclusions We detected decreased retinoic acid levels in HD patients compared to healthy controls. Lower concentrations of ATRA represent a significant predictor of mortality and provide additional information to retinol.

All-trans retinoic acid (ATRA)-induced differentiation of acute promyelocytic leukemia (APL) toward granulocytes may trigger APL differentiation syndrome (DS), but there is less knowledge about the mechano-chemical regulation mechanism of APL DS under the mechano-microenvironment. We found that ATRA-induced changes in proliferation, morphology, and adhesive molecule expression levels were either dose or stimulus time dependent. An optimal ATRA stimulus condition for differentiating HL60 cells toward neutrophils consisted of 1 x 10-6 M dose and 120 h of stimulus time. Under wall shear stresses, catch--slip bond transition governs P-selectin-mediated rolling for neutrophils and untreated or ATRA-treated (1 x 10-6 M, 120 h) HL60 cells. The ATRA stimuli slowed down the rolling of HL60 cells on immobilized P-selectin no matter whether ICAM-1 was engaged. The b2 integrin near the PSGL-1/P-selectin axis would be activated within sub-seconds for each cell group mentioned above, thus contributing to slow rolling. A faster b2 integrin activation rate and the higher expression levels of PSGL-1 and LFA-1 were assigned to induce the overenhancement of ATRA-treated HL60 adhesion in flow, causing APL DS development. These findings provided an insight into the mechanical-- chemical regulation for APL DS development via ATRA treatment of leukemia and a novel therapeutic strategy for APL DS through targeting the relevant adhesion molecules. [ABSTRACT FROM AUTHOR]

Background: Retinoid signaling is an important regulator of the epidermis and skin appendages. Therefore, synthetic retinoids have been developed for therapeutic use for skin disorders such as psoriasis and acne. Aims: In previous studies, we showed how the photostable retinoid EC23 induces neuronal differentiation in stem cell‐like cell populations, and here, we aim to investigate its ability to influence epidermal and hair follicle growth. Methods: EC23 influence on skin biology was investigated initially in cultures of monolayer keratinocytes and three‐dimentional in vitro models of skin, and finally in in vivo studies of mice back skin. Results: EC23 induces keratinocyte hyperproliferation in vitro and in vivo, and when applied to mouse skin increases the number of involucrin‐positive suprabasal cell layers. These phenotypic changes are similar in skin treated with the natural retinoid all‐trans retinoic acid (ATRA); however, EC23 is more potent; a tenfold lower dose of EC23 is sufficient to induce epidermal thickening, and resulting hyperproliferation is sustained for a longer time period after first dose. EC23 treatment resulted in a disorganized stratum corneum, reduced cell surface lipids and compromised barrier, similar to ATRA treatment. However, EC23 induces a rapid telogen to anagen transition and hair re‐growth in 6‐week‐old mice with synchronously resting back skin follicles. The impact of EC23 on the hair cycle was surprising as similar results have not been seen with ATRA. Conclusions: These data suggest that synthetic retinoid EC23 is a useful tool in exploring the turnover and differentiation of cells and has a potent effect on skin physiology. [ABSTRACT FROM AUTHOR]

Human intestinal microbiome plays vital role in maintaining intestinal homeostasis and interacting with xenobiotics. Few investigations have been conducted to understand the effect of arsenic-containing medicine exposure on gut microbiome. Most animal experiments are onerous in terms of time and resources and not in line with the international effort to reduce animal experiments. We explored the overall microbial flora by 16S rRNA genes analysis in fecal samples from acute promyelocytic leukemia (APL) patients treated with arsenic trioxide (ATO) plus all-trans retinoic acid (ATRA). Gut microbiomes were found to be overwhelmingly dominated by Firmicutes and Bacteroidetes after taking medicines containing arsenic in APL patients. The fecal microbiota composition of APL patients after treatment showed lower diversity and uniformity shown by the alpha diversity indices of Chao, Shannon, and Simpson. Gut microbiome operational taxonomic unit (OTU) numbers were associated with arsenic in the feces. We evaluated Bifidobacterium adolescentis and Lactobacillus mucosae to be a keystone in APL patients after treatment. Bacteroides at phylum or genus taxonomic levels were consistently affected after treatment. In the most common gut bacteria Bacteroides fragilis, arsenic resistance genes were significantly induced by arsenic exposure in anaerobic pure culture experiments. Without an animal model, without taking arsenicals passively, the results evidence that arsenic exposure by drug treatment is not only associated with alterations in intestinal microbiome development at the abundance and diversity level, but also induced arsenic biotransformation genes (ABGs) at the function levels which may even extend to arsenic-related health outcomes in APL. [ABSTRACT FROM AUTHOR]

Background: Choriocarcinoma is a malignant trophoblastic tumor that can degrade the uterine basement membrane to facilitate local and distant metastasis. Matrix metalloproteinase-2 (MMP-2) is a vital proteinase produced by trophoblasts and can cleave type IV collagen in the basement membrane of the uterine epithelium. In addition, E-cadherin controls cell adhesion, which is associated with tumorprogression, and loss of E-cadherin function is associated with metastasis. Vitamin A analogues, including all-trans retinoic acid (ATRA), exhibit anticancer properties, including metastasis inhibition. This study aimed to investigate the ability of ATRA to prevent trophoblast invasion and metastasis in choriocarcinoma by assessing MMP-2 and E-cadherin activity. Methods: This study administered various doses of ATRA to the BeWo (American Type Culture Collection CCL-98) choriocarcinoma cell line and assessed MMP-2 and E-cadherin activity through flow cytometry. The research was performed at the Biomedical Laboratory of the Faculty of Medicine of Universitas Brawijaya Malang, East Java, Indonesia. Results: BeWo cells were exposed to 0, 50, 100, 200, 400, or 800 µg/mL ATRA. MMP-2 was downregulated after ATRA treatment. The greatest reduction in MMP-2 level was observed after 200 µg/mL ATRA treatment, but this result was not statistically significant (P = 0.550). However, ATRA treatment significantly reduced the number of BeWo cells with low E-cadherin levels (P = 0.012). Conclusion: ATRA downregulates MMP-2 and upregulates E-cadherin. Further in vitro and animal studies are required to evaluate the ability of ATRA to inhibit metastasis. [ABSTRACT FROM AUTHOR]

The efficiency of drug biosynthesis depends on different transcriptional regulatory pathways in Streptomyces, and the protein degradation system adds another layer of complexity to the regulatory processes. AtrA, a transcriptional regulator in the A‐factor regulatory cascade, stimulates the production of daptomycin by binding to the dptE promoter in Streptomyces roseosporus. Using pull‐down assays, bacterial two‐hybrid system and knockout verification, we demonstrated that AtrA is a substrate for ClpP protease. Furthermore, we showed that ClpX is necessary for AtrA recognition and subsequent degradation. Bioinformatics analysis, truncating mutation, and overexpression proved that the AAA motifs of AtrA were essential for initial recognition in the degradation process. Finally, overexpression of mutated atrA (AAA‐QQQ) in S. roseosporus increased the yield of daptomycin by 225% in shake flask and by 164% in the 15 L bioreactor. Thus, improving the stability of key regulators is an effective method to promote the ability of antibiotic synthesis. [ABSTRACT FROM AUTHOR]

Adjuvant endocrine therapy (AET) is the treatment of choice for early-stage estrogen receptor alpha (ERα)-positive breast cancer (BC). However, almost 40% of tamoxifen-treated cases display no response or a partial response to AET, thus increasing the need for new treatment options and strong predictors of the therapeutic response of patients at high risk of relapse. In addition to ERα, BC research has focused on ERβ1 and ERβ2 (isoforms of ERβ), the second ER isotype. At present, the impact of ERβ isoforms on ERα-positive BC prognosis and treatment remains elusive. In the present study, we established clones of MCF7 cells constitutively expressing human ERβ1 or ERβ2 and investigated their role in the response of MCF7 cells to antiestrogens [4-hydroxytamoxifen (OHΤ) and fulvestrant (ICI182,780)] and retinoids [all-trans retinoic acid (ATRA)]. We show that, compared to MCF7 cells, MCF7-ERβ1 and MCF7-ERβ2 cells were sensitized and desensitized, respectively, to the antiproliferative effect of the antiestrogens, ATRA and their combination and to the cytocidal effect of the combination of OHT and ATRA. Analysis of the global transcriptional changes upon OHT–ATRA combinatorial treatment revealed uniquely regulated genes associated with anticancer effects in MCF7-ERβ1 cells and cancer-promoting effects in MCF7-ERβ2 cells. Our data are favorable to ERβ1 being a marker of responsiveness and ERβ2 being a marker of resistance of MCF7 cells to antiestrogens alone and in combination with ATRA. [ABSTRACT FROM AUTHOR]

Summary: Although a growing body of evidence demonstrates that altered mtDNA content (mtDNAc) has clinical implications in several types of solid tumours, its prognostic relevance in acute promyelocytic leukaemia (APL) patients remains largely unknown. Here, we show that patients with higher‐than‐normal mtDNAc had better outcomes regardless of tumour burden. These results were more evident in patients with low‐risk of relapse. The multivariate Cox proportional hazard model demonstrated that high mtDNAc was independently associated with a decreased cumulative incidence of relapse. Altogether, our data highlights the possible role of mitochondrial metabolism in APL patients treated with ATRA. [ABSTRACT FROM AUTHOR]