In acute promyelocytic leukemia (APL), the promyelocytic leukemia-retinoic acid receptor alpha (PML/RARα) fusion protein destroys PML nuclear bodies (NBs), leading to the formation of microspeckles. However, our understanding, largely learned from morphological observations, lacks insight into the mechanisms behind PML/RARα-mediated microspeckle formation and its role in APL leukemogenesis. This study presents evidence uncovering liquid-liquid phase separation (LLPS) as a key mechanism in the formation of PML/RARα-mediated microspeckles. This process is facilitated by the intrinsically disordered region containing a large portion of PML and a smaller segment of RARα. We demonstrate the coassembly of bromodomain-containing protein 4 (BRD4) within PML/RARα-mediated condensates, differing from wild-type PML-formed NBs. In the absence of PML/RARα, PML NBs and BRD4 puncta exist as two independent phases, but the presence of PML/RARα disrupts PML NBs and redistributes PML and BRD4 into a distinct phase, forming PML/RARα-assembled microspeckles. Genome-wide profiling reveals a PML/RARα-induced BRD4 redistribution across the genome, with preferential binding to super-enhancers and broad-promoters (SEBPs). Mechanistically, BRD4 is recruited by PML/RARα into nuclear condensates, facilitating BRD4 chromatin binding to exert transcriptional activation essential for APL survival. Perturbing LLPS through chemical inhibition (1, 6-hexanediol) significantly reduces chromatin co-occupancy of PML/RARα and BRD4, attenuating their target gene activation. Finally, a series of experimental validations in primary APL patient samples confirm that PML/RARα forms microspeckles through condensates, recruits BRD4 to coassemble condensates, and co-occupies SEBP regions. Our findings elucidate the biophysical, pathological, and transcriptional dynamics of PML/RARα-assembled microspeckles, underscoring the importance of BRD4 in mediating transcriptional activation that enables PML/RARα to initiate APL.

An 18-year-old female presented with sudden onset bilateral vision loss. Extensive retinal hemorrhages were seen in both eyes. Systemic examination lead to a diagnosis of acute promyelocytic leukemia. The patient was treated with all trans retinoic acid (ATRA) and other medications in the induction phase. Bilateral disc edema was noted during the second consolidation cycle with ATRA. Complete resolution of bilateral disc edema was attained in three weeks\' time after discontinuing ATRA.

Coagulopathy continues to be a major challenge in the management of patients with acute promyelocytic leukemia (APL). Novel differentiating agents have led to improved survival in these patients, but perturbations in coagulation continue to have an impact on their prognosis. The most worrisome of coagulation disturbances is bleeding, which is not an uncommon cause of early death in APL. Despite this, there are no consistent predictors of this high risk of fatal hemorrhage in APL. In this context, the fibrinolytic system has been identified as a crucial role player in APL coagulopathy. However, the current guidelines for the management of APL give little regard to tests that measure the fibrinolytic system while giving more importance to close monitoring of conventional coagulation tests and platelet counts to identify the coagulopathy. More recently, viscoelastic tests have come to usefulness in determining global hemostasis and have been widely used for \"diagnosing\" hyperfibrinolysis in selected clinical settings. In this review, we attempt to describe risk assessment models for diagnosing APL coagulopathy, describe the possible application of viscoelastic tests in this setting, and persuade clinicians to reconsider the use of antifibrinolytics to improve survival of APL patients.

UNASSIGNED: Acute promyelocytic leukemia (APL) is a distinct form of acute myeloid leukemia characterized by the presence of t(15;17)(q24;21) and the PML:RARA gene fusion. Frontline use of intravenous arsenic trioxide (i.v.-ATO) and all-trans retinoic acid (ATRA) has vastly improved cure rates in APL. Researchers in Hong Kong invented the oral formulation of ATO (oral-ATO) and have confirmed a bioavailability comparable to i.v.-ATO. A plethora of studies have confirmed the safety and efficacy of oral-ATO-based regimens in the frontline and relapsed setting.
UNASSIGNED: Aspects on the development of oral-ATO-based regimens for APL in the frontline and relapsed setting are discussed. The short-term and long-term safety and efficacy of oral-ATO-based regimens are discussed. The frontline use of oral-ATO in combination with ATRA and ascorbic acid (AAA) induction in a \'chemotherapy-free\' is highlighted.
UNASSIGNED: Current and ongoing data on the use of oral-ATO-based regimens in APL support the use of oral-ATO as an alternative to i.v.-ATO allowing a more convenient and economical approach to the management of APL.

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).

OBJECTIVE: To investigate the relationship between the treatment of acute promyelocytic leukemia (APL) with arsenic trioxide (ATO) and glycolysis, as well as its underlying molecular mechanism.
METHODS: The GEO database was used to analyze alterations in the expression of RPL22L1 in APL patients and its correlation with glycolysis. The levels of RPL22L1 and glycolysis were assessed in 9 paired clinical samples. NB4 cells and NB4 cells with knockdown of RPL22L1 were treated with ATO. The protein and mRNA of RPL22L1 were detected using RT-PCR and Western blot, and the content was determined by using glucose, pyruvate, and lactate detection kits. Finally, detection of cell proliferation using CCK8, migration by scratch assay, and apoptosis by flow cytometry, and the biological function of ATO in NB4 cells was examined.
RESULTS: The expression of RPL22L1 in GSE213742 and GSE234103 datasets exhibited a significant increase in human APL cells, specifically NB4 cells. RPL22L1 in GSE213742 and GSE234103 gene expression matrix was significantly elevated in human APL cells NB4 cells, and further analysis found RPL22L1 showed a strong positive correlation with glycolysis. Cellular experiments showed that ATO inhibited RPL22L1 in NB4 cells and inhibited glycolysis in APL cells. The ATO played a pivotal role in suppressing the proliferation, migration, as well as invasion of NH4 cells.
CONCLUSIONS: ATO regulates the blycolytic pathway in APL by inhibiting RPL22L1 expression, and this may contribute to its therapeutic effects.

All-trans retinoic acid (ATRA) plays a role in tissue development, neural function, reproduction, vision, cell growth and differentiation, tumor immunity, and apoptosis. ATRA can act by inducing autophagic signaling, angiogenesis, cell differentiation, apoptosis, and immune function. In the blood system ATRA was first used with great success in acute promyelocytic leukemia (APL), where ATRA differentiated leukemia cells into mature granulocytes. ATRA can play a role not only in APL, but may also play a role in other hematologic diseases such as immune thrombocytopenia (ITP), myelodysplastic syndromes (MDS), non-APL acute myeloid leukemia (AML), aplastic anemia (AA), multiple myeloma (MM), etc., especially by regulating mesenchymal stem cells and regulatory T cells for the treatment of ITP. ATRA can also increase the expression of CD38 expressed by tumor cells, thus improving the efficacy of daratumumab and CD38-CART. In this review, we focus on the mechanism of action of ATRA, its role in various hematologic diseases, drug combinations, and ongoing clinical trials.

The transformation of acute promyelocytic leukemia (APL) from the most fatal to the most curable subtype of acute myeloid leukemia (AML), with long-term survival exceeding 90%, has represented one of the most exciting successes in hematology and in oncology. APL is a paradigm for oncoprotein-targeted cure.APL is caused by a 15/17 chromosomal translocation which generates the PML-RARA fusion protein and can be cured by the chemotherapy-free approach based on the combination of two therapies targeting PML-RARA: retinoic acid (RA) and arsenic. PML-RARA is the key driver of APL and acts by deregulating transcriptional control, particularly RAR targets involved in self-renewal or myeloid differentiation, also disrupting PML nuclear bodies. PML-RARA mainly acts as a modulator of the expression of specific target genes: genes whose regulatory elements recruit PML-RARA are not uniformly repressed but also may be upregulated or remain unchanged. RA and arsenic trioxide directly target PML-RARA-mediated transcriptional deregulation and protein stability, removing the differentiation block at promyelocytic stage and inducing clinical remission of APL patients.

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