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-1ß, 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.

Cellular hierarchy insights reveal leukemic stem-like cells and early death risk in acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) represents a paradigm for targeted differentiation therapy, with a minority of patients experiencing treatment failure and even early death. We here report a comprehensive single-cell analysis of 16 APL patients, uncovering cellular compositions and their impact on all-trans retinoic acid (ATRA) response in vivo and early death. We unveil a cellular differentiation hierarchy within APL blasts, rooted in leukemic stem-like cells. The oncogenic PML/RARα fusion protein exerts branch-specific regulation in the APL trajectory, including stem-like cells. APL cohort analysis establishes an association of leukemic stemness with elevated white blood cell counts and FLT3-ITD mutations. Furthermore, we construct an APL-specific stemness score, which proves effective in assessing early death risk. Finally, we show that ATRA induces differentiation of primitive blasts and patients with early death exhibit distinct stemness-associated transcriptional programs. Our work provides a thorough survey of APL cellular hierarchies, offering insights into cellular dynamics during targeted therapy.

PML Nuclear bodies: the cancer connection and beyond.

Promyelocytic leukemia (PML) nuclear bodies, membrane-less organelles in the nucleus, play a crucial role in cellular homeostasis. These dynamic structures result from the assembly of scaffolding PML proteins and various partners. Recent crystal structure analyses revealed essential self-interacting domains, while liquid-liquid phase separation contributes to their formation. PML bodies orchestrate post-translational modifications, particularly stress-induced SUMOylation, impacting target protein functions. Serving as hubs in multiple signaling pathways, they influence cellular processes like senescence. Dysregulation of PML expression contributes to diseases, including cancer, highlighting their significance. Therapeutically, PML bodies are promising targets, exemplified by successful acute promyelocytic leukemia treatment with arsenic trioxide and retinoic acid restoring PML bodies. Understanding their functions illuminates both normal and pathological cellular physiology, guiding potential therapies. This review explores recent advancements in PML body biogenesis, biochemical activity, and their evolving biological roles.

High-Fat Diet Induced PPARδ Promotes Self-renewal of Preleukemic Progenitors in Development of Acute Promyelocytic Leukemia.

From risk association between acute promyelocytic leukemia (APL) and obese-overweight individuals, Mazzarella and colleagues hypothesized that a high-fat diet (HFD) promotes development of APL. Using mouse APL model (PML-RARα knock-in), the authors demonstrated that linoleic acid drives activation of PPARδ in hematopoietic progenitors, and that activation of PPARδ increases proliferation of progenitor cells with PML-RARA expression toward APL. Involvements of PPARδ on regulation of stem cell renewal and proliferation were shown in colorectal cancers earlier, but this study newly demonstrates in hematopoietic progenitors, while suggesting use of diet rich in linoleic acid with caution. See related article by Mazzarella et al., p. 59.

Cellular and micro-environmental responses influencing the antitumor activity of all-trans retinoic acid in breast cancer.

All-trans retinoic acid (ATRA) is the most relevant and functionally active metabolite of Vitamin-A. From a therapeutic standpoint, ATRA is the first example of pharmacological agent exerting its anti-tumor activity via a cell differentiating action. In the clinics, ATRA is used in the treatment of Acute Promyelocytic Leukemia, a rare form of myeloid leukemia with unprecedented therapeutic results. The extraordinary effectiveness of ATRA in the treatment of Acute Promyelocytic Leukemia patients has raised interest in evaluating the potential of this natural retinoid in the treatment of other types of neoplasias, with particular reference to solid tumors.The present article provides an overview of the available pre-clinical and clinical studies focussing on ATRA as a therapeutic agent in the context of breast cancer from a holistic point of view. In detail, we focus on the direct effects of ATRA in breast cancer cells as well as the underlying molecular mechanisms of action. In addition, we summarize the available information on the action exerted by ATRA on the breast cancer micro-environment, an emerging determinant of the progression and invasive behaviour of solid tumors. In particular we discuss the recent evidences of ATRA activity on the immune system. Finally, we analyse and discuss the results obtained with the few ATRA-based clinical trials conducted in the context of breast cancer.

Leukemia cells accumulate zinc for oncofusion protein stabilization.

Acute promyelocytic leukemia (APL) and chronic myeloid leukemia (CML) are both hematological malignancies characterized by genetic alterations leading to the formation of oncofusion proteins. The classical chromosomal aberrations in APL and CML result in the PML-RARα and BCR-ABL1 oncofusion proteins, respectively. Interestingly, our flow cytometric analyses revealed elevated free intracellular zinc levels in various leukemia cells, which may play a role in stabilizing oncofusion proteins in leukemia and thus support cell proliferation and malignancy. Long-term zinc deficiency resulted in the degradation of PML-RARα in NB4 cells (APL cell line) and of BCR-ABL1 in K562 cells (CML cell line). This degradation may be explained by increased caspase 3 activity observed in zinc deficient cells, whereas zinc reconstitution normalized the caspase 3 activity and abolished zinc deficiency-induced oncofusion protein degradation. In NB4 cells, fluorescence microscopic images further indicated enlarged and enriched lysosomes during zinc deficiency, suggesting increased rates of autophagy. Moreover, NB4 cells exhibited increased expression of the zinc transporters ZIP2, ZIP10 and ZnT3 during zinc deficiency and revealed excessive accumulation of zinc in contrast to healthy peripheral blood mononuclear cells (PBMCs), when zinc was abundantly available extracellularly. Our results highlight the importance of altered zinc homeostasis for some characteristics in leukemia cells, uncover potential pathways underlying the effects of zinc deficiency in leukemia cells, and provide potential alternative strategies by which oncofusion proteins can be degraded.

System analysis of surface CD markers during the process of granulocytic differentiation.

Plasma membrane proteins with extracellular-exposed domains are responsible for transduction of extracellular signals into intracellular responses, and their accessibility to therapeutic molecules makes them attractive targets for drug development. In this work, using omics technologies and immunochemical methods, we have studied changes in the content of markers of clusters of differentiation (CD markers) of neutrophils (CD33, CD97, CD54, CD38, CD18, CD11b, CD44, and CD71) at the level of transcripts and proteins in NB4, HL-60 and K562 cell lines, induced by the treatment with all-trans-retinoic acid (ATRA). Transcriptomic analysis revealed the induction of CD38, CD54, CD11b, and CD18 markers as early as 3 h after the addition of the inducer in the ATRA-responsive cell lines HL-60 and NB4. After 24 h, a line-specific expression pattern of CD markers could be observed in all cell lines. Studies of changes in the content of CD antigens by means of flow cytometry and targeted mass spectrometry (MS) gave similar results. The proteomic profile of the surface markers (CD38, CD54, CD11b, and CD18), characteristic of the NB4 and HL-60 lines, reflects different molecular pathways for the implementation of ATRA-induced differentiation of leukemic cells into mature neutrophils.

Structural Basis of PML-RARA Oncoprotein Targeting by Arsenic Unravels a Cysteine Rheostat Controlling PML Body Assembly and Function.

PML nuclear bodies (NB) are disrupted in PML-RARA-driven acute promyelocytic leukemia (APL). Arsenic trioxide (ATO) cures 70% of patients with APL, driving PML-RARA degradation and NB reformation. In non-APL cells, arsenic binding onto PML also amplifies NB formation. Yet, the actual molecular mechanism(s) involved remain(s) elusive. Here, we establish that PML NBs display some features of liquid-liquid phase separation and that ATO induces a gel-like transition. PML B-box-2 structure reveals an alpha helix driving B2 trimerization and positioning a cysteine trio to form an ideal arsenic-binding pocket. Altering either of the latter impedes ATO-driven NB assembly, PML sumoylation, and PML-RARA degradation, mechanistically explaining clinical ATO resistance. This B2 trimer and the C213 trio create an oxidation-sensitive rheostat that controls PML NB assembly dynamics and downstream signaling in both basal state and during stress response. These findings identify the structural basis for arsenic targeting of PML that could pave the way to novel cancer drugs. SIGNIFICANCE: Arsenic curative effects in APL rely on PML targeting. We report a PML B-box-2 structure that drives trimer assembly, positioning a cysteine trio to form an arsenic-binding pocket, which is disrupted in resistant patients. Identification of this ROS-sensitive triad controlling PML dynamics and functions could yield novel drugs. See related commentary by Salomoni, p. 2505. This article is featured in Selected Articles from This Issue, p. 2489.

miR-603 promotes cell proliferation and differentiation by targeting TrkB in acute promyelocytic leukemia.

Arsenic trioxide (ATO) treatment effectively prolongs the overall survival of patients with acute promyelocytic leukemia (APL). Mutations in the oncogene PML::RARA were found in patients with ATO-resistant and relapsed APL. However, some relapsed patients do not have such mutations. Here, we performed microarray analysis of samples from newly diagnosed and relapsed APL, and found different microRNA (miRNA) expression patterns between these two groups. Among the differentially expressed miRNAs, miR-603 was expressed at the lowest level in relapsed patients. The expression of miR-603 and its predicted target tropomyosin-related kinase B (TrkB) were determined by PCR and Western blot. Proliferation was measured using an MTT assay, while apoptosis, cell cycle and CD11b expression were analyzed using flow cytometry. In APL patients, the expression of miR-603 was negatively correlated with that of TrkB. miR-603 directly targeted TrkB and downregulated TrkB expression in the APL cell line NB4. miR-603 increased cell proliferation by promoting the differentiation and inhibiting the apoptosis of NB4 cells. This study shows that the miR-603/ TrkB axis may be a potent therapeutic target for relapsed APL.

Targeting DHODH reveals therapeutic opportunities in ATRA-resistant acute promyelocytic leukemia.

Although all-trans retinoic acid (ATRA)-induced differentiation has transformed acute promyelocytic leukemia (APL) from the most fatal to the most curable hematological disease, resistance to ATRA in high-risk APL patients remains a clinical challenge. In this paper, we discovered that dihydroorotate dehydrogenase (DHODH) inhibition overcame ATRA resistance. 416, a potent DHODH inhibitor previously obtained in our group, inhibited the occurrence of APL in cells and model mice. Excitingly, 416 effectively overcame ATRA resistance in vitro and in vivo by inducing apoptosis and differentiation. Further mechanistic studies showed that PML/RARα lost the regulation of Bcl-2 and c-Myc in NB4-R1 cells, which probably contributed to ATRA resistance. Notably, 416 maintained its Bcl-2 and c-Myc down-regulation effect in NB4-R1 cells and overcome ATRA resistance by inhibiting DHODH. In conclusion, our study highlights the potential of 416 for APL therapy and overcoming ATRA resistance, supporting the further development of DHODH inhibitors for clinical use in refractory and relapsed APL.

[JMJD3 Exerts Oncorepressor Activity in Acute Promyelocytic Leukemia by Promoting PU.1 Expression].

All-trans retinoic acid (ATRA) in acute promyelocytic leukemia (APL) has been the most famous differentiation induction therapy during which the expression of PU.1, a key transcription factor (TF) for myeloid lineage determination in normal hematopoiesis is restored. In our previous studies, we found a stress-inducible H3K27 demethylase, JMJD3, to directly upregulate PU.1 expression to promote myeloid commitment during normal myelopoiesis. In addition, JMJD3 acts as an oncorepressor and plays a critical regulatory role in the initiation and progression of malignant hematopoiesis. In this study, we further resolved the relationship between JMJD3 and PU.1 in APL therein JMJD3 exerts oncorepressor activity via promoting PU.1 expression.

Apoptotic Cell-Derived CD14(+) Microparticles Promote the Phagocytic Activity of Neutrophilic Precursor Cells in the Phagocytosis of Apoptotic Cells.

Membranous CD14 is crucial in the phagocytic activity of neutrophils. However, the role of CD14(+) microparticles (MPs) derived from apoptotic neutrophils (apo-MP) during the phagocytic process is not clear. All trans-retinoic acid (ATRA) induces acute promyelocytic leukemic NB4 cells along granulocytic differentiation. In this study, we investigated the role of CD14(+)apo-MP in the cell-cell interaction during the phagocytic process of apoptotic cells by viable ATRA-NB4 cells. We firstly demonstrate that CD14 expression and phagocytic activity of NB4 cells were upregulated simultaneously after ATRA treatment in a time-dependent manner, and both were significantly enhanced via concurrent lipopolysaccharide treatment. The phagocytic activity of ATRA-NB4 cells and lipopolysaccharide-treated ATRA-NB4 cells were both significantly attenuated by pre-treating cells with an antibody specific to either CD14 or TLR4. Further flow cytometric analysis demonstrates that apoptotic ATRA-NB4 cells release CD14(+)apo-MP in an idarubicin dosage-dependent manner. Both CD14 expression and the phagocytic activity of viable ATRA-NB4 cells were significantly enhanced after incubation with apo-MP harvested from apoptotic ATRA-NB4 cells, and the apo-MP-enhanced phagocytic activity was significantly attenuated by pre-treating apo-MP with an anti-CD14 antibody before incubation with viable cells. We conclude that CD14(+)apo-MP derived from apoptotic ATRA-NB4 cells promotes the phagocytic activity of viable ATRA-NB4 cells in engulfing apoptotic cells.

ATO Increases ROS Production and Apoptosis of Cells by Enhancing Calpain-Mediated Degradation of the Cancer Survival Protein TG2.

Transglutaminase 2 (TG2) is a critical cancer cell survival factor that activates several signalling pathways to foster drug resistance, cancer stem cell survival, metastasis, inflammation, epithelial-mesenchymal transition, and angiogenesis. All-trans retinoic acid (ATRA) and chemotherapy have been the standard treatments for acute promyelocytic leukaemia (APL), but clinical studies have shown that arsenic trioxide (ATO), alone or in combination with ATRA, can improve outcomes. ATO exerts cytotoxic effects in a variety of ways by inducing oxidative stress, genotoxicity, altered signal transduction, and/or epigenetic modification. In the present study, we showed that ATO increased ROS production and apoptosis ratios in ATRA-differentiated NB4 leukaemia cells, and that these responses were enhanced when TG2 was deleted. The combined ATRA + ATO treatment also increased the amount of nuclear factor erythroid 2-related factor 2 (NRF2) transcription factor, an adaptive regulator of the cellular oxidative stress response, and calpain proteolytic activity, resulting in TG2 degradation and the reduced survival of WT leukaemia cells. We further showed that the induced TG2 protein expression was degraded in the MCF-7 epithelial cell line and primary peripheral blood mononuclear cells upon ATO treatment, thereby sensitising these cell types to apoptotic signals.

Angiogenesis, coagulation, and fibrinolytic markers in acute promyelocytic leukemia (NB4): An evaluation of melatonin effects.

Melatonin is a powerful biological agent that has been shown to inhibit angiogenesis and also exerts anti-inflammatory effects. It is well known that new blood vessel formation (angiogenesis) has become an urgent issue in leukemia as well as solid tumors. Acute promyelocytic leukemia (APL) is a form of liquid cancer that manifests increased angiogenesis in the bone marrow of patients. Despite high-rate curable treatment with all-trans-retinoic acid (ATRA) and recently arsenic-trioxide (ATO), early death because of hemorrhage, coagulopathy, and Disseminated intravascular coagulation (DIC) remains still a concerning issue in these patients. It is, therefore, urgent to seek treatment strategies with antiangiogenic capabilities that also diminish coagulopathy and hyperfibrinolysis in APL patients. In this study, a coculture system with human umbilical vein endothelial cells (HUVECs) and NB4 APL cells was used to investigate the direct effect of melatonin on angiogenesis and its possible action on tissue factor (TF) and tissue-type plasminogen activator-1 (TPA-1) expression. Our experiments revealed that HUVEC-induced angiogenesis by cocultured NB4 cells was suppressed when melatonin alone or in combination with ATRA was added to the incubation medium. Melatonin at concentrations of 1 mM inhibited tube formation of HUVECs and also decreased interleukin-6 secretion and VEGF mRNA expression in HUVEC and NB4 cells. Taken together, the results of this study demonstrate that melatonin inhibits accelerated angiogenesis of HUVECs and ameliorates the coagulation and fibrinolysis indices stimulated by coculturing with NB4 cells.

Critical role of MXRA7 in differentiation blockade in human acute promyelocytic leukemia cells.

The biology of the matrix remodeling-associated 7 (MXRA7) gene has been ill defined. Bioinformatic analysis of public data sets revealed that MXRA7 messenger RNA (mRNA) was highly expressed in acute myeloid leukemia (AML), especially acute promyelocytic leukemia (APL). High expression of MXRA7 was associated with poor overall survival of patients with AML. We confirmed that MXRA7 expression was upregulated in patients with APL and cell lines. Knockdown or overexpression of MXRA7 did not affect the proliferation of NB4 cells directly. Knockdown of MXRA7 in NB4 cells promoted drug-induced cell apoptosis, whereas overexpression of MXRA7 had no obvious influence on drug-induced cell apoptosis. Lowering MXRA7 protein levels in NB4 cells promoted all-trans retinoic acid (ATRA)-induced cell differentiation possibly through decreasing the PML-RARα level and increasing PML and RARα levels. Correspondingly, overexpression of MXRA7 showed consistent results. We also demonstrated that MXRA7 altered the expression of genes involved in leukemic cell differentiation and growth. Knockdown of MXRA7 upregulated the expression levels of C/EBPB, C/EBPD, and UBE2L6, and downregulated the expression levels of KDM5A, CCND2, and SPARC. Moreover, knockdown of MXRA7 inhibited the malignancy of NB4 cells in a non-obese diabetic-severe combined immune-deficient mice model. In conclusion, this study demonstrated that MXRA7 influences the pathogenesis of APL via regulation of cell differentiation. The novel findings about the role of MXRA7 in leukemia not only shed light on the biology of this gene but also proposed this gene as a new target for APL treatment.

The clinically relevant CHK1 inhibitor MK-8776 induces the degradation of the oncogenic protein PML-RARα and overcomes ATRA resistance in acute promyelocytic leukemia cells.

Acute promyelocytic leukemia (APL) is a hematological disease characterized by the expression of the oncogenic fusion protein PML-RARα. The current treatment approach for APL involves differentiation therapy using all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). However, the development of resistance to therapy, occurrence of differentiation syndrome, and relapses necessitate the exploration of new treatment options that induce differentiation of leukemic blasts with low toxicity. In this study, we investigated the cellular and molecular effects of MK-8776, a specific inhibitor of CHK1, in ATRA-resistant APL cells. Treatment of APL cells with MK-8776 resulted in a decrease in PML-RARα levels, increased expression of CD11b, and increased granulocytic activity consistent with differentiation. Interestingly, we showed that the MK-8776-induced differentiating effect resulted synergic with ATO. We found that the reduction of PML-RARα by MK-8776 was dependent on both proteasome and caspases. Specifically, both caspase-1 and caspase-3 were activated by CHK1 inhibition, with caspase-3 acting upstream of caspase-1. Activation of caspase-3 was necessary to activate caspase-1 and promote PML-RARα degradation. Transcriptomic analysis revealed significant modulation of pathways and upstream regulators involved in the inflammatory response and cell cycle control upon MK-8776 treatment. Overall, the ability of MK-8776 to induce PML-RARα degradation and stimulate differentiation of immature APL cancer cells into more mature forms recapitulates the concept of differentiation therapy. Considering the in vivo tolerability of MK-8776, it will be relevant to evaluate its potential clinical benefit in APL patients resistant to standard ATRA/ATO therapy, as well as in patients with other forms of acute leukemias.

Clinical and genomic characterization of an ATRA-insensitive acute promyelocytic leukemia variant with a FNDC3B::RARB fusion.

The promyelocytic leukemia-retinoic acid receptor-α (PML::RARA) fusion is the hallmark of acute promyelocytic leukemia (APL) and is observed in over 95% of APL cases. RARA and homologous receptors RARB and RARG are occasionally fused to other gene partners, which differentially affect sensitivity to targeted therapies. Most APLs without RARA fusions have rearrangements involving RARG or RARB, both of which frequently show resistance to all-trans-retinoic acid (ATRA) and/or multiagent chemotherapy for acute myeloid leukemia (AML). We present a 13-year-old male diagnosed with variant APL with a novel FNDC3B::RARB in-frame fusion that showed no response to ATRA but responded well to conventional AML therapy. While FNDC3B has been identified as a rare RARA translocation partner in ATRA-sensitive variant APL, it has never been reported as a fusion partner with RARB and it is only the second known fusion partner with RARB in variant APL. We also show that this novel fusion confers an RNA expression signature that is similar to APL, despite clinical resistance to ATRA monotherapy.

Inhibition of splicing factors SF3A3 and SRSF5 contributes to As3+/Se4+ combination-mediated proliferation suppression and apoptosis induction in acute promyelocytic leukemia cells.

The low-dose combination of Arsenite (As3+) and selenite (Se4+) has the advantages of lower biological toxicity and better curative effects for acute promyelocytic leukemia (APL) therapy. However, the underlying mechanisms remain unclear. Here, based on the fact that the combination of 2 µM A3+ plus 4 µM Se4+ possessed a stronger anti-leukemic effect on APL cell line NB4 as compared with each individual, we employed iTRAQ-based quantitative proteomics to identify a total of 58 proteins that were differentially expressed after treatment with As3+/Se4+ combination rather than As3+ or Se4+ alone, the majority of which were involved in spliceosome pathway. Among them, eight proteins stood out by virtue of their splicing function and significant changes. They were validated as being decreased in mRNA and protein levels under As3+/Se4+ combination treatment. Further functional studies showed that only knockdown of two splicing factors, SF3A3 and SRSF5, suppressed the growth of NB4 cells. The reduction of SF3A3 was found to cause G1/S cell cycle arrest, which resulted in proliferation inhibition. Moreover, SRSF5 downregulation induced cell apoptosis through the activation of caspase-3. Taken together, these findings indicate that SF3A3 and SRSF5 function as pro-leukemic factors and can be potential novel therapeutic targets for APL.

Type 2 diabetes affects arsenic metabolism via transporters in arsenic trioxide treated acute promyelocytic leukemia patients.

Our study aimed to explore whether type 2 diabetes (T2DM) can affect arsenic metabolism in acute promyelocytic leukemia (APL) patients treated with arsenic trioxide. We found that compared with non-diabetic APL patients, the concentrations of arsenic metabolites in APL patients with T2DM increased significantly and positively correlated with blood glucose (P < 0.05). Meanwhile, APL patients with T2DM were more prone to liver injury and QTc interval prolongation due to altered arsenic methylation capacity. Then we cultured HEK293T cells at different glucose concentrations, and the results showed that the cells with high glucose had higher concentrations of arsenic metabolites compared to other cells. Meanwhile, the high glucose significantly increased the mRNA and protein expression levels of the arsenic uptake transporter AQP7 in HEK293T cells. Overall, our study demonstrated that T2DM can lead to elevated concentrations of arsenic metabolites in APL patients by increasing AQP7 expression.

ATRA treatment slowed P-selectin-mediated rolling of flowing HL60 cells in a mechano-chemical-dependent manner.

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 × 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 × 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 ß2 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 ß2 integrin activation rate and the higher expression levels of PSGL-1 and LFA-1 were assigned to induce the over-enhancement 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.