The expression of Slit2 and Robo1 increased during retinoic acid syndrome in acute promyelocytic leukemia and impacted differentiated cell migration

•

The upregulation of Robo1 and Slit2 was first found in APL patients.

•

The positive correlation between Robo1/Slit2 and retinoic acid syndrome was first demonstrated.

•

It was demonstrated for the first time that Slit2 induces the migration of differentiated cells.

•

Slit2 did not inhibit il8-induced differentiated cell migration.

Retinoic acid syndrome (RAS) is a serious complication developed during the induction therapy of acute promyelocytic leukemia (APL). Cytokines and differentiated cells migration play important roles in the development of RAS. Slit guidance ligand 2 (Slit2) and roundabout 1 (Robo1) involve in cell migration. Our study aimed to investigate the expression of Slit2 and Robo1 in APL and check whether they affected promyelocytes migration. 62 cases of newly diagnosed APL patients were involved and received all-trans retinoic acid (ATRA) and arsenic trioxide as induction therapy. Bone marrow cells (BMCs) were obtained on days 0 and 28, and promyelocytes and plasma were collected from day 1 to day 21. The expression of Robo1 in promyelocytes, and that of Slit2 and cytokines, including IL-8,IL-1β and others, in serum were monitored. 20 healthy individuals donated their cells as control. Of the 62 APL patients, 16 (25.81%) patients developed RAS. The expression of Robo1, Slit2 and IL-8 increased significantly with the development of RAS. In the 16 patients with RAS, levels of Slit2, Robo1 and IL-8 were higher during the development of RAS than before or after the RAS (P < 0.05). RhSlit2-N and rhIL-8 induced cells migration, and the migration induced by IL-8 was not inhibited by rhSlit2-N. Elevated Slit2 and Robo1 levels might be useful markers for the diagnosis and treatment of RAS. The levels of Slit2, Robo1 and IL-8 showed a positive correlation with the severity of RAS. Slit2 and IL-8 promoted the migration of differentiated cells.

Mechanistic Study of Triazole Based Aminodiol Derivatives in Leukemic Cells-Crosstalk between Mitochondrial Stress-Involved Apoptosis and Autophagy

Various derivatives that mimic ceramide structures by introducing a triazole to connect the aminodiol moiety and long alkyl chain have been synthesized and screened for their anti-leukemia activity. SPS8 stood out among the derivatives, showing cytotoxic selectivity between leukemic cell lines and human peripheral blood mononuclear cells (about ten times). DAPI nuclear staining and H&E staining revealed DNA fragmentation under the action of SPS8. SPS8 induced an increase in intracellular Ca²⁺ levels and mitochondrial stress in HL-60 cells identified by the loss of mitochondrial membrane potential, transmission electron microscopy (TEM) examination, and altered expressions of Bcl-2 family proteins. SPS8 also induced autophagy through the detection of Atg5, beclin-1, and LC3 II protein expression, as well as TEM examination. Chloroquine, an autophagy inhibitor, promoted SPS8-induced apoptosis, suggesting the cytoprotective role of autophagy in hindering SPS8 from apoptosis. Furthermore, SPS8 was shown to alter the expressions of a variety of genes using a microarray analysis and volcano plot filtering. A further cellular signaling pathways analysis suggested that SPS8 induced several cellular processes in HL-60, including the sterol biosynthesis process and cholesterol biosynthesis process, and inhibited some cellular pathways, in which STAT3 was the most critical nuclear factor. Further identification revealed that SPS8 inhibited the phosphorylation of STAT3, representing the loss of cytoprotective activity. In conclusion, the data suggest that SPS8 induces both apoptosis and autophagy in leukemic cells, in which autophagy plays a cytoprotective role in impeding apoptosis. Moreover, the inhibition of STAT3 phosphorylation may support SPS8-induced anti-leukemic activity.

Strategies to generate functionally normal neutrophils to reduce infection and infection-related mortality in cancer chemotherapy

Neutrophils form an essential part of innate immunity against infection. Cancer chemotherapy-induced neutropenia (CCIN) is a condition in which the number of neutrophils in a patient's bloodstream is decreased, leading to increased susceptibility to infection. Granulocyte colony-stimulating factor (GCSF) has been the only approved treatment for CCIN over two decades. To date, CCIN-related infection and mortality remain a significant concern, as neutrophils generated in response to administered GCSF are functionally immature and cannot effectively fight infection. This review summarizes the molecular regulatory mechanisms of neutrophil granulocytic differentiation and innate immunity development, dissects the biology of GCSF in myeloid expansion, highlights the shortcomings of GCSF in CCIN treatment, updates the recent advance of a selective retinoid agonist that promotes neutrophil granulocytic differentiation, and evaluates the benefits of developing GCSF biosimilars to increase access to GCSF biologics versus seeking a new mode to fundamentally advance GCSF therapy for treatment of CCIN.

Retinoic acid and 6-formylindolo(3,2-b)carbazole (FICZ) combination therapy reveals putative targets for enhancing response in non-APL AML

In non-acute promyelotic leukemia (APL)- non myelocytic leukemia (AML), identification of a signaling signature would predict potentially actionable targets to enhance differentiation effects of all-trans-retinoic acid (RA) and make combination differentiation therapy realizable. Components of such a signaling machine/signalsome found to drive RA-induced differentiation discerned in a FAB M2 cell line/model (HL-60) were further characterized and then compared against AML patient expression profiles. FICZ, known to enhance RA-induced differentiation, was used to experimentally augment signaling for analysis. FRET revealed novel signalsome protein associations: CD38 with pS376SLP76 and caveolin-1 with CD38 and AhR. The signaling molecules driving differentiation in HL-60 cluster in non-APL AML de novo samples, too. Pearson correlation coefficients for this molecular ensemble are nearer 1 in the FAB M2 subtype than in non-APL AML. SLP76 correlation to RXRα and p47phox were conserved in FAB M2 model and patient subtype but not in general non-APL AML. The signalsome ergo identifies potential actionable targets in AML.

Inducing cell proliferative prevention in human acute promyelocytic leukemia by miR-182 inhibition through modulation of CASP9 expression

MicroRNAs (miRNAs) are one class of endogenous non-coding RNAs that involved in post-transcriptional regulation of the gene. MiRNAs through interaction with messenger RNA (mRNA) involved in several biological processes such as cell cycle, differentiation, growth, metabolism, aging and apoptosis. MiRNAs may act as an oncogene or a tumor suppressor via up or down regulation in cancerous cells. MiR-182 located in a miR-183/-96/-182 cluster, this is the highly conserved cluster to have an important role in cancer development and tumorigenesis. Abnormal expression of miR-182 in a variety of human cancers has reported. Oncogenic features of miR-182 confirmed through negative regulation of various tumor suppressor genes. In this study, miR-182 inhibition in acute promyelocytic leukemia (APL) cell line (HL60) was performed by locked nucleic acid (LNA) anti-miR. MTT assay in three-time points 24, 48 and 72h after LNA-anti-miR-182 transfection was performed. Our study demonstrated inhibition of miR-182 can expansively decrease cell proliferation of APL cells. The Western blotting analysis presents that CASP9 expression associated with inhibition of miR-182. CASP9 protein has an important role in the mitochondrial cell death pathway as the initiator of apoptosis. These results can offer a way for inhibition of APL cells proliferates and produce translational medicine based on microgenomics and antisense therapy.

Inhibition of microRNA miR-92a induces apoptosis and inhibits cell proliferation in human acute promyelocytic leukemia through modulation of p63 expression

MicroRNAs (miRNAs) are endogenous non-coding RNAs, 19-25 nucleotides in length involved in post-transcriptional regulation of gene expression of great majority of the human protein coding genes. Different aspects of cellular activities like cell growth, proliferation, and differentiation are regulated by miRNAs through their interaction with particular RNA species. In many tumors up or down-regulation of different miRNAs has been reported. Human miR-17-92 gene cluster is located on 13q31.3, rooming several miRNAs including miR-17-5p, miR-17-3p, miR-18, miR-19a, miR-20a and miR-92a. Amplification or overexpression of this cluster has been reported in acute myeloid leukemia, acute lymphoblastic leukemia and several other cancer types. Here, we performed inhibition of miR-92a in an acute promyelocytic leukemia (APL) cell line (HL-60) using locked nucleic acid (LNA) antagomir. In different time points after LNA-anti-miR92a transfection, MTT assay and annexin/propidium iodide staining were performed. These assessments indicate that miR-92a inhibition can extensively decrease the viability of these cells which is mainly due to induction of apoptosis. Western blot analysis of p63 protein also revealed that miR-92a inhibition resulted in p63 expression, hence activation of cellular pathways which are normally controlled by p63 protein are retrieved. These findings could open up a path to the miRNAs based therapeutic approach for treatment of APL.

How I treat children and adolescents with acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APL) is a rare subtype of acute myeloid leukaemia. The outcome of paediatric APL has improved substantially over the past 20 years; cure rates above 80% are expected when all-trans retinoic acid (ATRA) is given with anthracycline-based regimens. The presenting features of paediatric APL may include severe bleeding and thrombotic complications, which contribute to the high early death rate. The incidence of leucocytosis and the microgranular subtype is greater in paediatric than adult APL, and children experience greater ATRA-related toxicity. It is crucial to begin ATRA therapy and intensive platelet and fibrinogen replacement on first suspicion of APL. Recent risk-adapted therapeutic trials have shown that patients at greater risk of relapse benefit from the introduction of high-dose cytarabine during consolidation. Combination therapy with ATRA and arsenic trioxide provides very effective frontline treatment and may reduce the need for subsequent anthracycline therapy.

Advances in understanding the pulmonary infiltration in acute promyelocytic leukaemia

In acute promyelocytic leukaemia (APL), differentiation therapy can be complicated by the development of a differentiation syndrome (DS). Pulmonary infiltration of differentiating leukaemic cells is a key event in the development of DS. Several mediators have been identified that may promote migration and extravasation of differentiating APL cells from the bloodstream into the tissue. Adhesion of APL cells to each other and to the endothelium is induced by upregulation of the expression of adhesion molecules and constitutively active β2-integrins during differentiation therapy. The expression of chemokines and their receptors is significantly upregulated as well. Pulmonary chemokine production can trigger transendothelial migration of differentiating APL cells from the bloodstream into the underlying tissue (initiation phase of DS). Massive production of chemokines by infiltrated APL cells can further enhance transendothelial migration of differentiating APL cells, causing an uncontrollable hyperinflammatory reaction in the lung (aggravation phase), which is not efficiently switched-off by corticosteroids.

Recurrent differentiation syndrome or septic shock? Unresolved dilemma in a patient with acute promyelocytic leukemia

Differentiation syndrome (DS) is a life-threatening complication observed in patients with acute promyelocytic leukemia (APL) receiving induction therapy with all-trans-retinoic acid (ATRA). A bimodal incidence of DS has been observed, with a majority of cases occurring during the first week of ATRA treatment ("early" DS), but a substantial number of cases occurring during the third or even fourth week of ATRA treatment ("late" DS). However, to our knowledge occurrence of both early and late DS in the same patient has not been reported. We report an APL patient treated with the AIDA regimen, who experienced both early and late DS, a situation where differential diagnosis was difficult.

Chemokine induction by all-trans retinoic acid and arsenic trioxide in acute promyelocytic leukemia: triggering the differentiation syndrome. Blood. 2009;114:5512-5521. [PMID: 19828696 DOI: 10.1182/blood-2009-02-204834]

In acute promyelocytic leukemia (APL), differentiation therapy with all-trans retinoic acid (ATRA) and/or arsenic trioxide can induce a differentiation syndrome (DS) with massive pulmonary infiltration of differentiating leukemic cells. Because chemokines are implicated in migration and extravasation of leukemic cells, chemokines might play a role in DS. ATRA stimulation of the APL cell line NB4 induced expression of multiple CC-chemokines (CCLs) and their receptors (> 19-fold), resulting in increased chemokine levels and chemotaxis. Induction of CCL2 and CCL24 was directly mediated by ligand-activated retinoic acid receptors. In primary leukemia cells derived from APL patients at diagnosis, ATRA induced chemokine production as well. Furthermore, in plasma of an APL patient with DS, we observed chemokine induction, suggesting that chemokines might be important in DS. Dexamethasone, which efficiently reduces pulmonary chemokine production, did not inhibit chemokine induction in APL cells. Finally, chemokine production was also induced by arsenic trioxide as single agent or in combination with ATRA. We propose that differentiation therapy may induce chemokine production in the lung and in APL cells, which both trigger migration of leukemic cells. Because dexamethasone does not efficiently reduce leukemic chemokine production, pulmonary infiltration of leukemic cells may induce an uncontrollable hyperinflammatory reaction in the lung.