Clinical networking results in continuous improvement of the outcome of patients with acute promyelocytic leukemia.

ABSTRACT: The introduction of all-trans retinoic acid combined with anthracyclines has significantly improved the outcomes for patients diagnosed with acute promyelocytic leukemia (APL), and this strategy remains the standard of care in countries in which arsenic trioxide is not affordable. However, data from national registries and real-world databases indicate that low- and middle-income countries (LMIC) still face disappointing results, mainly because of high induction mortality and suboptimal management of complications. The American Society of Hematology established the International Consortium on Acute Leukemias (ICAL) to address this challenge through international clinical networking. Here, we present the findings from the International Consortium on Acute Promyelocytic Leukemia study involving 806 patients with APL recruited from 2005 to 2020 in Brazil, Chile, Paraguay, Peru, and Uruguay. The induction mortality rate has notably decreased to 14.6% compared with the pre-ICAL rate of 32%. Multivariable logistic regression analysis revealed as factors associated with induction death: age of ≥40 years, Eastern Cooperative Oncology Group performance status score of 3, high-risk status based on the Programa Español de Tratamiento en Hematologia/Gruppo Italiano Malattie EMatologiche dell'Adulto classification, albumin level of ≤3.5 g/dL, bcr3 PML/RARA isoform, the interval between presenting symptoms to diagnosis exceeding 48 hours, and the occurrence of central nervous system and pulmonary bleeding. With a median follow-up of 53 months, the estimated 4-year overall survival rate is 81%, the 4-year disease-free survival rate is 80%, and the 4-year cumulative incidence of relapse rate is 15%. These results parallel those observed in studies conducted in high-income countries, highlighting the long-term effectiveness of developing clinical networks to improve clinical care and infrastructure in LMIC.

External validation and calibration of the HoLISTIC Consortium's advanced-stage Hodgkin lymphoma international prognostic index (A-HIPI) in the Brazilian Hodgkin lymphoma registry.

The Hodgkin lymphoma International Study for Individual Care (HoLISTIC) Consortium's A-HIPI model, developed in 2022 for advanced-stage classical Hodgkin lymphoma (cHL), predicts survival within 5 years amongst newly diagnosed patients. This study validates its performance in the Brazilian Hodgkin lymphoma registry. By 2022, the Brazilian HL registry included 1357 cHL patients, with a median 5-year follow-up. Probabilities for 5-year progression-free survival (PFS) and overall survival (OS) were calculated using A-HIPI-model equations. Discrimination (Harrell C-statistic/Uno C-statistic) and calibration measures assessed external validation and calibration. Lab values beyond the allowed range were excluded, mirroring the initial A-HIPI analysis. A total of 694 advanced-stage cHL patients met the original inclusion criteria (age 18-65 years, Stage IIB-IV). Median age was 31 years; 46.3% were females. Stage distribution was IIB (33.1%), III (27.4%), IV (39.5%). Bulky disease in 32.6%. Five-year PFS and OS were 68.4% and 86.0%, respectively. Harrell C-statistics were 0.60 for PFS and 0.69 for OS, and Uno C-statistics were 0.63 for PFS and 0.72 for OS. Calibration plots demonstrated well-calibrated predictions with calibration slopes of 0.91 and 1.03 for 5-year OS and PFS, respectively. Despite differing patient, clinical characteristics, and socioeconomic factors, the baseline prediction tool performed well in the Brazilian cohort, demonstrating adequate discrimination and calibration. This supports its reliability in diverse settings.

Antineoplastic effects of pharmacological inhibitors of aurora kinases in CSF3RT618I-driven cells.

Myeloproliferative neoplasms (MPN) are consolidated as a relevant group of diseases derived from the malfunction of the hematopoiesis process and have as a particular attribute the increased proliferation of myeloid lineage. Among these, chronic neutrophilic leukemia (CNL) is distinguished, caused by the T618I mutation of the CSF3R gene, a trait that generates ligand-independent receptor activation and downstream JAK2/STAT signaling. Previous studies reported that mutations in BCR::ABL1 and JAK2V617F increased the expression of the aurora kinase A (AURKA) and B (AURKB) in Ba/F3 cells and their pharmacological inhibition displays antineoplastic effects in human BCR::ABL1 and JAK2V617F positive cells. Delimiting the current scenario, aspects related to the AURKA and AURKB as a potential target in CSF3RT618I-driven models is little known. In the present study, the cellular and molecular effects of pharmacological inhibitors of aurora kinases, such as aurora A inhibitor I, AZD1152-HQPA, and reversine, were evaluated in Ba/F3 expressing the CSF3RT618I mutation. AZD1152-HQPA and reversine demonstrated antineoplastic potential, causing a decrease in cell viability, clonogenicity, and proliferative capacity. At molecular levels, all inhibitors reduced histone H3 phosphorylation, aurora A inhibitor I and reversine reduced STAT5 phosphorylation, and AZD1152-HQPA and reversine induced PARP1 cleavage and γH2AX expression. Reversine more efficiently modulated genes associated with cell cycle and apoptosis compared to other drugs. In summary, our findings shed new insights into the use of AURKB inhibitors in the context of CNL.

Clinical significance of mitochondrial DNA content in acute promyelocytic leukaemia.

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.

Treatment patterns and outcomes for Hodgkin Lymphoma patients aged 60 and older: a report from the Brazilian Prospective Hodgkin Lymphoma Registry.

The treatment of older patients with Hodgkin lymphoma (HL) remains a challenge. We sought to identify the treatment patterns and outcomes in older HL patients included in the Brazilian HL registry (NCT02589548). A total of 136 patients with HIV-negative classic HL, aged ≥ 60 years, diagnosed between 2009 and 2018, were analyzed. The median age was 66 years old (60-90), 72% had advanced disease, 62% had a high IPS, and 49% had a nodular sclerosis subtype. Median follow-up was 64 months for alive patients. ABVD was the front-line treatment in 96% of patients. Twenty-one patients (15%) died during front-line treatment. The 5-year PFS and 5-year OS rates were 55% and 59%, respectively. The 5-year OS rates in localized and advanced disease were 81% and 51% (p=0.013). Lung toxicity developed in 11% of the patients treated with ABVD. Bleomycin was administered for > 2 cycles in 65% of patients. Compared with 2009-2014, there was a decrease in the use of bleomycin for > 2 cycles in 2015-2018 (88% × 45%, p<0.0001). The impact of socioeconomic status (SES) on outcomes was studied in patients treated with ABVD. After adjusting for potential confounders, lower SES remained independently associated with poorer survival (HR 2.22 [1.14-4.31] for OS and HR 2.84 [1.48-5.45] for PFS). Treatment outcomes were inferior to those observed in developed countries. These inferior outcomes were due to an excess of deaths during front-line treatment and the excessive use of bleomycin. SES was an independent factor for shorter survival.

Isolated massive histiocytes renal interstitial infiltration: a case report of an unexpected cause of acute kidney injury in a kidney transplant recipient.

BACKGROUND: Acute kidney injury is a frequent cause of hospital readmission in kidney transplant recipients (KTR), usually associated with infections and graft rejection. Herein, we report a case of an unusual cause of acute kidney injury in a KTR (massive histiocytes renal interstitial infiltration). CASE PRESENTATION: A 40-year-old woman was submitted to a second kidney transplant. One year after surgery, she presented asthenia, myalgia, and fever, haemoglobin 6.1 g/dL; neutrophils: 1.3 × 109/µL; platelets: 143 × 109/µL; blood creatinine 11.8 mg/dL, requiring dialysis. A kidney biopsy revealed diffuse histiocytic infiltration, which was assumed due to dysregulated immunological activation triggered by infections. The patient had multiple infections, including cytomegalovirus infection (CMV), aspergillosis, bacteraemia, and urinary tract infections, which could trigger the immune response. Haemophagocytic lymphohistiocytosis (HLH) was ruled out. The present case highlights the occurrence of isolated massive renal interstitial infiltration of histiocytes that does not meet the criteria for HLH or other related pathologies. CONCLUSIONS: Renal histiocyte activation and infiltration may have been initiated by an immunological mechanism similar to what occurs in HLH and infectious processes. The present case highlights the occurrence of isolated massive renal interstitial infiltration of histiocytes that does not meet the criteria for HLH or other related pathologies.

Phenformin increases early hematopoietic progenitors in the Jak2V617F murine model.

BACKGROUND: Myeloproliferative neoplasms (MPN) are disorders characterized by an alteration at the hematopoietic stem cell (HSC) level, where the JAK2 mutation is the most common genetic alteration found in classic MPN (polycythemia vera, essential thrombocythemia, and primary myelofibrosis). We and others previously demonstrated that metformin reduced splenomegaly and platelets counts in peripheral blood in JAK2V617F pre-clinical MPN models, which highlighted the antineoplastic potential of biguanides for MPN treatment. Phenformin is a biguanide that has been used to treat diabetes, but was withdrawn due to its potential to cause lactic acidosis in patients. AIMS: We herein aimed to investigate the effects of phenformin in MPN disease burden and stem cell function in Jak2V617F-knockin MPN mice. RESULTS: In vitro phenformin treatment reduced cell viability and increased apoptosis in SET2 JAK2V67F cells. Long-term treatment with 40 mg/kg phenformin in Jak2V617F knockin mice increased the frequency of LSK, myeloid progenitors (MP), and multipotent progenitors (MPP) in the bone marrow. Phenformin treatment did not affect peripheral blood counts, spleen weight, megakaryocyte count, erythroid precursors frequency, or ex vivo clonogenic capacity. Ex vivo treatment of bone marrow cells from Jak2V617F knockin mice with phenformin did not affect hematologic parameters or engraftment in recipient mice. CONCLUSIONS: Phenformin increased the percentages of LSK, MP, and MPP populations, but did not reduce disease burden in Jak2V617F-knockin mice. Additional studies are necessary to further understand the effects of phenformin on early hematopoietic progenitors.

STMN1 is highly expressed and contributes to clonogenicity in acute promyelocytic leukemia cells.

Stathmin 1 (STMN1) is a microtubule-destabilizing protein highly expressed in hematological malignancies and involved in proliferation and differentiation. Although a previous study found that the PML-RARα fusion protein, which contributes to the pathophysiology of acute promyelocytic leukemia (APL), positively regulates STMN1 at the transcription and protein activity levels, little is known about the role of STMN1 in APL. In this study, we aimed to investigate the STMN1 expression levels and their associations with laboratory, clinical, and genomic data in APL patients. We also assessed the dynamics of STMN1 expression during myeloid cell differentiation and cell cycle progression, and the cellular effects of STMN1 silencing and pharmacological effects of microtubule-stabilizing drugs on APL cells. We found that STMN1 transcripts were significantly increased in samples from APL patients compared with those of healthy donors (all p < 0.05). However, this had no effect on clinical outcomes. STMN1 expression was associated with proliferation- and metabolism-related gene signatures in APL. Our data confirmed that STMN1 was highly expressed in early hematopoietic progenitors and reduced during cell differentiation, including the ATRA-induced granulocytic differentiation model. STMN1 phosphorylation was predominant in a pool of mitosis-enriched APL cells. In NB4 and NB4-R2 cells, STMN1 knockdown decreased autonomous cell growth (all p < 0.05) but did not impact ATRA-induced apoptosis and differentiation. Finally, treatment with paclitaxel (as a single agent or combined with ATRA) induced microtubule stabilization, resulting in mitotic catastrophe with repercussions for cell viability, even in ATRA-resistant APL cells. This study provides new insights into the STMN1 functions and microtubule dynamics in APL.

New germline GATA1 variant in females with anemia and thrombocytopenia.

Familial forms of bone marrow defects are rare disorders and description of new cases are valuable opportunities to clarify the molecular machinery that triggers hematopoiesis and blood formation, as well as risk to malignant transformation. We investigated the genetic scenario and possible patterns of transmission in a rare case of familial myeloid disorder with a history of exposure to pesticides. Blood counts of two proband sisters, age 41 and 42, revealed mild anemia, neutrophilia and thrombocytopenia with bone marrow finding mimicking primary myelofibrosis in the cellular phase. We analyzed the coding regions of 78 myeloid neoplasms-related genes and 16 encoding xenobiotic metabolizing genes using Next-Generation Sequencing. The GATA1 variant c.788C > T, p.T263M, located in the C-terminal zinc finger domain of GATA1, was detected in the DNA of the two sisters. The screening of the other kindreds also revealed the p.T263M variant in the mother and two daughters with the same bone marrow disorder. This is the first report of an alteration in the GATA1 CF domain causing anemia, thrombocytopenia and megakaryocyte proliferation with mild myelofibrosis, correlating a new GATA1 germline variant with myeloid disorder.

NT157, an IGF1R-IRS1/2 inhibitor, exhibits antineoplastic effects in pre-clinical models of chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is successfully treated with BCR-ABL1 tyrosine kinase inhibitors, but a significant percentage of patients develop resistance. Insulin receptor substrate 1 (IRS1) has been shown to constitutively associate with BCR-ABL1, and IRS1-specific silencing leads to antineoplastic effects in CML cell lines. Here, we characterized the efficacy of NT157, a pharmacological inhibitor of IGF1R-IRS1/2, in CML cells and observed significantly reduced cell viability and proliferation, accompanied by induction of apoptosis. In human K562 cells and in murine Ba/F3 cells, engineered to express either wild-type BCR-ABL1 or the imatinib-resistant BCR-ABL1T315I mutant, NT157 inhibited BCR-ABL1, IGF1R, IRS1/2, PI3K/AKT/mTOR, and STAT3/5 signaling, increased CDKN1A, FOS and JUN tumor suppressor gene expression, and reduced MYC and BCL2 oncogenes. NT157 significantly reduced colony formation of human primary CML cells with minimal effect on normal hematopoietic cells. Exposure of primary CML cells harboring BCR-ABL1T315I to NT157 resulted in increased apoptosis, reduced cell proliferation and decreased phospho-CRKL levels. In conclusion, NT157 has antineoplastic effects on BCR-ABL1 leukemogenesis, independent of T315I mutational status.

Autophagy inhibition potentiates ruxolitinib-induced apoptosis in JAK2V617F cells.

JAK2V617F can mimic growth factor signaling, leading to PI3K/AKT/mTOR activation and inhibition of autophagy. We hypothesized that selective inhibition of JAK1/2 by ruxolitinib could induce autophagy and limit drug efficacy in myeloproliferative neoplasms (MPN). Therefore, we investigated the effects of ruxolitinib treatment on autophagy-related genes and cellular processes, to determine the potential benefit of autophagy inhibitors plus ruxolitinib in JAK2V617F cells, and to verify the frequency and clinical impact of autophagy-related gene mutations in patients with MPNs. In SET2 JAK2V617F cells, ruxolitinib treatment induced autophagy and modulated 26 out of 79 autophagy-related genes. Ruxolitinib treatment reduced the expressions of important autophagy regulators, including mTOR/p70S6K/4EBP1 and the STAT/BCL2 axis, in a dose- and time-dependent manner. Pharmacological inhibition of autophagy was able to significantly suppress ruxolitinib-induced autophagy and increased ruxolitinib-induced apoptosis. Mutations in autophagy-related genes were found in 15.5% of MPN patients and were associated with increased age and a trend towards worse survival. In conclusion, ruxolitinib induces autophagy in JAK2V617F cells, potentially by modulation of mTOR-, STAT- and BCL2-mediated signaling. This may lead to inhibition of apoptosis. Our results suggest that the combination of ruxolitinib with pharmacological inhibitors of autophagy, such as chloroquine, may be a promising strategy to treat patients with JAK2V617F-mutated MPNs.

Acquired Angioedema due to C1 Inhibitor Deficiency Preceding Splenic Marginal Zone Lymphoma: Further Insights from Clinical Practice.

BACKGROUND: Acquired angioedema due to C1 inhibitor deficiency (AAE-C1-INH) is a very rare disease. In clinical practice, it may be difficult to differentiate AAE-C1-INH from hereditary angioedema due to C1-INH deficiency (HAE-C1-INH). In both conditions, patients are at an increased risk of death from asphyxiation due to upper airway obstruction. The association of AAE-C1-INH with lymphoproliferative and autoimmune diseases, and with presence of anti-C1-INH antibodies has been well documented, and treatment of the underlying condition may result in complete remission of angioedema. OBJECTIVES: To discuss the clinical evaluation, diagnosis, and treatment outcomes of AAE-C1-INH in the context of the care of 2 patients with recurrent isolated angioedema. METHODS: Two patients were followed up prospectively at our clinic. Measurements of C3, C4, C1-INH, and C1q levels were carried out by nephelometry, and the functional activity of C1-INH was determined by a chromogenic assay. Hematological investigation included morphological and immunophenotyping analysis of peripheral blood, bone marrow, and spleen histopathology. Sequencing of the 8 exons and adjacent intronic regions of the SERPING1 gene was performed using the Sanger method. RESULTS: Two patients were diagnosed with AAE-C1-INH associated with splenic marginal zone lymphoma during follow-up. CONCLUSIONS: Close follow-up, including detailed clinical history, physical examination, and laboratory tests, of our patients with AAE-C1-INH was essential for the early diagnosis and successful treatment of the lymphoproliferative disease, leading to the resolution of the angioedema attacks.

The U2AF homology motif kinase 1 (UHMK1) is upregulated upon hematopoietic cell differentiation.

UHMK1 (KIS) is a nuclear serine/threonine kinase that possesses a U2AF homology motif and phosphorylates and regulates the activity of the splicing factors SF1 and SF3b155. Mutations in these components of the spliceosome machinery have been recently implicated in leukemogenesis. The fact that UHMK1 regulates these factors suggests that UHMK1 might be involved in RNA processing and perhaps leukemogenesis. Here we analyzed UHMK1 expression in normal hematopoietic and leukemic cells as well as its function in leukemia cell line. In the normal hematopoietic compartment, markedly higher levels of transcripts were observed in differentiated lymphocytes (CD4+, CD8+ and CD19+) compared to the progenitor enriched subpopulation (CD34+) or leukemia cell lines. UHMK1 expression was upregulated in megakaryocytic-, monocytic- and granulocytic-induced differentiation of established leukemia cell lines and in erythrocytic-induced differentiation of CD34+ cells. No aberrant expression was observed in patient samples of myelodysplastic syndrome (MDS), acute myeloid (AML) or lymphoblastic (ALL) leukemia. Nonetheless, in MDS patients, increased levels of UHMK1 expression positively impacted event free and overall survival. Lentivirus mediated UHMK1 knockdown did not affect proliferation, cell cycle progression, apoptosis or migration of U937 leukemia cells, although UHMK1 silencing strikingly increased clonogenicity of these cells. Thus, our results suggest that UHMK1 plays a role in hematopoietic cell differentiation and suppression of autonomous clonal growth of leukemia cells.

IRS1/ß-Catenin Axis Is Activated and Induces MYC Expression in Acute Lymphoblastic Leukemia Cells.

Insulin-like growth factor 1 (IGF1) and its receptor IGF1R regulate normal cell growth and contribute to cell transformation through activation of downstream signaling pathways. In fibroblast cells, insulin receptor substrate 1 (IRS1), through IGF1 signaling, was found to be the key protein for nuclear translocation of ß-catenin and MYC transcription activation. We herein investigated the IRS1/ß-catenin axis in acute lymphoblastic leukemia (ALL) cells. Samples were obtained from 45 patients with ALL and 13 healthy donors. ALL cell lines were used. Gene expression was measured by quantitative PCR. Protein expression, associations, and cellular localization were evaluated by immunoprecipitation, subcellular fractionation, and confocal microscopy. Cells were submitted to IGF1 stimulation and/or IGF1R pharmacological inhibition (OSI-906). IRS1, ß-catenin, and MYC mRNA expression were significantly elevated in ALL patients, compared to normal controls. MYC mRNA expression positively correlated with ß-catenin and IRS1. Increased age and MYC expression negatively affected overall survival by univariate analysis. Total and phospho-IGF1R and IRS1, MYC and ß-catenin protein expression were higher in ALL cells, compared to normal peripheral blood mononuclear cells (PBMC). IRS1 and ß-catenin were found to be colocalized in the nuclei and the cytoplasm of ALL cell lines, whereas both proteins were only slightly detected in the cytoplasm of normal PBMC. In Jurkat cells, a constitutive IRS1 and ß-catenin protein interaction were observed; OSI-906 treatment decreased IGF1R tyrosine phosphorylation, IRS1 expression and phosphorylation, nuclear translocation of ß-catenin, IRS1 and ß-catenin association, and MYC protein expression. In conclusion, the IRS1/ß-catenin axis is activated in ALL cells. J. Cell. Biochem. 118: 1774-1781, 2017. © 2016 Wiley Periodicals, Inc.

Hematopoietic cell kinase (HCK) is a potential therapeutic target for dysplastic and leukemic cells due to integration of erythropoietin/PI3K pathway and regulation of erythropoiesis: HCK in erythropoietin/PI3K pathway.

New drug development for neoplasm treatment is nowadays based on molecular targets that participate in the disease pathogenesis and tumor phenotype. Herein, we describe a new specific pharmacological hematopoietic cell kinase (HCK) inhibitor (iHCK-37) that was able to reduce PI3K/AKT and MAPK/ERK pathways activation after erythropoietin induction in cells with high HCK expression: iHCK-37 treatment increased leukemic cells death and, very importantly, did not affect normal hematopoietic stem cells. We also present evidence that HCK, one of Src kinase family (SFK) member, regulates early-stage erythroid cell differentiation by acting as an upstream target of a frequently deregulated pathway in hematologic neoplasms, PI3K/AKT and MAPK/ERK. Notably, HCK levels were highly increased in stem cells from patients with some diseases, as Myelodysplastic Syndromes (MDS) and Acute Myeloid Leukemia (AML), that are associated with ineffective erythropoiesis These discoveries support the exploration of the new pharmacological iHCK-37 in future preclinical and clinical studies.

Characterization of Human AB Serum for Mesenchymal Stromal Cell Expansion.

BACKGROUND: So far, using human blood-derived components appears to be the most efficient and safest approach available for mesenchymal stromal cell (MSC) expansion. In this paper, we report on the characterization of human AB serum (AB HS) produced by using different plasma sources, and its use as an alternative supplement to MSC expansion. METHODS: Two plasma sources were used for AB HS production: plasma removed from whole blood after 24 h of collection (PC > 24 h) and plasma, cryoprecipitate reduced (PCryoR). The biochemical profile and quality of the produced AB HS batches were analyzed and their ability to support MSC cell growth after different storage times (0, 3, 6, 9 and 12 months) was evaluated. RESULTS: The two plasma sources used showed similar characteristics regarding biochemical constituents and quality parameters and were effective in promoting MSC growth. MSCs cultured in medium supplemented with 10% AB HS presented similar doubling times and cumulative population doublings when compared to the 10% fetal bovine serum(FBS)-supplemented culture while maintaining immunophenotype, functional features, and cytogenetic profile. CONCLUSION: Overall, the results indicate that AB HS is an efficient FBS substitute and can be used for at least 12 months after production without impairing cell proliferation and quality.

Imatinib restores VASP activity and its interaction with Zyxin in BCR-ABL leukemic cells.

Vasodilator-stimulated phosphoprotein (VASP) and Zyxin are interacting proteins involved in cellular adhesion and motility. PKA phosphorylates VASP at serine 157, regulating VASP cellular functions. VASP interacts with ABL and is a substrate of the BCR-ABL oncoprotein. The presence of BCR-ABL protein drives oncogenesis in patients with chronic myeloid leukemia (CML) due to a constitutive activation of tyrosine kinase activity. However, the function of VASP and Zyxin in BCR-ABL pathway and the role of VASP in CML cells remain unknown. In vitro experiments using K562 cells showed the involvement of VASP in BCR-ABL signaling. VASP and Zyxin inhibition decreased the expression of anti-apoptotic proteins, BCL2 and BCL-XL. Imatinib induced an increase in phosphorylation at Ser157 of VASP and decreased VASP and BCR-ABL interaction. VASP did not interact with Zyxin in K562 cells; however, after Imatinib treatment, this interaction was restored. Corroborating our data, we demonstrated the absence of phosphorylation at Ser157 in VASP in the bone marrow of CML patients, in contrast to healthy donors. Phosphorylation of VASP on Ser157 was restored in Imatinib responsive patients though not in the resistant patients. Therefore, we herein identified a possible role of VASP in CML pathogenesis, through the regulation of BCR-ABL effector proteins or the absence of phosphorylation at Ser157 in VASP.

ANKHD1 silencing inhibits Stathmin 1 activity, cell proliferation and migration of leukemia cells.

ANKHD1 is highly expressed in human acute leukemia cells and potentially regulates multiple cellular functions through its ankyrin-repeat domains. In order to identify interaction partners of the ANKHD1 protein and its role in leukemia cells, we performed a yeast two-hybrid system screen and identified SIVA, a cellular protein known to be involved in proapoptotic signaling pathways. The interaction between ANKHD1 and SIVA was confirmed by co-imunoprecipitation assays. Using human leukemia cell models and lentivirus-mediated shRNA approaches, we showed that ANKHD1 and SIVA proteins have opposing effects. While it is known that SIVA silencing promotes Stathmin 1 activation, increased cell migration and xenograft tumor growth, we showed that ANKHD1 silencing leads to Stathmin 1 inactivation, reduced cell migration and xenograft tumor growth, likely through the inhibition of SIVA/Stathmin 1 association. In addition, we observed that ANKHD1 knockdown decreases cell proliferation, without modulating apoptosis of leukemia cells, while SIVA has a proapoptotic function in U937 cells, but does not modulate proliferation in vitro. Results indicate that ANKHD1 binds to SIVA and has an important role in inducing leukemia cell proliferation and migration via the Stathmin 1 pathway. ANKHD1 may be an oncogene and participate in the leukemia cell phenotype.