Comprehensive characterization of IFNγ signaling in acute myeloid leukemia reveals prognostic and therapeutic strategies.

Interferon gamma (IFNγ) is a critical cytokine known for its diverse roles in immune regulation, inflammation, and tumor surveillance. However, while IFNγ levels were elevated in sera of most newly diagnosed acute myeloid leukemia (AML) patients, its complex interplay in AML remains insufficiently understood. We aim to characterize these complex interactions through comprehensive bulk and single-cell approaches in bone marrow of newly diagnosed AML patients. We identify monocytic AML as having a unique microenvironment characterized by IFNγ producing T and NK cells, high IFNγ signaling, and immunosuppressive features. IFNγ signaling score strongly correlates with venetoclax resistance in primary AML patient cells. Additionally, IFNγ treatment of primary AML patient cells increased venetoclax resistance. Lastly, a parsimonious 47-gene IFNγ score demonstrates robust prognostic value. In summary, our findings suggest that inhibiting IFNγ is a potential treatment strategy to overcoming venetoclax resistance and immune evasion in AML patients.

Safety and efficacy of zinpentraxin alfa as monotherapy or in combination with ruxolitinib in myelofibrosis: stage I of a phase II trial.

Pentraxin 2 (PTX-2; serum amyloid P component), a circulating endogenous regulator of the inflammatory response to tissue injury and fibrosis, is reduced in patients with myelofibrosis (MF). Zinpentraxin alfa (RO7490677, PRM-151) is a recombinant form of PTX-2 that has shown preclinical antifibrotic activity and no dose-limiting toxicities in phase I trials. We report results from stage 1 of a phase II trial of zinpentraxin alfa in patients with intermediate-1/2 or high-risk MF. Patients (n=27) received intravenous zinpentraxin α weekly (QW) or every 4 weeks (Q4W), as monotherapy or an additional therapy for patients on stable-dose ruxolitinib. The primary endpoint was overall response rate (ORR; investigatorassessed) adapted from International Working Group-Myeloproliferative Neoplasms Research and Treatment criteria. Secondary endpoints included modified Myeloproliferative Neoplasm-Symptom Assessment Form Total Symptom Score (MPN-SAF TSS) change, bone marrow (BM) MF grade reduction, pharmacokinetics, and safety. ORR at week 24 was 33% (n=9/27) and varied across individual cohorts (QW: 38% [3/8]; Q4W: 14% [1/7]; QW+ruxolitinib: 33% [2/6]; Q4W+ruxolitinib: 50% [3/6]). Five of 18 evaluable patients (28%) experienced a ≥50% reduction in MPN-SAF TSS, and six of 17 evaluable patients (35%) had a ≥1 grade improvement from baseline in BM fibrosis at week 24. Most treatment-emergent adverse events (AE) were grade 1-2, most commonly fatigue. Among others, anemia and thrombocytopenia were infrequent (n=3 and n=1, respectively). Treatment-related serious AE occurred in four patients (15%). Overall, zinpentraxin alfa showed evidence of clinical activity and tolerable safety as monotherapy and in combination with ruxolitinib in this open-label, non-randomized trial (clinicaltrials gov. Identifier: NCT01981850).

STAT3 Activates the Pentraxin 3 Gene in Chronic Lymphocytic Leukemia Cells.

Pentraxin-related protein 3 (PTX3), commonly produced by myeloid and endothelial cells, is a humoral pattern recognition protein of the innate immune system. Because PTX3 plasma levels of patients with chronic lymphocytic leukemia (CLL) are high and most circulating cells in patients with CLL are CLL cells, we reasoned that CLL cells produce PTX3. Western immunoblotting revealed that low-density cells from seven of seven patients with CLL produce high levels of PTX3, flow cytometry analysis revealed that the PTX3-producing cells are B lymphocytes coexpressing CD19 and CD5, and confocal microscopy showed that PTX3 is present in the cytoplasm of CLL cells. Because STAT3 is constitutively activated in CLL cells, and because we identified putative STAT3 binding sites within the PTX3 gene promoter, we postulated that phosphorylated STAT3 triggers transcriptional activation of PTX3. Immunoprecipitation analysis of CLL cells' chromatin fragments showed that STAT3 Abs precipitated PTX3 DNA. STAT3 knockdown induced a marked reduction in PTX3 expression, indicating a STAT3-induced transcriptional activation of the PTX3 gene in CLL cells. Using an EMSA, we established and used a dual-reporter luciferase assay to confirm that STAT3 binds the PTX3 gene promoter. Downregulation of PTX3 enhanced apoptosis of CLL cells, suggesting that inhibition of PTX3 might benefit patients with CLL.

GLI1 activates pro-fibrotic pathways in myelofibrosis fibrocytes.

Bone marrow (BM) fibrosis was thought to be induced exclusively by mesenchymal stromal cells (MSCs). However, we and others found that neoplastic fibrocytes induce BM fibrosis in myelofibrosis (MF). Because glioma-associated oncogene-1 (GLI1), an effector of the Hedgehog pathway, plays a role in the induction of BM fibrosis, we wondered whether GLI1 affects fibrocyte-induced BM fibrosis in MF. Multiplexed fluorescence immunohistochemistry analysis of MF patients' BM detected high levels of GLI1 in MF fibrocytes compared to MSCs or normal fibrocytes. Immunostaining, RNA in situ hybridization, gene expression analysis, and western immunoblotting detected high levels of GLI1 and GLI1-induced matrix metalloproteases (MMP) 2 and 9 in MF patients BM-derived cultured fibrocytes. Similarly, MF patients' BM-derived GLI1+ fibrocytes were found in BMs and spleens of MF xenograft mice. GLI1 silencing reduced the levels of MMP2/9, phosphorylated SMAD2/3, and procollagen-I, and knockdown or inhibition of GLI1 decreased fibrocyte formation and induced apoptosis of both fibrocytes and fibrocyte progenitors. Because Janus kinase (JAK)2-induced STAT3 is constitutively activated in MF and because STAT3 induces GLI1 expression, we sought to determine whether STAT3 activates GLI1 in MF fibrocytes. Imaging analysis detected phosphotyrosine STAT3 in MF patients' BM fibrocytes, and transfection of fibrocytes with STAT3-siRNA or treatment with a JAK1/2 inhibitor ruxolitinib reduced GLI1 and MMP2/9 levels. Chromatin immunoprecipitation and a luciferase assay revealed that STAT3 induced the expression of the GLI1 gene in both MF BM fibrocytes and fibrocyte progenitors. Together, our data suggest that STAT3-activated GLI1 contributes to the induction of BM fibrosis in MF.

STAT3 induces the expression of GLI1 in chronic lymphocytic leukemia cells.

The glioma associated oncogene-1 (GLI1), a downstream effector of the embryonic Hedgehog pathway, was detected in chronic lymphocytic leukemia (CLL), but not normal adult cells. GLI1 activating mutations were identified in 10% of patients with CLL. However, what induces GLI1 expression in GLI1-unmutated CLL cells is unknown. Because signal transducer and activator of transcription 3 (STAT3) is constitutively activated in CLL cells and sequence analysis detected putative STAT3-binding sites in the GLI1 gene promoter, we hypothesized that STAT3 induces the expression of GLI1. Western immunoblotting detected GLI1 in CLL cells from 7 of 7 patients, flow cytometry analysis confirmed that CD19+/CD5+ CLL cells co-express GLI1 and confocal microscopy showed co-localization of GLI1 and phosphorylated STAT3. Chromatin immunoprecipitation showed that STAT3 protein co-immunoprecipitated GLI1 as well as other STAT3-regulated genes. Transfection of CLL cells with STAT3-shRNA induced a mark decrease in GLI1 levels, suggesting that STAT3 binds to and induces the expression of GLI1 in CLL cells. An electromobility shift assay confirmed that STAT3 binds, and a luciferase assay showed that STAT3 activates the GLI1 gene. Transfection with GLI1-siRNA significantly increased the spontaneous apoptosis rate of CLL cells, suggesting that GLI1 inhibitors might provide therapeutic benefit to patients with CLL.

Altered T-cell subset repertoire affects treatment outcome of patients with myelofibrosis.

Phenotypic characterization of T cells in myelofibrosis (MF) is intriguing owing to increased inflammation, markedly elevated pro-inflammatory cytokines, and altered distribution of T-cell subsets. Constitutive activation of Janus kinase-2 (JAK2) in the majority of MF patients contributes to the expression of the programmed cell death protein-1 (PD1) and T-cell exhaustion. We wondered whether T-cell activation affects treatment outcome of patients with MF and sought to determine whether the JAK1/2 inhibitor ruxolitinib affects the activation of T-cell subsets. T cells from 47 MF patients were analyzed and the percent of either helper (CD4+) or cytotoxic (CD8+) naive, central memory, effector memory, or effector T cells; and fractions of PD1-expressing cells in each subset were assessed. An increased number of T cells coexpressing CD4/PD1 and CD8/PD1 in MF compared to healthy controls (n=28) was found, and the T cells were significantly skewed toward an effector phenotype in both CD4+ and CD8+ subsets, consistent with a shift from a quiescent to an activated state. Over the course of ruxolitinib treatment, the distribution of aberrant T-cell subsets significantly reversed towards resting cell phenotypes. CD4+ and CD8+ subsets at baseline correlated with monocyte and platelet counts, and their PD1-positive fractions correlated with leukocyte counts and spleen size. Low numbers of PD1+/CD4+ and PD1+/CD8+ cells were associated with complete resolution of palpable splenomegaly and improved survival rate, suggesting that low levels of exhausted T cells confer a favorable response to ruxolitinib treatment.

Primary myelofibrosis marrow-derived CD14+/CD34- monocytes induce myelofibrosis-like phenotype in immunodeficient mice and give rise to megakaryocytes.

To confirm that neoplastic monocyte-derived collagen- and fibronectin-producing fibrocytes induce bone marrow (BM) fibrosis in primary myelofibrosis (PMF), we injected PMF BM-derived fibrocyte-precursor CD14+/CD34- monocytes into the tail vein of NOD-SCID-γ (NSG) mice. PMF BM-derived CD14+/CD34- monocytes engrafted and induced a PMF-like phenotype with splenomegaly, myeloid hyperplasia with clusters of atypical megakaryocytes, persistence of the JAK2V617F mutation, and BM and spleen fibrosis. As control we used normal human BM-derived CD14+/CD34- monocytes. These monocytes also engrafted and gave rise to normal megakaryocytes that, like PMF CD14+/CD34--derived megakaryocytes, expressed HLA-ABC and human CD42b antigens. Using 2 clonogenic assays we confirmed that PMF and normal BM-derived CD14+/CD34- monocytes give rise to megakaryocyte colony-forming cells, suggesting that a subpopulation BM monocytes harbors megakaryocyte progenitor capacity. Taken together, our data suggest that PMF monocytes induce myelofibrosis-like phenotype in immunodeficient mice and that PMF and normal BM-derived CD14+/CD34- monocytes give rise to megakaryocyte progenitor cells.

Myelofibrosis osteoclasts are clonal and functionally impaired.

Bone marrow (BM) sclerosis is commonly found in patients with late-stage myelofibrosis (MF). Because osteoclasts (OCs) and osteoblasts play a key role in bone remodeling, and MF monocytes, the OC precursors, are derived from the neoplastic clone, we wondered whether decreased OC numbers or impairment in their osteolytic function affects the development of osteosclerosis. Analysis of BM biopsies from 50 MF patients showed increased numbers of multinucleated tartrate-resistant acid phosphatase (TRAP)/cathepsin K+ OCs expressing phosphorylated Janus kinase 2 (JAK2). Randomly microdissected TRAP+ OCs from 16 MF patients harbored JAK2 or calreticulin (CALR) mutations, confirming MF OCs are clonal. To study OC function, CD14+ monocytes from MF patients and healthy individuals were cultured and differentiated into OCs. Unlike normal OCs, MF OCs appeared small and round, with few protrusions, and carried the mutations and chromosomal abnormalities of neoplastic clones. In addition, MF OCs lacked F-actin-rich ring-like structures and had fewer nuclei and reduced colocalization signals, compatible with decreased fusion events, and their mineral resorption capacity was significantly reduced, indicating impaired osteolytic function. Taken together, our data suggest that, although the numbers of MF OCs are increased, their impaired osteolytic activity distorts bone remodeling and contributes to the induction of osteosclerosis.

Assessing serum albumin concentration, lymphocyte count and prognostic nutritional index might improve prognostication in patients with myelofibrosis.

BACKGROUND: Primary and secondary myelofibrosis (PMF and SMF) are malignant diseases of hematopoietic stem cell characterized by the neoplastic myeloproliferation and a strong inflammatory milieu. The prognostic nutritional index (PNI) integrates information on albumin and absolute lymphocyte count (ALC) and reflects the inflammatory, nutritional and immune status of a patient. The clinical and prognostic significance of albumin, ALC and PNI in patients with myelofibrosis has not been previously investigated. METHODS: We retrospectively analyzed a cohort of 83 myelofibrosis patients treated in our institution from 2006 to 2017. Albumin, ALC and PNI were assessed in addition to other disease specific markers. RESULTS: The PMF and SMF patients had significantly lower ALC and PNI but similar albumin compared to controls. Lower albumin was significantly associated with older age and parameters reflecting more aggressive disease biology (e.g. anemia, lower platelet levels, higher lactate dehydrogenase (LDH), circulatory blasts, transfusion dependency, blast phase disease), inflammation (higher C reactive protein (CRP), constitutional symptoms) and higher degree of bone marrow fibrosis. Lower ALC was significantly associated with lower white blood cells (WBC) and lower circulatory blasts. Low PNI was associated with lower albumin, lower ALC, anemia, lower WBCs, lower serum iron and lower transferrin saturation. There was no difference in albumin, ALC and PNI regarding the driver mutations. In multivariate analysis adjusted for age and gender, low albumin (hazard ratio [HR] = 4.61, P = 0.001), low ALC (HR = 3.54, P = 0.004) and Dynamic International Prognostic Scoring System (DIPSS) (HR = 2.45, P = 0.001) were able to predict inferior survival independently of each other. Accordingly, low PNI (HR = 4.32, P < 0.001) predicted poor survival independently of DIPSS (HR = 3.31, P < 0.001). CONCLUSION: Assessing albumin, ALC and PNI might improve prognostication in patients with myelofibrosis and could assist in recognition of patients under increased risk of death.

Activation of the B-cell receptor successively activates NF-κB and STAT3 in chronic lymphocytic leukemia cells.

In chronic lymphocytic leukemia (CLL) cells, both interleukin-6 (IL-6) and the B-cell receptor (BCR) activate Janus kinase 2 (JAK2) and induce the phosphorylation of signal transduction and activator of transcription 3 (STAT3) on tyrosine 705 residues. However, whereas IL-6 phosphorylates STAT3 within 15 min, stimulation of the BCR with anti-immunoglobulin M (IgM) antibodies phosphorylates STAT3 in 2-4 hr. Here, we show that this process takes longer because it requires transcriptional activity of NF-κB. Using an electromobility shift assay, we found that incubation with IgM antibodies for 4 or 18 hr, but not 15 min, increased NF-κB DNA-binding of CLL cells and increased binding was translated to increased transcriptional activity. Hence, 42% of the 83 NF-κB target genes were constitutively expressed in all CLL cells prior to any inducible stimuli. However, activation of the BCR increased the number of NF-κB target genes with detectable expression by 23%. Remarkably, prolonged incubation with anti-IgM antibodies induced a time-dependent transcription, production and secretion of IL-6 protein. The IgM-induced production of IL-6 prompted the phosphorylation of STAT3 on tyrosine residues. This effect was inhibited by the JAK1/2 inhibitor of the JAK/STAT3 pathway ruxolitinib. Taken together, these results suggest that in CLL cells, constitutive tonic activation of NF-κB can be further enhanced by the BCR and that the BCR-induced activation of the JAK/STAT3 pathway depends on the NF-κB induced production of IL-6.

Constitutive Phosphorylation of STAT3 by the CK2-BLNK-CD5 Complex.

In chronic lymphocytic leukemia (CLL), STAT3 is constitutively phosphorylated on serine 727 and plays a role in the pathobiology of CLL. However, what induces constitutive phosphorylation of STAT3 is currently unknown. Mass spectrometry was used to identify casein kinase 2 (CK2), a serine/threonine kinase that coimmunoprecipitated with serine phosphorylated STAT3 (pSTAT3). Furthermore, activated CK2 incubated with recombinant STAT3 induced phosphorylation of STAT3 on serine 727. Although STAT3 and CK2 are present in normal B- and T cells, STAT3 is not constitutively phosphorylated in these cells. Further study found that CD5 and BLNK coexpressed in CLL, but not in normal B- or T cells, are required for STAT3 phosphorylation. To elucidate the relationship of CD5 and BLNK to CK2 and STAT3, STAT3 was immunoprecipitated from CLL cells, and CK2, CD5, and BLNK were detected in the immunoprecipitate. Conversely, STAT3, CD5, and BLNK were in the immunoprecipitate of CLL cells immunoprecipitated with CK2 antibodies. Furthermore, siRNA knockdown of CD5 or BLNK, or treatment with CD5-neutralizing antibodies significantly reduced the levels of serine pSTAT3 in CLL cells. Finally, confocal microscopy determined that CD5 is cell membrane bound, and fractionation studies revealed that the CK2/CD5/BLNK/STAT3 complex remains in the cytoplasm, whereas serine pSTAT3 is shuttled to the nucleus.Implications: These data show that the cellular proteins CK2, CD5, and BLNK are required for constitutive phosphorylation of STAT3 in CLL. Whether this protein complex phosphorylates other proteins or inhibiting its activity would have clinical benefit in patients has yet to be determined. Mol Cancer Res; 15(5); 610-8. ©2017 AACR.

Ruxolitinib for symptom control in patients with chronic lymphocytic leukaemia: a single-group, phase 2 trial.

BACKGROUND: Disease-related symptoms impair the quality of life of patients with chronic lymphocytic leukaemia (CLL) who do not require systemic therapy. Available therapies are not specifically aimed at symptom control. Because stimulation of the B-cell receptor activates JAK2 in CLL cells and the JAK2 inhibitor ruxolitinib improves symptoms in patients with myelofibrosis, we postulated that ruxolitinib would improve disease-related symptoms in patients with CLL. We did a phase 2 trial of ruxolitinib to test this hypothesis. METHODS: Symptomatic patients with CLL who did not require systemic therapy were enrolled at MD Anderson Cancer Center (Houston, TX, USA) between Sept 15, 2014, and Sept 20, 2015. Participants were given 10 mg ruxolitinib orally twice a day. Scores on the Brief Fatigue Inventory (BFI), CLL module of the MD Anderson Symptom Inventory (MDASI) and symptom-associated interference in daily activities, were assessed before treatment and after 3 months. This trial is ongoing and is registered at ClinicalTrials.gov (NCT02131584). FINDINGS: 41 patients (25 previously untreated for CLL and 16 previously treated) were enrolled. At 3 months, the mean percentage change from baseline in BFI score was 44·3% (SD 35·0, p<0·0001), in symptom interference score was 43·4% (51·5, p<0·0001), and in MDASI score was 42·1% (37·4, p<0·0001). 32 (78%) of the patients experienced 20% or greater reduction in the mean BFI, and 24 (59%) had a reduction of two units or more in worst fatigue score in past 24 hours as assessed by the BFI. The most comment grade 3-4 adverse events were neutropenia (n=2 [5%]), hypertension (n=2 [5%]), insomnia (n=1 [2%]), tinnitus and dizziness (n=1 [2%]), and thrombocytopenia (n=1 [2%]). INTERPRETATION: In patients with CLL, ruxolitinib was associated with significant improvements in disease-related symptoms as measured by BFI, MDASI, and symptom interference scores. Further studies to test the therapeutic efficacy of ruxolitinib in CLL are warranted. FUNDING: Incyte, National Cancer Institute.