STAT5 is Expressed in CD34+/CD38- Stem Cells and Serves as a Potential Molecular Target in Ph-Negative Myeloproliferative Neoplasms

STAT5 phosphorylation plus minimal residual disease defines a novel risk classification in adult B-cell acute lymphoblastic leukaemia

The dysregulation of the Janus family tyrosine kinase-signal transducer and activator of transcription (JAK-STAT) is closely related to acute lymphoblastic leukaemia (ALL), whereas the clinical value of phosphorylated STAT5 (pSTAT5) remains elusive. Herein we performed a prospective study on clinical significance of flow cytometry-based pSTAT5 in adult B-ALL patients. A total of 184 patients were enrolled in the Precision-Classification-Directed-Target-Total-Therapy (PDT)-ALL-2016 cohort between January 2018 and December 2021, and STAT5 phosphorylation was detected by flow cytometry at diagnosis. Based on flow-pSTAT5, the population was classified into pSTAT5low (113/184, 61.1%) and pSTAT5high (71/184, 38.9%). Overall survival (OS) and event-free survival (EFS) were inferior in pSTAT5high patients than in those with pSTAT5low (OS, 44.8% vs. 65.2%, p = 0.004; EFS, 23.5% vs. 52.1%, p < 0.001), which was further confirmed in an external validation cohort. Furthermore, pSTAT5 plus flow-based minimal residual disease (MRD) postinduction defines a novel risk classification as being high risk (HR, pSTAT5high + MRD+), standard risk (SR, pSTAT5low + MRD-) and others as moderate-risk group. Three identified patient subgroups are distinguishable with disparate survival curves (3-year OS rates, 36.5%, 56.7% and 76.3%, p < 0.001), which was confirmed on multivariate analysis (hazard ratio 3.53, p = 0.003). Collectively, our study proposed a novel, simple and flow-based risk classification by integrating pSTAT5 and MRD in favour of risk-guided treatment for B-ALL.

Myeloproliferative Neoplasms: Diseases Mediated by Chronic Activation of Signal Transducer and Activator of Transcription (STAT) Proteins

Myeloproliferative neoplasms (MPNs) are hematopoietic diseases characterized by the clonal expansion of single or multiple lineages of differentiated myeloid cells that accumulate in the blood and bone marrow. MPNs are grouped into distinct categories based on key clinical presentations and distinctive mutational hallmarks. These include chronic myeloid leukemia (CML), which is strongly associated with the signature BCR::ABL1 gene translocation, polycythemia vera (PV), essential thrombocythemia (ET), and primary (idiopathic) myelofibrosis (PMF), typically accompanied by molecular alterations in the JAK2, MPL, or CALR genes. There are also rarer forms such as chronic neutrophilic leukemia (CNL), which involves mutations in the CSF3R gene. However, rather than focusing on the differences between these alternate disease categories, this review aims to present a unifying molecular etiology in which these overlapping diseases are best understood as disruptions of normal hematopoietic signaling: specifically, the chronic activation of signaling pathways, particularly involving signal transducer and activator of transcription (STAT) transcription factors, most notably STAT5B, leading to the sustained stimulation of myelopoiesis, which underpins the various disease sequalae.

Vienna Cancer Stem Cell Club (VCSCC): 20 year jubilee and future perspectives

INTRODUCTION

The Vienna Cancer Stem Cell Club (VCSCC) was launched by a group of scientists in Vienna in 2002.

AREAS COVERED

Major aims of the VCSCC are to support research on cancer stem cells (CSC) in hematopoietic malignancies and to translate CSC-related markers and targets into clinical application. A primary focus of research in the VCSCC is the leukemic stem cell (LSC). Between 2013 and 2021, members of the VCSCC established a special research program on myeloproliferative neoplasms and since 2008, members of the VCSCC run the Ludwig Boltzmann Institute for Hematology and Oncology. In all these years, the VCSCC provided a robust intellectual platform for translational hematology and LSC research in Vienna. Furthermore, the VCSCC interacts with several national and international study groups and societies in the field. Representatives of the VCSCC also organized a number of international meetings and conferences on neoplastic stem cells, including LSC, in the past 15 years, and contributed to the definition and classification of CSC/LSC and related pre-malignant and malignant conditions.

EXPERT OPINION

The VCSCC will continue to advance the field and to develop LSC-detecting and LSC-eradicating concepts through which diagnosis, prognostication, and therapy of blood cancer patients should improve.

Phenotypic characterization of disease-initiating stem cells in JAK2- or CALR-mutated myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are characterized by uncontrolled expansion of myeloid cells, disease-related mutations in certain driver-genes including JAK2, CALR, and MPL, and a substantial risk to progress to secondary acute myeloid leukemia (sAML). Although behaving as stem cell neoplasms, little is known about disease-initiating stem cells in MPN. We established the phenotype of putative CD34+ /CD38- stem cells and CD34+ /CD38+ progenitor cells in MPN. A total of 111 patients with MPN suffering from polycythemia vera, essential thrombocythemia, or primary myelofibrosis (PMF) were examined. In almost all patients tested, CD34+ /CD38- stem cells expressed CD33, CD44, CD47, CD52, CD97, CD99, CD105, CD117, CD123, CD133, CD184, CD243, and CD274 (PD-L1). In patients with PMF, MPN stem cells often expressed CD25 and sometimes also CD26 in an aberrant manner. MPN stem cells did not exhibit substantial amounts of CD90, CD273 (PD-L2), CD279 (PD-1), CD366 (TIM-3), CD371 (CLL-1), or IL-1RAP. The phenotype of CD34+ /CD38- stem cells did not change profoundly during progression to sAML. The disease-initiating capacity of putative MPN stem cells was confirmed in NSGS mice. Whereas CD34+ /CD38- MPN cells engrafted in NSGS mice, no substantial engraftment was produced by CD34+ /CD38+ or CD34- cells. The JAK2-targeting drug fedratinib and the BRD4 degrader dBET6 induced apoptosis and suppressed proliferation in MPN stem cells. Together, MPN stem cells display a unique phenotype, including cytokine receptors, immune checkpoint molecules, and other clinically relevant target antigens. Phenotypic characterization of neoplastic stem cells in MPN and sAML should facilitate their enrichment and the development of stem cell-eradicating (curative) therapies.

The Role of STATs in Ovarian Cancer: Exploring Their Potential for Therapy

Ovarian cancer (OvCa) is a deadly gynecologic malignancy that presents many clinical challenges due to late-stage diagnoses and the development of acquired resistance to standard-of-care treatment protocols. There is an increasing body of evidence suggesting that STATs may play a critical role in OvCa progression, resistance, and disease recurrence, and thus we sought to compile a comprehensive review to summarize the current state of knowledge on the topic. We have examined peer reviewed literature to delineate the role of STATs in both cancer cells and cells within the tumor microenvironment. In addition to summarizing the current knowledge of STAT biology in OvCa, we have also examined the capacity of small molecule inhibitor development to target specific STATs and progress toward clinical applications. From our research, the best studied and targeted factors are STAT3 and STAT5, which has resulted in the development of several inhibitors that are under current evaluation in clinical trials. There remain gaps in understanding the role of STAT1, STAT2, STAT4, and STAT6, due to limited reports in the current literature; as such, further studies to establish their implications in OvCa are necessitated. Moreover, due to the deficiency in our understanding of these STATs, selective inhibitors also remain elusive, and therefore present opportunities for discovery.

The prognostic effect on childhood acute lymphoblastic leukemia of CD34+CD38- expressed in leukemia cells

OBJECTIVE

Acute lymphoblastic leukemia is the most common malignant disease in children. CD34 and CD38 are expressed in both normal and leukemia cells, but studies of their prognostic associations in childhood acute lymphoblastic leukemia are limited. The aim of this study was to investigate the prognostic effect of CD34 ⁺CD38^- leukemia cells in this childhood cancer.

METHODS

From January 2014 to January 2019, children with newly diagnosed acute lymphoblastic leukemia were included in this study and followed up until July 2020. The participants were divided into CD34⁺ and CD34^- groups according to CD34 expression level at diagnosis, and the CD34⁺ group was further divided into CD34 ⁺CD38^- and CD34 ⁺CD38⁺ subgroups based on CD38 expression level. We tracked clinical biological features, therapeutic outcomes, and other patient data for comparisons.

RESULTS

The OS and EFS did not differ significantly between the CD34⁺ and CD34^- groups (both P > 0.05). CD34⁺CD38^- group and CD34⁺CD38⁺ group were further compared. OS differed significantly between these two groups (χ²= 3.89, P = 0.048), as did the recurrence rate (χ²= 5.04, P = 0.025), but EFS did not (χ²= 1.45, P > 0.05). Survival analysis in patients with recurrence showed a significantly higher OS for the CD34 ⁺CD38⁺ group compared with the CD34 ⁺CD38^- group (χ²= 5.08, P = 0.024). The CD34⁺CD38^- group and CD34⁺CD38⁺ group were matched for propensity scores. When recurrence was compared in the two groups after matching, the difference was statistically significant (P < 0.001).

CONCLUSION

CD34⁺ and CD34^- expression does not differ by prognosis in children with acute lymphoblastic leukemia, but CD34 ⁺CD38^- may indicate a poor prognosis.

Phenotypic characterization of leukemia-initiating stem cells in chronic myelomonocytic leukemia

Chronic myelomonocytic leukemia (CMML) is a stem cell-derived neoplasm characterized by dysplasia, uncontrolled expansion of monocytes, and substantial risk to transform to secondary acute myeloid leukemia (sAML). So far, little is known about CMML-initiating cells. We found that leukemic stem cells (LSC) in CMML reside in a CD34+/CD38- fraction of the malignant clone. Whereas CD34+/CD38- cells engrafted NSGS mice with overt CMML, no CMML was produced by CD34+/CD38+ progenitors or the bulk of CD34- monocytes. CMML LSC invariably expressed CD33, CD117, CD123 and CD133. In a subset of patients, CMML LSC also displayed CD52, IL-1RAP and/or CLL-1. CMML LSC did not express CD25 or CD26. However, in sAML following CMML, the LSC also expressed CD25 and high levels of CD114, CD123 and IL-1RAP. No correlations between LSC phenotypes, CMML-variant, mutation-profiles, or clinical course were identified. Pre-incubation of CMML LSC with gemtuzumab-ozogamicin or venetoclax resulted in decreased growth and impaired engraftment in NSGS mice. Together, CMML LSC are CD34+/CD38- cells that express a distinct profile of surface markers and target-antigens. During progression to sAML, LSC acquire or upregulate certain cytokine receptors, including CD25, CD114 and CD123. Characterization of CMML LSC should facilitate their enrichment and the development of LSC-eradicating therapies.

Targeting the JAK-STAT pathway in autoimmune diseases and cancers: A focus on molecular mechanisms and therapeutic potential

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway is characterized by diverse immune regulatory systems involving cell proliferation, survival, and inflammation and immune tolerance. Aberrant JAK/STAT transduction activates proinflammatory cytokine signaling that jeopardize the immune balance and thus contributes to the development of autoimmune diseases and cancer progression. The success of several small-molecule JAK inhibitors in the treatment of rheumatologic diseases demonstrates that targeting the JAK/STAT pathway is efficient in suppressing inflammation and sheds light on their therapeutic potential in several autoimmune diseases and cancers. In this review, we discuss the signal transduction and molecular mechanism involving immune function through the JAK-STAT pathway, outline the role of this pathway in autoimmunity and oncoimmunology, and explain the preclinical and clinical trial evidence for the therapeutic potential of targeting the JAK-STAT signaling pathway. Issues regarding the safety and clinical efficacy of JAK inhibitors are reviewed. Ongoing studies are addressed with a focus on emerging indications for JAK inhibition and explanations of the novel mechanisms of JAK-STAT signaling blockade.

A case of JAK2V617F-positive essential thrombocythemia where allele burden was reduced by a PD-1 inhibitor

The Janus kinase/signal transducers and activators of transcription signaling pathway induces programmed death ligand-1 (PD-L1) expression. JAK2 mutation at position 617 (JAK2V617) is a frequent driver of myeloproliferative neoplasms (MPN) through PD-L1 expression. Although PD-1 inhibitors should be effective against MPN with JAK2V617F mutation, this has not yet been reported in humans. Thus, we assessed the efficacy of a PD-1 inhibitor in a lung cancer patient with JAK2V617F-positive essential thrombocythemia (ET). A 71-year-old man was diagnosed with ET, and with lung carcinoma 3 years later. After right lobectomy and postoperative chemotherapy, pembrolizumab [a PD-1 inhibitor (200 mg, every 3 weeks)] was initiated for refractory lung carcinoma. Lung cancer progression did not occur for 1.5 years under treatment. Most megakaryocytes were PD-L1-positive, and after pembrolizumab initiation, platelet count remained below 45 × 10⁴/μL without the need for other cytoreductive therapies for ET. The JAK2V617F allele burden gradually decreased from 11.5% at diagnosis to 2.9% after 17 months of pembrolizumab treatment. Other peripheral blood lineages did not decrease, and pembrolizumab treatment was continued without any adverse events. This is the first report demonstrating the effectiveness of pembrolizumab in an MPN patient with JAK2V617F mutation.

Targeting STAT3 and STAT5 in Cancer

Insights into the mutational landscape of the human cancer genome coding regions defined about 140 distinct cancer driver genes in 2013, which approximately doubled to 300 in 2018 following advances in systems cancer biology studies [...].