Hedgehog pathway inhibition as a therapeutic target in acute myeloid leukemia

Identifying acute myeloid leukemia subtypes based on pathway enrichment

Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults and the second most common in children. Despite the introduction of targeted therapies, AML survival rates have shown limited improvement, particularly among older patients. This study explored personalized treatment strategies for AML by proposing a novel subtyping method. Through unsupervised clustering based on the enrichment scores of 14 pathways related to metabolism, immunity, DNA repair, and oncogenic signaling, we identified three AML subtypes: DNA repair (DR), immune-enriched (ImE), and immune-deprived (ImD), consistent in four independent datasets. DR is marked by high expression of DNA repair and metabolic pathways, high stemness and proliferation potential, as well as high sensitivity to chemotherapy. ImD is characterized by low expression of immune and oncogenic pathways, favorable survival prognosis, low mutation rates of RUNX1 and TP53, high homeostasis, and low migration potential. ImE exhibits high enrichment of immune and oncogenic pathways, low stemness and proliferation capacity, low homeostasis, high migration potential, and low sensitivity to chemotherapy. Our pathway enrichment-based subtyping approach would offer a promising framework for understanding the molecular heterogeneity of AML and guiding personalized treatment of this disease.

Hedgehog and PI3K/Akt/mTOR Signaling Pathways Involvement in Leukemic Malignancies: Crosstalk and Role in Cell Death

The Hedgehog (Hh) and PI3K/Akt/mTOR signaling pathways play a pivotal role in driving the initiation and progression of various cancers, including hematologic malignancies such as acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), and chronic lymphocytic leukemia (CLL). These pathways are often dysregulated in leukemia cells, leading to increased cell growth, survival, and drug resistance while also impairing mechanisms of cell death. In leukemia, the Hh pathway can be abnormally activated by genetic mutations. Additionally, the PI3K/Akt/mTOR pathway is frequently overactive due to genetic changes. A key aspect of these pathways is their interaction: activation of the PI3K/Akt pathway can trigger a non-canonical activation of the Hh pathway, which further promotes leukemia cell growth and survival. Targeted inhibitors of these pathways, such as Gli inhibitors and PI3K/mTOR inhibitors, have shown promise in preclinical and clinical studies.

GLI1 polymorphisms influence remission rate and prognosis of young de novo acute myeloid leukemia patients treated with cytarabine-based chemotherapy

Acute myeloid leukemia (AML) is a highly heterogeneous hematological malignancy. Cytarabine (Ara-C)-based chemotherapy is the primary treatment for AML, but currently known prognostic risk stratification factors cannot fully explain the individual differences in outcome of patients. In this article, we reported that patients with homozygous GLI1 rs2228224 mutation (AA genotype) had a significantly lower complete remission rate than those with GG wild type (54.17% vs.76.02%, OR = 1.993, 95% CI: 1.062-3.504, P = 0.031). GLI1 rs2229300 T allele carriers had remarkably shorter overall survival (513 vs. 645 days, P = 0.004) and disease-free survival (342 vs. 456 days, P = 0.033) than rs2229300 GG carriers. Rs2229300 G > T variation increased the transcriptional activity of GLI1. CCND1, CD44 and PROM1 were potential target genes differentially regulated by GLI1 rs2229300. Our results demonstrated for the first time that GLI1 polymorphisms influence chemosensitivity and prognosis of young de novo AML patients treated with Ara-C.

Proteomic Characterization of Acute Myeloid Leukemia for Precision Medicine

Acute myeloid leukemia (AML) is a highly heterogeneous cancer of the hematopoietic system with no cure for most patients. In addition to chemotherapy, treatment options for AML include recently approved therapies that target proteins with roles in AML pathobiology, such as FLT3, BLC2, and IDH1/2. However, due to disease complexity, these therapies produce very diverse responses, and survival rates are still low. Thus, despite considerable advances, there remains a need for therapies that target different aspects of leukemic biology and for associated biomarkers that define patient populations likely to respond to each available therapy. To meet this need, drugs that target different AML vulnerabilities are currently in advanced stages of clinical development. Here, we review proteomics and phosphoproteomics studies that aimed to provide insights into AML biology and clinical disease heterogeneity not attainable with genomic approaches. To place the discussion in context, we first provide an overview of genetic and clinical aspects of the disease, followed by a summary of proteins targeted by compounds that have been approved or are under clinical trials for AML treatment and, if available, the biomarkers that predict responses. We then discuss proteomics and phosphoproteomics studies that provided insights into AML pathogenesis, from which potential biomarkers and drug targets were identified, and studies that aimed to rationalize the use of synergistic drug combinations. When considered as a whole, the evidence summarized here suggests that proteomics and phosphoproteomics approaches can play a crucial role in the development and implementation of precision medicine for AML patients.

The signature based on seven genomic instability-related genes could predict the prognosis of acute myeloid leukemia patients

BACKGROUND

Acute myeloid leukemia (AML) is the most common acute blood malignancy in adults. The complicated and dynamic genomic instability (GI) is the most prominent feature of AML. Our study aimed to explore the prognostic value of GI-related genes in AML patients.

METHODS

The mRNA data and mutation data were downloaded from the TCGA and GEO databases. Differential expression analyses were completed in limma package. GO and KEGG functional enrichment was conducted using clusterProfiler function of R. Univariate Cox and LASSO Cox regression analyses were performed to screen key genes for Risk score model construction. Nomogram was built with rms package.

RESULTS

We identified 114 DEGs between high TMB patients and low TMB AML patients, which were significantly enriched in 429 GO terms and 13 KEGG pathways. Based on the univariate Cox and LASSO Cox regression analyses, seven optimal genes were finally applied for Risk score model construction, including SELE, LGALS1, ITGAX, TMEM200A, SLC25A21, S100A4 and CRIP1. The Risk score could reliably predict the prognosis of AML patients. Age and Risk score were both independent prognostic indicators for AML, and the Nomogram based on them could also reliably predict the OS of AML patients.

CONCLUSIONS

A prognostic signature based on seven GI-related genes and a predictive Nomogram for AML patients are finally successfully constructed.

Canonical Hedgehog Pathway and Noncanonical GLI Transcription Factor Activation in Cancer

The Hedgehog signaling pathway is one of the fundamental pathways required for development and regulation of postnatal regeneration in a variety of tissues. The pathway has also been associated with cancers since the identification of a mutation in one of its components, PTCH, as the cause of Basal Cell Nevus Syndrome, which is associated with several cancers. Our understanding of the pathway in tumorigenesis has expanded greatly since that initial discovery over two decades ago. The pathway has tumor-suppressive and oncogenic functions depending on the context of the cancer. Furthermore, noncanonical activation of GLI transcription factors has been reported in a number of tumor types. Here, we review the roles of canonical Hedgehog signaling pathway and noncanonical GLI activation in cancers, particularly epithelial cancers, and discuss an emerging concept of the distinct outcomes that these modes have on cancer initiation and progression.

Hedgehog/GLI signaling in hematopoietic development and acute myeloid leukemia-From bench to bedside

While the underlying genetic alterations and biology of acute myeloid leukemia (AML), an aggressive hematologic malignancy characterized by clonal expansion of undifferentiated myeloid cells, have been gradually unraveled in the last decades, translation into clinical treatment approaches has only just begun. High relapse rates remain a major challenge in AML therapy and are to a large extent attributed to the persistence of treatment-resistant leukemic stem cells (LSCs). The Hedgehog (HH) signaling pathway is crucial for the development and progression of multiple cancer stem cell driven tumors, including AML, and has therefore gained interest as a therapeutic target. In this review, we give an overview of the major components of the HH signaling pathway, dissect HH functions in normal and malignant hematopoiesis, and specifically elaborate on the role of HH signaling in AML pathogenesis and resistance. Furthermore, we summarize preclinical and clinical HH inhibitor studies, leading to the approval of the HH pathway inhibitor glasdegib, in combination with low-dose cytarabine, for AML treatment.

SPRY1 promotes cell proliferation and inhibits apoptosis by activating Hedgehog pathway in acute myeloid leukemia

OBJECTIVE

The aim of this study was to determine the biological function of Sprouty 1 (SPRY1) on acute myeloid leukemia (AML), and to investigate the potential mechanism.

METHODS

The expression of SPRY1 and the prognostic values of SPRY1 were assessed through the analysis of the Cancer Genome Atlas. Meanwhile, the expression of SPRY1 in AML cells was determined by qRT-PCR and western blot. Then, the biological function of SPRY1 on the proliferation, cell cycle and apoptosis in K-562 and HL-60 cells were tested using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, colony-formation assay, 5-ethynyl-20-deoxyuridine assay and flow cytometry. Additionally, the protein expressions were measured by western blot.

RESULTS

We found that SPRY1 was markedly overexpressed in the cells of the patients with AML, and the patients with AML having a high SPRY1 expression has a bad prognosis. The proliferation and cell cycle progression in K-562 and HL-60 cells were notably promoted by SPRY1 overexpression, but inhibited by SPRY1 knockdown. Meanwhile, the apoptosis of K-562 and HL-60 cells was significantly repressed by SPRY1 overexpression and facilitated by SPRY1 knockdown. In addition, we found that SPRY1 overexpression significantly activated the Hedgehog pathway in AML cells. The function of SPRY1 on the proliferation, cell cycle and apoptosis was reversed by Gli1 in K-562 and HL-60 cells.

DISCUSSION

Identifying new biomarkers and exploring the pathogenesis of AML is urgent to improve the disease surveillance for patients with AML.

CONCLUSIONS

SPRY1 could facilitate cell proliferation and cell cycle progression, and suppress cell apoptosis via activating the Hedgehog pathway in AML.

Cell signaling pathways as molecular targets to eliminate AML stem cells

Acute myeloid leukemia (AML) remains the most lethal of leukemias and a small population of cells called leukemic stem cells (LSCs) has been associated with disease relapses. Some cell signaling pathways play an important role in AML survival, proliferation and self-renewal properties and are abnormally activated or suppressed in LSCs. This includes the NF-κB, Wnt/β-catenin, Hedgehog, Notch, EGFR, JAK/STAT, PI3K/AKT/mTOR, TGF/SMAD and PPAR pathways. This review aimed to discuss these pathways as molecular targets for eliminating AML LSCs. Herein, inhibitors/activators of these pathways were summarized as a potential new anti-AML therapy capable of eliminating LSCs to guide future researches. The clinical use of cell signaling pathways data can be useful to enhance the anti-AML therapy.

Targeting multiple signaling pathways: the new approach to acute myeloid leukemia therapy

Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults and the second most common form of acute leukemia in children. Despite this, very little improvement in survival rates has been achieved over the past few decades. This is partially due to the heterogeneity of AML and the need for more targeted therapeutics than the traditional cytotoxic chemotherapies that have been a mainstay in therapy for the past 50 years. In the past 20 years, research has been diversifying the approach to treating AML by investigating molecular pathways uniquely relevant to AML cell proliferation and survival. Here we review the development of novel therapeutics in targeting apoptosis, receptor tyrosine kinase (RTK) signaling, hedgehog (HH) pathway, mitochondrial function, DNA repair, and c-Myc signaling. There has been an impressive effort into better understanding the diversity of AML cell characteristics and here we highlight important preclinical studies that have supported therapeutic development and continue to promote new ways to target AML cells. In addition, we describe clinical investigations that have led to FDA approval of new targeted AML therapies and ongoing clinical trials of novel therapies targeting AML survival pathways. We also describe the complexity of targeting leukemia stem cells (LSCs) as an approach to addressing relapse and remission in AML and targetable pathways that are unique to LSC survival. This comprehensive review details what we currently understand about the signaling pathways that support AML cell survival and the exceptional ways in which we disrupt them.

Emerging treatment options for patients with high-risk myelodysplastic syndrome

Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis with peripheral blood cytopenias, dysplastic cell morphology, and a variable risk of progression to acute myeloid leukemia (AML). The hypomethylating agents (HMA) azacitidine and decitabine have been used for over a decade in MDS treatment and lead to a modest survival benefit. However, response rates are only around 40% and responses are mostly transient. For HMA-refractory patients the prognosis is poor and there are no therapies approved by the United States Food and Drug Administration.

Combinations of HMAs, especially along with immune checkpoint inhibitors, have shown promising signals in both the frontline and HMA-refractory setting. Several other novel agents including orally available and longer acting HMAs, the BCL-2 inhibitor venetoclax, oral agents targeting driver mutations (IDH1/2, FLT3), immunotherapies, and new options for intensive chemotherapy have been studied with variable success and will be reviewed herein. Except for the minority of patients with targetable driver mutations, HMAs – likely as part of combination therapies – will remain the backbone of frontline MDS treatment. However, the wider use of genetic testing may enable a more targeted and individualized therapy of MDS patients.

Is outcome of older people with acute myeloid leukemia improving with new therapeutic approaches and stem cell transplantation?

Introduction: The clinical outcome of older patients with acute myeloid leukemia (AML) is still poor, especially for those who are unfit to treatments aimed at altering the natural course of the disease. Hypomethylating agents (HMA) offer an important therapeutic opportunity to a consistent number of patients, but long-term results are largely unsatisfactory.Area covered: Recently, a number of new agents have been registered for AML, some of which selectively available for older patient population, with promising results in terms of response rate and survival. Furthermore, the upper age limit for allogeneic stem cell transplantation is constantly increasing, so that this procedure is offered and actually given to an increasing number of older patients with AML. A literature review was conducted of the PubMed database for articles published in English as well as for abstracts from most important and recent hematology meetings on AML in older patients.Expert opinion: Appropriate selection among different options on the basis of clinical fitness and molecular findings at diagnosis as well as at relapse would result in improvement of therapeutic results, sparing unnecessary toxicity and optimizing health systems resources.

Beyond Ruxolitinib: Fedratinib and Other Emergent Treatment Options for Myelofibrosis

Myelofibrosis (MF) is a myeloproliferative neoplasm characterized by clonal proliferation of differentiated myeloid cells leading to bone marrow fibrosis, cytopenias and extramedullary hematopoiesis. In late 2019, the FDA approved the highly selective JAK2 inhibitor, fedratinib, for intermediate-2 or high-risk primary or secondary MF, making it the second drug approved for MF after ruxolitinib, a JAK1/2 inhibitor, which was approved for MF in 2011. The approval of fedratinib was based on phase II trials and the phase III JAKARTA trial, in which the drug significantly reduced splenomegaly and symptom burden compared to placebo, including some patients previously treated with ruxolitinib. The main side effects of fedratinib include anemia, gastrointestinal symptoms, and elevations in liver transaminases. Fedratinib also has ablack box warning for encephalopathy, although this occurred only in about 1% of the treated patients, most of which were ultimately felt not to represent Wernicke’s encephalopathy. Nonetheless, monitoring of thiamine levels and supplementation are recommended especially in high-risk patients. This concern has led to a prolonged clinical hold and delayed the drug approval by several years during which the drug exchanged manufacturers, highlighting the need for meticulous investigation and adjudication of serious, but rare, adverse events in drug development that could end up preventing drugs with favorable risk/benefit ratio from being approved. In this review, we discuss the pharmacokinetic data and efficacy, as well as the toxicity results of clinical trials of fedratinib. We also review ongoing trials of JAK inhibitors in MF and explore future treatment options for MF patients who are refractory to ruxolitinib.