Current management of juvenile myelomonocytic leukemia and the impact of RAS mutations

In vivo Targeting MEK and TNK2/SRC pathways in PTPN11 driven leukemia

PTPN11 encodes for a tyrosine phosphatase implicated in the pathogenesis of hematologic malignancies such as Juvenile Myelomonocytic Leukemia (JMML), Acute Myeloid Leukemia (AML), and Acute Lymphoblastic Leukemia (ALL). Since activating mutations of PTPN11 increase proliferative signaling and cell survival through the RAS/MAPK proliferative pathway there is significant interest in using MEK inhibitors for clinical benefit. Yet, single agent clinical activity has been minimal. Previously, we showed that PTPN11 is further activated by upstream tyrosine kinases TNK2/SRC, and that PTPN11-mutant JMML and AML cells are sensitive to TNK2 inhibition using dasatinib. In order to validate these findings, we adopted a genetically engineered mouse model of PTPN11 driven leukemia using the mouse strain 129S/Sv- Ptpn11 tm6Bgn /Mmucd crossed with B6.129P2- Lyz2 tm1(cre)Ifo /J. The F1 progeny expressing Ptpn11 D61Y within hematopoietic cells destined along the granulocyte-monocyte progenitor lineage developed a fatal myeloproliferative disorder characterized by neutrophilia and monocytosis, and infiltration of myeloid cells into the liver and spleen. Cohorts of Ptpn11 D61Y expressing animals treated with combination of dasatinib and trametinib for an extended period of time was well tolerated and had a significant effect in mitigating disease parameters compared to single agents. Finally, a primary patient-derived xenograft model using a myeloid leukemia with PTPN11 F71L also displayed improved disease response to combination. Collectively, these studies point to combined therapies targeting MEK and TNK2/SRC as a promising therapeutic potential for PTPN11-mutant leukemias.

Key Points

Combining MEK and TNK2/SRC inhibitors has therapeutic potential in PTPN11 mutant JMML and AML.

[Clinical features and prognosis of juvenile myelomonocytic leukemia: an analysis of 63 cases]

OBJECTIVES

To investigate the clinical features of juvenile myelomonocytic leukemia (JMML) and their association with prognosis.

METHODS

Clinical and prognosis data were collected from the children with JMML who were admitted from January 2008 to December 2016, and the influencing factors for prognosis were analyzed.

RESULTS

A total of 63 children with JMML were included, with a median age of onset of 25 months and a male/female ratio of 3.2∶1. JMML genetic testing was performed for 54 children, and PTPN11 mutation was the most common mutation and was observed in 23 children (43%), among whom 19 had PTPN11 mutation alone and 4 had compound PTPN11 mutation, followed by NRAS mutation observed in 14 children (26%), among whom 12 had NRAS mutation alone and 2 had compound NRAS mutation. The 5-year overall survival (OS) rate was only 22%±10% in these children with JMML. Of the 63 children, 13 (21%) underwent hematopoietic stem cell transplantation (HSCT). The HSCT group had a significantly higher 5-year OS rate than the non-HSCT group (46%±14% vs 29%±7%, P<0.05). There was no significant difference in the 5-year OS rate between the children without PTPN11 gene mutation and those with PTPN11 gene mutation (30%±14% vs 27%±10%, P>0.05). The Cox proportional-hazards regression model analysis showed that platelet count <40×10⁹/L at diagnosis was an influencing factor for 5-year OS rate in children with JMML (P<0.05).

CONCLUSIONS

The PTPN11 gene was the most common mutant gene in JMML. Platelet count at diagnosis is associated with the prognosis in children with JMML. HSCT can improve the prognosis of children with JMML.

Clinical Outcomes after Allogeneic Hematopoietic Stem Cell Transplantation in Children with Juvenile Myelomonocytic Leukemia: A Report from the Japan Society for Hematopoietic Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is the only curative treatment for juvenile myelomonocytic leukemia (JMML), but few large studies of HSCT for JMML exist. Using data from the Japan Society for Hematopoietic Cell Transplantation registry, we analyzed the outcomes of 129 children with JMML who underwent HSCT between 2000 and 2011. The 5-year overall survival (OS) rate and cumulative incidence of relapse were 64% and 34%, respectively. A regimen of busulfan/fludarabine/melphalan was the most commonly used (59 patients) and provided the best outcomes; the 5-year OS rate reached 73%, and the cumulative incidences of relapse and transplantation-related mortality were 26% and 9%, respectively. In contrast, the use of the irradiation-based myeloablative regimen was the most significant risk factor for OS (hazard ratio [HR], 2.92; P = .004) in the multivariate model. In addition, chronic graft-versus-host disease (GVHD) was strongly associated with lower relapse (HR, 0.37; P = .029) and favorable survival (HR, 0.22; P = .006). The current study has shown that a significant proportion of children with JMML can be cured with HSCT, especially those receiving the busulfan/fludarabine/melphalan regimen. Based on the lower relapse and better survival observed in patients with chronic GVHD, additional treatment strategies that focus on enhancing graft-versus-leukemia effects may further improve survival.

Rigosertib ameliorates the effects of oncogenic KRAS signaling in a murine model of myeloproliferative neoplasia

Aberrant signaling triggered by oncogenic or hyperactive RAS proteins contributes to the malignant phenotypes in a significant percentage of myeloid malignancies. Of these, juvenile myelomonocytic leukemia (JMML), an aggressive childhood cancer, is largely driven by mutations in RAS genes and those that encode regulators of these proteins. The Mx1-cre kras^+/G12D mouse model mirrors several key features of this disease and has been used extensively to determine the utility and mechanism of small molecule therapeutics in the context of RAS-driven myeloproliferative disorders. Treatment of disease-bearing KRAS^G12D mice with rigosertib (RGS), a small molecule RAS mimetic that is in phase II and III clinical trials for MDS and AML, decreased the severity of leukocytosis and splenomegaly and extended their survival. RGS also increased the frequency of HSCs and rebalanced the ratios of myeloid progenitors. Further analysis of KRAS^G12D HSPCs in vitro revealed that RGS suppressed hyperproliferation in response to GM-CSF and inhibited the phosphorylation of key RAS effectors. Together, these data suggest that RGS might be of clinical benefit in RAS-driven myeloid disorders.

Synthetic lethality of TNK2 inhibition in PTPN11-mutant leukemia

The protein tyrosine phosphatase PTPN11 is implicated in the pathogenesis of juvenile myelomonocytic leukemia (JMML), acute myeloid leukemia (AML), and other malignancies. Activating mutations in PTPN11 increase downstream proliferative signaling and cell survival. We investigated the signaling upstream of PTPN11 in JMML and AML cells and found that PTPN11 was activated by the nonreceptor tyrosine/serine/threonine kinase TNK2 and that PTPN11-mutant JMML and AML cells were sensitive to TNK2 inhibition. In cultured human cell-based assays, PTPN11 and TNK2 interacted directly, enabling TNK2 to phosphorylate PTPN11, which subsequently dephosphorylated TNK2 in a negative feedback loop. Mutations in PTPN11 did not affect this physical interaction but increased the basal activity of PTPN11 such that TNK2-mediated activation was additive. Consequently, coexpression of TNK2 and mutant PTPN11 synergistically increased mitogen-activated protein kinase (MAPK) signaling and enhanced colony formation in bone marrow cells from mice. Chemical inhibition of TNK2 blocked MAPK signaling and colony formation in vitro and decreased disease burden in a patient with PTPN11-mutant JMML who was treated with the multikinase (including TNK2) inhibitor dasatinib. Together, these data suggest that TNK2 is a promising therapeutic target for PTPN11-mutant leukemias.

Cellular and viral oncogenes: the key to unlocking unknowns of Kaposi's sarcoma-associated herpesvirus pathogenesis

Oncogenic viruses carry an extensive arsenal of oncogenes for hijacking cellular pathways. Notably, variations in oncogenes among tumor-producing viruses give rise to different mechanisms for cellular transformation. Specifically, Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus able to infect and transform a variety of cell types. The oncogenicity of KSHV disseminates from the virus' ability to induce and encode a wide variety of both cellular and viral oncogenes. Such an array of cellular and viral oncogenes enables KSHV to induce the malignant phenotype of a KSHV-associated cancer. Evolutionarily, KSHV has acquired many oncogenic homologues capable of inducing cell proliferation, cell differentiation, cell survival, and immune evasion. Integration between inducing and encoding oncogenes plays a vital role in KSHV pathogenicity. KSHV is alleged to harbor the highest number of potential oncogenes by which a virus promotes cellular transformation and malignancy. Many KSHV inducing/encoding oncogenes are mainly expressed during the latent phase of KSHV infection, a period required for virus establishment of malignant cellular transformation. Elucidation of the exact mechanism(s) by which oncogenes promote KSHV pathogenicity would not only give rise to potential novel therapeutic targets/drugs but would also add to our understanding of cancer biology. The scope of this review is to examine the roles of the most important cellular and viral oncogenes involved in KSHV pathogenicity.

Familial Myelodysplastic/Acute Leukemia Syndromes-Myeloid Neoplasms with Germline Predisposition

Although most cases of myeloid neoplasms are sporadic, a small subset has been associated with germline mutations. The 2016 revision of the World Health Organization classification included these cases in a myeloid neoplasm group with a predisposing germline mutational background. These patients must have a different management and their families should get genetic counseling. Cases identification and outline of the major known syndromes characteristics will be discussed in this text.

Potential Therapies by Stem Cell-Derived Exosomes in CNS Diseases: Focusing on the Neurogenic Niche

Neurodegenerative disorders are one of the leading causes of death and disability and one of the biggest burdens on health care systems. Novel approaches using various types of stem cells have been proposed to treat common neurodegenerative disorders such as Alzheimer's Disease, Parkinson's Disease, or stroke. Moreover, as the secretome of these cells appears to be of greater benefit compared to the cells themselves, the extracellular components responsible for its therapeutic benefit have been explored. Stem cells, as well as most cells, release extracellular vesicles such as exosomes, which are nanovesicles able to target specific cell types and thus to modify their function by delivering proteins, lipids, and nucleic acids. Exosomes have recently been tested in vivo and in vitro as therapeutic conveyors for the treatment of diseases. As such, they could be engineered to target specific populations of cells within the CNS. Considering the fact that many degenerative brain diseases have an impact on adult neurogenesis, we discuss how the modulation of the adult neurogenic niches may be a therapeutic target of stem cell-derived exosomes. These novel approaches should be examined in cellular and animal models to provide better, more effective, and specific therapeutic tools in the future.

Aberrant DNA Methylation Is Associated with a Poor Outcome in Juvenile Myelomonocytic Leukemia

Juvenile myelomonocytic leukemia (JMML), an overlap of myelodysplastic / myeloproliferative neoplasm, is an intractable pediatric myeloid neoplasm. Epigenetic regulation of transcription, particularly by CpG methylation, plays an important role in tumor progression, mainly by repressing tumor-suppressor genes. To clarify the clinical importance of aberrant DNA methylation, we studied the hypermethylation status of 16 target genes in the genomes of 92 patients with JMML by bisulfite conversion and the pryosequencing technique. Among 16 candidate genes, BMP4, CALCA, CDKN2A, and RARB exhibited significant hypermethylation in 72% (67/92) of patients. Based on the number of hypermethylated genes, patients were stratified into three cohorts based on an aberrant methylation score (AMS) of 0, 1–2, or 3–4. In the AMS 0 cohort, the 5-year overall survival (OS) and transplantation-free survival (TFS) were good (69% and 76%, respectively). In the AMS 1–2 cohort, the 5-year OS was comparable to that in the AMS 0 cohort (68%), whereas TFS was poor (6%). In the AMS 3–4 cohort, 5-year OS and TFS were markedly low (8% and 0%, respectively). Epigenetic analysis provides helpful information for clinicians to select treatment strategies for patients with JMML. For patients with AMS 3–4 in whom hematopoietic stem cell transplantation does not improve the prognosis, alternative therapies, including DNA methyltransferase inhibitors and new molecular-targeting agents, should be established as treatment options.

Determination of Serum Lost Goodwill Target Proteome in Patients with Severe Traumatic Brain Injury

This study investigates the biokinetics of LGT proteome, a potential biomarker of severe TBI, in serum of severe TBI patients. The LGT proteome presents in the serum of severe TBI patients. The abundance diversity of LGT proteome is closely associated with pathologic condition of TBI patients. Serum LGT proteome may be used as a promising marker for evaluating severity of severe TBI.

Myeloid Dysregulation in a Human Induced Pluripotent Stem Cell Model of PTPN11-Associated Juvenile Myelomonocytic Leukemia

Somatic PTPN11 mutations cause juvenile myelomonocytic leukemia (JMML). Germline PTPN11 defects cause Noonan syndrome (NS), and specific inherited mutations cause NS/JMML. Here, we report that hematopoietic cells differentiated from human induced pluripotent stem cells (hiPSCs) harboring NS/JMML-causing PTPN11 mutations recapitulated JMML features. hiPSC-derived NS/JMML myeloid cells exhibited increased signaling through STAT5 and upregulation of miR-223 and miR-15a. Similarly, miR-223 and miR-15a were upregulated in 11/19 JMML bone marrow mononuclear cells harboring PTPN11 mutations, but not those without PTPN11 defects. Reducing miR-223's function in NS/JMML hiPSCs normalized myelogenesis. MicroRNA target gene expression levels were reduced in hiPSC-derived myeloid cells as well as in JMML cells with PTPN11 mutations. Thus, studying an inherited human cancer syndrome with hiPSCs illuminated early oncogenesis prior to the accumulation of secondary genomic alterations, enabling us to discover microRNA dysregulation, establishing a genotype-phenotype association for JMML and providing therapeutic targets.

Management of Two Juvenile Myelomonocytic Leukemia Patients According to Clinical and Genetic Features

Juvenile myelomonocytic leukemia (JMML) is a rare clonal myeloproliferative disorder of childhood. Major progress has been achieved in diagnosis and the understanding of the pathogenesis of JMML by identifying the genetic pathologies that occur in patients. Mutations of RAS, NF1, PTPN11, and CBL are found in approximately 80% of JMML patients. Distinct clinical features have been reported to be associated with specific gene mutations. The advent of genomic studies and recent identification of novel genetic mutations in JMML are important not only in diagnosis but also in the management and prognosis of the disease. Herein, we present 2 patients with JMML harboring different mutations, NRAS and c-CBL, respectively, with distinct clinical features and different therapeutic approaches.

Biomarkers of Brain Damage and Postoperative Cognitive Disorders in Orthopedic Patients: An Update

The incidence of postoperative cognitive dysfunction (POCD) in orthopedic patients varies from 16% to 45%, although it can be as high as 72%. As a consequence, the hospitalization time of patients who developed POCD was longer, the outcome and quality of life were worsened, and prolonged medical and social assistance were necessary. In this review the short description of such biomarkers of brain damage as the S100B protein, NSE, GFAP, Tau protein, metalloproteinases, ubiquitin C terminal hydrolase, microtubule-associated protein, myelin basic protein, α-II spectrin breakdown products, and microRNA was made. The role of thromboembolic material in the development of cognitive decline was also discussed. Special attention was paid to optimization of surgical and anesthetic procedures in the prevention of postoperative cognitive decline.