Transcriptome Analysis of Monozygotic Twin Brothers with Childhood Primary Myelofibrosis

Deepening Our Understanding of the Factors Affecting Landscape of Myeloproliferative Neoplasms: What Do We Know about Them?

Myeloproliferative neoplasms (MPNs) arise from the uncontrolled proliferation of hematopoietic stem and progenitor cells in bone marrow. As with all tumors, the development of MPNs is a consequence of alterations in malignant cells and their interaction with other extrinsic factors that support and promote tumor progression. Since the discovery of driver mutations, much work has focused on studying and reviewing the genomic features of the disease but has neglected to delve into the important role that many other mechanisms may play. This review discusses the genetic component of MPNs but focuses mainly on some of the most relevant work investigating other non-genetic factors that may be crucial for the disease. The studies summarized here address MPN cell-intrinsic or -extrinsic factors and the interaction between them through transcriptomic, proteomic and microbiota studies, among others.

Definition, Epidemiology, Pathophysiology, and Essential Criteria for Diagnosis of Pediatric Chronic Myeloid Leukemia

Simple Summary

The low incidence (1:1,000,000) of chronic myeloid leukemia (CML) in the first two decades of life presents an obstacle to accumulation of pediatric experience and knowledge on this leukemia. Biological features of CML are shared but also differing between adult and pediatric patients. This review aims; (i) to define the disease based on an unified terminology, (ii) to list the diseases to be considered as a differential diagnosis in children, (iii) to outlines the morphological, histopathological and immuno-phenotypical findings of pediatric CML, (iv) to illustrate rare but classical complications resulting from high white cell and platelet counts at diagnosis, and (v) to recommend a uniform approach for the diagnostic procedures to be applied. Evidently, only a clear detailed picture of all relevant features can lay the basis for standardized treatment approaches.

Abstract

Depending on the analytical tool applied, the hallmarks of chronic myeloid leukemia (CML) are the Philadelphia Chromosome and the resulting mRNA fusion transcript BCR-ABL1. With an incidence of 1 per 1 million of children this malignancy is very rare in the first 20 years of life. This article aims to; (i) define the disease based on the WHO nomenclature, the appropriate ICD 11 code and to unify the terminology, (ii) delineate features of epidemiology, etiology, and pathophysiology that are shared, but also differing between adult and pediatric patients with CML, (iii) give a short summary on the diseases to be considered as a differential diagnosis of pediatric CML, (iv) to describe the morphological, histopathological and immunophenotypical findings of CML in pediatric patients, (v) illustrate rare but classical complications resulting from rheological problems observed at diagnosis, (vi) list essential and desirable diagnostic criteria, which hopefully in the future will help to unify the attempts when approaching this rare pediatric malignancy.

Pervasive Inter-Individual Variation in Allele-Specific Expression in Monozygotic Twins

Despite being developed from one zygote, heterokaryotypic monozygotic (MZ) co-twins exhibit discordant karyotypes. Epigenomic studies in biological samples from heterokaryotypic MZ co-twins are of the most significant value for assessing the effects on gene- and allele-specific expression of an extranumerary chromosomal copy or structural chromosomal disparities in otherwise nearly identical germline genetic contributions. Here, we use RNA-Seq data from existing repositories to establish within-pair correlations for the breadth and magnitude of allele-specific expression (ASE) in heterokaryotypic MZ co-twins discordant for trisomy 21 and maternal 21q inheritance, as well as homokaryotypic co-twins. We show that there is a genome-wide disparity at ASE sites between the heterokaryotypic MZ co-twins. Although most of the disparity corresponds to changes in the magnitude of biallelic imbalance, ASE sites switching from either strictly monoallelic to biallelic imbalance or the reverse occur in few genes that are known or predicted to be imprinted, subject to X-chromosome inactivation or A-to-I(G) RNA edited. We also uncovered comparable ASE differences between homokaryotypic MZ twins. The extent of ASE discordance in MZ twins (2.7%) was about 10-fold lower than the expected between pairs of unrelated, non-twin males or females. The results indicate that the observed within-pair dissimilarities in breadth and magnitude of ASE sites in the heterokaryotypic MZ co-twins could not solely be attributable to the aneuploidy and the missing allelic heritability at 21q.

Lineage-negative lymphoma with a helper innate lymphoid cell phenotype

Helper innate lymphoid cells (ILCs) were recently recognized as lineage-negative lymphoid cells that do not express rearranged receptors and have important effector and regulatory functions in innate immunity. However, to our knowledge, no cases of hematological malignancies arising from helper ILCs have ever been reported in the literature. Here, we report a case of a 17-year-old man with multiple lymphadenopathy who was diagnosed with lineage-negative lymphoma that displayed a helper ILC phenotype. Histological examination showed large monomorphic atypical lymphoid cells with prominent nucleoli and abundant eosinophilic cytoplasms with scattered and patchy distributions. Large amounts of histiocytes and infiltrating lymphocytes were observed in the background. Immunostaining revealed positive LCA and CD79a expression but negative expression of all lineage markers. IG and TCR rearrangement analysis showed no clonal rearrangements. Tumor cells strongly expressed helper ILC phenotypic markers, such as CD127, IL-1R, GATA3, ST2, IL-17Rβ, and RANKL, and helper ILC-produced cytokines, such as IL-4 and GM-CSF. PD-L1/PD-L2-positive histiocytes and FOXP3-positive Tregs were observed in the tumor microenvironment. Flow cytometry of bone marrow at recurrence was positive for IL-1R and negative for T, B, NK, and myelogenous lineage markers. TP53 sequencing showed that exon 5 was replaced with an intergenic sequence of chromosome 21. Next-generation sequencing demonstrated a novel IGLV2-14/IGLL5 fusion and mutations or deletions of tumor suppressor genes, such as PTPRB, PPP2CB, and UPK1A. This tumor was very aggressive, resistant to chemotherapy, recurred with bone marrow involvement, and caused the death of the patient within 6 months. To our knowledge, this is the first report of a hematological malignancy potentially arising from helper ILCs. We propose negativity for lineage markers and positivity for CD127/IL-1R in combination with specific transcription factor expression as markers of this tumor. This finding represents a novel addition to the growing spectrum of hematological malignancies.