Determining Acute Leukemia Lineage Using Mie Map Red Blood Cell

The determination of myeloid and lymphoid lineage is essential for the diagnosis and therapy of acute leukemia. Immunophenotyping is the gold standard to determine the lineage of acute leukemia, but it is still constrained and relatively expensive. Mie Map RBC in the ADVIA 2120i is a parameter that can give additional information about myeloid and lymphoid lineage but has never been studied before. It is expected that Mie Map RBC can be used to differentiate the lineage of acute myeloid and lymphoid leukemia if immunophenotyping is not present. This study aimed to analyze the diagnostic value of Mie Map RBC with ADVIA 2120i towards immunophenotyping in determining myeloid and lymphoid lineage in acute leukemia. Child and adult patients diagnosed with acute leukemia (n=30) that had peripheral blood smear and bone marrow aspiration with blasts > 20% were examined using ADVIA 2120i. The Mie Map RBC lineage results were compared to the lineage of immunophenotyping. The sensitivity and specificity of the Mie Map RBC myeloid series are respectively 60.00%, 93.33%. The sensitivity and specificity of the Mie Map RBC lymphoid series are respectively 93.33% and 60.00%. The diagnostic accuracy value of Mie Map RBC is 76.67%. The determination of acute leukemia myeloid series lineage has high specificity. If there is no population outside the matrix of Mie Map RBC, it highly suggests myeloid series. On the other hand, the determination of acute leukemia lymphoid series lineage has a relatively low specificity meaning that the population outside the matrix of Mie Map RBC does not always suggest a lymphoid lineage

Microbiota Signals Suppress B Lymphopoiesis With Aging in Mice

Aging is associated with significant changes in hematopoiesis that include a shift from lymphopoiesis to myelopoiesis and an expansion of phenotypic hematopoietic stem cells (HSCs) with impaired self-renewal capacity and myeloid-skewed lineage differentiation. Signals from commensal flora support basal myelopoiesis in young mice; however, their contribution to hematopoietic aging is largely unknown. Here, we characterize hematopoiesis in young and middle-aged mice housed under specific pathogen free (SPF) and germ-free (GF) conditions. The marked shift from lymphopoiesis to myelopoiesis that develops during aging of SPF mice is mostly abrogated in GF mice. Compared with aged SPF mice, there is a marked expansion of B lymphopoiesis in aged GF mice, which is evident at the earliest stages of B cell development. The expansion of phenotypic and functional HSCs that occurs with aging is similar in SPF and GF mice. However, HSCs from young GF mice have increased lymphoid lineage output, and the aging-associated expansion of myeloid-biased HSCs is significantly attenuated in GF mice. Consistent with these data, RNA expression profiling of phenotypic HSCs from aged GF mice show enrichment for non-myeloid biased HSCs. Surprisingly, the RNA expression profiling data also suggest that inflammatory signaling is increased in aged GF HSCs compared with aged SPF HSCs. Collectively, these data suggest that microbiota-related signals suppress B lymphopoiesis at multiple stages of development and contribute to the expansion of myeloid-biased HSCs that occurs with aging.

Lineage Plasticity in Cancer: The Tale of a Skin-Walker

Lineage plasticity, the switching of cells from one lineage to another, has been recognized as a cardinal property essential for embryonic development, tissue repair and homeostasis. However, such a highly regulated process goes awry when cancer cells exploit this inherent ability to their advantage, resulting in tumorigenesis, relapse, metastasis and therapy resistance. In this review, we summarize our current understanding on the role of lineage plasticity in tumor progression and therapeutic resistance in multiple cancers. Lineage plasticity can be triggered by treatment itself and is reported across various solid as well as liquid tumors. Here, we focus on the importance of lineage switching in tumor progression and therapeutic resistance of solid tumors such as the prostate, lung, hepatocellular and colorectal carcinoma and the myeloid and lymphoid lineage switch observed in leukemias. Besides this, we also discuss the role of epithelial-mesenchymal transition (EMT) in facilitating the lineage switch in biphasic cancers such as aggressive carcinosarcomas. We also discuss the mechanisms involved, current therapeutic approaches and challenges that lie ahead in taming the scourge of lineage plasticity in cancer.

Epigenetic regulator genes direct lineage switching in MLL-AF4 leukaemia

The fusion gene MLL-AF4 defines a high-risk subtype of pro-B acute lymphoblastic leukaemia. However, relapse can be associated with a switch from acute lymphoblastic to acute myeloid leukaemia. Here we show that these myeloid relapses share oncogene fusion breakpoints with their matched lymphoid presentations and can originate in either early, multipotent progenitors or committed B-cell precursors. Lineage switching is linked to substantial changes in chromatin accessibility and rewiring of transcriptional programmes indicating that the execution and maintenance of lymphoid lineage differentiation is impaired. We show that this subversion is recurrently associated with the dysregulation of repressive chromatin modifiers, notably the nucleosome remodelling and deacetylation complex, NuRD. In addition to mutations, we show differential expression or alternative splicing of NuRD members and other genes is able to reprogram the B lymphoid into a myeloid gene regulatory network. Lineage switching in MLL-AF4 leukaemia is therefore driven and maintained by defunct epigenetic regulation.

Telomere transcription in MLL-rearranged acute leukemia: increased levels of TERRA associate with lymphoid lineage and are independent of telomere length and ploidy

Telomere transcription into telomeric repeat-containing RNA (TERRA) is an integral component of all aspects of chromosome end protection consisting of telomerase- or recombination-dependent telomere elongation, telomere capping, and preservation of (sub)telomeric heterochromatin structure. The chromatin modifier and transcriptional regulator MLL associates with telomeres and regulates TERRA transcription in telomere length homeostasis and response to telomere dysfunction. MLL fusion proteins (MLL-FPs), the product of MLL rearrangements in leukemia, also associate with telomeric chromatin. However, an effect on telomere transcription in MLL-rearranged (MLL-r) leukemia has not yet been evaluated. Here, we show increased UUAGGG repeat-containing RNA levels in MLL-r acute lymphoblastic leukemia (ALL). MLL rearrangements do not affect telomere length and increased levels of UUAGGG repeat-containing RNA correlate with mean telomere length and reflect increased levels of TERRA. Also, increased levels of TERRA in MLL-r ALL occur in the presence of telomerase activity and are independent of ploidy, an underestimated source of variation on the overall transcriptome size in a cell. This MLL rearrangement-dependent and lymphoid lineage-associated increase in levels of TERRA supports a sustained telomere transcription by MLL-FPs that correlates with marked genomic stability previously reported in pediatric MLL-r ALL.

Lineage Plasticity in Cancer: The Tale of a Skin-walker

Lineage plasticity, the switching of cells from one lineage to another has been recognized to be a cardinal property essential for embryonic development, tissue repair and homeostasis. However, such a highly regulated process goes awry when cancer cells exploit this inherent ability to their advantage, resulting in tumorigenesis, relapse, metastasis and therapy resistance. In this review, we summarize our current understanding on the role of lineage plasticity in tumor progression and therapeutic resistance in multiple cancers. Lineage plasticity can be triggered by treatment itself and is reported across various solid as well as liquid tumors. Here we focus on the importance of lineage switching in tumor progression and therapeutic resistance of solid tumors such as the prostate, lung, hepatocellular and colorectal carcinoma and the myeloid and lymphoid lineage switch observed in leukemias. Besides this, we also discuss the role of Epithelial-Mesenchymal Transition (EMT) in facilitating the lineage switch in biphasic cancers such as aggressive carcinosarcomas. We also discuss the mechanisms involved, current therapeutic approaches and challenges that lie ahead in taming the scourge of lineage plasticity in cancer.

Mouse multipotent progenitor 5 cells are located at the interphase between hematopoietic stem and progenitor cells

Hematopoietic stem cells (HSCs) and distinct multipotent progenitor populations (MPP1-4) contained within the Lin- Sca-1+ c-Kit+ (LSK) compartment have previously been identified using diverse surface marker panels. Here, we phenotypically define and functionally characterize MPP5 (LSK CD34+ CD135- CD48- CD150-). Upon transplantation, MPP5 support initial emergency myelopoiesis followed by stable contribution to the lymphoid lineage. Since MPP5 are capable of generating MPP1-4, but not HSCs, they represent a dynamic and versatile component of the MPP network. To characterize all hematopoietic stem and progenitor cells (HSPCs), we performed RNA-seq analysis to identify specific transcriptomic landscapes of HSCs and MPP1-5. This was complemented by single-cell (sc) RNA-seq analysis of LSK cells to establish the differentiation trajectories from HSCs to MPP1-5. In agreement with the functional reconstitution activity, MPP5 are located immediately downstream of HSCs but upstream of the more committed MPP2-4. This study provides a comprehensive analysis of the LSK compartment, focusing on the functional and molecular characteristics of the newly defined MPP5 subset.

An in vivo screen of noncoding loci reveals that Daedalus is a gatekeeper of an Ikaros-dependent checkpoint during haematopoiesis

Haematopoiesis relies on tightly controlled gene expression patterns as development proceeds through a series of progenitors. While the regulation of hematopoietic development has been well studied, the role of noncoding elements in this critical process is a developing field. In particular, the discovery of new regulators of lymphopoiesis could have important implications for our understanding of the adaptive immune system and disease. Here we elucidate how a noncoding element is capable of regulating a broadly expressed transcription factor, Ikaros, in a lymphoid lineage-specific manner, such that it imbues Ikaros with the ability to specify the lymphoid lineage over alternate fates. Deletion of the Daedalus locus, which is proximal to Ikaros, led to a severe reduction in early lymphoid progenitors, exerting control over the earliest fate decisions during lymphoid lineage commitment. Daedalus locus deletion led to alterations in Ikaros isoform expression and a significant reduction in Ikaros protein. The Daedalus locus may function through direct DNA interaction as Hi-C analysis demonstrated an interaction between the two loci. Finally, we identify an Ikaros-regulated erythroid-lymphoid checkpoint that is governed by Daedalus in a lymphoid-lineage–specific manner. Daedalus appears to act as a gatekeeper of Ikaros’s broad lineage-specifying functions, selectively stabilizing Ikaros activity in the lymphoid lineage and permitting diversion to the erythroid fate in its absence. These findings represent a key illustration of how a transcription factor with broad lineage expression must work in concert with noncoding elements to orchestrate hematopoietic lineage commitment.

Progressive Histiocytosis of Non-Epitheliotropic Dendritic Cells in a Feline

Background: Histiocytic tumors in felines are nodules that commonly develop on limbs and head extremities. They can be divided into many subtypes including cutaneous histiocytoma, histiocytic sarcoma, reactive fibrohistiocytic nodule, Langerhans cell histiocytosis, and progressive feline dendritic cell. Despite the same origin, they have behaviors that differ from each other, thus it is important to confirm diagnosis with histopathological and immunohistochemical tests, because early identification can facilitate prognosis and treatment. In this study, we describe the pathological and immunohistochemical characteristics, enabling differentiation feline neoplasms derived from histiocytes. Case: A 5-year-old, crossbreed, male, feline presented with a nodulation at the base of the left ear. The mass was slow growing, partially alopecic, with no other changes associated with tumor development. The nodule was round and circumscribed, movable, with an elevated surface. He was referred for surgery and an elliptical sample around the tumor was carefully dissected. Routine histopathological evaluation was performed with hematoxylin and eosin (HE), as well as immunohistochemistry. Histopathology showed circumscribed proliferation of histiocytic cells, with abundant and eosinophilic cytoplasm. The proliferative cells were large and rounded, extending from the superficial dermis and basement membrane to the deep dermis. At the extremities, some cells had visible vacuoles. Mitotic activity ranged from 3 to 4 mitoses per field in 40x magnification. Immunohistochemistry showed positive staining for histocompatibility complex MCII and lysozyme antibodies, marking histiocytic cells. Labeling was positive for CD20 in cells of lymphoid lineage B and negative for E-cadherin. Histiocytic cells did not invade the epidermis; hence, proliferation was classified as nonepitheliotropic. These methods contribute to the literature regarding the diagnosis of this rare tumor. Therefore, histological as well as immunohistochemical evaluation are important bfor confirming clinical diagnosis of histiocytic proliferation non-epitheliotropic. Discussion: Progressive histiocytosis of feline dendritic cells, in both epitheliotropic and non-epitheliotropic forms, is considered a clinically progressive and rare disorder. There are reports which include cytological, clinical, histological and immunohistochemical examinations, but the diagnostic characteristics regarding the non-epitheliotropic classification have not yet been properly identified. Nodulations are predominantly observed in head and limb regions, usually non-ulcerated, which can both increase and decrease in size, and are typically painless. The tumor in the present case was restricted to the base of the ear and no evidence of infiltration or metastasis was found. Progressive histiocytosis may spread and reach the lymphatic system through the lymph nodes, subsequently becoming systemic. The non-aggressive behavior observed in this case is possibly related to the non-epitheliotropic pattern. In the present case, MHC II histocompatibility complex markers, a phenotype compatible with dendritic cells, were used. Lysozyme antibodies marked histiocytic cells and the reactive lymphoid infiltrate was composed of CD20-positive B lymphoid lineage cells. Staining for E-cadherin was negative, negative results in labeling experiments is common, it is dependent upon the cellular origin of the leukocytes present in the sample. Staining for these molecules is recommended for differentiating feline progressive histiocytosis from Langerhans cells. Langerhans cells can be characterized by E-cadherin expression in about 10% of cases and marked T lymphocyte and neutrophil expression in the affected tissue. In this case, the histopathological exam along with immunohistochemistry was essential for differentiating them.