Myelopoiesis and myeloproliferative disorders

Correlation of viral load with bone marrow and hematological changes in pale patients with chronic hepatitis C virus

Liver is considered the target of hepatitis C virus (HCV), which has marked tropism for hepatocytes. In this study, we investigated changes in bone marrow (BM) and blood and their correlation with viremia level in 30 pale patients with chronic HCV who were selected before antiviral therapy. Patients with BM positive for HCV RNA (53.33 %) showed moderate to high viremia, while patients with BM negative for RNA (46.67 %) had low viremia. There was no significant difference in the liver histopathology between patients with HCV-RNA-negative and positive BM. Patients with BM positive for HCV RNA showed significant changes in BM cells, including the degree of immune complex deposition and alterations in peripheral blood counts compared to patients with BM negative for RNA and healthy controls, suggesting that BM changes could be a sequel or a reservoir for HCV viremia.

X-Chromosome Inactivation Pattern Analysis for the Assessment of Cell Clonality in Cats

X-chromosome inactivation pattern (XCIP) analysis has been widely used to assess cell clonality in various types of neoplasms in humans. In the present study, a polymerase chain reaction–based feline XCIP analysis using the feline androgen receptor gene was developed. To construct the system of the analysis, polymorphism in CAG tandem repeats within the feline androgen receptor gene was explored using somatic DNAs from 50 male and 103 female cats. CAG tandem repeats in exon 1 of the feline androgen receptor gene were found to be polymorphic, containing 15 to 22 CAG repeats. Of the 103 female cats, 70 (68%) were heterozygous for the number of CAG repeats, indicating the possible usefulness of XCIP analysis in cats. Application of the feline XCIP analysis to 3 feline mammary gland adenocarcinoma cell lines revealed distinctly skewed XCIPs in these cell lines, indicating their clonal origins. Twelve (80%) of the 15 primary tissue/cell samples obtained from cats with various neoplastic diseases showed skewed XCIPs. Moreover, bone marrow samples from 3 cats with myelodysplastic syndrome were also found to have skewed XCIPs. The polymerase chain reaction–based XCIP analysis developed in this study can provide information on cell clonality in female cats, potentially facilitating the differential diagnosis of various disorders in cats.

Hematopoietic cytokine-induced transcriptional regulation and Notch signaling as modulators of MDSC expansion

Hematopoietic stem cells (HSCs) differentiate into mature lineage restricted blood cells under the influence of a complex network of hematopoietic cytokines, cytokine-mediated transcriptional regulators, and manifold intercellular signaling pathways. The classical model of hematopoiesis proposes that progenitor cells undergo a dichotomous branching into myelo-erythroid and lymphoid lineages. Nonetheless, erythroid and lymphoid restricted progenitors retain their myeloid potential, supporting the existence of an alternative 'myeloid-based' mechanism of hematopoiesis. In this case, abnormal pathology is capable of dysregulating hematopoiesis in favor of myelopoiesis. The accumulation of immature CD11b+Gr-1+ myeloid-derived suppressor cells (MDSCs) has been shown to correlate with the presence of several hematopoietic cytokines, transcription factors and signaling pathways, lending support to this hypothesis. Although the negative role of MDSCs in cancer development is firmly established, it is now understood that MDSCs can exert a paradoxical, positive effect on transplantation, autoimmunity, and sepsis. Our conflicted understanding of MDSC function and the complexity of hematopoietic cytokine signaling underscores the need to elucidate molecular pathways of MDSC expansion for the development of novel MDSC-based therapeutics.

Prognostic markers for myeloid neoplasms: a comparative review of the literature and goals for future investigation

Myeloid neoplasms include cancers associated with both rapid (acute myeloid leukemias) and gradual (myelodysplastic syndromes and myeloproliferative neoplasms) disease progression. Percentage of blast cells in marrow is used to separate acute (rapid) from chronic (gradual) and is the most consistently applied prognostic marker in veterinary medicine. However, since there is marked variation in tumor progression within groups, there is a need for more complex schemes to stratify animals into specific risk groups. In people with acute myeloid leukemia (AML), pretreatment karyotyping and molecular genetic analysis have greater utility as prognostic markers than morphologic and immunologic phenotypes. Karyotyping is not available as a prognostic marker for AML in dogs and cats, but progress in molecular genetics has created optimism about the eventual ability of veterinarians to discern conditions potentially responsive to medical intervention. In people with myelodysplastic syndromes (MDS), detailed prognostic scoring systems have been devised that use various combinations of blast cell percentage, hematocrit, platelet counts, unilineal versus multilineal cytopenias and dysplasia, karyotype, gender, age, immunophenotype, transfusion dependence, and colony-forming assays. Predictors of outcome for animals with MDS have been limited to blast cell percentage, anemia versus multilineal cytopenias, and morphologic phenotype. Prognostic markers for myeloproliferative neoplasms (eg, polycythemia vera, essential thrombocythemia) include clinical and hematological factors and in people also include cytogenetics and molecular genetics. Validation of prognostic markers for myeloid neoplasms in animals has been thwarted by the lack of a large case series that requires cooperation across institutions and veterinary specialties. Future progress requires overcoming these barriers.

Myelodysplastic syndromes and acute myeloid leukemia in cats infected with feline leukemia virus clone33 containing a unique long terminal repeat

Feline leukemia virus (FeLV) clone33 was obtained from a domestic cat with acute myeloid leukemia (AML). The long terminal repeat (LTR) of this virus, like the LTRs present in FeLV from other cats with AML, differs from the LTRs of other known FeLV in that it has 3 tandem direct 47-bp repeats in the upstream region of the enhancer (URE). Here, we injected cats with FeLV clone33 and found 41% developed myelodysplastic syndromes (MDS) characterized by peripheral blood cytopenias and dysplastic changes in the bone marrow. Some of the cats with MDS eventually developed AML. The bone marrow of the majority of cats with FeLV clone33 induced MDS produced fewer erythroid and myeloid colonies upon being cultured with erythropoietin or granulocyte-macrophage colony-stimulating factor (GM-SCF) than bone marrow from normal control cats. Furthermore, the bone marrow of some of the cats expressed high-levels of the apoptosis-related genes TNF-alpha and survivin. Analysis of the proviral sequences obtained from 13 cats with naturally occurring MDS reveal they also bear the characteristic URE repeats seen in the LTR of FeLV clone33 and other proviruses from cats with AML. Deletions and mutations within the enhancer elements are frequently observed in naturally occurring MDS as well as AML. These results suggest that FeLV variants that bear URE repeats in their LTR strongly associate with the induction of both MDS and AML in cats.

A dog with myelodysplastic syndrome: chronic myelomonocytic leukemia

An eleven-year-old female pug was referred to Yamaguchi University Animal Hospital for evaluation of anemia and thrombocytopenia. The cytological examination of the peripheral blood showed some giant monocytic lineage blast cells. A few granulocytes and platelets had dysplastic features. On day 7, in addition to increasing the monocytic lineage cells, the dysplastic features of the blood had also increased compared to the initial examination. We performed bone marrow aspiration upon her death. The bone marrow revealed dysplastic features in all three hematopoietic cell lines, and an increase in the monocytic cell line. Based on the features of the bone marrow and the peripheral blood, this case was confirmed to be myelodysplastic syndrome--Chronic myelomonocytic leukaemia (MDS-CMML).

Evaluation of dysmyelopoiesis in cats: 34 cases (1996–2005)

OBJECTIVE

To further classify dysmyelopoiesis as diagnosed by use of a general classification scheme and to determine clinical features and laboratory test results that could be used to differentiate between the various forms of dysmyelopoiesis in cats.

DESIGN

Retrospective case series. Sample Population-Bone marrow slides from 34 cats.

PROCEDURES

Medical records of cats in which dysmyelopoiesis was diagnosed on the basis of blood and bone marrow analyses from 1996 to 2005 were reviewed. Criteria for inclusion in the study were findings of > 10% dysplastic cells in 1 or more hematologic cell lines in the bone marrow and concurrent cytopenias in the blood. Cats that met these criteria were classified into subcategories of myelodysplastic syndromes or secondary dysmyelopoiesis on the basis of reevaluation of slides.

RESULTS

Of 189 bone marrow slides reviewed, 34 (14.9%) had > 10% dysplastic cells in 1 or more cell lines. Cats were subcategorized as having myelodysplastic syndrome with excessive numbers of blast cells (n = 13), myelodysplastic syndrome with refractory cytopenias (8), a variant form of myelodysplastic syndrome (1), and secondary dysmyelopoiesis (12). Findings of dysmyelopoiesis and autoagglutination in cats with myelodysplastic syndrome and in those with immune-mediated anemia complicated differentiating between the 2 conditions.

CONCLUSIONS AND CLINICAL RELEVANCE

Differentiating cats with myelodysplastic syndromes from cats with immune-mediated hemolytic anemia was difficult because severe anemia and autoagglutination may be concurrent findings in both conditions. Differentiating between myelodysplastic syndrome with excessive numbers of blast cells and myelodysplastic syndrome with refractory cytopenias was useful in predicting clinical outcome.

A cat with acute myeloblastic leukemia without maturation (M1) treated with combination chemotherapy

A 2-year-old domestic shorthair cat was presented to us with decreased activity and anorexia. Hematologic findings revealed a mild non-regenerative anemia, thrombocytopenia, and leukocytosis with an increase in blast cells. Bone marrow aspirates also revealed a marked increase of blasts. The blastic cells were shown to be positive for peroxidase. Acute myeloblastic leukemia without maturation (M1) was diagnosed according to the FAB classification. Chemotherapy was initiated with cyclophosphamide, vincristine, prednisolone, and cytosine arabinoside. The cat responded partially. In total, the cats were given 7 blood transfusions. The cat died 14 weeks after first being presented to us.

The kinetics of clonal dominance in myeloproliferative disorders

To study clonal evolution in myeloproliferative disorders, we used stochastic models of hematopoiesis for mouse and cat, species for which the in vivo kinetics of hematopoietic stem cells (HSCs) have been experimentally defined. We determined the consequence if 1 HSC became able to survive without the support of a microenvironmental niche while the rest of its behavior did not change. Neoplastic cells persisted and dominated hematopoiesis in 14% of mice and 17% of cats, requiring mean times of 2.5 +/- 0.5 and 7.0 +/- 1.2 years, respectively (n=1000 simulations/species). In both species, when the number of neoplastic HSCs exceeded 0.5% of all HSCs, clonal dominance was inevitable. Our results can explain the absence of clonal myeloproliferative disorders in mice (lifetime, 2 years), are consistent with clinical observations in cats, and provide insight into the progression of chronic myelogenous leukemia (CML) in humans. They also demonstrate that competition for microenvironmental support can lead to the suppression of normal hematopoiesis as neoplasia evolves. Toxic or immunologic suppression of normal HSCs is not required.

New insights into the physiology and treatment of acquired myelodysplastic syndromes and aplastic pancytopenia

MDS are a diverse group of primary and secondary bone marrow disorders that are characterized by cytopenias in blood, prominent dysplastic features in blood or bone marrow, and normal or hypercellular bone marrow. MDS in cats are typically associated with FeLV infection. Dogs with MDS-RC and MDS-Er seem to respond to erythropoietin administration and have prolonged survival. Dogs with MDS-EB respond poorly to present treatments, and survival is short. Prognosis and probability of progression to acute myelogenous leukemia can be predicted based on the percentage of myeloblasts in bone marrow. Several experimental therapeutic modalities in human beings have been described that may be useful in treating MDS-EB in dogs and cats. Aplastic pancytopenia is a relatively rare disorder in dogs and cats. Causes include Ehrlichia spp, Parvovirus, and FeLV infections; sepsis; chronic renal failure; drug and toxin exposure; and idiopathic causes. Diagnosis is based on identification of multiple cytopenias in the blood and hypoplastic/aplastic bone marrow, with the marrow space replaced by adipose tissue. Treatment and outcome are dependent on determining the underlying cause of the bone marrow failure.

Myelodysplasia: differentiating neoplastic from nonneoplastic syndromes of ineffective hematopoiesis in dogs

In the context of human hematopathology, the terms myelodysplasia and Myelodysplastic Syndromes (MDS) are applied to disorders of hematopoiesis that are clonal, neoplastic, and, in most forms, manifested as ineffective hematopoiesis with characteristic morphologic abnormalities in multiple cell lines. Studies of human patients have provided the conceptual framework that MDS evolve from a multipotential hematopoietic stem cell (CFU-GEMM) that has undergone neoplastic transformation as the result of acquired genetic mutations. The diagnosis of MDS in human patients is based largely on morphologic examination of marrow but can be confirmed by detection of cytogenetic abnormalities. Spontaneous, neoplastic myelodysplasia occurs in dogs, but rarely. Nonneoplastic syndromes of ineffective hematopoiesis are more common in dogs, can resemble MDS, and are probably immune mediated in many cases. Drugs and their metabolites are potential causes of dysmorphic maturation and ineffective hematopoiesis. Without methods to confirm clonality by cytogenetic analysis, the diagnosis of neoplastic myelodysplasia in dogs is based onlight microscopic examination of bone marrow smears. This paper discusses and illustrates the characteristic morphologic and cytochemical features of neoplastic myelodysplasia and nonneoplastic ineffective hematopoiesis in dogs.

Cytology of bone marrow

Cytologic examination of bone marrow aspirates can provide a wealth of diagnostic information. Practitioners should not hesitate to perform bone marrow aspirates when indicated. This article is designed to assist the practitioner in the evaluation of bone marrow aspiration biopsies. The indications for marrow evaluation, methods of sample collection, sample preparation, and cytologic examination of bone marrow are discussed. Cases are provided to demonstrate accurate interpretation of bone marrow aspirates.

Bethesda proposals for classification of nonlymphoid hematopoietic neoplasms in mice

The hematopathology subcommittee of the Mouse Models of Human Cancers Consortium recognized the need for a classification of murine hematopoietic neoplasms that would allow investigators to diagnose lesions as well-defined entities according to accepted criteria. Pathologists and investigators worked cooperatively to develop proposals for the classification of lymphoid and nonlymphoid hematopoietic neoplasms. It is proposed here that nonlymphoid hematopoietic neoplasms of mice be classified in 4 broad categories: nonlymphoid leukemias, nonlymphoid hematopoietic sarcomas, myeloid dysplasias, and myeloid proliferations (nonreactive). Criteria for diagnosis and subclassification of these lesions include peripheral blood findings, cytologic features of hematopoietic tissues, histopathology, immunophenotyping, genetic features, and clinical course. Differences between murine and human lesions are reflected in the terminology and methods used for classification. This classification will be of particular value to investigators seeking to develop, use, and communicate about mouse models of human hematopoietic neoplasms.

Cytologic evaluation of primary and secondary myelodysplastic syndromes in the dog

Myelodysplastic syndromes are a heterogeneous group of acquired primary and secondary alterations of hematopoietic stem cells that result in cytopenias in blood and cytologic features of dysplasia in blood and/or bone marrow. To better understand the cytologic features that would permit differentiation of primary and secondary forms of myelodysplasia, we reviewed 267 consecutive bone marrow reports from dogs. These reports indicated that 34 dogs (12.7%) had dysgranulopoiesis, dyserythropoiesis, and/or dysthrombopoiesis in >10% of granulopoietic cells, erythroid cells, and/or megakaryocytes, respectively. Thirteen dogs had primary myelodysplastic syndromes, and 21 had secondary myelodysplastic syndromes. Of the 13 dogs with primary myelodysplasia, 4 were subclassified as myelodysplastic syndrome with refractory anemia (MDS-RA), and 9 were subclassified as myelodysplastic syndrome with excess blasts (MDS-EB). Secondary conditions associated with dysplasia in the bone marrow included malignant lymphoma (n = 5), myelofibrosis (n = 3), immune-mediated thrombocytopenia (n = 4), immune-mediated hemolytic anemia (n = 5), multiple myeloma with melphalan administration (n = 1), pyometra with estrogen administration (n = 1), polycythemia vera (n = 1), and thrombopathia (n = 1). MDS-RA was characterized by <5% myeloblasts in bone marrow, normal granulocyte maturation ratio, increased erythroid maturation ratio, and dysplastic changes in >15% of erythroid cells. MSD-EB was characterized by >/=5% myeloblasts in bone marrow, high granulocyte maturation and erythroid maturation ratios, >/=32% dysplastic granulocytes, and the presence of small atypical immature myeloid cells. Secondary myelodysplastic syndromes were characterized by <5% myeloblasts in bone marrow, variable granulocyte maturation and erythroid maturation ratios, and variable dysplastic features. These results indicate that morphology alone cannot be used to distinguish primary and secondary myelodysplastic syndromes in dogs.

Neutrophilic leucocytosis in a dog with a rectal tumour

A nine-year-old cocker spaniel was presented with a three-year history of intermittent haematochezia and a palpable rectal mass. Routine haematological examination revealed a marked mature neutrophilia (86.04 x 10(9) neutrophils/litre). A friable mass in the middle portion of the rectum was detected on colonoscopy. Histopathological examination of mucosal pinch biopsies collected from the mass confirmed a diagnosis of adenomatous tubulopapillary polyp. Some evidence of malignant transformation was observed. Palliative treatment with piroxicam suppositories at a dose of 1.4 mg/kg administered rectally every third day was instituted. On re-evaluation, 47 days after starting medical therapy, the owner reported a significant reduction in haematochezia and tenesmus; however, frequency of defecation had remained unaltered. Routine haematology revealed a reduction in the mature neutrophil count (33.67 x 10(9) neutrophils/litre). This report describes a case of a rectal tumour associated with a neutrophilic leucocytosis, which responded to palliative therapy with piroxicam suppositories.