TGF-beta1 induces bone marrow reticulin fibrosis in hairy cell leukemia

Role of transforming growth factor-beta in hematologic malignancies

The transforming growth factor-beta (TGF-beta) signaling pathway is an essential regulator of cellular processes, including proliferation, differentiation, migration, and cell survival. During hematopoiesis, the TGF-beta signaling pathway is a potent negative regulator of proliferation while stimulating differentiation and apoptosis when appropriate. In hematologic malignancies, including leukemias, myeloproliferative disorders, lymphomas, and multiple myeloma, resistance to these homeostatic effects of TGF-beta develops. Mechanisms for this resistance include mutation or deletion of members of the TGF-beta signaling pathway and disruption of the pathway by oncoproteins. These alterations define a tumor suppressor role for the TGF-beta pathway in human hematologic malignancies. On the other hand, elevated levels of TGF-beta can promote myelofibrosis and the pathogenesis of some hematologic malignancies through their effects on the stroma and immune system. Advances in the TGF-beta signaling field should enable targeting of the TGF-beta signaling pathway for the treatment of hematologic malignancies.

Therapeutic strategies against TGF-beta signaling pathway in hepatic fibrosis

Hepatic fibrosis is the common wound-healing response to chronic liver injury. In this process, activation of hepatic stellate cells is characteristic of cell proliferation and migration, production of collagen and other extracellular matrix (ECM) molecules, and contraction after transforming into myofibroblasts. It has been shown that the fibrogenic process is prominently regulated by transforming growth factor-beta1 (TGF-beta1) and that the specific blockade of TGF-beta1/Smad3 signaling may therapeutically intervene the fibrosis of various tissues. In this review, we attempt to integrate recent advances in the understanding of the mechanisms underlying TGF-beta1/Smad3 pathway modulation of ECM gene expression in the context of liver fibrosis, discuss intervention strategies targeting the blockade of related signal pathways, and look into novel ways to the safe and efficacious prevention and treatment of hepatic fibrosis.

Pathogenesis of myelofibrosis with myeloid metaplasia

The primary disease process in myelofibrosis with myeloid metaplasia (MMM) is clonal myeloproliferation with varying degrees of phenotypic differentiation. This is characteristically accompanied by secondary intramedullary collagen fibrosis, osteosclerosis, angiogenesis, and extramedullary hematopoiesis. Modern clonality studies have confirmed the multipotent stem-cell origin of the neoplastic process in MMM. The nature of the specific oncogenic mutation(s) is currently being unraveled with the recent discovery of an association between a somatic point mutation of JAK2 tyrosine kinase (V617F) and bcr/abl-negative myeloproliferative disorders, including MMM. The pathogenetic mechanisms that underlie the secondary bone marrow stromal changes in MMM are also incompletely understood. Mouse models of this latter disease aspect have been constructed by either in vivo overexpression of thrombopoietin (TPOhigh mice) or megakaryocyte lineage restricted underexpression of the transcription factor GATA-1 (GATA-1low mice). Gene knockout experiments using such animal models have suggested the essential role of hematopoietic cell-derived transforming growth factor beta1 in inducing bone marrow fibrosis and stromal cell-derived osteoprotegerin in promoting osteosclerosis. However, experimental myelofibrosis in mice does not recapitulate clonal myeloproliferation that is fundamental to human MMM. Other cytokines that are implicated in mediating myelofibrosis and angiogenesis in MMM include basic fibroblast, platelet-derived, and vascular endothelial growth factors. It is currently assumed that such cytokines are abnormally released from clonal megakaryocytes as a result of a pathologic interaction with neutrophils (eg, emperipolesis). This latter phenomenon, through neutrophil-derived elastase, could also underlie the abnormal peripheral-blood egress of myeloid progenitors in MMM.

Immunohistochemistry in bone marrow pathology: a useful adjunct for morphologic diagnosis

Pathomorphological examination of trephine biopsies of the bone marrow (BM) represents a standard method for the diagnosis and staging of hematologic neoplasms and other disorders involving the BM. The increasing knowledge about the genetic basis and biology of hematologic neoplasms, as well as the recently proposed WHO classification system, provide the framework for an accurate diagnosis. Although conventional morphology remains the gold standard for paraffin-embedded BM trephines, immunohistochemical stainings have become an integral part of the diagnostic workup. Antibodies suitable for paraffin sections are generally applicable to BM trephines, but modifications of staining protocols may be necessary due to the alternative fixatives and decalcification procedures used for BM biopsies. The indications for immunostainings range from confirmation and classification of lymphoma involvement, subclassification of acute leukemias, and estimating blast counts in myelodysplastic and myeloproliferative syndromes to characterization of BM involvement in nonhematologic neoplasms. Although subtyping of NHL in the BM is more difficult from the point of morphology, classification of the entities that frequently involve the BM, especially the small B-cell lymphomas, can easily be achieved with the help of immunohistochemistry. In this review, we try to summarize the current state of the art in BM immunohistochemistry for the diagnosis of hematologic disorders. Moreover, diagnostic algorithms and useful antibody panels are proposed for a rational and cost-effective approach.

bcr/abl-negative, classic myeloproliferative disorders: diagnosis and treatment

Essential thrombocythemia, polycythemia vera, and myelofibrosis with myeloid metaplasia constitute the "classic" bcr/abl-negative myeloproliferative disorders (MPDs). Each of these MPDs represents a stem cell-derived clonal myeloproliferation with the respective features of thrombocytosis, erythrocytosis, and bone marrow fibrosis. Unlike with cases of chronic myeloid leukemia, in which the bcr/abl mutation is invariably detected, current diagnosis of essential thrombocythemia, polycythemia vera, and myelofibrosis with myeloid metaplasia is based on a consensus-driven set of clinical and laboratory criteria that have undergone substantial modification in recent times. The recent discovery of a recurrent activating Janus tyrosine kinase (JAK2) mutation (JAK2VG17F) in all 3 classic MPDs offers another opportunity for refining current diagnoses and disease classifications. In this article, we outline contemporary diagnostic algorithms for each of these disorders and provide an evidence-based approach to management.

Hairy cell leukemia (HCL) with extensive myelofibrosis responds to thalidomide

We present a 75-year-old man who was admitted to our hospital because of splenomegaly, transfusion-dependent anemia and thrombocytopenia. The diagnosis of idiopathic myelofibrosis was suggested by the bone marrow trephine biopsy, which was hypocellular with myelofibrosis. Thalidomide was started at a daily dose of 100 mg/d and increased to 400 mg/d. Within 12 weeks, thrombocytes increased to 100.000/microl, hemoglobin normalized, lasting for about 11 months. Then, thalidomide had to be discontinued because of mild polyneuropathy. A second bone marrow biopsy showed fibrosis as well as a diffuse infiltration of the bone marrow (80%) by lymphocytes with expression of CD11c, CD19, CD20, CD103. Tartrate resistant acid phosphatase test (TRAP) was also positive. Hairy cell leukemia was diagnosed and he was administered 2-chlorodeoxyadenosine (2-CDA) achieving a complete remission.