PubMed | Cancer and Blood Diseases Institute, Oklahoma Medical Research Foundation, Harvard University and University of Birmingham
Type: Journal Article | Journal: Blood | Year: 2016
Thrombin-mediated proteolysis is central to hemostatic function but also plays a prominent role in multiple disease processes. The proteolytic conversion of fII to -thrombin (fIIa) by the prothrombinase complex occurs through 2 parallel pathways: (1) the inactive intermediate, prethrombin; or (2) the proteolytically active intermediate, meizothrombin (fIIa(MZ)). FIIa(MZ) has distinct catalytic properties relative to fIIa, including diminished fibrinogen cleavage and increased protein C activation. Thus, fII activation may differentially influence hemostasis and disease depending on the pathway of activation. To determine the in vivo physiologic and pathologic consequences of restricting thrombin generation to fIIa(MZ), mutations were introduced into the endogenous fII gene, resulting in expression of prothrombin carrying 3 amino acid substitutions (R157A, R268A, and K281A) to limit activation events to yield only fIIa(MZ) Homozygous fII(MZ) mice are viable, express fII levels comparable with fII(WT) mice, and have reproductive success. Although in vitro studies revealed delayed generation of fIIa(MZ) enzyme activity, platelet aggregation by fII(MZ) is similar to fII(WT) Consistent with prior analyses of human fIIa(MZ), significant prolongation of clotting times was observed for fII(MZ) plasma. Adult fII(MZ) animals displayed significantly compromised hemostasis in tail bleeding assays, but did not demonstrate overt bleeding. More notably, fII(MZ) mice had 2 significant phenotypic advantages over fII(WT) animals: protection from occlusive thrombosis after arterial injury and markedly diminished metastatic potential in a setting of experimental tumor metastasis to the lung. Thus, these novel animals will provide a valuable tool to assess the role of both fIIa and fIIa(MZ) in vivo.
News Article | February 16, 2017
CINCINNATI - Genomic testing of biopsies from patients with deadly, treatment-resistant cancerous blood syndromes called histiocytoses allowed doctors to identify genes fueling the ailments and use targeted molecular drugs to successfully treat them. Researchers from the Cincinnati Children's Cancer and Blood Diseases Institute report their data in Journal of Clinical Investigation Insight (JCI Insight). They recommend the regular use of comprehensive genomic profiling at diagnosis to positively impact clinical care, as well as rigorous clinical trials to verify and extend the diagnostic and treatment conclusions in their study. Histiocytoses are a group of disorders in which abnormal accumulations of white blood cells form tumors on vital organs, leading to systemic organ damage or death. About half of the patients can be treated successfully with chemotherapy, but others are treatment resistant. Study authors conducted genomic profiling of biopsies from 72 child and adult patients with a variety of treatment-resistant histiocytoses, including the most common one in children, Langerhans cell histiocytosis (LCH), according to the lead investigator, Ashish Kumar, MD, PhD. Twenty-six patients with treatment-resistant disease had gene mutations involving either BRAF or MAP2K1 that directly activate the MAP-kinase cancer pathway. Researchers determined such patients would benefit from the targeted molecular therapies dabrafenib or trametinib, which block the MAP kinase pathway. The approved cancer drugs were prescribed off label to the histiocytosis patients. "In the last year, three patients we treated were infants with disease that was resistant to several rounds of intense chemotherapy. In the past, these children either would have suffered serious complications including death or would have had to endure more intensive treatments and the ensuing toxicities, including the risk of death," Kumar said. "All three are thriving now on one oral medication that put their disease into remission." In their JCI Insight paper, the researchers also offer detailed case summaries involving four histiocytosis patients between the ages of 9 months and 36 years. In one case a 22-month-old child was referred to Cincinnati Children's for treatment-resistant LCH that was complicated by a secondary diagnosis of HLH (hemophagocytic lymphohistiocytosis). HLH is a difficult-to-treat and often-fatal autoimmune disorder in which an overheated immune system causes uncontrolled inflammation and organ damage. The little girl, whose condition was worsening with organ failure, had a mutation in the BRAF gene. Two days after starting targeted treatment with oral dabrafenib (which blocks the MAP-kinase pathway) the little girl's fever disappeared and a week later her organ function returned to normal, according to study authors. For their JCI Insight research project, in addition to their own laboratory tests, study authors drew from data in previous research papers by a number of institutions, which examined genetic and molecular processes affecting white blood cell expansion in different types of histiocytosis. As Kumar and his colleagues continue their research, they plan to test methodologies that could expand the use of genomic profiling of patient biopsies and targeted molecular therapies in more patients with recurrent, treatment-resistant disease. "It's important for physicians and patients to know that LCH and other forms of histiocytosis are not that mysterious anymore," Kumar said. "We now have new treatments that dramatically improve outcomes for these patients." The JCI Insight study is a collaborative effort of investigators in several divisions at Cincinnati Children's, including first author and oncologist Lynn H. Lee, MD. Kumar is a member of the Division of Bone Marrow Transplant and Immune Deficiency and director of the Langerhans Cell Histiocytosis Center at Cincinnati Children's. Funding support for the research came from the National Heart, Lung, and Blood Institute (R01-HL111192) and the Leukemia and Lymphoma Society (TRP-6076-14).
He X.,University of Sichuan |
Zhang L.,Cancer and Blood Diseases Institute |
Chen Y.,Cancer and Blood Diseases Institute |
Chen Y.,Xiamen University |
And 26 more authors.
Nature Medicine | Year: 2014
Medulloblastoma, the most common malignant childhood brain tumor, exhibits distinct molecular subtypes and cellular origins. Genetic alterations driving medulloblastoma initiation and progression remain poorly understood. Herein, we identify GNAS, encoding the G protein Gα s, as a potent tumor suppressor gene that, when expressed at low levels, defines a subset of aggressive Sonic hedgehog (SHH)-driven human medulloblastomas. Ablation of the single Gnas gene in anatomically distinct progenitors in mice is sufficient to induce Shh-associated medulloblastomas, which recapitulate their human counterparts. Gαs is highly enriched at the primary cilium of granule neuron precursors and suppresses Shh signaling by regulating both the cAMP-dependent pathway and ciliary trafficking of Hedgehog pathway components. Elevation in levels of a G7alpha;s effector, cAMP, effectively inhibits tumor cell proliferation and progression in Gnas-ablated mice. Thus, our gain-and loss-of-function studies identify a previously unrecognized tumor suppressor function for Gαs that can be found consistently across Shh-group medulloblastomas of disparate cellular and anatomical origins, highlighting G protein modulation as a potential therapeutic avenue. © 2015 Nature America, Inc.
PubMed | Cancer and Blood Diseases Institute
Type: | Journal: Thrombosis research | Year: 2012
Genetics-based studies have established the critical importance of tumor cell-associated tissue factor, circulating and endothelial cell-associated regulators of thrombin function and multiple thrombin substrates in metastasis. There appear to be multiple pathways by which procoagulants influence tumor biology, but the capacity of hemostatic factors to regulate innate immune function is at least one emerging theme. Several reports have shown that the platelet/fibrin(ogen) axis supports metastasis by limiting natural killer cellmediated lysis of newly-localized micrometastases. Furthermore, there is increasingly compelling evidence that hemostatic and innate immune system interactions also support very early events in cancer development. Analyses of the role of fibrin(ogen) in inflammation-driven colon cancer established a major role for this provisional matrix protein in early tumor development. A seminal property of fibrin(ogen) driving tumor formation in this context is the capacity to support local leukocyte activation events through engagement of the leukocyte integrin (M)(2). More recent studies have also suggested that hemostatic factors can, in at least some settings, program the malignant phenotype in tumor cells. Platelet-derived TGF-1 and other platelet products were reported to trigger a more invasive and prometastatic epithelial-mesenchymal-like transition in embolic tumor cells. These findings support the intriguing concept that tumor cell functional properties can continue to evolve, even beyond the primary tumor site, in response to tumor cell-hemostatic factor interactions in the bloodstream. Taken together, there is strong evidence that the hemostatic system plays a multifaceted role in cancer pathogenesis and that therapies targeting selected hemostatic factors may present a powerful means to impede tumor development and metastasis.