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leukemia 446 leukemia viruses
Leukemia inhibitory factor. Resolution = 2.0 Å.
LIFR α
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gp130
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Leukemia inhibitory factor.
relief of symptoms attributable to hyperleukocytosis.
Conditioning of a donor with cytokines to mobilize
hematopoietic stem cells from the bone marrow into the
peripheral blood may be employed to enrich the donor
leukocyte preparation for hematopoietic stem cells.
leukemia
Clonal expansion of lymphohematopoietic cells. Acute
leukemias are characterized by elevated numbers of immature
lymphohematopoietic cells (blasts) in the blood and/or
bone marrow. By contrast, chronic leukemias are marked
by a neoplastic population of mature-appearing cells. With
increasing age, the incidence of acute and chronic myeloid
leukemias and of chronic lymphoid leukemias is increased.
By contrast, acute lymphoblastic leukemia occurs more frequently
among children, reaching a sharp age peak at 3 to 4
years of age. Leukemia cell biology classification has been
dramatically advanced through immunological characterization
of normal and leukemic hematopoietic cells, the
demonstration of immunoglobulin and T cell receptor gene
rearrangement, and the molecular elucidation of genetic
abnormalities associated with leukemogenesis.
leukemia inhibitory factor (LIF)
A lymphoid factor that facilitates maintenance of embryonic
stem cells through suppression of spontaneous generation.
It also induces mitogenesis of selected cell lines, stimulation
of bone remodeling, facilitation of megakaryocyte
formation in vivo, and suppression of cellular differentiation
in culture. The recombinant form is a 20-kDa protein comprised
of 180-amino acid residues. This cytokine has pleiotropic
activities. LIF is a member of the interleukin-6 (IL6)
family of cytokines which includes oncostatin m, ciliary
neurotrophic factor (CNTF), IL11, IL6, and cardiotrophin-1.
The receptors for these cytokines consist of a cytokinespecific
ligand-binding chain in the shared gp130 transducer
chain. Two signal-transducing pathways downstream
of gp130 include the Janus kinase (JAK)/signal transducer
and activator of transcription (STAT) and the Ras/mitogenactivated
protein kinase (MAPK) pathway. LIF can induce
the same acute-phase proteins as IL6. It is released at local
injury sites where monocytes and polymorphic nuclear cells
are recruited. LIF can induce stimulation of proliferation of
cancer cells. It also modulates tumor cell capacity to adhere
to matrix components.
leukemia viruses
Leukemia is a neoplasm of hematopoietic cells. It may have
a viral etiology in humans to produce adult T cell leukemia
as well as in mice, cats, cattle, and birds. The leukemiainducing
viruses are members of the Oncovirinae subfamily
of the Retroviridae family. Additional retroviruses comprise
the lentiviruses, a subfamily of pathogenic slow viruses
that include the human immunodeficiency virus (HIV) and
the spumaviruses and formiviruses that induce persistent
infections unaccompanied by clinical disease. Oncoviruses
infect target cells and cause their transformation to produce
infected cells with tumor-producing potential. Viral carcinogenesis
involves (1) overexpression of a viral onc gene;
(2) protooncogene (c-onc) capture in a retroviral vector and
the occurrence of mutations in the captured gene that render
it highly oncogenic (v-onc); (3) inclusion of two cooperation
v-oncs in the same provirus; (4) viral protein and activation
of a c-onc cooperation; and (5) reorganization of cellular
transcription processes by a viral transactivation protein.