229 research outputs found
In vitro growth characteristics of human lymphoid malignancies in primary cell culture
The experimental work presented in this thesis deals with the analysis
of the in vitro growth and differentiation characteristics of acute
lymphoblastic leukemia ( T end non-T), T cell non Hodgkin's lymphoma and B
cell chronic lymphocytic leukemia in primary cell culture. For these
studies, reproducible cell culture assays for the growth of these lymphoid
tumours first needed to be developed. Considerable attention has been paid
to the response of these neoplasms to the polypeptide hormone interleukin
2. The experiments described in chapters 2 and 3 deal with the in
vitro colony growth of non-T acute lymphoblastic leukemia (ALL) and with
the effect of interleukin 2 on these cells in combination with a factor
elaborated by feeder leukocytes. The requirements of the ALL cells for
activation with a lectin (PHA) or a phorbol ester (TPA) for colony growth
have also been investigated. To assess whether non-T ALL cells differentiate
toward more mature cell types during in vitro growth, the morphological
and immunological phenotypes of colony cells were determined. To compare
the differentiation capacities of ALL with those of acute leukemia of
the myeloid differentiation lineage (AML) the abilities of AML to produce
more mature progeny under comparable in vitro conditions were studied
(chapter 4). Chapter 5 deals with an analysis of growth requirements of
8 cell type chronic lymphocytic leukemia (CLL) in colony culture and
specifically with the role of IL2 in the proliferation of B CLL cells. This
analysis is extended in chapter 6, in which the results of binding experiments
with radiolabeled IL2 are presented. These experiments were carried
out to determine numbers and affinity of IL2 receptors expressed by B CLL
cells- In addition, the hypothesis that certain CLL cells might be capable
of self-stimulation via the autocrine production of IL2 is approached in
this chapter. In chapter 7, culture characteristics of acute lymphoblastic
leukemia and non Hodgkin's lymphoma (NHL) of the T cell differentiation
lineage are presented. The studies described in chapter 8 are our first
attempts toward the characterization of membrane phenotypes and growth
requirements of normal T -lymphocytic precursor cells in the human bone
marrow. For this purpose, we applied the human long-term bone marrow culture
system. Knowledge of the growth end differentiation features of normal
lymphoid progenitors is essential for our understanding of whether or how the leukemic counter parts of these cells reflect a modified response to
growth and differentiation stimuli. In chapter 9 a brief overview of our
current understanding of the role of IL2 in the proliferation of neoplastic
T and B cells is presented. Moreover, the results of this thesis are discussed
in this chapter with reference to their implications for our insight
into the control of proliferation and differentiation of the different
types of lymphoid leukemia/lymphom
RUNX1 Mutations in the Leukemic Progression of Severe Congenital Neutropenia
Somatic RUNX1 mutations are found in approximately 10% of patients with de novo acute myeloid leukemia (AML), but are more common in secondary forms of myelodysplastic syndrome (MDS) or AML. Particularly, this applies to MDS/AML developing from certain types of leukemia-prone inherited bone marrow failure syndromes. How these RUNX1 mutations contribute to the pathobiology of secondary MDS/AML is still unknown. This mini-review focusses on the role of RUNX1 mutations as the most common secondary leukemogenic hit in MDS/AML evolving from severe congenital neutropenia (SCN)
CD20 and CD40 mediated mitogenic responses in B-lineage acute lymphoblastic leukaemia
Activation of CD20, a cross-membrane ion channel, induces cell cycle progression from G0 to G1 in B lymphocytes. Subsequent activation of CD40, a membrane receptor of the nerve growth factor receptor superfamily, transits the B cells to the S phase. CD40 may also act synergistically in combination with IL-4 (B lymphocytes) or IL-3/IL-7 (B-cell precursors). We investigated the proliferative responses of B-lineage acute lymphoblastic leukaemia (ALL) cells to CD20/CD40 activation. In 18/56 ALL cases, CD20 activation resulted in significant increases in DNA synthesis. Similar, although more moderate, effects were seen of activation of CD40 in 10/44 cases. Responses to CD20 or CD40 activation were independent of co-stimulation with IL-3, IL-4 or IL-7, and various cocktails of the different growth stimuli did not act synergistically
Mutations in the gene for the granulocyte colony-stimulating-factor receptor in patients with acute myeloid leukemia preceded by severe congenital neutropenia
BACKGROUND. In severe congenital neutropenia the maturation of myeloid
progenitor cells is arrested. The myelodysplastic syndrome and acute
myeloid leukemia develop in some patients with severe congenital
neutropenia. Abnormalities in the signal-transduction pathways for
granulocyte colony-stimulating factor (G-CSF) may play a part in the
progression to acute myeloid leukemia. METHODS. We isolated genomic DNA
and RNA from hematopoietic cells obtained from two patients with acute
myeloid leukemia and histories of severe congenital neutropenia. The
nucleotide sequences encoding the cytoplasmic domain of the G-CSF receptor
were amplified by means of the polymerase chain reaction and sequenced.
Murine myeloid 32D.C10 cells were transfected with complementary DNA
encoding the wild-type or mutant G-CSF receptors and tested for their
responses to G-CSF. RESULTS. Point mutations in the gene for the G-CSF
receptor were identified in both patients. The mutations, a substitution
of thymine for cytosine at the codon for glutamine at position 718
(Gln718) in one patient and at the codon for glutamine at position
731(Gln731) in the other, caused a truncation of the C-terminal
cytoplasmic region of the receptor. Both mutant and wild-type genes for
the G-CSF receptor were present in leukemic cells from the two patients.
In one patient, the mutation was also found in the neutropenic stage,
before the progression to acute myeloid leukemia. The 32D.C10 cells
expressing mutant receptors had abnormally high proliferative responses
but failed to mature when cultured in G-CSF. The mutant G-CSF receptors
also interfered with terminal maturation mediated by the wild-type G-CSF
receptor in the 32D.C10 cells that coexpressed the wild-type and mutant
receptors. CONCLUSIONS. Mutations in the gene for the G-CSF receptor that
interrupt signals required for the maturation of myeloid cells are
involved in the pathogenesis of severe congenital neutropenia and
associated with the progression to acute myeloid leukemia
Distinct cytoplasmic regions of the human granulocyte colony-stimulating factor receptor involved in induction of proliferation and maturation
The granulocyte colony-stimulating factor receptor (G-CSF-R) transduces
signals important for the proliferation and maturation of myeloid
progenitor cells. To identify functionally important regions in the
cytoplasmic domain of the G-CSF-R, we compared the actions of the
wild-type receptor, two mutants, and a natural splice variant in
transfectants of the mouse pro-B cell line BAF3 and two myeloid cell
lines, 32D and L-GM. A region of 55 amino acids adjacent to the
transmembrane domain was found to be sufficient for generating a growth
signal. The immediate downstream sequence of 30 amino acids substantially
enhanced the growth signaling in the three cell lines. In contrast, the
carboxy-terminal part of 98 amino acids strongly inhibited growth
signaling in the two myeloid cell lines but not in BAF3 cells. Truncation
of this region lead to an inability of the G-CSF-R to transduce maturation
signals in L-GM cells. An alternative carboxy tail present in a splice
variant of the G-CSF-R also inhibited growth signaling, notably in both
the myeloid cells and BAF3 cells, but appeared not to be involved in
maturation
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