M-CSF and M-CSF-receptor gene expression in acute myelomonocytic leukemias

Peripheral blood-derived monocytes show neuronal properties and integration in immune-deficient rd1 mouse model upon phenotypic differentiation and induction with retinal growth factors

BACKGROUND

Cell therapy is one of the most promising therapeutic interventions for retinitis pigmentosa. In the current study, we aimed to assess if peripheral blood-derived monocytes which are highly abundant and accessible could be utilized as a potential candidate for phenotypic differentiation into neuron-like cells.

METHODS

The peripheral blood-derived monocytes were reconditioned phenotypically using extrinsic growth factors to induce pluripotency and proliferation. The reconditioned monocytes (RM) were further incubated with a cocktail of growth factors involved in retinal development and growth to induce retinal neuron-like properties. These cells, termed as retinal neuron-like cells (RNLCs) were characterized for their morphological, molecular and functional behaviour in vitro and in vivo.

RESULTS

The monocytes de-differentiated in vitro and acquired pluripotency with the expression of prominent stem cell markers. Treatment of RM with retinal growth factors led to an upregulation of neuronal and retinal lineage markers and downregulation of myeloid markers. These cells show morphological alterations resembling retinal neuron-like cells and expressed photoreceptor (PR) markers. The induced RNLCs also exhibited relative membrane potential change upon light exposure suggesting that they have gained some neuronal characteristics. Further studies showed that RNLCs could also integrate in an immune-deficient retinitis pigmentosa mouse model NOD.SCID-rd1 upon sub-retinal transplantation. The RNLCs engrafted in the inner nuclear layer (INL) and ganglion cell layer (GCL) of the RP afflicted retina. Mice transplanted with RNLCs showed improvement in depth perception, exploratory behaviour and the optokinetic response.

CONCLUSIONS

This proof-of-concept study demonstrates that reconditioned monocytes can be induced to acquire retinal neuron-like properties through differentiation using a defined growth media and can be a potential candidate for cell therapy-based interventions and disease modelling for ocular diseases.

Expression of mRNA and protein of macrophage colony-stimulating factor and its receptor in human follicular luteinized granulosa cells

OBJECTIVE

To evaluate the concentration of macrophage colony-stimulating factor (M-CSF) in serum and follicular fluid (FF) at the time of oocyte retrieval and to detect expression of M-CSF and its receptor by luteinized granulosa cells (GCs).

DESIGN

Collection of serum and FF at the time of oocyte retrieval.

SETTING

A university IVF- intracytoplasmic sperm injection (ICSI) program.

PATIENT(S)

Serum and FF were obtained from 85 women undergoing oocyte retrieval.

INTERVENTION(S)

Serum and FF were obtained from 85 women. The GCs were pooled from 15 (3 x 5) patients (3-14 oocytes each).

MAIN OUTCOME MEASURE(S)

The M-CSF concentration was determined by ELISA, the expression of M-CSF and its receptor by the immunocytochemical technique and reverse transcription polymerase chain reaction analysis. In addition, M-CSF expression was investigated by cell culture time course studies.

RESULTS

The median M-CSF concentration in FF (2,409.2 pg/mL) was significantly higher than that in serum (242.5 pg/mL). The M-CSF and its receptor were expressed by GCs.

CONCLUSION(S)

The significantly higher level of M-CSF in FF than in serum and the expression of M-CSF and its receptor in FF by GCs suggest an important role for this growth factor in ovarian function.

Membrane-bound macrophage colony-stimulating factor mediated auto-juxtacrine downregulates matrix metalloproteinase-9 release on J6-1 leukemic cell

Earlier studies indicate that J6-1 human leukemic cells proliferate and propagate via the membrane-bound macrophage colony-stimulating factor (M-CSF)-mediated auto-juxtacrine mechanism. Matrix metalloproteinases (MMPs) can modulate the activity of cell membrane molecules and influence many cellular behaviors. Therefore, we hypothesized that MMP may also be involved in the membrane-bound M-CSF-mediated juxtacrine mechanism. First, we investigated whether blocking of membrane-bound M-CSF by neutralizing antibody to M-CSF or M-CSF receptor and adding of exogenous M-CSF are able to influence MMP-9 release. Next, we determined whether MMP-9 participated in J6-1 cells proliferation and influence the shedding of membrane-bound M-CSF and its receptor. Current studies show that blockade of the interaction between membrane-bound M-CSF and M-CSF receptor by antibody to M-CSF or M-CSF receptor promotes MMP-9 release. Moreover, we demonstrated that because of M-CSF mediated juxtacrine, lack of MMP-9 promotes J6-1 cell proliferation, in which a decrease in the shedding of cell-surface M-CSFR is involved. Hence, we suggest that membrane-bound M-CSF inhibit MMP-9 release and down-regulated MMP-9 contribute to juxtacrine stimulating in leukemic cell growth.

Identification of the M-CSF Receptor in Endometriosis by Immunohistochemistry and RT-PCR

PROBLEM

The aim of this paper is to provide further evidence that the dystopic proliferation of endometriotic epithelia is caused by the stimulation of peritoneal macrophages. It is essential to show that endometriotic epithelial cells express the macrophage colony-stimulating factor receptor (M-CSFR) which binds the M-CSF produced by the peritoneal macrophages.

METHOD OF STUDY

For the detection of M-CSFR, samples of ectopic endometrium (n = 79) and eutopic endometrium (n = 18) were compared. The specimens were gained at operative laparoscopy in the proliferative phase of the cycle. Cryostat sections were used for immunohistochemical detection. For in vitro reverse transcriptase polymerase chain reaction (RT-PCR) tests, the tissue was immediately shock frozen on paraffin sections. For the in situ RT-PCR technique the specimens were placed in a para-formaldehyde solution, embedded in paraffin and later processed. The Gene Amp 1000 in situ PCR system (Perkin Elmer) was used as the thermal cycler.

RESULTS

M-CSF and the M-CSF receptor are present in eutopic and ectopic endometrium. Qualitatively, with both PCR techniques we found the M-CSF receptor to be present in all samples examined. Using the histochemical detection technique, the M-CSF receptor was found in nearly 70% of endometriosis patients compared with a statistically significant lower percentage in normal endometrium.

CONCLUSIONS

The in situ RT-PCR technique and immunohistochemistry elaborated the need to trace the cellular sources of the M-CSF receptor. The identification of the M-CSF receptor in endometriotic tissue and in endometrium is apt to open a new experimental field in endometriosis research.

Lack of KIT or FMS internal tandem duplications but co-expression with ligands in AML

KIT and FMS, members of the class III receptor tyrosine kinase family, are expressed on normal hematopoietic cells and have important roles in normal hematopoiesis. FLT3 is also a member of the class III receptor tyrosine kinase family and plays important role in hematopoietic stem/progenitor cells, NK, and dendritic cells. Recently, internal tandem duplication (ITDs) mutations have been found in the juxtamembrane (JM) region of FLT3 receptor expressed by patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). The mutations result in the constitutive dimerization and activation of the receptor, contributing to leukemic transformation. KIT and FMS are also frequently expressed in AML and are closely related to FLT3. Thus, similar ITD mutations could also occur in the KIT and/or FMS gene of patients with AML. To explore this possibility, 13 human leukemia-lymphoma cell lines and 44 AML patient samples were examined by reverse transcription-polymerase chain reaction (RT-PCR) for the presence of ITD mutations in the JM region of the KIT or FMS receptor. None of the 13 human leukemia-lymphoma cell lines or 44 AML primary bone marrow samples express ITDs in either KIT or FMS in the JM region that is involved in FLT3 mutations. The 13 cell lines and 44 AML samples were also examined for the possible co-expression of KIT and/or FMS receptors with their respective ligands, as we have seen for FLT3 and its ligand, FL. This co-expression could contribute to leukemic transformation through autocrine, paracrine, or intracrine activation mechanisms. And 6/13 cell lines and 27/44 primary AML samples exhibit co-expression of the KIT receptor and ligand (SCF) while 10/13 cell lines and 35/44 primary AML samples exhibit co-expression of the FMS receptor and ligand (CSF-1). Therefore, while ITD mutations were not found, the findings of co-expression of KIT and/or FMS with their respective ligands implies these receptors might contribute to leukemogenesis in some patients with AML through autocrine, paracrine, or intracrine interactive stimulation.

Bis(1H-2-indolyl)-1-methanones as inhibitors of the hematopoietic tyrosine kinase Flt3

Aberrant expression and activating mutations of the class III receptor tyrosine kinase Flt3 (Flk-2, STK-1) have been linked to poor prognosis in acute myeloid leukemia (AML). Inhibitors of Flt3 tyrosine kinase activity are, therefore, of interest as potential therapeutic compounds. We previously described bis(1H-2-indolyl)-1-methanones as a novel class of selective inhibitors for platelet-derived growth factor receptors (PDGFR). Several bis(1H-2-indolyl)-1-methanone derivatives, represented by the compounds D-64406 and D-65476, are also potent inhibitors of Flt3. They inhibit proliferation of TEL-Flt3-transfected BA/F3 cells with IC(50) values of 0.2-0.3 microM in the absence of IL-3 but >10 microM in the presence of IL-3. Ligand-stimulated autophosphorylation of Flt3 in EOL-1 cells and corresponding downstream activation of Akt/PKB are effectively inhibited by bis(1H-2-indolyl)-1-methanones whereas autophosphorylation of c-Kit/SCF receptor or c-Fms/CSF-1 receptor is less sensitive or insensitive, respectively. Flt3 kinase purified by different methods is potently inhibited in vitro, demonstrating a direct mechanism of inhibition. 32D cells, expressing a constitutively active Flt3 variant with internal tandem duplication are greatly sensitized to radiation-induced apoptosis in the presence of D-64406 or D-65476 in the absence but not in the presence of IL-3. Thus, bis(1H-2-indolyl)-1-methanones are potential candidates for the treatment of Flt3-driven leukemias.

Inhibition of FLT3-mediated transformation by use of a tyrosine kinase inhibitor

FLT3 is a member of the type III receptor tyrosine kinase (RTK) family. These receptors all contain an intrinsic tyrosine kinase domain that is critical to signaling. Aberrant expression of the FLT3 gene has been documented in both adult and childhood leukemias including AML, ALL and CML. In addition, 17-27% of pediatric and adult patients with AML have small internal tandem duplication mutations in FLT3. Patients expressing the mutant form of the receptor have been shown to have a decreased chance for cure. Our previous study, using a constitutively activated FLT3, demonstrated transformation of Ba/F3 cells and leukemic development in an animal model. Thus, there is accumulating evidence for a role for FLT3 in human leukemias. This has prompted us to search for inhibitors of FLT3 as a possible therapeutic approach in these patients. AG1296 is a compound of the tyrphostin class that is known to selectively inhibit the tyrosine kinase activity of the PDGF and KIT receptors. Since FLT3 is a close relative of KIT, we wanted to test the possible inhibitory activity of AG1296 on FLT3. In transfected Ba/F3 cells, AG1296 selectively and potently inhibited autophosphorylation of FL-stimulated wild-type and constitutively activated FLT3. Treatment by AG1296 abolished IL-3-independent proliferation of Ba/F3 cells expressing the constitutively activated FLT3 and thus, reversed the transformation mediated by activated FLT3. Inhibition of FLT3 activity by AG1296 in cells transformed by activated FLT3 resulted in apoptotic cell death, with no deleterious effect on their parental counterparts. Addition of IL-3 rescued the growth of cells expressing activated FLT3 in the presence of AG1296. This demonstrates that the inhibition is specific to the FLT3 pathway in that it leaves the kinases of the IL-3 pathway and other kinases further downstream involved in proliferation intact. Several proteins phosphorylated by the activated FLT3 signaling pathway, including STAT 5A, STAT 5B and CBL, were no longer phosphorylated when these cells were treated with AG1296. The activity against FLT3 suggests a potential therapeutic application for AG1296 or similar drugs in the treatment of leukemias involving deregulated FLT3 tyrosine kinase activity and as a tool for studying the biology of FLT3.

Constitutive activation of FLT3 stimulates multiple intracellular signal transducers and results in transformation

Aberrant expression of FLT3 has been found in most cases of B-lineage ALL and AML, and subsets of T cell ALL, CML in blast crisis and CLL. In 20% of patients with AML the receptor has small internal tandem duplications of the juxtamembrane region which appear to contitutively activate the receptor. To investigate whether FLT3 activation could play a role in leukemia, we generated a constitutively activated FLT3 by fusing its cytoplasmic domain to the helix-loop-helix domain of TEL in analogy to the fusion that occurs with TEL-PDGFR in CMML. In vitro translation assays demonstrated oligomerization and intrinsic tyrosine kinase activity of the TEL-FLT3 chimeric receptor. Constitutively activated TEL-FLT3 conferred IL-3 independence and long-term proliferation to transfected Ba/F3 cells. Immunoblot analyses showed that JAK 2, STAT 3, STAT 5a, STAT 5b and CBL were tyrosine-phosphorylated in TEL-FLT3 expressing Ba/F3 cells in the absence of IL-3. These data suggest a possible role for the JAK/STAT pathway in FLT3 signaling. Transplantation of TEL-FLT3 expressing Ba/F3 cells into syngeneic mice caused mortality in all mice by 3 weeks after injection. Histopathologic analysis demonstrated a massive infiltration of mononuclear cells in the liver, spleen and bone marrow. The mimicking of naturally occurring TEL fusions provides an approach to assess aspects of the biology of activated FLT3, or other receptor-type tyrosine kinases (RTKs) in leukemic transformation.

In vitro-staining specificity of the antibody 5-D-4 for microglia but not for monocytes and macrophages indicates that microglia are a unique subgroup of the myelomonocytic lineage

We have previously shown that (i) the ramified phenotype and (ii) the microglia-specific pattern of membrane currents are induced not only in microglia, but also in monocytes and macrophages if they are cultured in the presence of astrocytes. These findings indicated that microglia are not a separate type of cell of the myelomonocytic lineage, but are induced to take on their unique characteristics by astrocytes. Recently, it was discovered that the antibody 5-D-4 selectively stains ramified microglia in situ. We therefore studied the influence of astrocytes and other epithelial cells on the expression of the keratan sulfate epitope recognized by 5-D-4 in microglia and other myelomonocytic cells. Our findings show that this antigen is exclusively expressed in microglia only if they are induced to ramify by coculture with either astrocytes or epithelial cells. By contrast monocytes and macrophages, even if induced to take on the ramified phenotype do not stain positive with 5-D-4. These findings indicate (i) that 5-D-4 is a specific marker for ramified microglia in vitro, and (ii) that microglia are a separate class of myelomonocytic cells, distinct from monocytes and macrophages.

Enhancement of J6-1 human leukemic cell proliferation by membrane-bound M-CSF through a cell-cell contact mechanism II. Role of an M-CSF receptor-like membrane protein

We have isolated an M-CSF-like membrane-associated growth factor from human leukemic J6-1 cells that can enhance the growth and colony formation of J6-1 cells in vitro. Indirect evidence suggests that this membrane-associated M-CSF-like growth factor may do so by stimulating a corresponding receptor co-expressed on the adjacent J6-1 cells. The objective of this study is to isolate the putative receptor in J6-1 cells by virtue of its ability to bind and thus "block" the growth of J6-1 cells. Based on this approach, we have isolated from the J6-1 cell membrane an inhibitory activity that can inhibit the clonal growth of J6-1 cells. The activity of this inhibitor can be readily neutralized by either anti-M-CSFR MAb or anti-M-CSFR antiserum, suggesting that it is related to M-CSFR, a product of c-fms proto-oncogene. Judging from Sephadex G-200 gel filtration, the molecular weight (MW) of this putative M-CSFR-like inhibitor was estimated to be approx. 150-180 kDa, comparable with that of M-CSFR. The specificity of M-CSFR-like protein to recognize and block membrane-bound M-CSF also was implicated by its ability to upregulate the steady-state levels of c-fms mRNA in J6-1 cells. Besides its antiproliferative activity in vitro, treatment of J6-1 cells with the putative receptor protein before inoculation effectively blocked the growth and tumor formation in vivo by J6-1 cells in a nude mouse model. These findings suggest that the growth and tumor development by J6-1 leukemic cells may involve a contact-mediated "juxtacrine mechanism".

Allelic loss of the FMS gene in acute myeloid leukaemia

The FMS proto-oncogene encodes for the colony stimulating factor-1 receptor expressed on monocytes and B lymphocytes within the peripheral blood system. Allelic loss of the FMS gene occurs in patients with refractory anaemia and the 5q- syndrome associated with the myelodysplastic syndromes. To determine the frequency of FMS gene loss in patients with myeloid malignancy, 50 DNA samples from patients with acute myeloid leukaemia (AML) and 30 samples from haematologically normal samples were analysed using a quantitative Southern blotting technique. Allelic loss of one allele (hemizygous) was detected in five of 18 samples of AM-M4 and eight of 27 samples of AML M1, M2 and M3. In addition, loss of both FMS alleles (homozygous) was demonstrated in three of 18 samples of AML M4 and 0127 samples of AML M1, M2 and M3. One patient with AML M5 and one with AML M6 were assessed although no allelic loss of FMS was detected. Three samples from patients with secondary AML were also analysed and hemizygous loss was detected in one case. Homozygous or hemizygous loss of FMS was not detected in any of 30 DNA samples isolated from haematologically normal individuals. These data indicate that loss of the FMS gene is common in AML, with an increased frequency in those patients with AML subtype M4.

Blood monocytes and spleen macrophages differentiate into microglia-like cells on monolayers of astrocytes: morphology

Several morphological and functional properties of microglial cells, the resident immunoeffector cells of the central nervous system (CNS), differ from those of monocytes/macrophages in other tissues. Microglia are assumed to derive from myelonocytic lineage, possibly as a distinct subpopulation that diverges from a common cell line early in ontogeny, invades the CNS, proliferates, and differentiates into ameboid and then ramified microglia. We tested the hypothesis that some morphological and functional properties of microglia are induced in myelomonocytic cells by nervous tissue, specifically astrocytes. In the present in vitro studies we compared the differentiation of microglia, blood monocytes, and spleen macrophages on acellular substrates and on monolayers of astrocytes and fibroblasts. On acellular substrates, microglial cells at first acquire an ameboid morphology; later they show a few short, unbranched processes. On monolayers of pure astrocytes, microglial cells at first also differentiate into ameboid cells, but after 5 to 7 days they start to develop processes with large lamellopodial tips. These lengthen and branch continuously during the next 2 weeks in vitro, demarcating a round to oval territory around the small ellipsoid cell body. By contrast, on monolayers of fibroblasts the microglial cells develop an ameboid morphology, but do not grow the typical long branched processes of the ramified form. Blood monocytes and spleen macrophages behave indistinguishably from microglia both on acellular and cellular substrates, i.e., on astroglia they develop the ramified form, while on fibroblasts they retain the ameboid shape. When microglia, macrophages, or monocytes are cultured on coverslips on top of astrocytic monolayers, i.e., physically separated from the astroglia, but exposed to the medium conditioned by astrocytes, a significant proportion of them also develop the ramified shape. These findings indicate that the ramified shape of microglia is induced by astrocytes. Since this morphology can also be induced in blood monocytes and macrophages, we take this to be further evidence for the proposition that microglial cells are derived from the myelomonocytic lineage, and, moreover, that properties of resident macrophages are largely determined by tissue components of their host organ.

The expression of FMS, KIT and FLT3 in hematopoietic malignancies

Three receptor molecules, belonging to the class III of receptor tyrosine kinases, namely the receptors for colony-stimulating factor 1, CSF1R (product of the FMS proto-oncogene) and Steel factor, SLFR (product of the KIT proto-oncogene), as well as the recently identified FLT3/FLK2 gene product, appear to play distinct roles in normal hematopoietic differentiation. Their potential role in leukemic hematopoiesis has been approached by expression studies in hematopoietic malignancies, especially in acute leukemias of the myeloid and lymphoid lineages. We present here a review of available data, and discuss the possible significance and potential applications of these results.

Blood monocytes and spleen macrophages differentiate into microglia-like cells when cultured on astrocytes

Microglial cells are resident immunoeffector cells of the central nervous system. They differ from most other resident macrophages by their ramified shape, their capacity to proliferate, and by a distinct pattern of ion channels. They have therefore been proposed to be a subpopulation of macrophages that arise from a distinct pool of myelomonocytes by early determination of their lineage within the bone marrow. Here we present data which show that distinct properties of the microglial cells are not intrinsic to this subpopulation of macrophages, but are acquired subsequent to their interaction with astroglial cells, since similar properties can be induced in both blood monocytes and spleen macrophages, when these are cultured on astrocytes. These findings add further evidence to the proposition that microglial cells are derived from the myelomonocytic lineage, and also indicate that the properties of resident macrophages are largely determined by tissue components of the host organ.

Regulation of hematopoietic cell function by protein tyrosine kinase-encoding oncogenes, a review

Tyrosine phosphorylation of proteins by protein tyrosine kinases (PTKs) is an important mechanism in the regulation of various cellular processes such as proliferation, differentiation, and transformation. Accumulating data implicate PTKs as essential intermediates in the transduction of extracellular signals to the interior of the cell. This review summarizes the mechanism of action of PTKs from the major subclasses and the involvement of PTK-encoding oncogenes in the regulation of hematopoietic cell function.

Insulin-like growth factor-1 stimulates proliferation of myeloid FDC-P1 cells overexpressing the human colony-stimulating factor-1 receptor

Retrovirally expressed human CSF-1 receptor can induce CSF-1-dependent growth of IL-3-dependent hemopoietic cells FDC-P1. Here we show that expression of the human CSF-1 receptor also allowed FDC-P1 cells to grow in response to Insulin-like Growth Factor-1 (IGF-I). The authentic receptor for IGF-I was identified by affinity cross-linking and binding analysis on both control (infected with a neo vector) and CSF-1 receptor expressing FDC-P1 cells. DNA and RNA analysis of these cells and of five clones of IGF-I responsive cells demonstrated that the IGF-I receptor gene was not rearranged nor was it abnormally expressed in IGF-I responsive cells. These results suggest that myeloid cells over-expressing CSF-1R (c-fms protooncogene product) might have a proliferative advantage over normal myeloid cells in a physiological situation, independently of the presence of CSF-1 or the capacity of the cells to respond to CSF-1. This would indicate a possible role for c-fms in human neoplasia.