Ligand For Colony-stimulating Factor-1 Receptor Research Articles

Comparison of serum interleukin 34 levels in chronic periodontitis patients before and after periodontal flap surgery

Background: Interleukin-34 (IL-34) is a recently identified alternative ligand for colony-stimulating factor-1 receptor which plays an important role in osteoclastogenesis. The aim of this study was to evaluate the IL-34 levels in serum in subjects with chronic periodontitis and to evaluate the effect of surgical periodontal therapy on the serum IL-34 levels. Materials and Methods: Thirty individuals (age range: above 20 years) with chronic periodontitis were selected and divided into groups: Group I (chronic periodontitis patients before periodontal flap surgery), while Group II patients after periodontal flap surgery Ramfjord periodontal diseases index and sulcus bleeding index (Muhlemman and Sons 1971) were examined. Serum samples were collected to estimate the levels of IL-34 using enzyme-linked immunosorbent assay kit. Results: The mean IL-34 concentration in serum was highest for Group I and it significantly decreased after periodontal flap surgery. The difference between them was statistically significant (P < 0.05). Conclusion: IL-34 can be considered as an “inflammatory marker” of periodontal disease and can be explored in the future as a potential therapeutic target in the treatment of periodontal disease.

Triggering Receptor Expressed on Myeloid Cells-2 (TREM2) Interacts With Colony-Stimulating Factor 1 Receptor (CSF1R) but Is Not Necessary for CSF1/CSF1R-Mediated Microglial Survival.

Triggering receptor expressed on myeloid cells-2 (TREM2) and colony-stimulating factor 1 receptor (CSF1R) are crucial molecules for microgliopathy, which is characterized by microglia dysfunction and has recently been proposed as the neuropathological hallmark of neurological disorders. TREM2 and CSF1R are receptors expressed primarily in microglia in the brain and modulate microglial activation and survival. They are thought to be in close physical proximity. However, whether there is a direct interaction between these receptors remains elusive. Moreover, the physiological role and mechanism of the interaction of TREM2 and CSF1R remain to be determined. Here, we found that TREM2 interacted with CSF1R based on a co-immunoprecipitation assay. Additionally, we found that CSF1R knockdown significantly reduced the survival of primary microglia and increased the Trem2 mRNA level. In contrast, CSF1R expression was increased in Trem2-deficient microglia. Interestingly, administration of CSF1, the ligand of CSF1R, partially restored the survival of Trem2-deficient microglia in vitro and in vivo. Furthermore, CSF1 ameliorated Aβ plaques deposition in Trem2-/-; 5XFAD mouse brain. These findings provide solid evidence that TREM2 and CSF1R have intrinsic abilities to form complexes and mutually modulate their expression. These findings also indicate the potential role of CSF1 in therapeutic intervention in TREM2 variant-bearing patients with a high risk of Alzheimer’s disease (AD).

JTE-952 Suppresses Bone Destruction in Collagen-Induced Arthritis in Mice by Inhibiting Colony Stimulating Factor 1 Receptor

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and structural destruction of the joints. Bone damage occurs in an early stage after onset and osteoclast activation plays a substantial role in its progression. Colony stimulating factor 1 receptor (CSF1R) is a receptor protein tyrosine kinase specifically expressed in monocytic-lineage cells such as macrophages and osteoclasts. Here, we investigated the effect of JTE-952, a novel CSF1R tyrosine kinase inhibitor, on osteoclast formation in vitro and on bone destruction in a mouse model of collagen-induced arthritis. JTE-952 completely inhibited osteoclast differentiation from human monocytes, with an IC50 of 2.8 nmol/L, and reduced osteoclast formation from the synovial cells of RA patients. Detectable levels of colony stimulating factor 1 (CSF1), a ligand of CSF1R, were observed in the synovial tissues of the arthritis model, similar to those observed in the pathology of human RA. JTE-952 significantly suppressed increases in the bone destruction score, the number of tartrate-resistant-acid-phosphatase-positive cells, and the severity of arthritis in the model mice. We also examined the efficacy of JTE-952 combined with methotrexate. This combination therapy more effectively reduced the severity of bone destruction and arthritis than monotherapy with either agent alone. In summary, JTE-952 potently inhibited human osteoclast formation in vitro and suppressed bone destruction in an experimental arthritis model, especially when combined with methotrexate. These results indicate that JTE-952 should strongly inhibit bone destruction and joint inflammation in RA patients and effectively prevent the progression of the structural destruction of joints.

Effects of IL-34 on Macrophage Immunological Profile in Response to Alzheimer's-Related Aβ42 Assemblies.

Interleukin-34 (IL-34) is a recently discovered cytokine that acts as a second ligand of the colony stimulating factor 1 receptor (CSF1R) in addition to macrophage colony-stimulating factor (M-CSF). Similar to M-CSF, IL-34 also stimulates bone marrow (BM)-derived monocyte survival and differentiation into macrophages. Growing evidence suggests that peripheral BM-derived monocyte/macrophages (BMMO) play a key role in the physiological clearance of cerebral amyloid β-protein (Aβ). Aβ42 forms are especially neurotoxic and highly associated with Alzheimer's disease (AD). As a ligand of CSF1R, IL-34 may be relevant to innate immune responses in AD. To investigate how IL-34 affects macrophage phenotype in response to structurally defined and stabilized Aβ42 oligomers and preformed fibrils, we characterized murine BMMO cultured in media containing M-CSF, IL-34, or regimens involving both cytokines. We found that the immunological profile and activation phenotype of IL-34-stimulated BMMO differed significantly from those cultured with M-CSF alone. Specifically, macrophage uptake of fibrillar or oligomeric Aβ42 was markedly reduced following exposure to IL-34 compared to M-CSF. Surface expression of type B scavenger receptor CD36, known to facilitate Aβ recognition and uptake, was modified following treatment with IL-34. Similarly, IL-34 macrophages expressed lower levels of proteins involved in both Aβ uptake (triggering receptor expressed on myeloid cells 2, TREM2) as well as Aβ-degradation (matrix metallopeptidase 9, MMP-9). Interestingly, intracellular compartmentalization of Aβ visualized by staining of early endosome antigen 1 (EEA1) was not affected by IL-34. Macrophage characteristics associated with an anti-inflammatory and pro-wound healing phenotype, including processes length and morphology, were also quantified, and macrophages stimulated with IL-34 alone displayed less process elongation in response to Aβ42 compared to those cultured with M-CSF. Further, monocytes treated with IL-34 alone yielded fewer mature macrophages than those treated with M-CSF alone or in combination with IL-34. Our data indicate that IL-34 impairs monocyte differentiation into macrophages and reduces their ability to uptake pathological forms of Aβ. Given the critical role of macrophage-mediated Aβ clearance in both murine models and patients with AD, future work should investigate the therapeutic potential of modulating IL-34 in vivo to increase macrophage-mediated Aβ clearance and prevent disease development.

Interleukin-34 expression in ovarian cancer: a possible correlation with disease progression.

Ovarian cancer is the second-most lethal gynecological malignancy and the seventh-commonest cause of cancer-related death in women around the world. Most of the ovarian cancer patients are diagnosed at advanced stages and suffer from recurrence after primary cytoreductive surgery and standard first-line chemotherapy. Thus, the successful management of ovarian cancer patients requires the identification of factors that contribute to progression and relapse. Interleukin-34 (IL-34) is a novel cytokine that acts as a tissue-specific ligand of colony-stimulating factor-1 receptor (CSF-1R). In cancer, IL-34 exerts pro-tumorigenic functions that promote tumor growth, metastasis, angiogenesis, immune suppression and therapeutic resistance. In this study, we evaluate the impact of IL-34 on progression and survival of ovarian cancer patients. First, IL-34 was found to be expressed in several human ovarian cancer cell lines and cancer tissues from patients. The expression of IL-34 was enhanced by cytotoxic chemotherapy in ovarian cancer cell lines and cancer tissues from chemotherapy-treated ovarian cancer patients. Importantly, high IL-34 expression correlated with worse progression-free survival (PFS) and overall survival in different cohorts. The assessment of PFS based on a combination between IL34 expression and other related genes such as CSF1R and CD163 helped further to reach more statistical significance compared with IL34 alone. Furthermore, in the murine ovarian cancer cell HM-1 in vivo model, it was suggested that IL-34-derived tumor cells was correlated with tumor progression and survival by modulating the immune environment. Collectively, these findings indicate a possible correlation between IL-34 expression and disease progression in ovarian cancer patients and the mouse model.

Pharmacological inhibition of CSF1R by GW2580 reduces microglial proliferation and is protective against neuroinflammation and dopaminergic neurodegeneration.

Increased pro-inflammatory cytokine levels and proliferation of activated microglia have been found in Parkinson's disease (PD) patients and animal models of PD, suggesting that targeting of the microglial inflammatory response may result in neuroprotection in PD. Microglial proliferation is regulated by many factors, but colony stimulating factor-1 receptor (CSF1R) has emerged as a primary factor. Using data mining techniques on existing microarray data, we found that mRNA expression of the CSF1R ligand, CSF-1, is increased in the brain of PD patients compared to controls. In two different neurotoxic mouse models of PD, acute MPTP and sub-chronic LPS treatment, mRNA and protein levels of CSF1R and CSF-1 were significantly increased. Treatment with the CSF1R inhibitor GW2580 significantly attenuated MPTP-induced CSF1R activation and Iba1-positive cell proliferation, without a reduction of the basal Iba1-positive population in the substantia nigra. GW2580 treatment also significantly decreased mRNA levels of pro-inflammatory factors, without alteration of anti-inflammatory mediators, and significantly attenuated the MPTP-induced loss of dopamine neurons and motor behavioral deficits. Importantly, these effects were observed in the absence of overt microglial depletion, suggesting that targeting CSF1R signaling may be a viable neuroprotective strategy in PD that disrupts pro-inflammatory signaling, but maintains the beneficial effects of microglia.

Abstract C087: Phase 1 study of DCC-3014, an oral inhibitor of CSF1R, to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics in patients with advanced solid tumors, including diffuse-type tenosynovial giant cell tumor

Abstract Background: DCC-3014 is an orally administered kinase inhibitor targeting the switch pocket of colony-stimulating factor 1 receptor (CSF1R). DCC-3014 exhibits approximately 100-fold selectivity from kinases homologous to CSF1R, such as KIT, and greater selectivity against 300 other human kinases. Tumor-associated macrophages (TAMs) are dependent on CSF1R kinase activity for proliferation and maintenance of the immunosuppressive phenotype. TAMs are known to enable tumor cells escape from immune surveillance. DCC-3014 is designed to exhibit an antitumor effect by inhibition of immunosuppressive TAMs or other CSF1R signaling-dependent pro-tumor activities. In addition, tenosynovial giant cell tumor (TGCT) is a rare, monoarticular disease known to be caused by the translocation in the CSF1 gene leading to overexpression of CSF1. Anti-CSF1R therapies have shown clinical activity in diffuse TGCT. Methods: This study is a multicenter, first-in-human study of DCC-3014 to determine a recommended Phase 2 dose (RP2D) or maximally tolerated dose (MTD) with a 3+3 dose escalation design and evaluate the safety, efficacy, pharmacokinetics (PK) and pharmacodynamics (PD) of DCC-3014 in advanced solid tumors, including diffuse-type TGCT [NCT03069469]. Results: As of June 2, 2019, the study is ongoing in the dose escalation phase and has enrolled 32 patients with advanced solid tumors in 7 cohorts. The first cohort was initiated at 10 mg daily. Based on preliminary PK analysis from the first cohort, subsequent cohorts utilized a loading dose followed by a maintenance dosing schedule to achieve steady-state exposures more rapidly. The median age of patients was 61 years old and 69% were female with the median of 4 lines of prior anti-cancer treatment. No dose limiting toxicities (DLTs) have been seen in the assessed cohorts. Most commonly seen treatment-emergent adverse events (TEAEs >20%) were constipation (38%), vomiting (34%), diarrhea (31%), nausea (31%), decreased appetite (25%), abdominal pain (22%), and dyspnea (22%) whereas diarrhea, nausea and fatigue were reported as treatment-related AEs seen in >10% of all patients (13%). TEAEs were mostly Grade 1 or 2. Serious AEs (SAEs) were seen in 16 patients, none of which were related to DCC-3014. Exposure was approximately dose proportional. PD effects were seen for dose levels at 10 mg and above, and induction of the CSF1R ligand, CSF-1, was seen up to 148-fold from baseline. The RP2D or MTD has not been selected or reached. Conclusion: DCC-3014 in this study was generally well tolerated in patients with advanced solid tumors and showed approximately dose-proportional exposure and PD changes as expected. Further evaluation is ongoing to determine the RP2D or MTD. Data from the TGCT cohort will be presented at a future meeting. Citation Format: Matthew H Taylor, Stephen Leong, Ying Su, Cynthia B Leary, Xiaoyan Li, Keisuke Kuida, Rodrigo Ruiz-Soto, Todd Bauer. Phase 1 study of DCC-3014, an oral inhibitor of CSF1R, to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics in patients with advanced solid tumors, including diffuse-type tenosynovial giant cell tumor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C087. doi:10.1158/1535-7163.TARG-19-C087

IL-34 causes inflammation and beta cell apoptosis and dysfunction in gestational diabetes mellitus

ObjectiveGestational diabetes mellitus (GDM) is characterized by glucose intolerance during gestation. It is associated with a series of maternal and foetal complications. Interleukin (IL)-34 is a recently discovered pro-inflammatory cytokine that functions as a ligand for colony-stimulating factor-1 receptor (CSF-1R). The contribution of IL-34 in the development of multiple chronic inflammatory diseases and autoimmune diseases has been recently discovered. The aim of this study was to evaluate whether IL-34 participates in the pathogenesis of GDM.MethodA total of 120 women were enrolled in this study, which included 60 GDM patients and age- and sex-matched healthy pregnant women. The expression of IL-34 in serum, cord blood and placental tissues was analysed by ELISA and Western blot assays. The association between IL-34 levels and clinical features was also studied. We additionally evaluated the effect of recombinant mouse IL-34 (rmIL-34) on apoptosis and pancreatic β cell function.ResultsWe found that IL-34 expression is highly increased in serum, cord blood and placental tissues in patients with GDM. In addition, there was a positive association between serum IL-34 and insulin resistance and glucose concentrations. Our data also revealed that IL-34 contributes to the apoptosis of pancreatic β cells in GDM caused by CSF-1R. Furthermore, functional studies found that IL-34 inhibited pancreatic β cell function and cell viability, while CSF-1R inhibitor blocked this effect.ConclusionIL-34 plays a crucial role in the development of GDM by targeting CSF-1R, insulin production and β cell function.

CSF1R inhibitors exhibit antitumor activity in acute myeloid leukemia by blocking paracrine signals from support cells

AbstractTo identify new therapeutic targets in acute myeloid leukemia (AML), we performed small-molecule and small-interfering RNA (siRNA) screens of primary AML patient samples. In 23% of samples, we found sensitivity to inhibition of colony-stimulating factor 1 (CSF1) receptor (CSF1R), a receptor tyrosine kinase responsible for survival, proliferation, and differentiation of myeloid-lineage cells. Sensitivity to CSF1R inhibitor GW-2580 was found preferentially in de novo and favorable-risk patients, and resistance to GW-2580 was associated with reduced overall survival. Using flow cytometry, we discovered that CSF1R is not expressed on the majority of leukemic blasts but instead on a subpopulation of supportive cells. Comparison of CSF1R-expressing cells in AML vs healthy donors by mass cytometry revealed expression of unique cell-surface markers. The quantity of CSF1R-expressing cells correlated with GW-2580 sensitivity. Exposure of primary AML patient samples to a panel of recombinant cytokines revealed that CSF1R inhibitor sensitivity correlated with a growth response to CSF1R ligand, CSF1, and other cytokines, including hepatocyte growth factor (HGF). The addition of CSF1 increased the secretion of HGF and other cytokines in conditioned media from AML patient samples, whereas adding GW-2580 reduced their secretion. In untreated cells, HGF levels correlated significantly with GW-2580 sensitivity. Finally, recombinant HGF and HS-5–conditioned media rescued cell viability after GW-2580 treatment in AML patient samples. Our results suggest that CSF1R-expressing cells support the bulk leukemia population through the secretion of HGF and other cytokines. This study identifies CSF1R as a novel therapeutic target of AML and provides a mechanism of paracrine cytokine/growth factor signaling in this disease.

Reverse genetic screen reveals that Il34 facilitates yolk sac macrophage distribution and seeding of the brain.

ABSTRACTMicroglia are brain-resident macrophages, which have specialized functions important in brain development and in disease. They colonize the brain in early embryonic stages, but few factors that drive the migration of yolk sac macrophages (YSMs) into the embryonic brain, or regulate their acquisition of specialized properties, are currently known. Here, we present a CRISPR/Cas9-based in vivo reverse genetic screening pipeline to identify new microglia regulators using zebrafish. Zebrafish larvae are particularly suitable due to their external development, transparency and conserved microglia features. We targeted putative microglia regulators, by Cas9/gRNA complex injections, followed by Neutral-Red-based visualization of microglia. Microglia were quantified automatically in 3-day-old larvae using a software tool we called SpotNGlia. We identified that loss of zebrafish colony-stimulating factor 1 receptor (Csf1r) ligand, Il34, caused reduced microglia numbers. Previous studies on the role of IL34 in microglia development in vivo were ambiguous. Our data, and a concurrent paper, show that, in zebrafish, il34 is required during the earliest seeding of the brain by microglia. Our data also indicate that Il34 is required for YSM distribution to other organs. Disruption of the other Csf1r ligand, Csf1, did not reduce microglia numbers in mutants, whereas overexpression increased the number of microglia. This shows that Csf1 can influence microglia numbers, but might not be essential for the early seeding of the brain. In all, we identified il34 as a modifier of microglia colonization, by affecting distribution of YSMs to target organs, validating our reverse genetic screening pipeline in zebrafish.This article has an associated First Person interview with the joint first authors of the paper.

Increased Microglial CSF1R Expression in the SIV/Macaque Model of HIV CNS Disease.

Chronic microglial activation and associated neuroinflammation are key factors in neurodegenerative diseases including HIV-associated neurocognitive disorders. Colony stimulating factor 1 receptor (CSF1R)-mediated signaling is constitutive in cells of the myeloid lineage, including microglia, promoting cell survival, proliferation, and differentiation. In amyotrophic lateral sclerosis and Alzheimers disease, CSF1R is upregulated. Inhibiting CSF1R signaling in animal models of these diseases improved disease outcomes. In our studies, CNS expression of the CSF1R ligand, colony-stimulating factor 1 (CSF1) was significantly increased in a SIV/macaque model of HIV CNS disease. Using a Nanostring nCounter immune panel, we found CSF1 overexpression was strongly correlated with upregulation of microglial genes involved in antiviral and oxidative stress responses. Using in situ hybridization, we found that CSF1R mRNA was only present in Iba-1 positive microglia. By ELISA and immunostaining with digital image analysis, SIV-infected macaques had significantly higher CSF1R levels in frontal cortex than uninfected macaques (p = 0.018 and p = 0.02, respectively). SIV-infected macaques treated with suppressive ART also had persistently elevated CSF1R similar to untreated SIV-infected macaques. Coordinate upregulation of CSF1 and CSF1R expression implicates this signaling pathway in progressive HIV CNS disease.

Effect of nonsurgical periodontal therapy on interleukin-34 levels in periodontal health and disease.

Interleukin-34 (IL-34) is a recently identified alternative ligand for colony-stimulating factor-1 receptor plays an important role in osteoclastogenesis. The aim of this study was to evaluate the IL-34 levels in gingival crevicular fluid (GCF) and plasma in subjects with chronic periodontitis and to evaluate the effect of nonsurgical periodontal therapy on the GCF and plasma IL-34 levels. Thirty individuals (age range: 30-56 years) were selected and divided into groups based on the gingival index, probing pocket depth, clinical attachment level, and radiologic parameters (bone loss): Group I (15 individuals with healthy periodontium), Group II (15 individuals with chronic generalized periodontitis) while Group II patients after 8 weeks of the treatment (scaling and root planning) constituted Group III. GCF samples and plasma samples were collected to estimate the levels of IL-34 using enzyme-linked immunosorbent assay kit. The mean IL-34 concentration in GCF and plasma was highest for Group II compared to Group I and decreased after nonsurgical periodontal therapy in chronic generalized periodontitis group. The difference between them was statistically significant (P < 0.05). IL-34 can be considered as an "inflammatory marker" of periodontal disease and can be explored in the future as a potential therapeutic target in the treatment of periodontal disease.

Colony stimulating factor 1 receptor inhibition delays recurrence of glioblastoma after radiation by altering myeloid cell recruitment and polarization.

Glioblastoma (GBM) may initially respond to treatment with ionizing radiation (IR), but the prognosis remains extremely poor because the tumors invariably recur. Using animal models, we previously showed that inhibiting stromal cell-derived factor 1 signaling can prevent or delay GBM recurrence by blocking IR-induced recruitment of myeloid cells, specifically monocytes that give rise to tumor-associated macrophages. The present study was aimed at determining if inhibiting colony stimulating factor 1 (CSF-1) signaling could be used as an alternative strategy to target pro-tumorigenic myeloid cells recruited to irradiated GBM. To inhibit CSF-1 signaling in myeloid cells, we used PLX3397, a small molecule that potently inhibits the tyrosine kinase activity of the CSF-1 receptor (CSF-1R). Combined IR and PLX3397 therapy was compared with IR alone using 2 different human GBM intracranial xenograft models. GBM xenografts treated with IR upregulated CSF-1R ligand expression and increased the number of CD11b+ myeloid-derived cells in the tumors. Treatment with PLX3397 both depleted CD11b+ cells and potentiated the response of the intracranial tumors to IR. Median survival was significantly longer for mice receiving combined therapy versus IR alone. Analysis of myeloid cell differentiation markers indicated that CSF-1R inhibition prevented IR-recruited monocyte cells from differentiating into immunosuppressive, pro-angiogenic tumor-associated macrophages. CSF-1R inhibition may be a promising strategy to improve GBM response to radiotherapy.

Interleukin 34: a new modulator of human and experimental inflammatory bowel disease.

IBD (inflammatory bowel disease), where CD (Crohn's disease) and UC (ulcerative colitis) represent the two main forms, are chronic inflammatory conditions of the intestine. Macrophages play a central role in IBD pathogenesis and are regulated by major differentiation factors such as CSF-1 (colony-stimulating factor 1) in homoeostasis and inflammation. IL (interleukin)-34 has recently been discovered as a second ligand for CSF-1R (CSF-1 receptor). However, expression and involvement of IL-34 in IBD remain unknown. In the present paper, we investigated the expression of IL34, CSF1 and their shared receptor CSF1R in normal human ileum and colon, in inflamed and non-inflamed tissues of CD and UC patients, and in a mouse model of experimental colitis. We found distinct expression patterns of IL34 and CSF1 in ileum and colon, with higher IL34 in ileum and, in contrast, higher CSF1 in colon. Furthermore, IL34 and CSF1 expression was increased with inflammation in IBD patients and in experimental colitis. In humans, infiltrating cells of the lamina propria and intestinal epithelial cells expressed IL-34, and TNF-α (tumour necrosis factor α) regulated IL-34 expression in intestinal epithelial cells through the NF-κB (nuclear factor κB) pathway. These data demonstrate the expression pattern of IL-34 in ileum and colon and suggest IL-34 as a new modulator of inflammation in IBD.

Abstract 1160: Novel CSF-1 receptor ligand IL-34 modulates macrophage-breast cancer cell crosstalk

Abstract Crosstalk between stromal cells and malignant cells within the tumor microenvironment is important for tumorigenesis. According to current clinical and experimental evidence, tumor associated macrophages (TAMs) play a major role in tumor progression to metastasis in different cancers. In breast cancer, increased number of TAMs is associated with poor prognosis. Previous work in our laboratory has shown that depletion of TAMs by blocking colony-stimulating factor-1 (CSF-1) suppresses tumor growth, matrix metalloprotease production and further recruitment of macrophages in a MCF-7 breast cancer xenograft model. In this study, we aim to investigate Interleukin-34 (IL-34), a novel ligand for the colony stimulating factor-1 receptor (CSF-1R). IL-34 functions as a specific and independent ligand and as an agonist to the CSF-1R. Furthermore it is known to induce proliferation through mitogen activated protein kinase (MAPK) activation in macrophages and cancer cells. To date, nothing is known about the role of IL-34 in breast cancer and its effects on downstream signalling pathway modulation in cancer cell-macrophage crosstalk. Our real-time PCR data shows that in co-cultures with murine macrophages, human MCF-7 and MDA-MB-231 breast cancer cells express increased levels of IL-34. In addition, in vitro migration assays demonstrated that recombinant human and murine IL-34 significantly increases the migration of murine macrophages, MCF-7 and MDA-MB-231 breast cancer cells. IL-34 also increased the proliferation of murine macrophages and breast cancer cells. Experiments on the protein level demonstrated the activation of MAPK/ERK in murine macrophages and breast cancer cells by recombinant IL-34. These preliminary data indicate that TAM-breast cancer cell interactions induce IL-34 production associated with induction of proliferation and the migratory capacity of tumor and stromal cells, which together may influence the invasiveness of the developing tumor. Here we propose IL-34 as a target for the treatment of breast cancer which may affect the accumulation of TAMs and improve breast cancer prognosis. Citation Format: Sandun Gunawardhana, Karin Zins, Trevor Lucas, Dietmar Abraham. Novel CSF-1 receptor ligand IL-34 modulates macrophage-breast cancer cell crosstalk. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1160. doi:10.1158/1538-7445.AM2014-1160

Identification of an Isoform of Colony-Stimulating Factor 1 Receptor mRNA in the Rat Testis

Because alternative RNA splicing regulation in the testis is prevalent, we explored testes of Sprague-Dawley rats for existence of alternatively spliced colony-stimulating factor 1 receptor (CSF-1R) mRNA. Using RT-PCR and sequencing, we identified a variant of CSF-1R mRNA that was 284 bp shorter than the full-length CSF-1R transcript. This variant was present in the testis (late fetal stage to adult) and in other organs of rats (7 and 60 days old). The deletion of 284 bp disrupted the open reading frame, resulting in a noncoding mRNA product. When testicular macrophages were stimulated with CSF-1R ligand and lipopolysaccharide, proportionally increased expression of both short isoform and full-length CSF-1R mRNA was observed. Thus, the identified isoform of CSF-1R mRNA may interfere with the expression of full-length CSF-1R mRNA, thereby affecting the biological activity of the ligand/receptor signaling axis in Sprague-Dawley rats.

Spleen serves as a reservoir of osteoclast precursors through vitamin D-induced IL-34 expression in osteopetrotic op/op mice

Osteoclasts are generated from monocyte/macrophage-lineage precursors in response to colony-stimulating factor 1 (CSF-1) and receptor activator of nuclear factor-κB ligand (RANKL). CSF-1-mutated CSF-1(op/op) mice as well as RANKL(-/-) mice exhibit osteopetrosis (OP) caused by osteoclast deficiency. We previously identified RANKL receptor (RANK)/CSF-1 receptor (CSF-1R) double-positive cells as osteoclast precursors (OCPs), which existed in bone in RANKL(-/-) mice. Here we show that OCPs do not exist in bone but in spleen in CSF-1(op/op) mice, and spleen acts as their reservoir. IL-34, a newly discovered CSF-1R ligand, was highly expressed in vascular endothelial cells in spleen in CSF-1(op/op) mice. Vascular endothelial cells in bone also expressed IL-34, but its expression level was much lower than in spleen, suggesting a role of IL-34 in the splenic generation of OCPs. Splenectomy (SPX) blocked CSF-1-induced osteoclastogenesis in CSF-1(op/op) mice. Osteoclasts appeared in aged CSF-1(op/op) mice with up-regulation of IL-34 expression in spleen and bone. Splenectomy blocked the age-associated appearance of osteoclasts. The injection of 2-methylene-19-nor-(20S)-1α,25(OH)(2)D(3) (2MD), a potent analog of 1α,25-dihidroxyvitamin D(3), into CSF-1(op/op) mice induced both hypercalcemia and osteoclastogenesis. Administration of 2MD enhanced IL-34 expression not only in spleen but also in bone through a vitamin D receptor-mediated mechanism. Either splenectomy or siRNA-mediated knockdown of IL-34 suppressed 2MD-induced osteoclastogenesis. These results suggest that IL-34 plays a pivotal role in maintaining the splenic reservoir of OCPs, which are transferred to bone in response to diverse stimuli, in CSF-1(op/op) mice. The present study also suggests that the IL-34 gene in vascular endothelial cells is a unique target of vitamin D.

遺伝性白質脳症とhereditary diffuse leukoencephalopathy with spheroids（HDLS）の分子病態

Adult-onset leukoencephalopathy involving the white matter of the brain is a heterogeneous disorder that exhibits a wide range of clinical manifestations. Recent advances in molecular genetics enable gene-based diagnosis of some forms of adult-onset leukoencephalopathy. In this review, the classification of adult-onset leukoencephalopathy based on molecular genetic findings is proposed. The autosomal dominant forms of adult-onset leukoencephalopathy include hereditary diffuse leukoencephalopathy with spheroids (HDLS), autosomal dominant adult-onset leukoencephalopathy (ALDL), cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), and Alexander disease. The autosomal recessive forms of adult-onset leukoencephalopathy include cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), vanishing white matter (VWM) with leukoencephalopathy, Nasu-Hakola disease, and metachromatic leukodystrophy (MDL). X-chromosome-linked disorders include fragile X-associated tremor and ataxia syndrome (FXTAS) and adrenoleukodystrophy (ALD). Identification of the genes responsible for adult-onset leukoencephalopathy provides an important clue for elucidation of molecular pathophysiology underlying white matter disorders. One example is the identification of mutations in colony stimulating factor 1 receptor (CSF-1R) in patients with HDLS. Missense and splice site mutations have been found in the tyrosine kinase domain of CSF-1R. CSF-1R is highly expressed in microglia in the brain. It has been demonstrated that mice depleted of CSF-1R exhibit loss of microglia in the brain. In addition, stimulation of IL-34, a ligand of CSF-1R, induces proliferation and activation of microglia. These findings raise an intriguing possibility that dysfunction of microglia may play a role in the pathogenesis of white matter lesions occurring in patients with HDLS.

A novel function of colony-stimulating factor 1 receptor in hTERT immortalization of human epithelial cells

The receptor for macrophage colony-stimulating factor 1 receptor (CSF1R) is a product of the proto-oncogene c-fms and a member of the class III transmembrane tyrosine kinase receptor family. Earlier, we described increased mRNA expression of CSF1R in human telomerase reverse transcriptase (hTERT) immortalized human ovarian surface epithelial (IOSE) cell lines derived from a single donor. Here, we further describe that CSF1R is upregulated at both the mRNA and protein level in hTERT immortalized human normal OSE cells from two different donors and in hTERT immortalized human pancreatic ductal epithelial cells. CSF1R was not upregulated in hTERT immortalized epithelial clones that subsequently underwent senescence or in immortalized fibroblasts. Upon stimulation by the CSF1R ligand CSF1, the immortalized epithelial cell lines showed rapid internalization of CSF1R with concomitant down-modulation and colocalization of phosphorylated NFkappaBp65 with hTERT protein, hTERT translocation into the nucleus and the binding of c-Myc to the hTERT promoter region. Reducing the expression of CSF1R using short hairpin interfering RNA abolished these effects and also decreased cell survival and the number of population doublings under suboptimal culture conditions. The telomerase inhibitor GRN163L confirmed a role for telomerase in the cleavage of the intracellular domain of CSF1R. On the basis of these findings, we suggest that CSF1R may be a critical factor facilitating hTERT immortalization of epithelial cells.