Efficacy of durvalumab plus chemotherapy in advanced biliary duct cancer and biomarkers exploration.

BACKGROUND: The anti-PD-L1 antibody durvalumab has been approved for use in first-line advanced biliary duct cancer (ABC). So far, predictive biomarkers of efficacy are lacking. METHODS: ABC patients who underwent gemcitabine-based chemotherapy with or without durvalumab were retrospectively enrolled, and their baseline clinical pathological indices were retrieved from medical records. Overall (OS) and progression free survival (PFS) were calculated and analyzed. The levels of peripheral biomarkers from 48 patients were detected with assay kits including enzyme-linked immunosorbent assay. Genomic alterations in 27 patients whose tumor tissues were available were depicted via targeted next-generation sequencing. RESULTS: A total of 186 ABC patients met the inclusion criteria between January 2020 and December 2022 were finally enrolled in this study. Of these, 93 patients received chemotherapy with durvalumab and the rest received chemotherapy alone. Durvalumab plus chemotherapy demonstrated significant improvements in PFS (6.77 vs. 4.99 months; hazard ratio 0.65 [95% CI 0.48-0.88]; P = 0.005), but not OS (14.29 vs. 13.24 months; hazard ratio 0.91 [95% CI 0.62-1.32]; P = 0.608) vs. chemotherapy alone in previously untreated ABC patients. The objective response rate (ORR) in patients receiving chemotherapy with and without durvalumab was 19.1% and 7.8%, respectively. Pretreatment sPD-L1, CSF1R and OPG were identified as significant prognosis predictors in patients receiving durvalumab. ADGRB3 and RNF43 mutations were enriched in patients who responded to chemotherapy plus durvalumab and correlated with superior survival. CONCLUSION: This retrospective real-world study confirmed the clinical benefit of durvalumab plus chemotherapy in treatment-naïve ABC patients. Peripheral sPD-L1 and CSF1R are promising prognostic biomarkers for this therapeutic strategy. Presence of ADGRB3 or RNF43 mutations could improve the stratification of immunotherapy outcomes, but further studies are warranted to explore the underlying mechanisms.

Pexidartinib Upfront in a Case of Tenosynovial Giant Cell Tumor: Proof of Concept for a Treatment Paradigm Shift.

BACKGROUND: Tenosynovial giant cell tumor (TGCT) is a rare, locally aggressive tumor of the joints, bursa, and tendon sheath that can cause considerable pain and substantial morbidity. Although surgery is the primary treatment for patients with TGCT, surgical resection is associated with high rates of recurrence, particularly for patients with diffuse TGCT. Pexidartinib, a colony-stimulating factor 1 receptor inhibitor, is approved by the US Food and Drug Administration for the treatment of adult patients with symptomatic TGCT associated with severe morbidity or functional limitations and not amenable to improvement with surgery. CASE DESCRIPTION: A 32-year-old man presented with intra-articular diffuse TGCT with pain and received noncurative treatment for 5 years (2014-2019). In 2019, the patient was found to have extensive disease accompanied by pain and limited range of motion. The patient's case was presented to a sarcoma multidisciplinary tumor board, who determined that surgery would cause significant morbidity and macroscopic residual tumor. As a result of the extent of disease, young age, and otherwise good health, treatment with pexidartinib was started through a compassionate use program at 800 mg/day. After dose reductions to pexidartinib at 400 mg/day and then 200 mg/day as a result of creatine phosphokinase elevations, the patient achieved a complete response after 2 years of treatment; pain was reduced and mobility was restored. The patient reported no side effects related to pexidartinib treatment. Treatment was stopped in 2022 for future family planning. After pexidartinib therapy was interrupted, the patient's wife had a successful pregnancy and delivery; however, the disease showed a slow but constant clinical deterioration, with a reduction in the range of movement of the affected knee and an apparent increase in widespread TGCT nodules. CONCLUSION: Our case is unique because it provides support for pexidartinib use as upfront therapy for TGCT, instead of surgery, in selected cases.

LncRNA018392 promotes the proliferation of Liaoning cashmere goat skin fibroblasts by upregulating CSF1R through binding to SPI1.

BACKGROUND: Liaoning cashmere goat is recognized as a valuable genetic resource breed, with restrictions on genetic outflow in China. Hair follicle development in the cashmere goat is influenced by melatonin and long non-coding RNAs (lncRNAs). However, the role of lncRNAs in facilitating melatonin-promoted cashmere growth remains poorly understood. Previous studies have identified a new lncRNA, lncRNA018392, which is involved in the melatonin-promoted proliferation of cashmere skin fibroblasts. METHOD: Flow cytometry and CCK-8 assays confirmed that silencing lncRNA018392 negates the effects of melatonin on cell proliferation, and that proliferation was reduced when the gene CSF1R, located near lncRNA018392, was inhibited. Further investigation using a dual-luciferase reporter assay showed that lncRNA018392 could positively regulate the promoter of CSF1R. RESULTS: Results from RNA-binding protein immunoprecipitation (RIP) and chromatin immunoprecipitation sequencing (ChIP-Seq) revealed that lncRNA018392 interacts with the transcription factor SPI1, with CSF1R being a downstream target gene regulated by SPI1. This interaction was confirmed by ChIP-PCR, which demonstrated SPI1's binding to CSF1R. CONCLUSIONS: This study found that the melatonin-responsive lncRNA018392 accelerates the cell cycle and promotes cell proliferation by recruiting SPI1 to upregulate the expression of the neighboring gene CSF1R. These findings provide a theoretical foundation for elucidating the molecular mechanisms of cashmere growth and for the molecular breeding of cashmere goats.

Identification of Immune Gene Signature Associated with T Cells and Natural Killer Cells in Type 1 Diabetes.

Purpose: This study aimed to investigate the abnormal infiltration of immune cells in type 1 diabetes mellitus (T1D) and elucidate their regulatory mechanisms. Methods: Public T1D-related gene expression data were obtained from the Gene Expression Omnibus database.The GSE123658 dataset analyzed whole blood RNA-seq data from type 1 diabetic patients and healthy volunteers. The GSE110914 dataset analyzed neutrophils purified from peripheral blood of patients with symptomatic and pre-symptomatic type 1 diabetes (T1D), at risk of T1D, and healthy controls. Immune cell infiltration analysis was performed to identify abnormally infiltrating immune cells. Differentially expressed immune genes (DEIGs) in T1D samples were identified, followed by the construction of an immune gene signature (IGS) using a protein-protein interaction (PPI) network and Least absolute shrinkage and selection operator Cox regression analyses (LASSO Cox regression analyses). The regulatory mechanisms underlying IGS were explored using gene set enrichment analysis. Furthermore, expression validation, diagnostic efficacy evaluation, and upstream miRNA prediction of hub signature genes were performed. We verified the miRNA expression of the key gene colony stimulating factor 1 (CSF1) and microRNA-326 (miR-326) by reverse transcription-quantitative PCR (RT‒qPCR). Results: The proportion of infiltrating T and natural killer (NK) cells differed between the T1D and control samples, and 207 immune genes (IGs) related to these immune cells were extracted. After differential expression, PPI, and LASSO Cox regression analyses, four signature DEIGs were identified for IGS construction: notch receptor 1 (NOTCH1), Janus kinase 3 (JAK3), tumor necrosis factor receptor superfamily member 4(TNFRSF4), and CSF1. Key pathways such as the Toll-like receptor signaling pathway were significantly activated in the high-risk group. Moreover, the upregulation of CSF1 in T1D samples was confirmed using a validation dataset, and CSF1 showed high diagnostic efficacy for T1D. Furthermore, CSF1 was targeted by miR-326.We used validated key genes in T1D patients, several of which were confirmed by RT‒qPCR. Conclusion: In conclusion, the identified key IGs may play an important role in T1D. CSF1 can be developed as a novel diagnostic biomarker for T1D.

Phagocytosis Checkpoints in Glioblastoma: CD47 and Beyond.

Glioblastoma multiforme (GBM) is one of the deadliest human cancers with very limited treatment options available. The malignant behavior of GBM is manifested in a tumor which is highly invasive, resistant to standard cytotoxic chemotherapy, and strongly immunosuppressive. Immune checkpoint inhibitors have recently been introduced in the clinic and have yielded promising results in certain cancers. GBM, however, is largely refractory to these treatments. The immune checkpoint CD47 has recently gained attention as a potential target for intervention as it conveys a "don't eat me" signal to tumor-associated macrophages (TAMs) via the inhibitory SIRP alpha protein. In preclinical models, the administration of anti-CD47 monoclonal antibodies has shown impressive results with GBM and other tumor models. Several well-characterized oncogenic pathways have recently been shown to regulate CD47 expression in GBM cells and glioma stem cells (GSCs) including Epidermal Growth Factor Receptor (EGFR) beta catenin. Other macrophage pathways involved in regulating phagocytosis including TREM2 and glycan binding proteins are discussed as well. Finally, chimeric antigen receptor macrophages (CAR-Ms) could be leveraged for greatly enhancing the phagocytosis of GBM and repolarization of the microenvironment in general. Here, we comprehensively review the mechanisms that regulate the macrophage phagocytosis of GBM cells.

Brain volume and microglial density changes are correlated in a juvenile mouse model of cranial radiation and CSF1R inhibitor treatment.

Microglia have been shown to proliferate and become activated following cranial radiotherapy (CRT), resulting in a chronic inflammatory response. We investigated the role of microglia in contributing to widespread volume losses observed in the brain following CRT in juvenile mice. To manipulate microglia, we used low-dose treatment with a highly selective CSF1R inhibitor called PLX5622 (PLX). We hypothesized that alteration of the post-CRT microglia population would lead to changes in brain development outcomes, as evaluated by structural MRI. Wild-type C57BL/6J mice were provided with daily intraperitoneal injections of PLX (25 mg/kg) or vehicle from postnatal day (P)14 to P19. Mice also received whole-brain irradiation (7 Gy) or sham irradiation (0 Gy) at 16 days of age. In one cohort of mice, immunohistochemical assessment in tissue sections was conducted to assess the impact of the selected PLX and CRT doses as well as their combination. In a separate cohort, mice were imaged using MRI at P14 (pretreatment), P19, P23, P42 and P63 in order to assess induced volume changes, which were measured based on structures from a predefined atlas. We observed that PLX and radiation treatments led to sex-specific changes in the microglial cell population. Across treatment groups, MRI-detected anatomical volumes at P19 and P63 were associated with microglia and proliferating microglia densities, respectively. Overall, our study demonstrates that low-dose PLX treatment produces a sex-dependent response in juvenile mice, that manipulation of microglia alters CRT-induced volume changes and that microglia density and MRI-derived volume changes are correlated in this model.

Chondroid Synoviocytic Neoplasm: A Clinicopathologic, Immunohistochemical, and Molecular Genetic Study of a Distinctive Tumor of Synoviocytes.

Tumors resembling tenosynovial giant cell tumor (TGCT) but additionally forming chondroid matrix are rare and most often involve the temporomandibular joint (TMJ). We studied 21 tumors consisting of synoviocytes (large, eosinophilic mononuclear cells containing hemosiderin) and chondroid matrix to better understand these unusual neoplasms. The tumors occurred in 10 males and 11 females, in the age group of 31 to 80 years (median, 50 years) and involved the TMJ region (16), extremities (4), and spine (1). As in conventional TGCT, all were composed of synoviocytes, small histiocytes, foamy macrophages, siderophages, and osteoclast-like giant cells in variably hyalinized background. Expansile nodules of large, moderately atypical synoviocytes were present, in addition to "chondroblastoma-like," "chondroma-like," or "phosphaturic mesenchymal tumor-like" calcified matrix. The synoviocytes expressed clusterin (17/19) and less often desmin (3/15). The tumors were frequently CSF1 positive by chromogenic in situ hybridization (8/13) but at best weakly positive for CSF1 by immunohistochemistry (0/3). Background small histiocytes were CD163 positive (12/12). All were FGF23 negative (0/10). Cells within lacunae showed a synoviocytic phenotype (clusterin positive; S100 protein and ERG negative). RNA-Seq was successful in 13 cases; fusions were present in 7 tumors, including FN1::TEK (5 cases); FN1::PRG4 (2 cases); and MALAT1::FN1, PDGFRA::USP35, and TIMP3::ZCCHC7 (1 case each). Three tumors contained more than 1 fusion (FN1::PRG4 with TIMP3::ZCCHC7, FN1::TEK with FN1::PRG4, and FN1::TEK with MALAT1::FN1). Clinical follow-up (17 patients; median follow-up duration 38 months; range 4-173 months) showed 13 (76%) to be alive without evidence of disease and 4 (24%) to be alive with persistent/recurrent local disease. No metastases or deaths from disease were observed. We conclude that these unusual tumors represent a distinct category of synoviocytic neoplasia, which we term "chondroid synoviocytic neoplasm," rather than simply ordinary TGCT with cartilage. Despite potentially worrisome morphologic features, they appear to behave in at most a locally aggressive fashion.

Heterozygous missense CSF1R variants hamper in vitro CD34+-derived dendritic cell generation but not in vivo dendritic cell development.

Colony stimulating factor 1 receptor (CSF1R) is an essential receptor for both colony stimulating factor 1 (CSF1) and interleukin (IL) 34 signaling expressed on monocyte precursors and myeloid cells, including monocytes, dendritic cells (DC), and microglia. In humans, dominant heterozygous pathogenic variants in CSF1R cause a neurological condition known as CSF1R-related disorder (CSF1R-RD), typically with late onset, previously referred to as adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP). CSF1R-RD is characterized by microglia reduction and altered monocyte function; however, the impact of pathogenic CSF1R variants on the human DC lineage remains largely unknown. We previously reported that cord blood CD34+ stem cell-derived DCs generated in vitro originate specifically from CSF1R expressing precursors. In this study, we examined the DC lineage of four unrelated patients with late-onset CSF1R-RD who carried heterozygous missense CSF1R variants (c.2330G>A, c.2375C>A, c.2329C>T, and c.2381T>C) affecting different amino acids in the protein tyrosine kinase domain of CSF1R. CD34+ stem cells and CD14+ monocytes were isolated from peripheral blood and subjected to an in vitro culture protocol to differentiate towards conventional DCs and monocyte-derived DCs, respectively. Flow cytometric analysis revealed that monocytes from patients with late-onset CSF1R-RD were still able to differentiate into monocyte-derived DCs in vitro, whereas the ability of CD34+ stem cells to differentiate into conventional DCs was impaired. Strikingly, the peripheral blood of patients contained all naturally occurring DC subsets. We conclude that the in vitro abrogation of DC-development in patients with heterozygous pathogenic missense CSF1R variants does not translate to an impairment in DC development in vivo and speculate that CSF1R signalling in vivo is compensated, which needs further study.

JDF promotes the apoptosis of M2 macrophages and reduces epithelial-mesenchymal transition and migration of liver cancer cells by inhibiting CSF-1/PI3K/AKT signaling pathway.

Background: The interaction between cancer cells and the tumor microenvironment is of critical importance in liver cancer. Jiedu Granule formula (JDF) has been shown to minimize the risk of recurrence and metastasis following liver cancer resection. Investigating the mechanism underlying the therapeutic effects of JDF can extend its field of application and develop novel treatment approaches. Methods: We established a rat liver orthotopic transplantation tumor model, and recorded the prognostic effects of JDF adjuvant therapy on the recurrence and metastasis of liver cancer. Liver and lung tissues were collected for immunofluorescence staining and H&E staining, respectively. In addition, THP-1 cells were incubated with PMA and IL-4 to induce them to differentiate into M2 macrophages. CSF-1 expression was knocked down using lentivirus to determine the function of CSF-1. Liver cancer cells were cultured with a conditioned medium (CM) or co-cultured with macrophages. Cell viability was determined using the MTT assay. The levels of CSF-1, CSF-1R, E-cadherin, N-cadherin, PI3K, AKT, and cleaved caspase-3 were detected using ELISA, Western blotting and qPCR. The ability of cells to migrate was assessed using cell scratch and transwell assays. Apoptosis was evaluated using flow cytometry. Results: The JDF treatment decreased the risk of liver cancer metastasis after surgery and the infiltration of CD206/CD68 cells in liver cancer tissue. In cell experiments, JDF showed effects in suppressing M2 macrophages activity and downregulating the expression of CSF-1 and CSF-1R. The concentration of CSF-1 in the supernatant was also lower in the JDF-treated group. Futhermore, M2-CM was found to promote cancer cell migration and epithelial-mesenchymal transition (EMT); however, these effects were weakened after administering JDF. Knocking down endogenous CSF-1 in M2 macrophages resulted in a comparable suppression of cancer cell migration and EMT. Additionally, JDF treatment inhibited activation of the PI3K/AKT pathway, thus promoting the apoptosis of M2 macrophages. Conclusions: Treatment with JDF reduced the EMT and migratory capacity of liver cancer cells, which might be attributed to the inhibition of M2 macrophage infiltration and interruption of the CSF-1/PI3K/AKT signaling pathway. This mechanism may hold significant implications for mitigating the risk of metastatic spread in the aftermath of hepatic surgery.

Deciphering glial contributions to CSF1R-related disorder via single-nuclear transcriptomic profiling: a case study.

CSF1R-related disorder (CSF1R-RD) is a neurodegenerative condition that predominantly affects white matter due to genetic alterations in the CSF1R gene, which is expressed by microglia. We studied an elderly man with a hereditary, progressive dementing disorder of unclear etiology. Standard genetic testing for leukodystrophy and other neurodegenerative conditions was negative. Brain autopsy revealed classic features of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), including confluent white matter degeneration with axonal spheroids and pigmented glial cells in the affected white matter, consistent with CSF1R-RD. Subsequent long-read sequencing identified a novel deletion in CSF1R that was not detectable with short-read exome sequencing. To gain insight into potential mechanisms underlying white matter degeneration in CSF1R-RD, we studied multiple brain regions exhibiting varying degrees of white matter pathology. We found decreased CSF1R transcript and protein across brain regions, including intact white matter. Single nuclear RNA sequencing (snRNAseq) identified two disease-associated microglial cell states: lipid-laden microglia (expressing GPNMB, ATG7, LGALS1, LGALS3) and inflammatory microglia (expressing IL2RA, ATP2C1, FCGBP, VSIR, SESN3), along with a small population of CD44+ peripheral monocyte-derived macrophages exhibiting migratory and phagocytic signatures. GPNMB+ lipid-laden microglia with ameboid morphology represented the end-stage disease microglia state. Disease-associated oligodendrocytes exhibited cell stress signatures and dysregulated apoptosis-related genes. Disease-associated oligodendrocyte precursor cells (OPCs) displayed a failure in their differentiation into mature myelin-forming oligodendrocytes, as evidenced by upregulated LRP1, PDGFRA, SOX5, NFIA, and downregulated NKX2-2, NKX6.2, SOX4, SOX8, TCF7L2, YY1, ZNF488. Overall, our findings highlight microglia-oligodendroglia crosstalk in demyelination, with CSF1R dysfunction promoting phagocytic and inflammatory microglia states, an arrest in OPC differentiation, and oligodendrocyte depletion.

Novel variants in CSF1R associated with adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP).

The CSF1R gene, located on chromosome 5, encodes a 108 kDa protein and plays a critical role in regulating myeloid cell function. Mutations in CSF1R have been identified as a cause of a rare white matter disease called adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP, also known as CSF1R-related leukoencephalopathy), characterized by progressive neurological dysfunction. This study aimed to broaden the genetic basis of ALSP by identifying novel CSF1R variants in patients with characteristic clinical and imaging features of ALSP. Genetic analysis was performed through whole-exome sequencing or panel analysis for leukodystrophy genes. Variant annotation and classification were conducted using computational tools, and the identified variants were categorized following the recommendations of the American College of Medical Genetics and Genomics (ACMG). To assess the evolutionary conservation of the novel variants within the CSF1R protein, amino acid sequences were compared across different species. The study identified six previously unreported CSF1R variants (c.2384G>T, c.2133_2919del, c.1837G>A, c.2304C>A, c.2517G>T, c.2642C>T) in seven patients with ALSP, contributing to the expanding knowledge of the genetic diversity underlying this rare disease. The analysis revealed considerable genetic and clinical heterogeneity among these patients. The findings emphasize the need for a comprehensive understanding of the genetic basis of rare diseases like ALSP and underscored the importance of genetic testing, even in cases with no family history of the disease. The study's contribution to the growing spectrum of ALSP genetics and phenotypes enhances our knowledge of this condition, which can be crucial for both diagnosis and potential future treatments.

Microglia contribute to nociception via CSF-1R signaling pathway in rat orofacial carcinoma.

OBJECTIVE: Cancer-induced pain is the most common complication of the head and neck cancer. The microglia colony-stimulating factor receptor 1 (CSF1R) plays a crucial role in the inflammation and neuropathic pain. However, the effect of CSF1R on orofacial cancer-induced pain is unclear. Here, we aimed to determine the role of CSF1R in orofacial pain caused by cancer. METHODS: We established an animal model of cancer-induced orofacial pain with Walker 256B cells. Von Frey filament test and laser-intensity pain tester were used to evaluate tumor-induced mechanical and thermal hypersensitivity. Minocycline and PLX3397 were used to alter tumor-induced mechanical and thermal hyperalgesia. Additionally, we evaluated the effect of PLX3397 on immunoinflammatory mediators and neuronal activation within the trigeminal spinal subnucleus caudalis (Vc). RESULTS: Walker 256B cell-induced tumor growth resulted in mechanical and thermal hyperalgesia, accompanying by microglia activation and CSF1R upregulation. Treatment with minocycline or PLX3397 reversed the associated nocifensive behaviors and microglia activation triggered by tumor. As a result of PLX3397 treatment, tumor-induced increases in pro-inflammatory cytokine expression and neuronal activation of the Vc were significantly inhibited. CONCLUSIONS: The results of our study showed that blocking microglial activation via CSF1R may help prevent cancer-induced orofacial pain.

IL-34 and its receptors as predictors of brain metastasis and prognosis in lung adenocarcinoma: Unveiling insights through bioinformatic and immunohistochemical investigations.

Background: Brain metastasis (BM) is a prevalent form of metastasis in lung adenocarcinoma (LUAD), necessitating investigations into the underlying mechanisms. Interleukin 34 (IL-34) and its receptors, macrophage colony-stimulating factor-1 receptor (CSF-IR), Syndecan-1 (SDC-1), and protein-tyrosine phosphatase zeta receptor (PTPRZ1), are known to play pivotal roles in the metastasis of malignant tumors, thereby holding promise as potential biomarkers for studying BM in LUAD. Methods: We performed immunohistochemistry to analyze the expression of IL-34, CSF-1R, SDC-1, and PTPRZ1 in 10 pairs of LUAD primary tissues and BMs, along with 96 unpaired primary tissues and 68 unpaired BMs. Subsequently, we evaluated the association between protein expression and the occurrence of BM. Furthermore, Kaplan-Meier survival curve analysis was conducted on both network and clinical data to explore the association between protein expression and patient prognosis and survival. Results: At the protein level, the expression of IL-34 and its receptors showed significant variation between paired primary tumors and BMs in 10 LUAD patients. The levels of IL-34, CSF-1R, and SDC-1 expression are typically elevated in brain metastatic lesions of LUAD compared to primary LUAD tumors. Furthermore, patients with high CSF-1R expression in primary LUAD are at a greater risk of developing brain metastases. High expression of IL-34 and CSF-1R in primary LUAD lesions indicated poor disease-free survival (DFS) and overall survival (OS), while high expression of SDC-1 indicated poor OS. Cox multivariate analysis further revealed that CSF-1R and IL-34+CSF-1R positivity independently affected LUAD OS. These findings were further substantiated in unpaired samples. Conclusions: Our results indicate significant alterations in the expression of IL-34 and its receptors, CSF-1R and SDC-1, between LUAD primary lesions and BMs, with increased expression observed in BMs. LUAD patients with positive CSF-1R expression in primary lesions exhibited a higher likelihood of developing BM, and high expression of IL-34, CSF-1R, and SDC-1 correlated with poor prognosis. These findings contribute novel insights towards identifying potential treatment or diagnostic targets for metastatic LUAD.

CSF1R inhibition depletes brain macrophages and reduces brain virus burden in SIV-infected macaques.

Perivascular macrophages (PVMs) and, to a lesser degree, microglia are targets and reservoirs of HIV and simian immunodeficiency virus (SIV) in the brain. Previously, we demonstrated that colony-stimulating factor 1 receptor (CSF1R) in PVMs was upregulated and activated in chronically SIV-infected rhesus macaques with encephalitis, correlating with SIV infection of PVMs. Herein, we investigated the role of CSF1R in the brain during acute SIV infection using BLZ945, a brain-penetrant CSF1R kinase inhibitor. Apart from three uninfected historic controls, nine Indian rhesus macaques were infected acutely with SIVmac251 and divided into three groups (n = 3 each): an untreated control and two groups treated for 20-30 days with low- (10 mg/kg/day) or high- (30 mg/kg/day) dose BLZ945. With the high-dose BLZ945 treatment, there was a significant reduction in cells expressing CD163 and CD206 across all four brain areas examined, compared with the low-dose treatment and control groups. In 9 of 11 tested regions, tissue viral DNA (vDNA) loads were reduced by 95%-99% following at least one of the two doses, and even to undetectable levels in some instances. Decreased numbers of CD163+ and CD206+ cells correlated significantly with lower levels of vDNA in all four corresponding brain areas. In contrast, BLZ945 treatment did not significantly affect the number of microglia. Our results indicate that doses as low as 10 mg/kg/day of BLZ945 are sufficient to reduce the tissue vDNA loads in the brain with no apparent adverse effect. This study provides evidence that infected PVMs are highly sensitive to CSF1R inhibition, opening new possibilities to achieve viral clearance.

Pexidartinib and Immune Checkpoint Inhibitors Combine to Activate Tumor Immunity in a Murine Colorectal Cancer Model by Depleting M2 Macrophages Differentiated by Cancer-Associated Fibroblasts.

Tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs) are known to play supportive roles in tumor development and progression, but their interactions in colorectal cancer (CRC) remain unclear. Here, we investigated the effects of colon-cancer-derived CAFs on TAM differentiation, migration, and tumor immunity, both in vitro and in vivo. When co-cultured with monocytes, CAFs attracted monocytes and induced their differentiation into M2 macrophages. Immunohistology of surgically resected human CRC specimens and orthotopically transplanted mouse tumors revealed a correlation between numbers of CAFs and numbers of M2 macrophages. In a mouse model of CRC orthotopic transplantation, treatment with an inhibitor of the colony-stimulating factor-1 receptor (PLX3397) depleted M2 macrophages and increased CD8-positive T cells infiltrating the tumor nest. While this treatment had a minor effect on tumor growth, combining PLX3397 with anti-PD-1 antibody significantly reduced tumor growth. RNA-seq following combination therapy showed activation of tumor immunity. In summary, CAFs are involved in the induction and mobilization of M2 macrophage differentiation in the CRC tumor immune microenvironment, and the combination of cancer immunotherapy and PLX3397 may represent a novel therapeutic option for CRC.

Targeting CSF1R in myeloid-derived suppressor cells: insights into its immunomodulatory functions in colorectal cancer and therapeutic implications.

OBJECTIVE: This study aimed to investigate the critical role of MDSCs in CRC immune suppression, focusing on the CSF1R and JAK/STAT3 signaling axis. Additionally, it assessed the therapeutic efficacy of LNCs@CSF1R siRNA and anti-PD-1 in combination. METHODS: Single-cell transcriptome sequencing data from CRC and adjacent normal tissues identified MDSC-related differentially expressed genes. RNA-seq analysis comprehensively profiled MDSC gene expression in murine CRC tumors. LNCs@CSF1R siRNA nanocarriers effectively targeted and inhibited CSF1R. Flow cytometry quantified changes in MDSC surface markers post-CSF1R inhibition. RNA-seq and pathway enrichment analyses revealed the impact of CSF1R on MDSC metabolism and signaling. The effect of CSF1R inhibition on the JAK/STAT3 signaling axis was validated using Colivelin and metabolic assessments. Glucose and fatty acid uptake were measured via fluorescence-based flow cytometry. The efficacy of LNCs@CSF1R siRNA and anti-PD-1, alone and in combination, was evaluated in a murine CRC model with extensive tumor section analyses. RESULTS: CSF1R played a significant role in MDSC-mediated immune suppression. LNCs@CSF1R siRNA nanocarriers effectively targeted MDSCs and inhibited CSF1R. CSF1R regulated MDSC fatty acid metabolism and immune suppression through the JAK/STAT3 signaling axis. Inhibition of CSF1R reduced STAT3 activation and target gene expression, which was rescued by Colivelin. Combined treatment with LNCs@CSF1R siRNA and anti-PD-1 significantly slowed tumor growth and reduced MDSC abundance within CRC tumors. CONCLUSION: CSF1R via the JAK/STAT3 axis critically regulates MDSCs, particularly in fatty acid metabolism and immune suppression. Combined therapy with LNCs@CSF1R siRNA and anti-PD-1 enhances therapeutic efficacy in a murine CRC model, providing a strong foundation for future clinical applications.

Redefining the ontogeny of hyalocytes as yolk sac-derived tissue-resident macrophages of the vitreous body.

BACKGROUND: The eye is a highly specialized sensory organ which encompasses the retina as a part of the central nervous system, but also non-neural compartments such as the transparent vitreous body ensuring stability of the eye globe and a clear optical axis. Hyalocytes are the tissue-resident macrophages of the vitreous body and are considered to play pivotal roles in health and diseases of the vitreoretinal interface, such as proliferative vitreoretinopathy or diabetic retinopathy. However, in contrast to other ocular macrophages, their embryonic origin as well as the extent to which these myeloid cells might be replenished by circulating monocytes remains elusive. RESULTS: In this study, we combine transgenic reporter mice, embryonic and adult fate mapping approaches as well as parabiosis experiments with multicolor immunofluorescence labeling and confocal laser-scanning microscopy to comprehensively characterize the murine hyalocyte population throughout development and in adulthood. We found that murine hyalocytes express numerous well-known myeloid cell markers, but concomitantly display a distinct immunophenotype that sets them apart from retinal microglia. Embryonic pulse labeling revealed a yolk sac-derived origin of murine hyalocytes, whose precursors seed the developing eye prenatally. Finally, postnatal labeling and parabiosis established the longevity of hyalocytes which rely on Colony Stimulating Factor 1 Receptor (CSF1R) signaling for their maintenance, independent of blood-derived monocytes. CONCLUSION: Our study identifies hyalocytes as long-living progeny of the yolk sac hematopoiesis and highlights their role as integral members of the innate immune system of the eye. As a consequence of their longevity, immunosenescence processes may culminate in hyalocyte dysfunction, thereby contributing to the development of vitreoretinal diseases. Therefore, myeloid cell-targeted therapies that convey their effects through the modification of hyalocyte properties may represent an interesting approach to alleviate the burden imposed by diseases of the vitreoretinal interface.

Therapeutic potential of human microglia transplantation in a chimeric model of CSF1R-related leukoencephalopathy.

Microglia replacement strategies are increasingly being considered for the treatment of primary microgliopathies like adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP). However, available mouse models fail to recapitulate the diverse neuropathologies and reduced microglia numbers observed in patients. In this study, we generated a xenotolerant mouse model lacking the fms-intronic regulatory element (FIRE) enhancer within Csf1r, which develops nearly all the hallmark pathologies associated with ALSP. Remarkably, transplantation of human induced pluripotent stem cell (iPSC)-derived microglial (iMG) progenitors restores a homeostatic microglial signature and prevents the development of axonal spheroids, white matter abnormalities, reactive astrocytosis, and brain calcifications. Furthermore, transplantation of CRISPR-corrected ALSP-patient-derived iMG reverses pre-existing spheroids, astrogliosis, and calcification pathologies. Together with the accompanying study by Munro and colleagues, our results demonstrate the utility of FIRE mice to model ALSP and provide compelling evidence that iMG transplantation could offer a promising new therapeutic strategy for ALSP and perhaps other microglia-associated neurological disorders.

Allogenic microglia replacement: A novel therapeutic strategy for neurological disorders.

Microglia are resident immune cells in the central nervous system (CNS) that play vital roles in CNS development, homeostasis and disease pathogenesis. Genetic defects in microglia lead to microglial dysfunction, which in turn leads to neurological disorders. The correction of the specific genetic defects in microglia in these disorders can lead to therapeutic effects. Traditional genetic defect correction approaches are dependent on viral vector-based genetic defect corrections. However, the viruses used in these approaches, including adeno-associated viruses, lentiviruses and retroviruses, do not primarily target microglia; therefore, viral vector-based genetic defect corrections are ineffective in microglia. Microglia replacement is a novel approach to correct microglial genetic defects via replacing microglia of genetic defects with allogenic healthy microglia. In this paper, we systematically review the history, rationale and therapeutic perspectives of microglia replacement, which would be a novel strategy for treating CNS disorders.

Leukoencephalopathy with calcifications, developmental brain abnormalities and skeletal dysplasia due to homozygosity for a hypomorphic CSF1R variant: A report of three siblings.

We report three siblings homozygous for CSF1R variant c.1969 + 115_1969 + 116del to expand the phenotype of "brain abnormalities, neurodegeneration, and dysosteosclerosis" (BANDDOS) and discuss its link with "adult leukoencephalopathy with axonal spheroids and pigmented glia" (ALSP), caused by heterozygous CSF1R variants. We evaluated medical, radiological, and laboratory findings and reviewed the literature. Patients presented with developmental delay, therapy-resistant epilepsy, dysmorphic features, and skeletal abnormalities. Secondary neurological decline occurred from 23 years in sibling one and from 20 years in sibling two. Brain imaging revealed multifocal white matter abnormalities and calcifications during initial disease in siblings two and three. Developmental brain anomalies, seen in all three, were most severe in sibling two. During neurological decline in siblings one and two, the leukoencephalopathy was progressive and had the MRI appearance of ALSP. Skeletal survey revealed osteosclerosis, most severe in sibling three. Blood markers, monocytes, dendritic cell subsets, and T-cell proliferation capacity were normal. Literature review revealed variable initial disease and secondary neurological decline. BANDDOS presents with variable dysmorphic features, skeletal dysplasia, developmental delay, and epilepsy with on neuro-imaging developmental brain anomalies, multifocal white matter abnormalities, and calcifications. Secondary neurological decline occurs with a progressive leukoencephalopathy, in line with early onset ALSP. Despite the role of CSF1R signaling in myeloid development, immune deficiency is absent. Phenotype varies within families; skeletal and neurological manifestations may be disparate.