Caren Yu-Ju Wu, Ph.D., is a postdoctoral researcher at the Department of Neurosurgery.
Dr. Wu is interested in the biology of neuro-inflammation, and malignant brain tumors, namely glioma. She is involved in basic, translational, immunological, and clinical research of adults that are diagnosed with brain cancer and has integral experience in research projects centering on cell adhesion mechanisms, cell-cell communication, and the interaction between neuronal or glioma cells and the immune system.
Michael Lim, Postdoctoral Faculty Sponsor
Current Research and Scholarly Interests
Basic, translational, immunological and clinical research
PP2Ac/STRN4 negatively regulates STING-Type I interferon signaling in tumor associated macrophages.
The Journal of clinical investigation
STING-Type I interferon (IFN) signaling in myeloid cells plays a critical role in effective antitumor immune responses, but STING agonist as monotherapy has shown limited efficacy in clinical trials. The mechanisms that downregulate STING signaling are not fully understood. Here, we report that Protein phosphatase 2A (PP2A) with its specific B regulatory subunit STRN4 negatively regulated STING-Type I IFN in macrophages. Mice with macrophages PP2A deficiency exhibited reduced tumor progression. The tumor microenvironment showed decreased immunosuppressive and increased IFN-activated macrophages and CD8+ T cells. Mechanistically, we demonstrated that hippo kinase MST1/2 was required for STING activation. STING agonist induced dissociation of PP2A from MST1/2 in normal macrophages, but not in tumor conditioned macrophages. Furthermore, our data showed that STRN4 mediated PP2A binding to and dephosphorylation of hippo kinase MST1/2, resulting in stabilization of YAP/TAZ to antagonize STING activation. In human GBM patients, YAP/TAZ was highly expressed in tumor-associated macrophages but not in non-tumor macrophages. We also demonstrated that PP2A/STRN4 deficiency in macrophages reduced YAP/TAZ expression and sensitized tumor conditioned macrophages to STING stimulation. In summary, we demonstrated that PP2A/STRN4-YAP/TAZ is a previously unappreciated mechanism that mediate immunosuppression in tumor-associated macrophages and targeting PP2A/STRN4-YAP/TAZ axis can sensitize tumors to immunotherapy.
View details for DOI 10.1172/JCI162139
View details for PubMedID 36757811
The Role of Myeloid Cells in GBM Immunosuppression.
Frontiers in immunology
2022; 13: 887781
Gliomas are intrinsic brain tumors that originate from glial cells. Glioblastoma (GBM) is the most aggressive glioma type and resistant to immunotherapy, mainly due to its unique immune environment. Dimensional data analysis reveals that the intra-tumoral heterogeneity of immune cell populations in the glioma microenvironment is largely made up of cells of myeloid lineage. Conventional therapies of combined surgery, chemotherapy and radiotherapy have achieved limited improvements in the prognosis of glioma patients, as myeloid cells are prominent mediators of immune and therapeutic responses-like immunotherapy resistance-in glioma. Myeloid cells are frequently seen in the tumor microenvironment (TME), and they are polarized to promote tumorigenesis and immunosuppression. Reprogramming myeloid cells has emerged as revolutionary, new types of immunotherapies for glioma treatment. Here we detail the current advances in classifying epigenetic, metabolic, and phenotypic characteristics and functions of different populations of myeloid cells in glioma TME, including myeloid-derived suppressor cells (MDSCs), glioma-associated microglia/macrophages (GAMs), glioma-associated neutrophils (GANs), and glioma-associated dendritic cells (GADCs), as well as the mechanisms underlying promotion of tumorigenesis. The final goal of this review will be to provide new insights into novel therapeutic approaches for specific targeting of myeloid cells to improve the efficacy of current treatments in glioma patients.
View details for DOI 10.3389/fimmu.2022.887781
View details for PubMedID 35711434
CCL5 of glioma-associated microglia/macrophages regulates glioma migration and invasion via calcium-dependent matrix metalloproteinase 2
2020; 22 (2): 253-266
Glioma-associated microglia/macrophages (GAMs) comprise macrophages of peripheral origin and brain-intrinsic microglia, which support tumor progression. Chemokine C-C ligand 5 (CCL5) is an inflammatory mediator produced by immune cells and is involved in tumor growth and migration in several cancers, including glioma. However, the mechanisms detailing how CCL5 facilitates glioma invasion remain largely unresolved.Glioma migration and invasion were determined by wound healing, transwell assay, and 3D µ-slide chemotaxis assay. The expression levels of CCL5, CD68, matrix metalloproteinase 2 (MMP2), phosphorylated Ca2+/calmodulin-dependent protein kinase II (p-CaMKII), p-Akt, and phosphorylated proline-rich tyrosine kinase 2 were determined by cytokine array, quantitative PCR, western blot, or immunohistochemistry. Zymography and intracellular calcium assays were used to analyze MMP2 activity and intracellular calcium levels, respectively.CCL5 modulated the migratory and invasive activities of human glioma cells in association with MMP2 expression. In response to CCL5, glioma cells underwent a synchronized increase in intracellular calcium levels and p-CaMKII and p-Akt expression levels. CCL5-directed glioma invasion and increases in MMP2 were suppressed after inhibition of p-CaMKII. Glioma cells tended to migrate toward GAM-conditioned media activated by granulocyte-macrophage colony-stimulating factor (GM-CSF) in which CCL5 was abundant. This homing effect was associated with MMP2 upregulation, and could be ameliorated either by controlling intracellular and extracellular calcium levels or by CCL5 antagonism. Clinical results also revealed the associations between CCL5 and GAM activation.Our results suggest that modulation of glioma CaMKII may restrict the effect of CCL5 on glioma invasion and could be a potential therapeutic target for alleviating glioma growth.
View details for DOI 10.1093/neuonc/noz189
View details for Web of Science ID 000518531900012
View details for PubMedID 31593589
View details for PubMedCentralID PMC7032635
Functional Change of Effector Tumor-Infiltrating CCR5(+)CD38(+)HLA-DR(+)CD8(+) T Cells in Glioma Microenvironment
FRONTIERS IN IMMUNOLOGY
2019; 10: 2395
Human glioma facilitates an impaired anti-tumor immunity response, including defects in circulation of T lymphocytes. The level of CD8+ T-cell activation acts as an immune regulator associated with disease progression. However, little is known about the characteristics of peripheral and tumor-infiltrating CD8+ T cells in patients with glioma. In this study, we examined the level of CD8+ T-cell activation in a group of 143 patients with glioma and determined that peripheral CD3+ T cells decreased in accordance with disease severity. The patients' peripheral CD8+ T-cell populations were similar to that of healthy donors, and a small amount of CD8+ tumor-infiltrating lymphocytes was identified in glioma tissues. An increase in activated CD8+ T cells, characterized as CD38+HLA-DR+, and their association with disease progression were identified in the patients' peripheral blood and glioma, and shown to display enriched CCR5+ and TNFR2+ expression levels. Ex vivo examination of CD38+HLA-DR+CD8+ T cells indicated that this subset of cells displayed stronger secretion of IFN-γ and IL-2 before and after a 6-h stimulation with phorbol 12-myristate 13-acetate (PMA) and ionomycin (ION) relative to healthy CD38+HLA-DR+CD8+ T cells, indicating the functional feasibility of CD38+HLA-DR+CD8+ T cells. Higher CCL5 protein and mRNA levels were identified in glioma tissues, which was consistent with the immunohistochemistry results revealing both CCL5 and CD38+HLA-DR+CD8+ T cell expression. Patients' CCR5+CD38+HLA-DR+CD8+ T cells were further validated and shown to display increases in CD45RA+CCR7- and T-bet+ accompanied by substantial CD107-a, IFN-γ, and Granzyme B levels in response to glioma cells.
View details for DOI 10.3389/fimmu.2019.02395
View details for Web of Science ID 000496987500001
View details for PubMedID 31649684
View details for PubMedCentralID PMC6794477
Naringenin Suppresses Neuroinflammatory Responses Through Inducing Suppressor of Cytokine Signaling 3 Expression
2016; 53 (2): 1080-1091
Accumulating evidence suggests that neuroinflammation is closely associated with the pathogenesis of neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. The hallmark of neuroinflammation is considered to be microglial activation in the central nervous system (CNS). Activated microglia release pro-inflammatory cytokines which cause neuroinflammation and progressive neuronal cell death. Therefore, inhibition of microglial activation is considered an important strategy in the development of neuroprotective strategy. Naringenin, a flavonoid found in citrus fruits and tomatoes, has been reported to have anti-oxidant, anti-cancer, and anti-inflammatory properties. However, the mechanism of its beneficial anti-inflammatory effects in the CNS is poorly understood. In this study, we demonstrated that naringenin inhibites the release of nitric oxide (NO), the expression of inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2), as well as pro-inflammatory cytokines in microglial cells. Treatment of naringenin also induced suppressors of cytokine signaling (SOCS)-3 expression in microglia. The SOCS-3 expression and anti-inflammatory effects of naringenin were found to be regulated by adenosine monophosphate-activated protein kinase α (AMPKα) and protein kinase C δ (PKCδ). Besides, naringenin exerted protective property against neurotoxicity caused by LPS-induced microglial activation. Our findings suggest that naringenin-inhibited iNOS and COX-2 expression is mediated by SOCS-3 activation through AMPKα and PKCδ signaling pathways. In a mouse model, naringenin also showed significant protective effects on microglial activation and improved motor coordination function as well. Therefore, naringenin that involves in anti-neuroinflammatory responses and neuroprotection might be a potential agent for treatment of inflammation-associated disorders.
View details for DOI 10.1007/s12035-014-9042-9
View details for Web of Science ID 000370187100023
View details for PubMedID 25579382
Regulatory Effects of Caffeic Acid Phenethyl Ester on Neuroinflammation in Microglial Cells
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
2015; 16 (3): 5572-5589
Microglial activation has been widely demonstrated to mediate inflammatory processes that are crucial in several neurodegenerative disorders. Pharmaceuticals that can deliver direct inhibitory effects on microglia are therefore considered as a potential strategy to counter balance neurodegenerative progression. Caffeic acid phenethyl ester (CAPE), a natural phenol in honeybee propolis, is known to possess antioxidant, anti-inflammatory and anti-microbial properties. Accordingly, the current study intended to probe the effects of CAPE on microglia activation by using in vitro and in vivo models. Western blot and Griess reaction assay revealed CAPE significantly inhibited the expressions of inducible nitric oxide synthase (NOS), cyclooxygenase (COX)-2 and the production of nitric oxide (NO). Administration of CAPE resulted in increased expressions of hemeoxygenase (HO)-1and erythropoietin (EPO) in microglia. The phosphorylated adenosine monophosphate-activated protein kinase (AMPK)-α was further found to regulate the anti-inflammatory effects of caffeic acid. In vivo results from immunohistochemistry along with rotarod test also revealed the anti-neuroinflammatory effects of CAPE in microglia activation. The current study has evidenced several possible molecular determinants, AMPKα, EPO, and HO-1, in mediating anti-neuroinflammatory responses in microglial cells.
View details for DOI 10.3390/ijms16035572
View details for Web of Science ID 000352955500070
View details for PubMedID 25768341
View details for PubMedCentralID PMC4394493
Palmitic acid-induced lipotoxicity and protection by (+)-catechin in rat cortical astrocytes
2014; 66 (6): 1106-1113
Astrocytes do not only maintain homeostasis of the extracellular milieu of the neurons, but also play an active role in modulating synaptic transmission. Palmitic acid (PA) is a saturated fatty acid which, when being excessive, is a significant risk factor for lipotoxicity. Activation of astrocytes by PA has been shown to cause neuronal inflammation and demyelination. However, direct damage by PA to astrocytes is relatively unexplored. The aim of this study was to identify the mechanism(s) of PA-induced cytotoxicity in rat cortical astrocytes and possible protection by (+)-catechin.Cytotoxicity and endoplasmic reticulum (ER) markers were assessed by MTT assay and Western blotting, respectively. Cytosolic Ca(2+) and mitochondrial membrane potential (MMP) were measured microfluorimetrically using fura-2 and rhodamine 123, respectively. Intracellular reactive oxygen species (ROS) production was assayed by the indicator 2'-7'-dichlorodihydrofluorescein diacetate.Exposure of astrocytes to 100μM PA for 24h resulted in apoptotic cell death. Whilst PA-induced cell death appeared to be unrelated to ER stress and perturbation in cytosolic Ca(2+) signaling, it was likely a result of ROS production and subsequent MMP collapse, since ascorbic acid (anti-oxidant, 100μM) prevented PA-induced MMP collapse and cell death. Co-treatment of astrocytes with (+)-catechin (300μM), an anti-oxidant found abundantly in green tea, significantly prevented PA-induced ROS production, MMP collapse and cell death.Our results suggest that PA-induced cytotoxicity in astrocytes may involve ROS generation and MMP collapse, which can be prevented by (+)-catechin.
View details for DOI 10.1016/j.pharep.2014.07.009
View details for Web of Science ID 000344906700026
View details for PubMedID 25443742
Exogenous endothelin-1 induces cell migration and matrix metalloproteinase expression in U251 human glioblastoma multiforme
JOURNAL OF NEURO-ONCOLOGY
2014; 118 (2): 257-269
Glioblastoma multiforme (GBM) is the most common and lethal type of primary brain tumor characterized by its rapid infiltration to surrounding tissues during the early stages. The fast spreading of GBM obscures the initiation of the tumor mass making the treatment outcome undesirable. Endothelin-1 is known as a secretory protein presented in various types of brain cells, which has been indicated as a factor for cancer pathology. The aim of the present study was to investigate the molecular mechanism of cell migration in GBM. We found that various malignant glioma cells expressed higher amounts of endothelin-1, ETA, and ETB receptors than nonmalignant human astrocytes. The application of endothelin-1 enhanced the migratory activity in human U251 glioma cells corresponding to increased expression of matrix metalloproteinase (MMP)-9 and MMP-13. The endothelin-1-induced cell migration was attenuated by MMP-9 and MMP-13 inhibitors and inhibitors of mitogen-activated protein (MAP) kinase and PI3 kinase/Akt. Furthermore, the elevated levels of phosphate c-Jun accumulation in the nucleus and activator protein-1 (AP-1)-DNA binding activity were also found in endothelin-1 treated glioma cells. In migration-prone sublines, cells with greater migration ability showed higher endothelin-1, ETB receptor, and MMP expressions. These results indicate that endothelin-1 activates MAP kinase and AP-1 signaling, resulting in enhanced MMP-9 and MMP-13 expressions and cell migration in GBM.
View details for DOI 10.1007/s11060-014-1442-1
View details for Web of Science ID 000337024300005
View details for PubMedID 24756349
Anti-Neuroinflammatory Effects of the Calcium Channel Blocker Nicardipine on Microglial Cells: Implications for Neuroprotection
2014; 9 (3): e91167
Nicardipine is a calcium channel blocker that has been widely used to control blood pressure in severe hypertension following events such as ischemic stroke, traumatic brain injury, and intracerebral hemorrhage. However, accumulating evidence suggests that inflammatory processes in the central nervous system that are mediated by microglial activation play important roles in neurodegeneration, and the effect of nicardipine on microglial activation remains unresolved.In the present study, using murine BV-2 microglia, we demonstrated that nicardipine significantly inhibits microglia-related neuroinflammatory responses. Treatment with nicardipine inhibited microglial cell migration. Nicardipine also significantly inhibited LPS plus IFN-γ-induced release of nitric oxide (NO), and the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, nicardipine also inhibited microglial activation by peptidoglycan, the major component of the Gram-positive bacterium cell wall. Notably, nicardipine also showed significant anti-neuroinflammatory effects on microglial activation in mice in vivo.The present study is the first to report a novel inhibitory role of nicardipine on neuroinflammation and provides a new candidate agent for the development of therapies for inflammation-related neurodegenerative diseases.
View details for DOI 10.1371/journal.pone.0091167
View details for Web of Science ID 000332845300055
View details for PubMedID 24621589
View details for PubMedCentralID PMC3951295