PERK-Mediated Cholesterol Excretion from IDH Mutant Glioma Determines Anti-Tumoral Polarization of Microglia

Isocitrate dehydrogenase (IDH) mutation, a known pathologic classifier, initiates metabolic reprogramming in glioma cells and has been linked to the reaction status of glioma-associated microglia/macrophages (GAMs). However, it remains unclear how IDH genotypes contribute to GAM phenotypes. Here, it is demonstrated that gliomas expressing mutant IDH determine M1-like polarization of GAMs, while archetypal IDH induces M2-like polarization. Intriguingly, IDH-mutant gliomas secrete excess cholesterol, resulting in cholesterol-rich, pro-inflammatory GAMs without altering their cholesterol biosynthesis, and simultaneously exhibiting low levels of tumoral cholesterol due to expression remodeling of cholesterol transport molecules, particularly upregulation of ABCA1 and downregulation of LDLR. Mechanistically, a miR-19a/LDLR axis-mediated novel post-transcriptional regulation of cholesterol uptake is identified, modulated by IDH mutation, and influencing tumor cell proliferation and invasion. IDH mutation-induced PERK activation enhances cholesterol export from glioma cells via the miR-19a/LDLR axis and ABCA1/APOE upregulation. Further, a synthetic PERK activator, CCT020312 is introduced, which markedly stimulates cholesterol efflux from IDH wild-type glioma cells, induces M1-like polarization of GAMs, and consequently suppresses glioma cell invasion. The findings reveal an essential role of the PERK/miR-19a/LDLR signaling pathway in orchestrating gliomal cholesterol transport and the subsequent phenotypes of GAMs, thereby highlighting a novel potential target pathway for glioma therapy

Nano-Crystalline &Amorphous Silicon PhotoTransistor Performance Analysis

In this thesis, we compared electrical performance and stability of a novel nanocrystalline Si (nc-Si) thin film phototransistor (TFT) phototransistor and a regular amorphous silicon (a-Si:H) TFT phototransistor for large area imaging applications. The electrical performance parameters of nc-Si TFT phototransistor were extracted from the electrical (current-voltage) testing in dark and under illumination. The field-effect mobility is found to be around 1.2 cm2V-1s-1, the threshold voltage around 3.9V and the sub-threshold voltage slope around 0.47V/Dec. Optical properties of nc-Si TFT phototransistor have been evaluated under the green light illumination in the range of 1014 – 1017 lum, and the photocurrent gain and the external quantum efficiency were extracted from the experimental results. By comparing the results with those for a-Si:H TFTs measured under the same conditions, we found that nc-Si TFT has higher photo current gain under low illumination intensity, 5 ×1014 to 7 ×1015 lum. This thesis shows the relations bewteen the photo current gain, the external quantum efficiency, TFT drain and TFT gate bias; the photo current gain and the external quantum efficiency can be controlled by the Vds and the Vgs

Clinical impact of anti-inflammatory microglia and macrophage phenotypes at glioblastoma margins

Glioblastoma is a devastating brain cancer for which effective treatments are required. Tumour-associated microglia and macrophages (TAMs) promote glioblastoma growth in an immune-suppressed microenvironment. Most recurrences occur at the invasive margin with surrounding brain, yet the relationships between TAM phenotypes, T cells and Programmed death-ligand 1 (PD-L1, an immune checkpoint) across human glioblastoma regions are understudied. We performed quantitative immunohisto chemical analysis of 15 markers of TAM phenotypes (including anti-inflammatory markers TREM2 and CD163, and the low-affinity activating receptor CD32a), T cells, natural killer (NK) cells and PD-L1, in 59 human IDH1-wild-type glioblastoma multi-regional samples (n = 177; 1 sample at tumour core, 2 samples at the margins: the infiltrating zone and leading edge). Assessment was made for the prognostic value of markers; the results were validated in an independent cohort. TAM motility and activation (Iba1, CD68), PD-L1, and CD4+ T cells were reduced, and homeostatic microglia (P2RY12) were increased in the invasive margins compared to the tumour core. There were significant positive correlations between TAM markers CD68 (phagocytic)/TREM2 (anti-inflammatory) and CD8+ T cells in the invasive margins but not in the tumour core (P<0.01). PD-L1 expression was associated with TAM markers (including anti-inflammatory) CD68, CD163, CD32a and TREM2, only in the leading edge of glioblastomas (P<0.01). Similarly, there was a positive correlation between PD-L1 expression and CD8+ T cell infiltration in the leading edge (P<0.001). There was no relationship between CD64 (a receptor for autoreactive T cell responses) and CD8+/CD4+ T cells, or between the antigen presentation TAM marker HLA-DR and microglial motility (Iba1) in the tumour margins. NK cell infiltration (CD335+) correlated with CD8+ T cells, and with CD68/CD163/TREM2 anti-inflammatory TAMs at the leading edge. In an independent large glioblastoma cohort with transcriptomic data, positive correlations between anti-inflammatory TAM markers (TREM2, CD163 and CD32a) and CD4+/CD8+/PD-L1 RNA expression were validated (P < 0.001). Finally, multivariate analysis showed high TREM2, PD-L1 and CD32a expression at the leading edge were significantly associated with poorer overall patient survival (hazard ratio = 2.05, 3.42 and 2.11 respectively), independent of clinical variables.In conclusion, anti-inflammatory TAMs, CD8+ T cells and PD-L1 are correlated in the invasive margins of glioblastoma, consistent with immune-suppressive interactions. High TREM2, PD-L1 and CD32a expression at the human glioblastoma leading edge are predictors of poorer overall survival. Given substantial interest in targeting TAMs together with immune checkpoint inhibitors in cancer, these data have major clinical implications

Mutant IDH sensitizes gliomas to endoplasmic reticulum stress and triggers apoptosis via miR-183-mediated inhibition of Semaphorin 3E

Human astrocytomas and oligodendrogliomas are defined by mutations of the metabolic enzymes isocitrate dehydrogenase (IDH) 1 or 2, resulting in the production of the abnormal metabolite D-2 hydroxyglutarate. Here, we studied the effect of mutant IDH on cell proliferation and apoptosis in a glioma mouse model. Tumors were generated by inactivating Pten and p53 in forebrain progenitors and compared with tumors additionally expressing the Idh1 R132H mutation. Idh-mutant cells proliferated less in vitro and mice with Idh-mutant tumors survived significantly longer compared with Idh-wildtype mice. Comparison of miRNA and RNA expression profiles of Idh-wildtype and Idh-mutant cells and tumors revealed miR-183 was significantly upregulated in IDH-mutant cells. Idh-mutant cells were more sensitive to endoplasmic reticulum (ER) stress, resulting in increased apoptosis and thus reduced cell proliferation and survival. This was mediated by the interaction of miR-183 with the 5' untranslated region of semaphorin 3E, downregulating its function as an apoptosis suppressor. In conclusion, we show that mutant Idh1 delays tumorigenesis and sensitizes tumor cells to ER stress and apoptosis. This may open opportunities for drug treatments targeting the miR-183-semaphorin axis. SIGNIFICANCE: The pathologic metabolite 2-hydroxyglutarate, generated by IDH-mutant astrocytomas, sensitizes tumor cells to ER stress and delays tumorigenesis. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/19/4994/F1.large.jpg.</p