The Roles of AGTRAP, ALKBH3, DIVERSIN, NEDD8 and RRM1 in Glioblastoma Pathophysiology and Prognosis.

This study determined the expression of five novel biomarker candidates in IDH wild-type glioblastoma (GBM) tissues compared to non-malign brain parenchyma, as well as their prognostic relevance for the GBM patients' outcomes. The markers were analysed by immunohistochemistry in tumour tissues (n = 186) and healthy brain tissues (n = 54). The association with the patients' overall survival (OS) and progression-free survival (PFS) was assessed by Kaplan-Meier and log-rank test. The prognostic value of the markers was determined using multivariate Cox proportional hazard models. AGTRAP, DIVERSIN, cytoplasmic NEDD8 (NEDD8c) and RRM1 were significantly overexpressed in tumour tissues compared to the healthy brain, while the opposite was observed for ALKBH3. AGTRAP, ALKBH3, NEDD8c and RRM1 were significantly associated with OS in univariate analysis. AGTRAP and RRM1 were also independent prognostic factors for OS in multivariate analysis. For PFS, only AGTRAP and NEDD8c reached significance in univariate analysis. Additionally, AGTRAP was an independent prognostic factor for PFS in multivariate models. Finally, combined analysis of the markers enhanced their prognostic accuracy. The combination AGTRAP/ALKBH3 had the strongest prognostic value for the OS of GBM patients. These findings contribute to a better understanding of the GBM pathophysiology and may help identify novel therapeutic targets in this type of cancer.

Progesterone Receptor Membrane Component 1 (PGRMC1) Modulates Tumour Progression, the Immune Microenvironment and the Response to Therapy in Glioblastoma.

Progesterone Receptor Membrane Component 1 (PGRMC1) is a tumour-promoting factor in several types of cancer but its role in brain tumours is poorly characterized thus far. Our study aimed to determine the effect of PGRMC1 on glioblastoma (GBM) pathophysiology using two independent cohorts of IDH wild-type GBM patients and stable knockdown GBM models. We found that high levels of PGRMC1 significantly predicted poor overall survival in both cohorts of GBM patients. PGRMC1 promoted the proliferation, anchorage-independent growth, and invasion of GBM cells. We identified Integrin beta-1 (ITGB1) and TCF 1/7 as potential members of the PGRMC1 pathway in vitro. The levels of ITGB1 and PGRMC1 also correlated in neoplastic tissues from GBM patients. High expression of PGRMC1 rendered GBM cells less susceptible to the standard GBM chemotherapeutic agent temozolomide but more susceptible to the ferroptosis inducer erastin. Finally, PGRMC1 enhanced Interleukin-8 production in GBM cells and promoted the recruitment of neutrophils. The expression of PGRMC1 significantly correlated with the numbers of tumour-infiltrating neutrophils also in tissues from GBM patients. In conclusion, PGRMC1 enhances tumour-related inflammation and promotes the progression of GBM. However, PGRMC1 might be a promising target for novel therapeutic strategies using ferroptosis inducers in this type of cancer.

PLOD2 Is a Prognostic Marker in Glioblastoma That Modulates the Immune Microenvironment and Tumor Progression.

This study aimed to investigate the role of Procollagen-Lysine, 2-Oxoglutarate 5-Dioxygenase 2 (PLOD2) in glioblastoma (GBM) pathophysiology. To this end, PLOD2 protein expression was assessed by immunohistochemistry in two independent cohorts of patients with primary GBM (n1 = 204 and n2 = 203, respectively). Association with the outcome was tested by Kaplan−Meier, log-rank and multivariate Cox regression analysis in patients with confirmed IDH wild-type status. The biological effects and downstream mechanisms of PLOD2 were assessed in stable PLOD2 knock-down GBM cell lines. High levels of PLOD2 significantly associated with (p1 = 0.020; p2< 0.001; log-rank) and predicted (cohort 1: HR = 1.401, CI [95%] = 1.009−1.946, p1 = 0.044; cohort 2: HR = 1.493; CI [95%] = 1.042−2.140, p2 = 0.029; Cox regression) the poor overall survival of GBM patients. PLOD2 knock-down inhibited tumor proliferation, invasion and anchorage-independent growth. MT1-MMP, CD44, CD99, Catenin D1 and MMP2 were downstream of PLOD2 in GBM cells. GBM cells produced soluble factors via PLOD2, which subsequently induced neutrophils to acquire a pro-tumor phenotype characterized by prolonged survival and the release of MMP9. Importantly, GBM patients with synchronous high levels of PLOD2 and neutrophil infiltration had significantly worse overall survival (p < 0.001; log-rank) compared to the other groups of GBM patients. These findings indicate that PLOD2 promotes GBM progression and might be a useful therapeutic target in this type of cancer.

Dynein Light Chain Protein Tctex1: A Novel Prognostic Marker and Molecular Mediator in Glioblastoma.

The purpose of this study was to determine the role of Tctex1 (DYNLT1, dynein light chain-1) in the pathophysiology of glioblastoma (GBM). To this end, we performed immunohistochemical analyses on tissues from GBM patients (n = 202). Tctex1 was additionally overexpressed in two different GBM cell lines, which were then evaluated in regard to their proliferative and invasive properties. We found that Tctex1 levels were significantly higher in GBM compared to healthy adjacent brain tissues. Furthermore, high Tctex1 expression was significantly associated with the short overall- (p = 0.002, log-rank) and progression-free (p = 0.028, log-rank) survival of GBM patients and was an independent predictor of poor overall survival in multivariate Cox-regression models. In vitro, Tctex1 promoted the metabolic activity, anchorage-independent growth and proliferation of GBM cells. This phenomenon was previously shown to occur via the phosphorylation of retinoblastoma protein (phospho-RB). Here, we found a direct and significant correlation between the levels of Tctex1 and phospho-RB (Ser807/801) in tissues from GBM patients (p = 0.007, Rho = 0.284, Spearman's rank). Finally, Tctex1 enhanced the invasiveness of GBM cells and the release of pro-invasive matrix metalloprotease 2 (MMP2). These findings indicate that Tctex1 promotes GBM progression and therefore might be a useful therapeutic target in this type of cancer.

Activated Tissue-Resident Mesenchymal Stromal Cells Regulate Natural Killer Cell Immune and Tissue-Regenerative Function.

The interaction of mesenchymal stromal cells (MSCs) with natural killer (NK) cells is traditionally thought of as a static inhibitory model, whereby resting MSCs inhibit NK cell effector function. Here, we use a dynamic in vitro system of poly(I:C) stimulation to model the interaction of NK cells and tissue-resident MSCs in the context of infection or tissue injury. The experiments suggest a time-dependent system of regulation and feedback, where, at early time points, activated MSCs secrete type I interferon to enhance NK cell effector function, while at later time points TGF-ß and IL-6 limit NK cell effector function and terminate inflammatory responses by induction of a regulatory senescent-like NK cell phenotype. Importantly, feedback of these regulatory NK cells to MSCs promotes survival, proliferation, and pro-angiogenic properties. Our data provide additional insight into the interaction of stromal cells and innate immune cells and suggest a model of time-dependent MSC polarization and licensing.

Ceramide metabolism determines glioma cell resistance to chemotherapy.

Tumor cell resistance to chemotherapy constitutes a major problem in the treatment of malignant tumors. We here investigated the role of ceramide metabolism for the resistance of glioma cells to treatment with the chemotherapeutic drug, gemcitabine. Gemcitabine triggers a marked release of ceramide in drug-sensitive cells, while glioma cells that are resistant to gemcitabine, fail to accumulate ceramide. While the release of ceramide is very similar in gemcitabine-sensitive and resistant glioma cells upon stimulation, resistant glioma cells rapidly consume ceramide upon gemcitabine treatment or exogenous sphingomyelinase stimulation. Pharmacologic or genetic inhibition of glucosyltransferases prevents ceramide consumption in resistant cells and restores sensitivity of resistant glioma cells to gemcitabine. These data suggest that glioma cell resistance to at least some chemotherapeutic drugs is mediated by rapid consumption of ceramide to prevent cell death.

Ceramide: a novel player in reactive oxygen species-induced signaling?

Generation of ceramide in the plasma membrane, with the subsequent formation of large ceramide-enriched membrane platforms, serves signal transduction via receptors, but also nonreceptor-mediated activation of cells. Recent studies demonstrate that enzymes mediating release of reactive oxygen species (ROS) localize to membrane rafts, and the integrity of these rafts is required for cellular ROS release. The authors and others noted that in a feed-forward mechanism, ROS are able to stimulate ceramide-releasing enzymes, for instance, acid sphingomyelinase, resulting in the formation of ceramide-enriched membrane platforms that may mediate cellular activation initiated by oxidative stress.

Doxorubicin enhances TRAIL-induced cell death via ceramide-enriched membrane platforms.

Previous studies indicated that signalling via CD95 and DR5 is greatly enhanced by the formation of ceramide-enriched membrane platforms. Here, we employed this concept to convert doses of subtherapeutic TRAIL that were unable to release ceramide and kill leukemic B-cells or ex vivo T lymphocytes, into a very effective apoptotic stimulus. Ceramide production was induced by application of sub-toxic doses of doxorubicin that resulted in an activation of the acid sphingomyelinase (ASM), release of ceramide and formation of ceramide-enriched membrane platforms. The latter served DR5 to cluster after application of very low doses of TRAIL in combination with doxorubicin. Genetic deficiency of the ASM abrogated doxorubicin-induced ceramide release, as well as clustering of DR5 and apoptosis induced by the combined treatment of doxorubicin and TRAIL. These data show that local release of ceramide potentiates very low, otherwise inactive doses of TRAIL that may represent a novel therapeutic concept to treat tumors.

Rhinoviral infections activate p38MAP-kinases via membrane rafts and RhoA.

Rhinoviral infections belong to the most frequent human infections characterized by common cold, chronic bronchitis, exacerbations of asthma, otitis media and sinusitis. Here, we define molecular mechanisms that mediate infections of human epithelial cells with human rhinovirus strain 14 (RV14). We demonstrate that RV14 activates p38-MAPKinase (p38-K) in a biphasic time course. Early stimulation of p38-K by RV14 was observed a few minutes after initiation of the infection, while the late increase of p38-K activity occurred 7-12 hrs upon infection. The stimulation of p38-K was mediated by the small G-protein RhoA,which was activated by RV14. Transfection of a genetic construct preventing RhoA activation blocked RV14-induced p38-K activation. Further, integrity of cholesterol and sphingolipid-enriched membrane domains was required for RV14-mediated p38-K activation, which was inhibited by destruction of membrane rafts. The data indicate that RV employs a signaling cascade from membrane rafts via the small G-protein RhoA to p38-K to infect human cells.