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The discovery of extracellular RNA (exRNA) has shifted our understanding of the role of RNA in complex cellular functions such as cell-to-cell communication and a variety of pathologies. ExRNAs constitute a heterogenous group of RNAs ranging from small (such as microRNAs) and long non-coding to coding RNAs or ribosomal RNAs. ExRNAs can be liberated from cells in a free form or bound to proteins as well as in association with microvesicles (MVs), exosomes, or apoptotic bodies. Their composition and quantity depend heavily on the cellular or non-cellular component, the origin, and the RNA species being investigated; ribosomal RNA provides the majority of exRNA and miRNAs are predominantly associated with exosomes or MVs. Several studies showed that ribosomal exRNA (rexRNA) constitutes a proinflammatory and prothrombotic alarmin. It is released by various cell types upon inflammatory stimulation and by damaged cells undergoing necrosis or apoptosis and contributes to innate immunity responses. This exRNA has the potential to directly promote the release of cytokines such as tumor necrosis factor factor-α (TNF-α) or interleukin-6 from immune cells, thereby leading to a proinflammatory environment and promoting cardiovascular pathologies. The potential role of exRNA in different pathologies of the central nervous system (CNS) has become of increasing interest in recent years. Although various exRNA species including both ribosomal exRNA as well as miRNAs have been associated with CNS pathologies, their precise roles remain to be further elucidated. In this review, the different entities of exRNA and their postulated roles in CNS pathologies including tumors, vascular pathologies and neuroinflammatory diseases will be discussed. Furthermore, the potential role of exRNAs as diagnostic markers for specific CNS diseases will be outlined, as well as possible treatment strategies addressing exRNA inhibition or interference.

Recent evidence suggests that dysregulation of iron regulatory factors may play essential roles in cancer pathophysiology. Six-transmembrane epithelial antigen of prostate 3 (STEAP3) is a metalloreductase, which is vital for cellular iron uptake and homeostasis. However, the clinical significance and function of STEAP3 in the development of human gliomas remain unclear. Through analysis of publicly available databases, we found that STEAP3 was highly expressed in malignant gliomas, especially in the mesenchymal glioma molecular subtype and isocitrate dehydrogenase 1/2 (IDH1/2) wild-type gliomas. Expression levels of STEAP3 in gliomas correlated inversely with patient overall survival (OS) and served as an independent prognostic marker by multivariate Cox regression analysis. In functional assays performed with RNA knockdown, loss of STEAP3 attenuated aggressive phenotypes in glioma cells, including cell proliferation, invasion, and sphere formation in vitro and tumor growth in vivo. Finally, STEAP3 drives these activities by inducing mesenchymal transition, promoting transferrin receptor (TfR) expression, and activating STAT3-FoxM1 axis signaling. Taken together, these results indicate that STEAP3 functions as an oncogenic mediator in glioma progression and is thus a potential therapeutic target for the treatment of the disease. [ABSTRACT FROM AUTHOR]

Background: Golgi Membrane Protein 1 (GOLM1), a protein involved in the trafficking of proteins through the Golgi apparatus, has been shown to be oncogenic in a variety of human cancers. Here, we examined the role of GOLM1 in the development of human glioma. Methods: qRT-PCR, immunohistochemistry, and western blot analysis were performed to evaluate GOLM1 levels in cell lines and a cohort of primary human glioma and non-neoplastic brain tissue samples. Glioma cell lines were modified with lentiviral constructs expressing short hairpin RNAs targeting GOLM1 or overexpressing the protein to assess function in proliferation, viability, and migration and invasion in vitro using EdU, CCK8, clone-forming, Transwell assays, 3D tumor spheroid invasion assay and in vivo in orthotopic implantations. Protein lysates were used to screen a membrane-based antibody array to identify kinases mediated by GOLM1. Specific inhibitors of PDGFRα (AG1296) and AKT (MK-2206) were used to examine the regulation of PDGFA/PDGFRα on GOLM1 and the underlying pathway respectively. Results: qRT-PCR, immunohistochemistry and western blot analysis revealed GOLM1 expression to be elevated in glioma tissues and cell lines. Silencing of GOLM1 attenuated proliferation, migration, and invasion of U251, A172 and P3#GBM (primary glioma) cells, while overexpression of GOLM1 enhanced malignant behavior of U87MG cells. We further demonstrated that activation of AKT is the driving force of GOLM1-promoted glioma progression. The last finding of this research belongs to the regulation of PDGFA/PDGFRα on GOLM1, while GOLM1 was also a key element of PDGFA/PDGFRα-mediated activation of AKT, as well as the progression of glioma cells. Conclusions: PDGFA/PDGFRα-regulated GOLM1 promotes glioma progression possibly through activation of a key signaling kinase, AKT. GOLM1 interference may therefore provide a novel therapeutic target and improve the efficacy of glioma treatment, particularly in the case of the proneural molecular subtype of human glioma. [ABSTRACT FROM AUTHOR]

Background: Glioblastoma multiforme (GBM) is characterized by lethal aggressiveness and patients with GBM are in urgent need for new therapeutic avenues to improve quality of life. Current studies on tumor invasion focused on roles of cytokines in tumor microenvironment and numerous evidence suggests that TGF-β2 is abundant in glioma microenvironment and vital for glioma invasion. Autopagy is also emerging as a critical factor in aggressive behaviors of cancer cells; however, the relationship between TGF-β2 and autophagy in glioma has been poorly understood. Methods: U251, T98 and U87 GBM cell lines as well as GBM cells from a primary human specimen were used in vitro and in vivo to evaluate the effect of TGF-β2 on autophagy. Western blot, qPCR, immunofluorescence and transmission-electron microscope were used to detect target molecular expression. Lentivirus and siRNA vehicle were introduced to establish cell lines, as well as mitotracker and seahorse experiment to study the metabolic process in glioma. Preclinical therapeutic efficacy was evaluated in orthotopic xenograft mouse models. Results: Here we demonstrated that TGF-β2 activated autophagy in human glioma cell lines and knockdown of Smad2 or inhibition of c-Jun NH2-terminal kinase, attenuated TGF-β2-induced autophagy. TGF-β2-induced autophagy is important for glioma invasion due to the alteration of epithelial-mesenchymal transition and metabolism conversion, particularly influencing mitochondria trafficking and membrane potential (ΔΨm). Autopaghy also initiated a feedback on TGF-β2 in glioma by keeping its autocrine loop and affecting Smad2/3/7 expression. A xenograft model provided additional confirmation on combination of TGF-β inhibitor (Galunisertib) and autophagy inhibitor (CQ) to better "turn off" tumor growth. Conclusion: Our findings elucidated a potential mechanism of autophagy-associated glioma invasion that TGF-2 could initiate autophagy via Smad and non-Smad pathway to promote glioma cells' invasion. [ABSTRACT FROM AUTHOR]

Background: Resistance to adjuvant radiotherapy is a major cause of treatment failure in patients with glioblastoma (GBM). Autophagy inhibitors have been shown to enhance the efficacy of radiotherapy for certain solid tumors. However, current inhibitors do not penetrate the blood-brain-barrier (BBB). Here, we assessed the radiosensitivity effects of the antipsychotic drug trifluoperazine (TFP) on GBM in vitro and in vivo. Methods: U251 and U87 GBM cell lines as well as GBM cells from a primary human biopsy (P3), were used in vitro and in vivo to evaluate the efficacy of TFP treatment. Viability and cytotoxicity was evaluated by CCK-8 and clonogenic formation assays. Molecular studies using immunohistochemistry, western blots, immunofluorescence and qPCR were used to gain mechanistic insight into the biological activity of TFP. Preclinical therapeutic efficacy was evaluated in orthotopic xenograft mouse models. Results: IC50 values of U251, U87 and P3 cells treated with TFP were 16, 15 and 15.5 μM, respectively. TFP increased the expression of LC3B-II and p62, indicating a potential disruption of autophagy flux. These results were further substantiated by a decreased Lysotracker Red uptake, indicating impaired acidification of the lysosomes. We show that TFP and radiation had an additive effect when combined. This effect was in part due to impaired TFP-induced homologous recombination. Mechanistically we show that down-regulation of cathepsin L might explain the radiosensitivity effect of TFP. Finally, combining TFP and radiation resulted in a significant antitumor effect in orthotopic GBM xenograft models. Conclusions: This study provides a strong rationale for further clinical studies exploring the combination therapy of TFP and radiation to treat GBM patients. [ABSTRACT FROM AUTHOR]

The acquisition of drug resistance is a persistent clinical problem limiting the successful treatment of human cancers, including glioblastoma (GBM). However, the molecular mechanisms by which initially chemoresponsive tumors develop therapeutic resistance remain poorly understood. In this study, we report that Pol κ, an error-prone polymerase that participates in translesion DNA synthesis, was significantly upregulated in GBM cell lines and tumor tissues following temozolomide treatment. Overexpression of Pol κ in temozolomide- sensitive GBM cells conferred resistance to temozolomide, whereas its inhibition markedly sensitized resistant cells to temozolomide in vitro and in orthotopic xenograft mouse models. Mechanistically, depletion of Pol κ disrupted homologous recombination (HR)-mediated repair and restart of stalled replication forks, impaired the activation of ATR-Chk1 signaling, and delayed cell-cycle re-entry and progression. Further investigation of the relationship between Pol κ and temozolomide revealed that Pol κ inactivation facilitated temozolomide-induced Rad17 ubiquitination and proteasomal degradation, subsequently silencing ATR-Chk1 signaling and leading to defective HR repair and the reversal of temozolomide resistance. Moreover, overexpression of Rad17 in Pol κ-depleted GBM cells restored HR efficiency, promoted the clearance of temozolomide-induced DNA breaks, and desensitized cells to the cytotoxic effects of temozolomide observed in the absence of Pol κ. Finally, we found that Pol κ overexpression correlated with poor prognosis in GBM patients undergoing temozolomide therapy. Collectively, our findings identify a potential mechanism by which GBM cells develop resistance to temozolomide and suggest that targeting the DNA damage tolerance pathway may be beneficial for over-coming resistance. [ABSTRACT FROM AUTHOR]