Complexities of lysophospholipid signalling in glioblastoma

A mass spectrometry imaging and lipidomic investigation reveals aberrant lipid metabolism in the orthotopic mouse glioma

Lipids perform multiple biological functions and reflect the physiology and pathology of cells, tissues, and organs. Here, we sought to understand lipid content in relation to tumor pathology by characterizing phospholipids and sphingolipids in the orthotopic mouse glioma using MALDI MS imaging (MSI) and LC-MS/MS. Unsupervised clustering analysis of the MALDI-MSI data segmented the coronal tumoral brain section into 10 histopathologically salient regions. Heterogeneous decrease of the common saturated phosphatidylcholines (PCs) in the tumor was accompanied by the increase of analogous PCs with one or two additional fatty acyl double bonds and increased lyso-PCs. Polyunsaturated fatty acyl-PCs and ether PCs highlighted the striatal tumor margins, whereas the distributions of other PCs differentiated the cortical and striatal tumor parenchyma. We detected a reduction of SM d18:1/18:0 and the heterogeneous mild increase of SM d18:1/16:0 in the tumor, whereas ceramides accumulated only in a small patch deep in the tumoral parenchyma. LC-MS/MS analyses of phospholipids and sphingolipids complemented the MALDI-MSI observation, providing a snapshot of these lipids in the tumor. Finally, the proposed mechanisms responsible for the tumoral lipid changes were contrasted with our interrogation of gene expression in human glioma. Together, these lipidomic results unveil the aberrant and heterogeneous lipid metabolism in mouse glioma where multiple lipid-associated signaling pathways underline the tumor features, promote the survival, growth, proliferation, and invasion of different tumor cell populations, and implicate the management strategy of a multiple-target approach for glioma and related brain malignancies.

Will CRISPR-Cas9 Have Cards to Play Against Cancer? An Update on its Applications

Genome editing employs targeted nucleases as powerful tools to precisely alter the genome of target cells and regulate functional genes. Various strategies have been risen so far as the molecular scissors-mediated genome editing that includes zinc finger nuclease, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats-CRISPR-related protein 9. These tools allow researchers to understand the basics of manipulating the genome, create animal models to study human diseases, understand host-pathogen interactions and design disease targets. Targeted genome modification utilizing RNA-guided nucleases are of recent curiosity, as it is a fast and effective strategy that enables the researchers to manipulate the gene of interest, carry out functional studies, understand the molecular basis of the disease and design targeted therapies. CRISPR-Cas9, a bacterial defense system employed against viruses, consists of a single-strand RNA-guided Cas9 nuclease connected to the corresponding complementary target sequence. This powerful and versatile tool has gained tremendous attention among the researchers, owing to its ability to correct genetic disorders. To help illustrate the potential of this gene editor in unexplored corners of oncology, we describe the history of CRISPR-Cas9, its rapid progression in cancer research as well as future perspectives.

Disentangling the therapeutic tactics in GBM: From bench to bedside and beyond

Glioblastoma multiforme (GBM) is one of the most common and malignant form of adult brain tumor with a high mortality rate and dismal prognosis. The present standard treatment comprising surgical resection followed by radiation and chemotherapy using temozolomide can broaden patient's survival to some extent. However, the advantages are not palliative due to the development of resistance to the drug and tumor recurrence following the multimodal treatment approaches due to both intra- and intertumoral heterogeneity of GBM. One of the major contributors to temozolomide resistance is O⁶ -methylguanine-DNA methyltransferase. Furthermore, deficiency of mismatch repair, base excision repair, and cytoprotective autophagy adds to temozolomide obstruction. Rising proof additionally showed that a small population of cells displaying certain stem cell markers, known as glioma stem cells, adds on to the resistance and tumor progression. Collectively, these findings necessitate the discovery of novel therapeutic avenues for treating glioblastoma. As of late, after understanding the pathophysiology and biology of GBM, some novel therapeutic discoveries, such as drug repurposing, targeted molecules, immunotherapies, antimitotic therapies, and microRNAs, have been developed as new potential treatments for glioblastoma. To help illustrate, "what are the mechanisms of resistance to temozolomide" and "what kind of alternative therapeutics can be suggested" with this fatal disease, a detailed history of these has been discussed in this review article, all with a hope to develop an effective treatment strategy for GBM.

Microglial lysophosphatidic acid promotes glioblastoma proliferation and migration via LPA1 receptor

Glioblastomas (GBMs) are highly aggressive primary brain tumors characterized by cellular heterogeneity, insensitivity to chemotherapy and poor patient survival. Lysophosphatidic acid (LPA) is a lysophospholipid that acts as a bioactive signaling molecule and plays important roles in diverse biological events during development and disease, including several cancer types. Microglial cells, the resident macrophages of the central nervous system, express high levels of Autotaxin (ATX,Enpp2), an enzyme that synthetizes LPA. Our study aimed to investigate the role of LPA on tumor growth and invasion in the context of microglia-GBM interaction. First, through bioinformatics studies, patient data analysis demonstrated that more aggressive GBM expressed higher levels of ENPP2, which was also associated with worse patient prognosis with proneural GBM. Using GBM-microglia co-culture system we then demonstrated that GBM secreted factors were able to increase LPA₁ and ATX in microglia, which could be further enhanced by hypoxia. On the other hand, interaction with microglial cells also increased ATX expression in GBM. Furthermore, microglial-induced GBM proliferation and migration could be inhibited by pharmacological inhibition of LPA₁ , suggesting that microglial-derived LPA could support tumor growth and invasion. Finally, increased LPA₁ expression was observed in GBM comparing with other gliomas and could be also associated with worse patient survival. These results show for the first time a microglia-GBM interaction through the LPA pathway with relevant implications for tumor progression. A better understanding of this interaction can lead to the development of new therapeutic strategies setting LPA as a potential target for GBM treatment.

Sphingosine-1-Phosphate in the Tumor Microenvironment: A Signaling Hub Regulating Cancer Hallmarks

As a key hub of malignant properties, the cancer microenvironment plays a crucial role intimately connected to tumor properties. Accumulating evidence supports that the lysophospholipid sphingosine-1-phosphate acts as a key signal in the cancer extracellular milieu. In this review, we have a particular focus on glioblastoma, representative of a highly aggressive and deleterious neoplasm in humans. First, we highlight recent advances and emerging concepts for how tumor cells and different recruited normal cells contribute to the sphingosine-1-phosphate enrichment in the cancer microenvironment. Then, we describe and discuss how sphingosine-1-phosphate signaling contributes to favor cancer hallmarks including enhancement of proliferation, stemness, invasion, death resistance, angiogenesis, immune evasion and, possibly, aberrant metabolism. We also discuss the potential of how sphingosine-1-phosphate control mechanisms are coordinated across distinct cancer microenvironments. Further progress in understanding the role of S1P signaling in cancer will depend crucially on increasing knowledge of its participation in the tumor microenvironment.

Pleotropic Roles of Autotaxin in the Nervous System Present Opportunities for the Development of Novel Therapeutics for Neurological Diseases

Autotaxin (ATX) is a soluble extracellular enzyme that is abundant in mammalian plasma and cerebrospinal fluid (CSF). It has two known enzymatic activities, acting as both a phosphodiesterase and a phospholipase. The majority of its biological effects have been associated with its ability to liberate lysophosphatidic acid (LPA) from its substrate, lysophosphatidylcholine (LPC). LPA has diverse pleiotropic effects in the central nervous system (CNS) and other tissues via the activation of a family of six cognate G protein-coupled receptors. These LPA receptors (LPARs) are expressed in some combination in all known cell types in the CNS where they mediate such fundamental cellular processes as proliferation, differentiation, migration, chronic inflammation, and cytoskeletal organization. As a result, dysregulation of LPA content may contribute to many CNS and PNS disorders such as chronic inflammatory or neuropathic pain, glioblastoma multiforme (GBM), hemorrhagic hydrocephalus, schizophrenia, multiple sclerosis, Alzheimer's disease, metabolic syndrome-induced brain damage, traumatic brain injury, hepatic encephalopathy-induced cerebral edema, macular edema, major depressive disorder, stress-induced psychiatric disorder, alcohol-induced brain damage, HIV-induced brain injury, pruritus, and peripheral nerve injury. ATX activity is now known to be the primary biological source of this bioactive signaling lipid, and as such, represents a potentially high-value drug target. There is currently one ATX inhibitor entering phase III clinical trials, with several additional preclinical compounds under investigation. This review discusses the physiological and pathological significance of the ATX-LPA-LPA receptor signaling axis and summarizes the evidence for targeting this pathway for the treatment of CNS diseases.

Roles of lysophosphatidic acid and sphingosine-1-phosphate in stem cell biology

Stem cells are unique in their ability to self-renew and differentiate into various cell types. Because of these features, stem cells are key to the formation of organisms and play fundamental roles in tissue regeneration and repair. Mechanisms controlling their fate are thus fundamental to the development and homeostasis of tissues and organs. Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are bioactive phospholipids that play a wide range of roles in multiple cell types, during developmental and pathophysiological events. Considerable evidence now demonstrates the potent roles of LPA and S1P in the biology of pluripotent and adult stem cells, from maintenance to repair. Here we review their roles for each main category of stem cells and explore how those effects impact development and physiopathology.