ABSTRACT
Hypothyroidism is commonly detected in patients with medulloblastoma (MB). A possible link between thyroid hormone (TH) signaling and MB pathogenicity has not been reported. Here, we find that TH plays a critical role in promoting tumor cell differentiation. Reduction in TH levels frees the TH receptor, TRα1, to bind to EZH2 and repress expression of NeuroD1, a transcription factor that drives tumor cell differentiation. Increased TH reverses EZH2-mediated repression of NeuroD1 by abrogating the binding of EZH2 and TRα1, thereby stimulating tumor cell differentiation and reducing MB growth. Importantly, TH-induced differentiation of tumor cells is not restricted by the molecular subgroup of MB. These findings establish an unprecedented association between TH signaling and MB pathogenicity, providing solid evidence for TH as a promising modality for MB treatment.
ABSTRACT
Lysophosphatidic acid (LPA) induces a wide range of cellular processes and its signaling is increased in several cancers including glioblastoma (GBM), a high-grade astrocytoma, which is the most common malignant brain tumor. LPA1 receptor is expressed in GBM cells and its signaling pathways activate protein kinases C (PKCs). A downstream target of PKC, involved in GBM progression, is the intracellular progesterone receptor (PR), which can be phosphorylated by this enzyme, increasing its transcriptional activity. Interestingly, in GBM cells, PKCα isotype translocates to the nucleus after LPA stimulation, resulting in an increase in PR phosphorylation. In this study, we determined that LPA1 receptor activation induces protein-protein interaction between PKCα and PR in human GBM cells; this interaction increased PR phosphorylation in serine400. Moreover, LPA treatment augmented VEGF transcription, a known PR target. This effect was blocked by the PR selective modulator RU486; also, the activation of LPA1/PR signaling promoted migration of GBM cells. Interestingly, using TCGA data base, we found that mRNA expression of LPAR1 increases according to tumor malignancy and correlates with a lower survival in grade III astrocytomas. These results suggest that LPA1/PR pathway regulates GBM progression.
Subject(s)
Brain Neoplasms/metabolism , Glioblastoma/metabolism , Protein Kinase C-alpha/metabolism , Receptors, Lysophosphatidic Acid/metabolism , Receptors, Progesterone/metabolism , Brain Neoplasms/genetics , Brain Neoplasms/pathology , Cell Line, Tumor , Cell Movement/drug effects , Cell Nucleus/drug effects , Cell Nucleus/metabolism , ErbB Receptors/genetics , ErbB Receptors/metabolism , Gene Expression Regulation, Neoplastic/drug effects , Glioblastoma/genetics , Glioblastoma/pathology , Humans , Lysophospholipids/pharmacology , Phosphoric Diester Hydrolases/metabolism , Phosphorylation/drug effects , Phosphoserine/metabolism , Promoter Regions, Genetic/genetics , Protein Binding/drug effects , Protein Transport/drug effects , RNA, Messenger/genetics , RNA, Messenger/metabolism , Survival Analysis , Vascular Endothelial Growth Factor A/genetics , Vascular Endothelial Growth Factor A/metabolismABSTRACT
Lysophosphatidic acid (LPA) is a ubiquitous lysophospholipid that induces a wide range of cellular processes such as wound healing, differentiation, proliferation, migration, and survival. LPA signaling is increased in a number of cancers. In Glioblastoma (GBM), the most aggressive brain tumor, autotaxin the enzyme that produces LPA and its receptor LPA1 are overexpressed. LPA1 is preferentially couple to Gαq proteins in these tumors that in turn activates PKCs. PKCs are involved in many cellular processes including proliferation and metastasis. In this study, we aimed to determine if a classical PKC (α isozyme), could be activated through LPA1 in GBM cell lines and if this activation impacts on cell number. We found that LPA1 induces PKCα translocation to the nucleus, but not to the cell membrane after LPA treatment and the cell number diminished when LPA1/PKCα signaling was blocked, suggesting a relevant role of LPA1 and PKCα in GBM growth.
Subject(s)
Cell Nucleus/metabolism , Glioblastoma/pathology , Protein Kinase C-alpha/metabolism , Receptors, Lysophosphatidic Acid/metabolism , Active Transport, Cell Nucleus , Cell Line, Tumor , Gene Expression Regulation, Neoplastic , Humans , Phosphoric Diester Hydrolases/metabolismABSTRACT
Glioblastoma multiforme (GBM) is the most hostile type of brain cancer. Its aggressiveness is due to increased invasion, migration, proliferation, angiogenesis, and a decreased apoptosis. In this review, we discuss the role of key regulators of apoptosis in GBM and glioblastoma stem cells. Given their importance in the etiology and pathogenesis of GBM, these signaling molecules may represent potential therapeutic targets.
Subject(s)
Apoptosis/genetics , Cell Movement/genetics , Cell Proliferation/genetics , Glioblastoma/genetics , Glioblastoma/pathology , Humans , Neoplasm Invasiveness/genetics , Neoplasm Invasiveness/pathology , Signal Transduction/geneticsABSTRACT
Lysophosphatidic acid (LPA) is a ubiquitous lysophospholipid and one of the main membrane-derived lipid signaling molecules. LPA acts as an autocrine/paracrine messenger through at least six G protein-coupled receptors (GPCRs), known as LPA1-6, to induce various cellular processes including wound healing, differentiation, proliferation, migration, and survival. LPA receptors and autotaxin (ATX), a secreted phosphodiesterase that produces this phospholipid, are overexpressed in many cancers and impact several features of the disease, including cancer-related inflammation, development, and progression. Many ongoing studies aim to understand ATX-LPA axis signaling in cancer and its potential as a therapeutic target. In this review, we discuss the evidence linking LPA signaling to cancer-related inflammation and its impact on cancer progression.
