EMT related lncrnas’ as novel biomarkers in glioblastoma: a review article

Glioma is the most common type of brain tumor and according to the 2016 WHO classification, based on invasion level, it is divided into four categories. The most severe and invasive type is grade IV glioma or glioblastoma (GBM), which has a very poor prognosis and a survival rate of only 15 months. However, the molecular pathway of invasion in malignant glioma tumors has not yet been clearly elucidated. Like other cancers, brain tumors are thought to migrate and metastasize to other tissues via epithelial-to-mesenchymal transition (EMT). EMT is a process by which epithelial cells lose their cell polarity and cell-cell adhesion, and gain migratory and invasive properties to become mesenchymal stem cells. Studies have shown that EMT and angiogenesis can help brain tumors to migrate to other parts of the brain as well as surrounding tissues. Thus they can induce metastasis. EMT is controlled by three gene families, including SNAIL, TWIST, and ZEB. During EMT, the expression of epithelial-related genes is silenced, and, conversely, the expression of mesenchymal-related genes is increased. In this way, the cells acquire the mesenchymal tissue’s features and can be prepared for invasion and metastasis. On the other hand, only about 1% of the genome can take its role in the translation of functional proteins, and the large remaining part of the genome is made up of non-coding sequences. Therefore, much attention has recently been paid to the role of such noncoding transcripts, at the top of them, long non-coding RNAs (lncRNAs), in regulating the expression of genes involved in important molecular pathways such as apoptosis, proliferation, invasion, and migration in cancer progression and metastasis. Any interference in regulating the expression of genes involved in each of these molecular pathways leads to cancer in different ways. Understanding and identifying lncRNAs involved in tumorigenesis and invasion of brain tumors, while helping to better identify the molecular mechanisms of metastasis in glioma, can also be effective as biomarkers in the diagnosis, prognosis, treatment, and drug resistance of glioma. Therefore, in this review study, the most important lncRNAs involved in EMT in glioma have been investigated.