**1. Introduction**

Primary brain tumors are a distinct group of pathologies due to their location, low incidence compared to other human tumors, histopathologic diversities, and unexpected response to treatment methods mainly caused by their peculiar genetic and molecular characteristics. Evaluating new important biomarkers which affect the etiopathogenesis of brain tumors may also help clinicians in consulting patients about prognosis, potential clinical studies, and following response to the treatment strategies [1]. Nowadays, the value of early detection of various types of cancer before metastasis has become a very significant issue. This approach may increase life expectancy and the quality of life in these patients [2]. It is known that one of the best management strategies of cancer is to predict its prognosis and response to the updated therapeutic procedures. In orderto achieve this, it is significant to considerthe blood, serum, plasma, or tissue biomarkers. Although the value of liquid biopsy in different human tumors is established, there is a lack of data regarding primary brain tumors [3]. Confluence of information suggested that genetic, epigenetic, functional or compositional heterogeneity of diseased and healthy tissues presented a major challenge to strategies to improve clinical outcome. [4]. Many molecules found in various fluids, tissues, and cell lines are produced either by the tumor itself, other tissues, or tumor microenvironment, in response to the presence of cancer or other associated conditions including inflammation. The scientists study on cancer search for proper candidate tumor markers and for identifying patients who face different diagnosis or clinical stages of cancer. This type of biomarkers must have some characteristics which can be used to estimate tumor volume, determine response to treat‐ ment, and assess disease recurrence through monitoring. Recent advancements have shown that amplifications/translocations, genetic mutations and changes in microarray-generated profiles (genetic signatures) are contributory in cancer development, metastasis and develop‐ ment of resistance against different therapeutics. These genetic signatures are referred according to the type of tumor marker or profile and may be associated with clinical out‐ comes or good prognosis or enhanced quality of life [3,4]. An ideal tumor marker is descri‐ bed as easily measurable, reliable, and cost-effective by use of an assay with high analytical sensitivity and specificity. Although we have developed a deeper understanding of the underlying mechanisms, there are only a few markers which have been used in routine applications and only a limited number of them can be used to identify patients or monitor progression of cancer types and clinical staging.

Gene overexpression is described as increase in copy number of genes or chromosomes (i.e., gene amplification) through increased transcriptional activity. It is known that imbalance between the gene repressors and gene activators or some epigenetic changes as DNA methylation or chromosomal translocations can alter transcriptional activity of the gene [3,4].
