Page 4 Hines, Marcum, Strong, Wade • Differential MicroRNA Expression miR-9/9*. (An asterisk is added to the name of the miRNA strand to denote the star strand.) Abundant in CD133+ GSCs, these miRNAs seem to contribute to glioblastoma’s high resistance to modern therapy (Sana et al., 2018). The cluster containing miR-106-5p, miR-93-5p, and miR-93-3p seems to have a close connection to the biology of stem cells. Research shows the inhibition of this cluster in CD44+ gastric cancer stem-like cells suppresses the TGF-ß/Smad pathway (Sana et al., 2018). MiR-153 was shown to have a high expression in GSCs, and its overexpression reduced GSC’s tumorigenic capacity (Sana et al., 2018). Of the nine upregulated miRNA, miR-652, miR-345, and miR-9* all positively contributed to a higher risk score and poorer prognosis, while miR-301, miR153, miR-93, and miR-106b negatively contributed (Sana et al., 2018). These results signify that miRNAs are closely involved in the biological characteristics in GSCs, making them ideal targets for therapeutic treatment. MicroRNA Expression as a Biomarker The increase of certain microRNA strands allows them to be used as a biomarker by comparing their levels in the supposed cancerous tissue to levels in a known normal tissue of the same type. More research is needed until miRNA can act as a useful and reliable biomarker. The benefits of uncovering this diagnostic method are undoubtedly great as evident in breast cancer (BC), which already has research into its microRNA being reviewed as a possible diagnostic tool (Adhami et al., 2017). For miRNA to be used as a biomarker, there must be actual upregulation and downregulation of the different strands in cancerous tissue when compared to normal tissue. Studies show there are around 144 different miRNAs found with 74 being upregulated and 70 being downregulated (Adhami et al., 2017). In total, there are at least 30 differentially expressed miRNA across multiple studies. These were all expressed in a constant direction (Adhami et al., 2017) making them useful for use as a biomarker. Using this kind of detection shows great promise for modern day medicine. The current mammography technique is useful for catching early-stage breast cancer, but the technology is still unreliable and can lead to false positives as well as overdiagnosis and subsequent overtreatment of some minor cases (Adhami et al., 2017). And then there are those that do not get caught at all and are thus never treated. Using this new biomarker diagnosis via miRNA could help catch false positives or false negatives before any major harm is done. There are also a few miRNAs, specifically MiR-21, which have altered expression in many different types of human cancer (Adhami et al., 2017). Despite the potential of this study, there are still some drawbacks to using this kind of diagnostic marker. The first is the wide range of inconsistency found between research for most biomarker targets (Adhami et al., 2017). Second, researchers would need to compile a large library of all the consistently different regulations in order to be the most effective and accurate. Generally, the subject needs more research because of the major inconsistencies among studies and reviews regarding miRNA and its regulation (Adhami et al., 2017). MicroRNA as a Therapeutic Target MicroRNAs and their expression in glioblastoma cells may serve as a potential therapeutic target to treat this aggressive form of brain cancer. An overall lack of balance between tumor suppressor
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