## 6 Biomarker Detection
### Transcriptomics-Based Biomarkers  
MicroRNA is a group of functional non-coding RNA molecules that have about 22 nucleotides each. They contribute to gene control after transcription, and they have about 22 nucleotides in each. Many diseases start and get worse when there are problems with the way microRNAs are made. This is because microRNAs control so many important biological processes, such as advancement, divergence, and cell cycles [14; 15]. Tus miRNAs might be used as biomarkers for a variety of illnesses, including neurodevelopmental disorders ([PERSON] et al. 2014), cancer, and cardiovascular disease [24; 65]. A microarray analysis of 20 human whole-blood specimens on 1200 miRNAs revealed OSCC-specific signature biomarkers. Then qRT-PCR was used to validate the most important miRNAs, which showed a two-fold upregulation for miR-494 and miR-3651 and a two-fold downregulation for miR-186. Another study with microarray data using Affymetrix U133A platform revealed that 51 genes were upregulated and found that most of genes were related to OSCC [66]. Their findings also showed a new set of OSCC-related genes (RHEB, SOD2, SKP2, IFI16, IFI44, STATI, and GREM1) and three genes (MMP1, SOCS3, and ACOX1) that differentiate the normal tissue from the cancer [67]. Microarray and qPCR were used to examine a group of 23 CXC-chemokine ligands and receptors that were then connected to therapeutic response by using a logistic regression technique. CXCL10 expression was found to be substantially associated with radiotherapy response, with the group with CXCL10 overexpression having a poor outcome [68]. Similar study was also observed where miRNAs showed different levels of expression between normal tissue and OSCC tissue. In this study, miR-375 showed the greatest inhibition, whereas miR-31 recorded overexpression. Moreover, 61 miRNAs were found to establish a 93 percent accurate molecular categorization of OSCC [65]. [PERSON] and his group found that HPV causes changes to 21 miRNAs, the most important of which are miR-127-3p and miR-363 [69]. The influence of HPV might explain why HPV-infected malignancies have variable clinical outcomes on miRNA profile.  
MiR-375 downregulation, miR-127 overexpression, and miR-137 hypermethylation were discovered in another study of OSCC. Another interesting biomarker which is epigenetically activated in tumor tissue was observed with miR-200 and miR-205. Observing changes in miR-375 and miR-200a methylation, and also changes in miR-200c methylation, is a useful non-invasive biomarker, as shown by a study that compared the saliva of OSCC patients and healthy people. It has been suggested that salivary miRNA profiles could be used as a biomarker for initial evaluation of patients in OSCC [70]. The first lncRNA heat map for usual oral cavity vs. a pre-malignant abscess was made and publicly disclosed [71]. Many recent research studies have shown that new lncRNA can be used as non-invasive saliva biological markers for prediction and diagnosis. HOTAIR identified in saliva was shown to have considerable predictive relevance in a recent research study, with the expression level associated with lymph node metastases.