## 2 The RNA Sequence and Kidney Cancer  
MiRNA is a small non-coding RNA, and its length is approximately 19-25 nucleotides, which is relatively short. It has considerable biological importance at the molecular level and acts to control the miRNAs post-transcriptionally in plants, animals, and some viruses. In the human genome, there are thousands of classified miRNAs and they are responsible for targeting about 60% of protein-coding [7; 8]. MiRNA plays an important role in basic biological processes inside our bodies such as proliferation, cell cycle control, apoptosis, differentiation, migration, and metabolism. Although many features of the miRNA biogenesis conduct are still hazy, the key processes have been characterized. MiRNA dysregulation can result in numerous types of cancers. Microarray expression data collected from a wide range of cancers have since proved that aberrant miRNA is the initial factor that influences cancer [9; 10; 11; 12; 13]. Recent studies on mouse strains have shown that individual miRNAs or miRNA clusters are responsible for a range of diseases. It has been stated that low levels of mature miRNAs are linked to cancerous diseases [10] and miRNAs have been proven to be among the most promising biomarkersfor providing information about cancer sub-type differentiation and prognosis [14]. For more details and an understanding of the miRNA and cancer correlation, please refer to [9]. Researchers are seeking to address the significant miRNA bio-factors and to identify the exact miRNAs with the greatest discriminative power as biomarkers which precise diagnosis depends on, especially for the task of identifying kidney cancer sub-types and staging. The following summarizes some of these research efforts done in this field to help understand the relationship between miRNA and kidney cancer sub-types and staging identification. [PERSON] et al. [15] performed combinatorial analysis on previously reported dysregulated miRNAs and identified 62 miRNAs out of the 133 miRNAs previously reported by other researchers. In [16], 35 miRNAs were found to distinguish between clear cell Renal Cell Carcinoma (ccRCC) and patient-matched normal kidney tissue. Among this group of 35 miRNA, nine were up-regulated and 26 were down-regulated and miRNA 106b was selected as the reference point as endogenous control. [PERSON] et al. [17] reported that over-expressed levels of miR-210 were found in ccRCC with higher levels of expression in metastatic tumors, where high expression was considered as an independent biomarker of poor prognosis in ccRCC. Higher levels noticed in the clear cell and papillary sub-types compared with chromophore renal cell carcinoma and oncocytoma. In [18], the authors stated that significantly higher expression levels of exosomal miR-210 and miR-1233 were found in ccRCC patients than in healthy samples. A combined expression level of miR-21 and miR-126 can be used to predict cancer-specific survival in two independent RCC groups depending on the sensitivity of the up-regulation of the mir-21 and down-regulation of mir-126 [19]. Studies reported in [20] showed that the up-regulation of the miR-21 was correlated with clinical characteristics of renal cancer which led to lowering kidney cancer survival time. From these studies, the reader can deduce that there is a level of uncertainty among the researchers' claims that a specific group of miRNAs is the best candidate to differentiate among the sub-types or has a significant role in detection. [PERSON] et al. [21] performed micro-array analysis and stated that RCC was a variety of different entities, each having a distinguishable molecular pattern. The high similarity in miRNA expression was observed between matched tumor and normal tissue taken from the same RCC case. Recent studies tried to understand the linkage between RCC tumors or tumor entities and miRNAs. [PERSON] et al. [22] used 35 miRNAs in a cluster analysis to discriminate between the corresponding pairs of the ccRCC and normal samples.