Dynamic Signature of tRNA-Derived small RNAs in Cancer Pathogenesis as a Promising Valuable Approach CURRENT

Background: Non-coding RNAs are a cluster of RNAs that do not encode functional proteins, and involve infrastructural and regulatory types, which transfer RNAs (tRNAs) belong to former and small RNAs (sRNA) to the latter one. Recently, tRNA-derived small RNAs (tDRs) were discovered among small non-coding RNA, as the newly discovered regulatory small RNA. It plays a role in pathological and physiological processes, which is frequently dysregulated in gene expression regulation. tsRNAs can be bounded to argonaute proteins and piwi proteins such as miRNAs and piRNAs sequentially. In addition, it can interact with DNA and histone methylation machinery Results: In initial searching, 2744 unique articles were identified by bio electronically search of following databases: PubMed, Embase, Web of Science, Scopus, and google scholar up to 25 February 2020. Finally, after Full-text assessment 48 related article to gene expression profiling tsRNA in cancer were achieved. Conclusions: In this systematic review, we summarized the most recent findings related to the expression of tsRNAs in 17 cancer types. We suggested that tsRNA in cancer field attracted the researchers' focus and effectively facilitated diagnostic and therapy approaches.


Study Exclusion
The publications with the following characteristics were excluded from this study: (I) evidence on tsRNAs expression review, short report, letters, seminars, and books chapters, (II) non English articles, (III) any intervention that applied on experimental researches such as induction of drug resistance.

Quality Assessment
Newcastle Ottawa Scale (NOS) was applied for risk of bias assessment in observational studies [26].
This platform included score between 0 to 9. NOS score was developed to assess the quality of nonrandomised studies that scores above six were classified as high quality article.

Statistical analysis
Meta-analysis was not conducted due to heterogeneity in the assessments of varied tsRNA expression.

Microrna And Tsrna Association
Advanced analysis of bioinformatics has introduced a huge number of rapid noncoding small RNAs.
Some of miRNAs that were annotated on miRBase earlier, have been recently shown to be derived from tRNAs [27]. Thus, these cross mapping and mis-annotation lead to be incorrectly identified as miRNAs (miR-tRFs) based on mirBase literature review, which was finally removed from database, and 5 are listed in detail in Table 1 [28,29]. In fact, 20 tRNA-derived miRNAs were determined that have similar sequences with tRFs. Moreover, lysine degradation pathway was considered as a common regulatory pathway using DIANA-mirPath [30]. Since tRFs can be produced in a similar pathway to miRNA such as Argonaute/tRF interactions as well as dicer and drosha dependent [31]; hence, it is also notable that focusing on identifying miRNA processing details is crucial for understanding the biogenesis of tRF [5,32].

Results
In initial searching, 2744 unique articles were identified, and finally, 258 of them were selected based on the title and abstract review evaluation. Full-text assessment yielded 48 relevant articles for final inclusion that has been drawn in Fig. 2. In this systematic review, according to discovery of tsRNAs importance in cancer field, we aimed at highlighting these biomarkers expressions and their potential role in cancers. Our analysis showed that, tsRNAs were investigated by researchers among 17 types of cancer. To clarify, here we classified the results based on the abundance of publications separately 6 for each cancer.

Breast Cancer
Breast cancer leads 25% of women cancer cases to death in over 100 countries [33]. Aggressive Triple-negative breast cancer (TNBC) patients are suffering from shorter overall survival. The biogenesis and function of tRNA-derived microRNAs, as a gene regulator, should also be subjected to investigate [31]. Goodarzi et al., observed that, metastatic cells under the hypoxic conditions evade the up-regulation of these fragments and revealed a tumor suppressor function. The extracted data are summarized in Table 2 [23].
By comparing the extra vesicles (EV) of miRNA profiles, it was indicated that, combination of tRNAderived small RNA with miR signatures could determine tumor-derived EVs levels. To specify, miR-100, miR-125b, and let-7a are mirrored in the EVs, and correlations in tRNA-derived miRNA levels are only found in the EVs in comparison with cell line. [38]. Also, Honda et al. reported sex hormonedependent tRNA-derived RNAs (SHOT-RNAs) as a transfer RNA (tRNA)-derived small RNA that was expressed in breast and prostate cancers and assisted in cell proliferation [39].
In another study, miR-1280 (tRNA Leu-derived fragment) levels significantly increased in control < < early cancer < metastatic cancer prior to therapy. Besides, miR-1260, miR1280, and miR-720 up-regulated in ER-positive breast cancer [41]. Additionally, 5'-tiRNA-Val by inhibition of FZD3/Wnt/β-Catenin signaling pathway served as diagnostic markers. TRNA-Val and tRNA-Asp were the most prevalent as well as lower levels of tRNA-Val-CAC (AS-tDR-001430) in tumor tissues and serum of the patients with higher TNM stages and lymph node metastasis and inhibition progression [42]. tsRNA-26576 upregulation induced migration while suppressing the cellular apoptosis, and served as a potential target therapy and also a predictive marker [43]. In another research, down-regulation of tRF-32-Q99P9P9NH57SJ and tRF-17-79MP9PP were indicated as well as up regulation of tRF-32-XSXMSL73VL4YK [44]. Using high-throughput sequencing, circulating tDR-7816 was predicted as an oncogene effect on xenobiotic metabolic processes in early non-TNBC breast cancer. [45]. tRF3E derived from mature tRNA-Glu levels, as a tumor suppressor, significantly decreased in the blood of the patients with HER2 positive (control > early cancer > metastatic cancer) [46].

Prostate Cancer
Prostate cancer is ranked as the fifth cancer causing death among men [33]. SHOT-RNAs are abundantly expressed in androgen receptor (AR)-positive prostate lines as well as the patients' cancer tissues [39]. Lee et al. measured tRF-1001 (tRNA-SerTGA), which is expressed in cancer cell lines much more than tissues, and is also associated with cell proliferation [47].

Lung Cancer
Lung cancer is accompanied with high incidence and mortality, representing close to 18.4% cancer deaths [33]. Also, ts-3676 and ts-4521 are downregulated and linked with Piwi proteins. Besides, 8 downregulation of ts-46 and ts-47 in lung cancer are documented [35,51]. The upregulated expression level of tRF-Leu-CAG in cell lines, serum, and tissues was detected. It was proved that, they cooperate in cell proliferation and cycle [52].
RNA-sequencing results indicated that, tRF-5 and then tRF-3 are the most prevalent ones. Besides, eight tRFs that were enriched in cancer-related pathways such as Wnt signaling and carbon metabolism, were reported. They indicated that, knockdown of AStDR-007333 and AS-tDR-010968 suppressed the cell apoptosis, proliferation, and migration [5].

Ovarian Cancer
This cancer is ranked as the fourth leading cancer death in women, and has the second rank in incidence and mortality next to breast cancer [33]. The scientists found that, ts-29 was overexpressed as compared with normal, and then verified that tRF5-Glu binds to a site in the 3'UTR of BRAC3 to cancer proliferation. Moreover, upregulation of Ts-3 is proved in CLL as well as ovarian cancer [35,53]. High percentage of small total RNA was allocated to circulating tsncRNAs, which are enriched in Gly-tRNA and can predict abnormal cell proliferation with a high accuracy [54].
Zhang et al., reported that tRFs were involved in cell transcription, migration, and interaction with the MAPK and Wnt signaling pathways. Moreover, tRF-03357 was predictively targeted, due to promoting cell proliferation, migration, and invasion [55].

Colorectal cancer (CRC)
Colorectal cancer is considered as the second cancer leading to death [33].

Renal cancer (RCC)
In clear cell renal cell carcinoma tissues of the patients, tRNA-Arg-CCT, tRNA-Glu-CTC, and -tRNA-Lys-TTT were circulated at lower levels, as a tumor suppressor [57]. tRFHis-GTG, as a novel tRNA-derived miRNA-like smRNA, which is probably induced by oxidative stress, is upregulated in metastatic form and promote migration [58]. In another study, researchers identified the expression of 32 tRNAs and down-regulation of 5'tRNA4-Val-AAC in tissues, which were correlated with staging and grading [59].

Liver Cancer
Fourth cancer leading to death is liver cancer that its screening is so painful [33]. Zhu

Gastric Cancer
The second most cancer-related deaths worldwide is gastric cancer. Increased standards of hygiene in food and personal care and Helicobacter pylori eradication lead to steady decline in cancer incidence rates [67]. tiRNA-5034-GluTTC-2 was down regulated in tissues and plasmas, and was associated with tumor size and lower overall survival rate [68].

Lymphoma cancer
Maute et al., suggested that, CU1276 is tRNA-Gly-GCC independently expressed at three stages of mature B-cell differentiation, and one GC-derived is down regulated in lymphoma cell line [69]. 11. Chronic Lymphocytic Leukemia (cll): 10 The most common human hematological malignancy was known to be chronic lymphocytic leukemia

Myelodysplastic Syndromes And Acute Myeloid Leukemia
Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are hematopoietic cell disorders, which frequently affect older adults [32]. The patients with AML had significantly more tDRs for Val and Gly compared with MDS supporting a biological phenomenon rather than the random cleavage events [74]. In another study, four tRNAs-derived small RNAs (tDRs) and 13 mitochondrial tDRs (mt-tDRs) were identified, which the response to treatment was predicted with DNMTIs [75].

Head And Neck Squamous Cell Carcinoma
Sixth most common human cancer is the Head and Neck Squamous Cell Carcinoma (HNSCC).

Chondrosarcoma
The second most common bone primary cancer next to osteosarcoma is named chondrosarcoma.
Green et al. found miR-140, as a significant part in embryonic bone development, which is highly expressed in advanced tumors as well as tRF-Gly-TCC as a tumor suppressor [81].

Uveal Melanoma (uvm)
The most primary intraocular malignancy considered ad uveal melanoma (UVM) with abovementioned half of the patients with developing metastatic. Londin et al., findings indicated that, tRFs of nuclear origin are mostly 5′-tRFs, whereas mitochondrial tRFs are predominantly 3′-tRFs.
Additionally, nearly three quarters of the UVM tRFs are produced by ten tRNA isoacceptors that are listed by detail in the following Table [82]. The quality of all articles related to the evaluation of tsRNA expression was assessed using the Newcastle-Ottawa Scale (NOS), and then reported in Table S2. Out of the 48 related articles, 42%, 27%, 20%, and 2% scored 6, 7, 8, and 9, respectively, and 9% could were scored x ≤ 5.

Discussion
In recent years, tRNA derivatives including tRNA-derived stress-induced RNAs (tiRNAs), tRNA-derived fragments (tRFs), tRNA-derived small noncoding RNAs (tDRs), and tRNA-derived small RNAs (tsRNAs), as 0.2 -4% of sRNAs were generated by cleavage of the pre/ mature tRNAs under various environmental stress [13]. The most modified RNAs in any cell type are also tRNAs and mutations in biogenesis statuary tRNA modification enzymes that are correlated with a disease [96]. These biomarkers are involved under the stress condition; therefore, they play pivotal roles in cancer via RNA silencing and microenvironment manipulating. tRFs formed by Dicer or Rnase Z at other positions can shape a complex with argonaute (Ago) protein [97]. Our results stated that the experimental and bioinformatics studies in this field must be focused on the elucidation of common regulatory pathways [98]. Extracellular small non-coding RNAs are known to regulate the expression of genes involved in cell metabolism, and are produced via all cells by including extracellular vesicles [99].
Accumulating data discussed that, tRNAs and tRNA derivatives are important in translation reprograming [100], inhibition of the eIF4F function, and binding to YB-1 [23,101]. In response to exposure namely stress under unfavourable conditions, this molecules can affect cell survival [102,103]. It was also worthy to declare that, they were observed in the fluid of the stressful and cancerous people. Packaging and delivery of the circulating tsRNA derived occurred in the extracellular environment, and also the inside functions contributed to malignancy [76].
Proto-oncogenes and tumor suppressor genes affected the transcription of tRNA by RNA pol III. There are 625 human tRNA genes, which are able to produce small RNAs [104]. Moreover, tRNA overexpression affected the metastasis and invasion abilities, which are due to their high stability and codon-rich transcripts translation [105].

Conclusion
The lack of functional data and mechanistic for most of the tRFs need more scientific search, which must be performed related to tsRNA expression and their molecular mechanism to an expansion of evidence in the above-mentioned cancers. The other view that must be noted is that, in reaching a better understanding, the gap between common and standard nomenclatures must be covered by the researcher.
Additionally, this potential biomarker could be evaluated in another common cancer, that it was not reported yet. Accumulating of all data's together can effectively assist scientists to properly identify the signature of tsRNA.
To sum up, in this systematic review, we perused the expression of tsRNA in 17 cancers that are listed in details in Table 2, and it was indicated that, the advent of this biomarker in cancer attracted the researchers' focus and effectively facilitated diagnostic and therapy approaches.   Request for waiver .docx Table S1.docx Table S2.docx