Global profile of tRNA-derived small RNAs in gastric cancer patient plasma and identification of tRF-33-P4R8YP9LON4VDP as a new tumor suppressor

The regulatory role of tRNA-derived small RNAs in the prognosis of gastric cancer

In recent years, tRNA-derived small RNAs (tsRNAs) including tRNA-derived stress-induced RNAs (tiRNAs) and tRNA-derived fragments (tRFs), with specific structure and enriched in body fluids, have been found to have specific biological functions. In this paper, the biogenesis, classification, subcellular localization, and biological functions of tsRNAs were summarized. It has been proved that tsRNAs affected tumor cells in proliferation, apoptosis, migration and invasion, and played roles in regulating the occurrence and development of various tumors. In gastric cancer (GC), the imbalance of tsRNAs, such as tRF-33-P4R8YP9LON4VDP, tRF-17-WS7K092, tRF-23-Q99P9P9NDD and others, was closely related to the clinicopathological characteristics of GC patients. Some tsRNAs, such as tRF-23-Q99P9P9NDD, tRF-31-U5YKFN8DYDZDD, and tRF-27-FDXXE6XRK45 promoted the proliferation, migration and invasion of GC cells. Other tsRNAs, such as tRF-41-YDLBRY73W0K5KKOVD, tRF-18-79MP9PO4, and tRF-Glu-TTC-027 inhibited the proliferation, migration and invasion of GC cells. The tsRNAs played roles in the occurrence of GC were through several signaling pathways, such as phosphoinositide 3-kinase (PI3K)-AKT serine/threonine kinase (AKT), Wnt-β-Catenin, and mitogen-activated protein kinase (MAPK) pathways. These findings may provide new strategies for the diagnosis and treatment of GC.

tRNA-derived fragments: Unveiling new roles and molecular mechanisms in cancer progression

tRNA-derived fragments (tRFs) are novel small noncoding RNAs (sncRNAs) that range from approximately 14 to 50 nt. They are generated by the cleavage of mature tRNAs or precursor tRNAs (pre-tRNAs) at specific sites. Based on their origin and length, tRFs can be classified into three categories: (1) tRF-1 s; (2) tRF-3 s, tRF-5 s, and internal tRFs (i-tRFs); and (3) tRNA halves. They play important roles in stress response, signal transduction, and gene expression processes. Recent studies have identified differential expression of tRFs in various tumors. Aberrantly expressed tRFs have critical clinical value and show promise as new biomarkers for tumor diagnosis and prognosis and as therapeutic targets. tRFs regulate the malignant progression of tumors via various mechanisms, primarily including modulation of noncoding RNA biogenesis, global chromatin organization, gene expression regulation, modulation of protein translation, regulation of epigenetic modification, and alternative splicing regulation. In conclusion, tRF-mediated regulatory pathways could present new avenues for tumor treatment, and tRFs could serve as promising therapeutic targets for cancer therapy.

Oncogenic-tsRNA: A novel diagnostic and therapeutic molecule for cancer clinic

tsRNA (tRNA-derived small RNA) is derived from mature tRNA or precursor tRNA (pre-tRNAs). It is lately found that tsRNA's aberrant expression is associated with tumor occurrence and development, it may be used a molecule of diagnosis and therapy. Based on the cleavage position of pre-tRNAs or mature tRNAs, tsRNAs are classified into two categories: tRNA-derived fragments (tRFs) and tRNA halves (also named tiRNAs or tRHs). tsRNAs display more stability within cells, tissues, and peripheral blood than other small non-coding RNAs (sncRNAs), and play a role of stable entities that function in various biological contexts, thus, they may serve as functional molecules in human disease. Recently, tsRNAs have been found in a large number of tumors including such as lung cancer, breast cancer, gastric cancer, colorectal cancer, liver cancer, and prostate cancer. Although the biological function of tsRNAs is still poorly understood, increasing evidences have indicated that tsRNAs have a great significance and potential in early tumor screening and diagnosis, therapeutic targets and application, and prognosis. In the present review, we mainly describe tsRNAs in tumors and their potential clinical value in early screening and diagnosis, therapeutic targets and application, and prognosis, it provides theoretical support and guidance for further revealing the therapeutic potential of tsRNAs in tumor.

tRF-33-P4R8YP9LON4VDP inhibits gastric cancer progression via modulating STAT3 signaling pathway in an AGO2-dependent manner

It has been demonstrated that tRNA-derived small RNAs (tsRNAs) perform essential functions in the pathophysiology of cancer. In this study, we focused on the possible mechanisms of tRF-33-P4R8YP9LON4VDP (tRF-33) underlying the development of gastric malignancy. In total, 454 tissue samples with different gastric mucosal lesions were collected. The tRF-33 expression level in different cohorts was determined, and its value for diagnostic efficiency and prognosis evaluation were assessed. Cell proliferation assays, Transwell assay, flow cytometry, and xenotransplantation model were used to evaluate its effect on gastric cancer cells. The molecular mechanism was verified by fluorescence in situ hybridization, dual luciferase assay, Western blot, and RNA binding protein immunoprecipitation. The results showed that the expression of tRF-33 exhibited a gradual modification from normal control samples to gastritis tissues, early and latent stage of gastric cancer tissues. Consequently, tRF-33 holds significant potential as a predictive and diagnostic biomarker for gastric malignancy. Over-expression of tRF-33 inhibited gastric cancer cell progression and metastatic viability, and induced cell apoptosis. Tumorigenicity in nude mice showed the suppressive characteristics of tRF-33. Mechanistic investigation revealed that tRF-33 exerted silencing on STAT3 mRNA via binding to AGO2. In conclusion, tRF-33 exhibited values in diagnosing gastric cancer and evaluating its prognosis, and suppressed tumor cell viability by inhibiting STAT3 signaling pathway. The schematic mechanisms underlying tRF-33 regulating gastric cancer occurrence. tRF-33 binds to AGO2 proteins and then negatively regulates STAT3 expression through targeting its 3'UTR. The downregulated expression of STAT3 results in the decrease of STAT3 and p-STAT3 and further blocks the transcription of the downstream genes and finally inhibits the gastric cancer occurrence. MMP-9, matrix metalloproteinase-9; Bcl-2, B-cell lymphoma-2; STAT3, signal transducer and activator of transcription 3; UTR, untranslated region.

Transfer RNA‑derived small RNAs: A class of potential biomarkers in multiple cancers (Review)

Transfer (t)RNA-derived small RNAs (tsRNAs) are a class of novel non-coding small RNAs that are created via precise cleavage of tRNAs or tRNA precursors by different enzymes. tsRNAs are specific biological molecules that serve essential roles in cell proliferation, apoptosis, transcriptional regulation, post-transcriptional modification and translational regulation. Additionally, tsRNAs participate in the pathogenesis of several diseases, particularly in the development of malignant tumors. At present, the process of discovering and understanding the functions of tsRNAs is still in its early stages. The present review introduces the known biological functions and mechanisms of tsRNAs, and discusses the tsRNAs progression in several types of cancers as well as the possibility of tsRNAs becoming novel tumor biomarkers. Furthermore, tsRNAs may promote and hinder tumor formation according to different mechanisms and act as oncogenic or oncostatic molecules. Therefore, tsRNAs may be future potential tumor biomarkers or therapeutic targets.

The 'Not-So-Famous Five' in tumorigenesis: tRNAs, tRNA fragments, and tRNA epitranscriptome in concert with AARSs and AIMPs

RNA profiling studies have revealed that ∼75% of the human genome is transcribed to RNA but only a meagre fraction of it is translated to proteins. Majority of transcribed RNA constitute a specialized pool of non-coding RNAs. Human genome contains approximately 506 genes encoding a set of 51 different tRNAs, constituting a unique class of non-coding RNAs that not only have essential housekeeping functions as translator molecules during protein synthesis, but have numerous uncharted regulatory functions. Intriguing findings regarding a variety of non-canonical functions of tRNAs, tRNA derived fragments (tRFs), esoteric epitranscriptomic modifications of tRNAs, along with aminoacyl-tRNA synthetases (AARSs) and ARS-interacting multifunctional proteins (AIMPs), envision a 'peripheral dogma' controlling the flow of genetic information in the backdrop of qualitative information wrung out of the long-live central dogma of molecular biology, to drive cells towards either proliferation or differentiation programs. Our review will substantiate intriguing peculiarities of tRNA gene clusters, atypical tRNA-transcription from internal promoters catalysed by another distinct RNA polymerase enzyme, dynamically diverse tRNA epitranscriptome, intricate mechanism of tRNA-charging by AARSs governing translation fidelity, epigenetic regulation of gene expression by tRNA fragments, and the role of tRNAs and tRNA derived/associated molecules as quantitative determinants of the functional proteome, covertly orchestrating the process of tumorigenesis, through a deregulated tRNA-ome mediating selective codon-biased translation of cancer related gene transcripts.

Clinical value assessment for serum hsa_tsr013526 in the diagnosis of gastric carcinoma

Gastric carcinoma (GC) is a malignant tumor that is detrimental to human health. Transfer RNA-derived small RNAs are a newly identified class of noncoding small RNAs with specific biological functions that are aberrantly expressed in cancer. The aim of this study was to investigate the potential of hsa_tsr013526 as a biomarker for GC. Quantitative real-time fluorescence polymerase chain reaction was used to detect the expression level of hsa_tsr013526. The molecular characteristics of hsa_tsr013526 were verified by agarose gel electrophoresis, Sanger sequencing, and separation of nuclear and cytoplasmic RNA fractions. By testing the receiver operating characteristic (ROC) curves, the diagnostic efficiency of GC using hsa_tsr013526 was determined. Finally, we predicted the downstream of hsa_tsr013526 using functional assays and bioinformatics analysis. Serum expression of hsa_tsr013526 was higher in GC patients than in healthy donors. Serum expression showed differential changes in GC patients, gastritis patients, and healthy donors. Chi-squared tests showed that high expression of hsa_tsr013526 was significantly correlated with T stage, lymphatic metastasis, and tumor node metastasis stage. ROC curve analysis indicated that GC patients could be discriminated from healthy donors or gastritis patients based on their serum levels of hsa_tsr013526. Furthermore, hsa_tsr013526 expression was significantly reduced in postoperative GC patients (p = .0016). High expression of hsa_tsr013526 promotes gastric cancer cell proliferation, invasion, and migration. Serum hsa_tsr013526 was stable and specific, and could be used for dynamic monitoring of GC patients. Therefore, hsa_tsr013526 may be a new biomarker for the diagnosis and postoperative monitoring of GC patients.

Global progress and future prospects of early gastric cancer screening

Gastric cancer is a prevalent malignancy that poses a serious threat to global health. Despite advances in medical technologies, screening methods, and public awareness, gastric cancer remains a significant cause of morbidity and mortality worldwide. Early gastric cancer frequently does not present with characteristic symptoms, while advanced stage disease is characterized by a dismal prognosis. As such, early screening in gastric cancer is of great importance. In recent years, advances have been made globally in both clinical and basic research for the screening of early gastric cancer. The current predominant screening methods for early gastric cancer include imaging screening, endoscopic screening and serum biomarker screening. Imaging screening encompasses upper gastrointestinal barium meal, multidimensional spiral computed tomography (MDCT), Magnetic resonance imaging (MRI), and ultrasonography. Endoscopic screening methods include white light endoscopy, chromoendoscopy, computed virtual chromoendoscopy, and other endoscopic techniques like endocytoscopy, confocal laser endomicroscopy, optical coherence tomography and so on. Biomarkers screening involves the assessment of conventional biomarkers such as CEA, CA19-9 and CA72-4 as well as more emerging biomarkers such as peptides (PG, G-17, GCAA, TAAs and others), DNA (cfDNA, DNA methylation, MSI), noncoding RNA (miRNA, lncRNA, circRNA, and tsRNA) and others. Each screening method has its strengths and limitations. This article systematically summarizes worldwide progress and future development of early gastric cancer screening methods to provide new perspectives and approaches for early diagnostic and treatment advancements in gastric cancer worldwide.

tRNA-derived fragments: Key determinants of cancer metastasis with emerging therapeutic and diagnostic potentials

Metastasis is a significant clinical challenge responsible for cancer mortality and non-response to treatment. However, the molecular mechanisms driving metastasis remain unclear, limiting the development of efficient diagnostic and therapeutic approaches. Recent breakthroughs in cancer biology have discovered a group of small non-coding RNAs called tRNA-derived fragments (tRFs), which play a critical role in the metastatic behavior of various tumors. tRFs are produced from cleavage modifications of tRNAs and have different functional classes based on the pattern of these modifications. They perform post-transcriptional regulation through microRNA-like functions, displacing RNA-binding proteins, and play a role in translational regulation by inducing ribosome synthesis, translation initiation, and epigenetic regulation. Tumor cells manipulate tRFs to develop and survive the tumor mass, primarily by inducing metastasis. Multiple studies have demonstrated the potential of tRFs as therapeutic, diagnostic, and prognostic targets for tumor metastasis. This review discusses the production and function of tRFs in cells, their aberrant molecular contributions to the metastatic environment, and their potential as promising targets for anti-metastasis treatment strategies.

Multiple regulatory roles of the transfer RNA-derived small RNAs in cancers

With the development of sequencing technology, transfer RNA (tRNA)-derived small RNAs (tsRNAs) have received extensive attention as a new type of small noncoding RNAs. Based on the differences in the cleavage sites of nucleases on tRNAs, tsRNAs can be divided into two categories, tRNA halves (tiRNAs) and tRNA-derived fragments (tRFs), each with specific subcellular localizations. Additionally, the biogenesis of tsRNAs is tissue-specific and can be regulated by tRNA modifications. In this review, we first elaborated on the classification and biogenesis of tsRNAs. After summarizing the latest mechanisms of tsRNAs, including transcriptional gene silencing, post-transcriptional gene silencing, nascent RNA silencing, translation regulation, rRNA regulation, and reverse transcription regulation, we explored the representative biological functions of tsRNAs in tumors. Furthermore, this review summarized the clinical value of tsRNAs in cancers, thus providing theoretical support for their potential as novel biomarkers and therapeutic targets.

Biological function and clinical application prospect of tsRNAs in digestive system biology and pathology

tsRNAs are small non-coding RNAs originating from tRNA that play important roles in a variety of physiological activities such as RNA silencing, ribosome biogenesis, retrotransposition, and epigenetic inheritance, as well as involvement in cellular differentiation, proliferation, and apoptosis. tsRNA-related abnormalities have a significant influence on the onset, development, and progression of numerous human diseases, including malignant tumors through affecting the cell cycle and specific signaling molecules. This review introduced origins together with tsRNAs classification, providing a summary for regulatory mechanism and physiological function while dysfunctional effect of tsRNAs in digestive system diseases, focusing on the clinical prospects of tsRNAs for diagnostic and prognostic biomarkers. Video Abstract.

A comprehensive evaluation of serum tRF-29-R9J8909NF5JP as a novel diagnostic and prognostic biomarker for gastric cancer

Gastric cancer (GC) is a common malignant digestive system tumor. Since the early symptoms of GC are usually vague and the positive rate of common biomarkers of GC is low, it is of urgent need to find new biomarkers with good sensitivity and specificity to screen and diagnose GC patients. The tRNA-derived small RNAs (tsRNAs) are emerging small noncoding RNAs that play an essential role in cancer progression. In this study, we explored whether novel tsRNAs have the potential to serve as biomarkers for GC. Three tsRNAs significantly upregulated in GC were screened by the tsRFun database. The expression level of tRF-29-R9J8909NF5JP was detected by real-time fluorescence quantitative polymerase chain reaction. Agarose gel electrophoresis and Sanger sequencing were used to verify the characteristics of tRF-29-R9J8909NF5JP. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic efficacy of tRF-29-R9J8909NF5JP. The χ2 test was used to analyze the correlation between tRF-29-R9J8909NF5JP expression level and clinicopathological parameters. Kaplan-Meier survival curves were used to analyze the correlation between tRF-29-R9J8909NF5JP expression levels and survival time of GC patients. In this study, the expression level of tRF-29-R9J8909NF5JP was significantly increased in GC tissues. The expression level of tRF-29-R9J8909NF5JP was considerably higher in the serum of GC patients than in the serum of gastritis patients and in the serum of healthy donors, and the expression level of tRF-29-R9J8909NF5JP was significantly decreased in the serum of GC patients after surgery. In addition, the χ2 test showed that the expression level of tRF-29-R9J8909NF5JP in GC serum was correlated with differentiation grade, T-stage, lymph node metastasis, tumor node metastasis stage, and neurological/vascular invasion. The results of the survival curve showed that the high expression of serum tRF-29-R9J8909NF5JP was associated with a low survival rate. ROC analysis showed that serum tRF-29-R9J8909NF5JP had higher diagnostic efficiency than common GC biomarkers, and the diagnostic efficiency was further improved by combining them. At the end of the study, we predicted the downstream of tRF-29-R9J8909NF5JP. The expression level of tRF-29-R9J8909NF5JP in the serum of GC patients can effectively identify GC patients and has higher efficacy than conventional biomarkers. In addition, serum tRF-29-R9J8909NF5JP can monitor the postoperative condition of GC patients, suggesting that it has the potential to become a biomarker for GC.

Transfer RNA-derived small RNAs (tsRNAs) in gastric cancer

Transfer RNA-derived small RNAs (tsRNAs) are newly discovered noncoding RNAs (ncRNAs). According to the specific cleavage of nucleases at different sites of tRNAs, the produced tsRNAs are divided into tRNA-derived stress-inducible RNAs (tiRNAs) and tRNA-derived fragments (tRFs). tRFs and tiRNAs have essential biological functions, such as mRNA stability regulation, translation regulation and epigenetic regulation, and play significant roles in the occurrence and development of various tumors. Although the roles of tsRNAs in some tumors have been intensively studied, their roles in gastric cancer are still rarely reported. In this review, we focus on recent advances in the generation and classification of tsRNAs, their biological functions, and their roles in gastric cancer. Sixteen articles investigating dysregulated tsRNAs in gastric cancer are summarized. The roles of 17 tsRNAs are summarized, of which 9 were upregulated and 8 were downregulated compared with controls. Aberrant regulation of tsRNAs was closely related to the main clinicopathological factors of gastric cancer, such as lymph node metastasis, Tumor-Node-Metastasis (TNM) stage, tumor size, and vascular invasion. tsRNAs participate in the progression of gastric cancer by regulating the PTEN/PI3K/AKT, MAPK, Wnt, and p53 signaling pathways. The available literature suggests the potential of using tsRNAs as clinical biomarkers for gastric cancer diagnosis and prognosis and as therapeutic targets for gastric cancer treatment.

The diagnostic and prognostic value of tsRNAs in gastric cancers: a systematic review and meta-analysis

BACKGROUND

Gastric cancer (GC) is one of the most common types of cancer worldwide. Recent studies have shown that tsRNAs play important roles in GC and that changes in the expression levels of tsRNAs can be used for GC diagnosis and treatment response prediction.

RESEARCH DESIGN AND METHODS

Hazard ratios (HRs), odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the correlation between tsRNA expression and prognosis and other clinicopathologic features of GC patients. The sensitivity, specificity, area under the receiver operating characteristic curve (AUC) and diagnostic odds ratio (DOR) were analyzed to evaluate the diagnostic value of tsRNAs.

RESULTS

The results showed that patients with tsRNA upregulation had a poor prognosis (HR = 2.48, 95% CI: 1.85-3.34), while patients with tsRNA downregulation had a favorable prognosis (HR = 0.55, 95% CI: 0.31-0.98). In addition, tsRNA expression was significantly correlated with various clinicopathological features in patients with GC. Finally, in diagnostic studies, GC-related tsRNAs could differentiate healthy controls (AUC = 0.81, DOR = 7.74) from patients with inflammation (AUC = 0.74, DOR = 4.44).

CONCLUSIONS

tsRNAs have potential clinical application in GC diagnosis and prognosis evaluation. It is necessary to further assess and verify the practicability and feasibility of additional specific tsRNAs as GC markers in the future.

Emerging roles of tRNA-derived small RNAs in cancer biology

Transfer RNAs (tRNAs) play an essential role in mRNA translation by delivering amino acids to growing polypeptide chains. Recent data demonstrate that tRNAs can be cleaved by ribonucleases, and the resultant cleavage products, tRNA-derived small RNAs (tsRNAs), have crucial roles in physiological and pathological conditions. They are classified into more than six types according to their size and cleavage positions. Since the initial discovery of the physiological functions of tsRNAs more than a decade ago, accumulating data have demonstrated that tsRNAs play critical roles in gene regulation and tumorigenesis. These tRNA-derived molecules have various regulatory functions at the transcriptional, post-transcriptional, and translational levels. More than a hundred types of modifications are found on tRNAs, affecting the biogenesis, stability, function, and biochemical properties of tsRNA. Both oncogenic and tumor suppressor functions have been reported for tsRNAs, which play important roles in the development and progression of various cancers. Abnormal expression patterns and modification of tsRNAs are associated with various diseases, including cancer and neurological disorders. In this review, we will describe the biogenesis, versatile gene regulation mechanisms, and modification-mediated regulation mechanisms of tsRNA as well as the expression patterns and potential therapeutic roles of tsRNAs in various cancers.

An old friend with a new face: tRNA-derived small RNAs with big regulatory potential in cancer biology

Transfer RNAs (tRNAs) are small non-coding RNAs (sncRNAs) essential for protein translation. Emerging evidence suggests that tRNAs can also be processed into smaller fragments, tRNA-derived small RNAs (tsRNAs), a novel class of sncRNAs with powerful applications and high biological relevance to cancer. tsRNAs biogenesis is heterogeneous and involves different ribonucleases, such as Angiogenin and Dicer. For many years, tsRNAs were thought to be just degradation products. However, accumulating evidence shows their roles in gene expression: either directly via destabilising the mRNA or the ribosomal machinery, or indirectly via regulating the expression of ribosomal components. Furthermore, tsRNAs participate in various biological processes linked to cancer, including apoptosis, cell cycle, immune response, and retroviral insertion into the human genome. It is emerging that tsRNAs have significant therapeutic potential. Endogenous tsRNAs can be used as cancer biomarkers, while synthetic tsRNAs and antisense oligonucleotides can be employed to regulate gene expression. In this review, we are recapitulating the regulatory roles of tsRNAs, with a focus on cancer biology.

Emerging roles of tRNA in cancer

Transfer RNAs (tRNAs) play pivotal roles in the transmission of genetic information, and abnormality of tRNAs directly leads to translation disorders and causes diseases, including cancer. The complex modifications enable tRNA to execute its delicate biological function. Alteration of appropriate modifications may affect the stability of tRNA, impair its ability to carry amino acids, and disrupt the pairing between anticodons and codons. Studies confirmed that dysregulation of tRNA modifications plays an important role in carcinogenesis. Furthermore, when the stability of tRNA is impaired, tRNAs are cleaved into small tRNA fragments (tRFs) by specific RNases. Though tRFs have been found to play vital regulatory roles in tumorigenesis, its formation process is far from clear. Understanding improper tRNA modifications and abnormal formation of tRFs in cancer is conducive to uncovering the role of metabolic process of tRNA under pathological conditions, which may open up new avenues for cancer prevention and treatment.

The role and mechanism of action of tRNA-derived fragments in the diagnosis and treatment of malignant tumors

Cancer is a leading cause of morbidity and death worldwide. While various factors are established as causing malignant tumors, the mechanisms underlying cancer development remain poorly understood. Early diagnosis and the development of effective treatments for cancer are important research topics. Transfer RNA (tRNA), the most abundant class of RNA molecules in the human transcriptome, participates in both protein synthesis and cellular metabolic processes. tRNA-derived fragments (tRFs) are produced by specific cleavage of pre-tRNA and mature tRNA molecules, which are highly conserved and occur widely in various organisms. tRFs were initially thought to be random products with no physiological function, but have been redefined as novel functional small non-coding RNA molecules that help to regulate RNA stability, modulate translation, and influence target gene expression, as well as other biological processes. There is increasing evidence supporting roles for tRFs in tumorigenesis and cancer development, including the regulation of tumor cell proliferation, invasion, migration, and drug resistance. Understanding the regulatory mechanisms by which tRFs impact these processes has potential to inform malignant tumor diagnosis and treatment. Further, tRFs are expected to become new biological markers for early diagnosis and prognosis prediction in patients with tumors, as well as a targets for precision cancer therapies. Video abstract.

Clinical Diagnostic Values of Transfer RNA-Derived Fragment tRF-41-YDLBRY73W0K5KKOVD and its Effects on the Growth of Gastric Cancer Cells

Gastric cancer (GC) is a serious disease with high mortality and poor prognosis. It is known that tRNA halves play key roles in the progression of cancer. This study explored the function of the tRNA half tRF-41-YDLBRY73W0K5KKOVD in GC. Quantitative real-time reverse transcription-polymerase chain reaction was used to measure RNA levels. The level of tRF-41-YDLBRY73W0K5KKOVD in GC cells was regulated by its mimics or inhibitor. Cell proliferation was evaluated by using a Cell Counting Kit-8 and EdU cell proliferation assay. A Transwell assay was used to detect cell migration. Flow cytometry was used to measure cell cycle and apoptosis. The results showed that tRF-41-YDLBRY73W0K5KKOVD expression was decreased in GC cells and tissues. Functionally, overexpression of tRF-41-YDLBRY73W0K5KKOVD inhibited cell proliferation, reduced migration, repressed the cell cycle, and promoted cell apoptosis in GC cells. Based on RNA sequencing results and luciferase reporter assays, 3'-phosphoadenosine-5'-phosphosulfate synthase 2 (PAPSS2) was identified as a target gene of tRF-41-YDLBRY73W0K5KKOVD. These findings indicated that tRF-41-YDLBRY73W0K5KKOVD inhibited GC progression, suggesting that tRF-41-YDLBRY73W0K5KKOVD might be a potential therapeutic target in GC.

Emerging roles of tRNA-derived fragments in cancer

tRNA-derived fragments (tRFs) are an emerging category of small non-coding RNAs that are generated from cleavage of mature tRNAs or tRNA precursors. The advance in high-throughput sequencing has contributed to the identification of increasing number of tRFs with critical functions in distinct physiological and pathophysiological processes. tRFs can regulate cell viability, differentiation, and homeostasis through multiple mechanisms and are thus considered as critical regulators of human diseases including cancer. In addition, increasing evidence suggest the extracellular tRFs may be utilized as promising diagnostic and prognostic biomarkers for cancer liquid biopsy. In this review, we focus on the biogenesis, classification and modification of tRFs, and summarize the multifaceted functions of tRFs with an emphasis on the current research status and perspectives of tRFs in cancer.

Absolute quantification of a plasma tRNA-derived fragment for the diagnosis and prognosis of gastric cancer

Background

The transition from a healthy gastric mucosa to gastric cancer is a multi-step process. Early screening can significantly improve the survival rate of gastric cancer patients. A reliable liquid biopsy for gastric cancer prediction is urgently needed and since tRNA-derived fragments (tRFs) are abundant in various body fluids, tRFs are possible new biomarkers for gastric cancer.

Methods

A total of 438 plasma samples from patients with different gastric mucosal lesions as well as healthy individuals were collected. A specific reverse transcription primer, a forward primer, a reverse primer, and a TaqMan probe were designed. A standard curve was constructed and an absolute quantitation method was devised for detection of tRF-33-P4R8YP9LON4VDP in plasma samples of individuals with differing gastric mucosa lesions. Receiver operating characteristic curves were constructed to evaluate the diagnostic values of tRF-33-P4R8YP9LON4VDP for individual with differing gastric mucosa. A Kaplan-Meier curve was established to calculate the prognostic value of tRF-33-P4R8YP9LON4VDP for advanced gastric cancer patients. Finally, a multivariate Cox regression analysis was performed to assess the independent prognostic value of tRF-33-P4R8YP9LON4VDP for advanced gastric cancer patients.

Results

A detection method for plasma tRF-33-P4R8YP9LON4VDP was successfully established. Levels of plasma tRF-33-P4R8YP9LON4VDP were shown to reflect a gradient change from healthy individuals to gastritis patients to early and advanced gastric cancer patients. Significant differences were found among individuals with differing gastric mucosa, with reduced levels of tRF-33-P4R8YP9LON4VDP significantly related to a poor prognosis. tRF-33-P4R8YP9LON4VDP was found to be an independent predictor of an unfavorable survival outcome.

Conclusions

In this study, we developed a quantitative detection method for plasma tRF-33-P4R8YP9LON4VDP that exhibited hypersensitivity, convenience, and specificity. Detection of tRF-33-P4R8YP9LON4VDP was found to be a valuable means by which to monitor different gastric mucosa and to predict patient prognosis.

Establishment of an Absolute Quantitative Method to Detect a Plasma tRNA-Derived Fragment and Its Application in the Non-Invasive Diagnosis of Gastric Cancer

(1) Transfer RNA (tRNA)-derived fragments (tRFs) are a new category of regulatory non-coding RNAs with distinct biological functions in cancer. They are produced from pre-tRNAs or mature tRNAs and their sequences are relatively short; thus, the amplification of tRFs, especially those in body fluids, is faced with certain technical difficulties. In this study, we established a quantitative method to detect plasma tRF-27-87R8WP9N1E5 (tRF-27) and used it to screen gastric cancer patients. (2) A specific stem-loop-structure reverse transcription primer, a TaqMan probe, and amplification primers for tRF-27 were prepared, and the absolute quantitative method was used to measure plasma tRF-27 levels. To determine the noninvasive diagnostic value of tRF-27 in gastric cancer, plasma tRF-27 levels in patients with benign and malignant lesions (120 healthy individuals, 48 patients with benign lesions, 48 patients with precancerous lesions, and 72 patients with early gastric cancer) were analyzed. Plasma tRF-27 levels were also analyzed in 106 preoperative gastric cancer patients, 106 postoperative gastric cancer patients, and 120 healthy individuals. Survival curves and Cox regression models were established and analyzed. (3) A new absolute quantitative method to determine the plasma tRF-27 copy number was established. Plasma tRF-27 levels were significantly increased in gastric cancer patients compared to healthy individuals, and the area under the receiver operating characteristic curve was 0.7767, when the cutoff value was 724,807 copies/mL, with sensitivity and specificity values of 0.6226 and 0.8917, respectively. The positive predictive and negative predictive values were 83.50% and 72.80%, respectively. Plasma tRF-27 levels in postoperative gastric cancer patients were significantly decreased compared to preoperative gastric cancer patients and tended to the levels of healthy individuals. Moreover, tRF-27 levels were closely related to tumor size and Ki67 expression in gastric cancer patients. Prognostic analysis showed that tRF-27 may be an independent predictor of overall survival. (4) This novel and non-invasive method of measuring plasma tRF-27 levels was valuable in the early diagnosis of gastric cancer.

Detecting plasma hsa_circ_0061276 in patients with gastric cancer by reverse transcription-digital polymerase chain reaction

Background

The role of circular RNAs (circRNAs) in the occurrence of gastric cancer is still unclear. Therefore, the diagnostic value and mechanisms underlying hsa_circ_0061276 in the occurrence of gastric cancer were explored.

Methods

Reverse transcription-droplet digital polymerase chain reaction was used to detect the copy number of hsa_circ_0061276 in plasma from healthy individuals, as well as from patients with gastric precancerous lesions or early-stage or advanced gastric cancer. Plasmids overexpressing or knocking down hsa_circ_0061276 expression were transfected into gastric cancer cells. The effects on the growth, migration, and cell cycle distribution of gastric cancer cells were then analyzed. Finally, miRanda and RNAhybrid were used to explore the binding sites between hsa_circ_0061276 and microRNAs (miRNAs). A double luciferase reporter gene assay was used to confirm the miRNA sponge effect.

Results

The results show that plasma hsa_circ_0061276 copy number showed a trend of a gradual decrease when comparing healthy controls to the early cancer group and advanced gastric cancer group. Overexpression of hsa_circ_0061276 inhibited the growth and migration of gastric cancer cells. Through bioinformatic analyses combined with cellular experiments, it was found that hsa_circ_0061276 inhibited the growth of gastric cancer by binding to hsa-miR-7705.

Conclusion

Hsa_circ_0061276 may be a new biomarker for gastric cancer. The tumor suppressor role of hsa_circ_0061276 on gastric cancer likely occurs through a sponge effect on miRNAs such as hsa-miR-7705.

Comprehensive Evaluation of Serum tRF-17-WS7K092 as a Promising Biomarker for the Diagnosis of Gastric Cancer

Background

Gastric cancer (GC) is a malignant tumor of the gastrointestinal system. Since the early symptoms of GC are not obvious and lack efficient diagnostic markers, it is urgent to find new diagnostic markers with good sensitivity and specificity. tRNA-derived small RNAs (tsRNAs) are an emerging class of small noncoding RNAs with good abundance in body fluids. We aim to find new tsRNAs as biomarkers for GC diagnosis.

Methods

High-throughput sequencing was used to identify differentially expressed tsRNAs in GC tissues, and quantitative real-time PCR was used to detect the expression level of tRF-17-WS7K092. Agarose gel electrophoresis and Sanger sequencing were performed to verify the characteristics of tRF-17-WS7K092. The diagnostic efficacy of tRF-17-WS7K092 was analyzed by the receiver operating characteristic curve.

Results

In this study, the expression levels of tRF-17-WS7K092 were significantly increased in GC tissues, cells, and serum. After GC surgery, the expression level of serum tRF-17-WS7K092 decreased, and its high expression was associated with low survival rates. In addition, the expression level of serum tRF-17-WS7K092 was correlated with the T stage, TNM stage, lymph node metastasis, and nerve/vascular invasion and could distinguish GC patients from gastritis patients and healthy donors as well.

Conclusions

The expression of serum tRF-17-WS7K092 was significantly increased in GC and decreased after GC surgery, suggesting that serum tRF-17-WS7K092 may serve as a promising biomarker for the diagnostic and prognostic monitoring of GC.

tRNA-derived fragments in gastric cancer: Biomarkers and functions

tRNA‐derived fragments (tRFs), non‐coding RNAs that regulate protein expression after transcription, have recently been identified as potential biomarkers. We identified differentially expressed tRFs in gastric cancer (GC) and the biological properties of tRFs in predicting the malignancy status of GCs as possible biomarkers. Until 15 February 2022, two independent reviewers did a thorough search in electronic databases of Scopus, EMBASE and PubMed. The QUADAS scale was used for quality assessment of the included studies. Ten articles investigating the clinical significance of tRFs, including 928 patients, were analysed. In 10 GC studies, seven tRFs were considerably upregulated and five tRFs were significantly downregulated when compared to controls. Risk of bias was rated low for index test, and flow as well as timing domains in relation to the review question. The applicability of the index test, flow and timing and patient selection for 10 studies was deemed low. In this study, we review the advances in the study of tRFs in GC and describe their functions in gene expression regulation, such as suppression of translation, cell differentiation, proliferation and the related signal transduction pathways associated with them. Our findings may offer researchers new ideas for cancer treatment as well as potential biomarkers for further research in GC.

Transfer RNA-derived small RNA: an emerging small non-coding RNA with key roles in cancer

Transfer RNAs (tRNAs) promote protein translation by binding to the corresponding amino acids and transporting them to the ribosome, which is essential in protein translation. tRNA-derived small RNAs (tsRNAs) are derived fragments of tRNAs that are cleaved explicitly under certain conditions. An increasing amount of research has demonstrated that tsRNAs have biological functions rather than just being degradation products. tsRNAs can exert functions such as regulating gene expression to influence cancer progression. Their dysregulation is closely associated with various cancers and can serve as diagnostic and prognostic biomarkers for cancer. This review summarizes the generation, classification, and biological functions of tsRNAs, and highlights the roles of tsRNAs in different cancers and their applications as tumor markers.

Transfer RNA-Derived Small RNAs: Novel Regulators and Biomarkers of Cancers

Transfer RNA-derived small RNAs (tsRNAs) are conventional non-coding RNAs (ncRNAs) with a length between18 and 40 nucleotides (nt) playing a crucial role in treating various human diseases including tumours. Nowadays, with the use of high-throughput sequencing technologies, it has been proven that certain tsRNAs are dysregulated in multiple tumour tissues as well as in the blood serum of cancer patients. Meanwhile, data retrieved from the literature show that tsRNAs are correlated with the regulation of the hallmarks of cancer, modification of tumour microenvironment, and modulation of drug resistance. On the other side, the emerging role of tsRNAs as biomarkers for cancer diagnosis and prognosis is promising. In this review, we focus on the specific characteristics and biological functions of tsRNAs with a focus on their impact on various tumours and discuss the possibility of tsRNAs as novel potential biomarkers for cancer diagnosis and prognosis.

Extracellular vesicles-associated tRNA-derived fragments (tRFs): biogenesis, biological functions, and their role as potential biomarkers in human diseases

Traditionally, transfer RNAs (tRNAs) specifically decoded messenger RNA (mRNA) and participated in protein translation. tRNA-derived fragments (tRFs), also known as tRNA-derived small RNAs (tsRNAs), are generated by the specific cleavage of pre- and mature tRNAs and are a class of newly defined functional small non-coding RNAs (sncRNAs). Following the different cleavage positions of precursor or mature tRNA, tRFs are classified into seven types, 5′-tRNA half, 3′-tRNA half, tRF-1, 5′U-tRF, 3′-tRF, 5′-tRF, and i-tRF. It has been demonstrated that tRFs have a diverse range of biological functions in cellular processes, which include inhibiting protein translation, modulating stress response, regulating gene expression, and involvement in cell cycles and epigenetic inheritance. Emerging evidences have indicated that tRFs in extracellular vesicles (EVs) seem to act as regulatory molecules in various cellular processes and play essential roles in cell-to-cell communication. Furthermore, the dysregulation of EV-associated tRFs has been associated with the occurrence and progression of a variety of cancers and they can serve as novel potential biomarkers for cancer diagnosis. In this review, the biogenesis and classification of tRFs are summarized, and the biological functions of EV-associated tRFs and their roles as potential biomarkers in human diseases are discussed.

tRNA-derived small RNAs: mechanisms and potential roles in cancers

Transfer RNAs (tRNAs) are essential for protein synthesis. Mature or pre-tRNAs may be cleaved to produce tRNA-derived small RNAs (tsRNAs). tsRNAs, divided into tRNA-derived stress-induced RNA (tiRNAs) and tRNA-derived fragments (tRFs), play versatile roles in a number of fundamental biological processes. tsRNAs not only play regulatory roles in gene silencing, RNA stability, reverse transcription, and translation, but are also closely related to cell proliferation, migration, cell cycle, and apoptosis. Their abnormal expression is associated with the occurrence and development of various human diseases, especially cancer. This paper reviews the classification, biogenesis, and mechanism of action of tsRNAs, and the research progress to date on tsRNAs in cancers. These findings provide new opportunities for diagnostic biomarkers and treatment targets of several types of cancers including gastric cancer, colorectal cancer, hepatocellular carcinomas, pancreatic cancer, breast cancer, prostate cancer, renal cell carcinoma, ovarian cancer, lung cancer, bladder cancer, thyroid cancer, oral cancer, and leukemia.

Hsa_circ_0003195 as a biomarker for diagnosis and prognosis of gastric cancer

PURPOSE

Recent studies have shown that circular RNAs (circRNAs) are closely related to the occurrence and development of gastric cancer. In this paper, we analyzed the value of hsa_circ_0003195 in diagnosis and prognosis of gastric cancer.

METHODS

Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to determine the level of hsa_circ_0003195 in 100 paired gastric cancer tissues and paracancerous tissues, 74 paired fasting plasma from gastric cancer patients before and 10 days after operation, and 74 fasting plasmas from healthy controls. A receiver operating characteristic (ROC) curve was generated to evaluate the diagnostic value. The survival analysis and Cox proportional-hazards model were used to evaluate the efficiency of hsa_circ_0003195 in predicting overall survival (OS) in patients with gastric cancer.

RESULTS

The expression of hsa_circ_0003195 was down-regulated in gastric cancer tissues and plasma from patients with gastric cancer. The expression level of hsa_circ_0003195 was correlated with differentiation, TNM stages, lymphatic metastasis, and distal metastasis. The area under the ROC curve (AUC) of tissue and plasma hsa_circ_0003195 was 0.684 and 0.695, respectively. The plasma hsa_circ_0003195 can be used as predictors of survival of patients with gastric cancer.

CONCLUSION

Hsa_circ_0003195 may be a new diagnostic and prognostic marker of gastric cancer.

tRNA-derived small RNAs: novel regulators of cancer hallmarks and targets of clinical application

tRNAs are a group of conventional noncoding RNAs (ncRNAs) with critical roles in the biological synthesis of proteins. Recently, tRNA-derived small RNAs (tsRNAs) were found to have important biological functions in the development of human diseases including carcinomas, rather than just being considered pure degradation material. tsRNAs not only are abnormally expressed in the cancer tissues and serum of cancer patients, but also have been suggested to regulate various vital cancer hallmarks. On the other hand, the application of tsRNAs as biomarkers and therapeutic targets is promising. In this review, we focused on the basic characteristics of tsRNAs, and their biological functions known thus far, and explored the regulatory roles of tsRNAs in cancer hallmarks including proliferation, apoptosis, metastasis, tumor microenvironment, drug resistance, cancer stem cell phenotype, and cancer cell metabolism. In addition, we also discussed the research progress on the application of tsRNAs as tumor biomarkers and therapeutic targets.

Elucidating the Role of Serum tRF-31-U5YKFN8DYDZDD as a Novel Diagnostic Biomarker in Gastric Cancer (GC)

Background

Gastric cancer (GC) is one of the malignant tumors with the highest morbidity and mortality in the world. Early diagnosis combined with surgical treatment can significantly improve the prognosis of patients. Therefore, it is urgent to seek higher sensitivity and specificity biomarkers in GC. tRNA-derived small RNAs are a new non-coding small RNA that widely exists in tumor cells and body fluids. In this study, we explore the expression and biological significance of tRNA-derived small RNAs in GC.

Materials and Methods

First of all, we screened the differentially expressed tRNA-derived small RNAs in tumor tissues by high-throughput sequencing. Agarose gel electrophoresis (AGE), Sanger sequencing, and Nuclear and Cytoplasmic RNA Separation Assay were used to screen tRF-31-U5YKFN8DYDZDD as a potential tumor biomarker for the diagnosis of GC. Then, we detected the different expressions of tRF-31-U5YKFN8DYDZDD in 24 pairs of GC and paracancerous tissues, the serum of 111 GC patients at first diagnosis, 89 normal subjects, 48 superficial gastritis patients, and 28 postoperative GC patients by quantitative real-time PCR (qRT-PCR). Finally, we used the receiver operating characteristic (ROC) curve to analyze its diagnostic efficacy.

Results

The expression of tRF-31-U5YKFN8DYDZDD has good stability and easy detection. tRF-31-U5YKFN8DYDZDD was highly expressed in tumor tissue, serum, and cell lines of GC, and the expression was significantly related to TNM stage, depth of tumor invasion, lymph node metastasis, and vascular invasion. The expression of serum tRF-31-U5YKFN8DYDZDD in the GC patients decreased after the operation (P = 0.0003). Combined with ROC curve analysis, tRF-31-U5YKFN8DYDZDD has better detection efficiency than conventional markers.

Conclusions

The expressions of tRF-31-U5YKFN8DYDZDD in the tumor and paracancerous tissues, the serum of GC patients and healthy people, and the serum of GC patients before and after operation were different. tRF-31-U5YKFN8DYDZDD is not only a diagnostic biomarker of GC but also a predictor of poor prognosis.

The tRNA-derived fragment 5026a inhibits the proliferation of gastric cancer cells by regulating the PTEN/PI3K/AKT signaling pathway

Background

Recently, tRNA-derived fragments (tRFs) have been shown to serve important biological functions. However, the role of tRFs in gastric cancer has not been fully elucidated. This study aimed to identify the tumor suppressor role of tRF-5026a (tRF-18-79MP9P04) in gastric cancer.

Methods

Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was first used to detect tRF-5026a expression levels in gastric cancer tissues and patient plasma. Next, the relationship between tRF-5026a levels and clinicopathological features in gastric cancer patients was assessed. Cell lines with varying tRF-5026a levels were assessed by measuring tRF-5026a using qRT-PCR. After transfecting cell lines with a tRF-5026a mimic or inhibitor, cell proliferation, colony formation, migration, apoptosis, and cell cycle were evaluated. The expression levels of related proteins in the PTEN/PI3K/AKT pathway were also analyzed by Western blotting. Finally, the effect of tRF-5026a on tumor growth was tested using subcutaneous tumor models in nude mice.

Results

tRF-5026a was downregulated in gastric cancer patient tissues and plasma samples. tRF-5026a levels were closely related to tumor size, had a certain diagnostic value, and could be used to predict overall survival. tRF-5026a was also downregulated in gastric cancer cell lines. tRF-5026a inhibited the proliferation, migration, and cell cycle progression of gastric cancer cells by regulating the PTEN/PI3K/AKT signaling pathway. Animal experiments showed that upregulation of tRF-5026a effectively inhibited tumor growth.

Conclusions

tRF-5026a (tRF-18-79MP9P04) is a promising biomarker for gastric cancer diagnostics and has tumor suppressor effects mediated through the PTEN/PI3K/AKT signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02497-1.

Serum hsa_tsr016141 as a Kind of tRNA-Derived Fragments Is a Novel Biomarker in Gastric Cancer

Background

Gastric cancer (GC) is one of the most common malignant tumors globally and the third leading cause of cancer-related death. Currently, the sensitivity and specificity of diagnostic markers for GC are low, so it is urgent to find new biomarkers with higher sensitivity and specificity. tRNA-derived small RNAs are a kind of small non-coding RNAs derived from tRNAs. It is abundant in cancer cells and body fluids. Our goal is to find the differentially expressed tRNA-derived small RNAs in GC to explore their potential as a GC biomarker.

Methods

Quantitative real-time PCR was used to detect the expression level of hsa_tsr016141. The molecular characteristics of hsa_tsr016141 were verified by agarose gel electrophoresis, Sanger sequencing, Actinomycin D Assay, and Nuclear and Cytoplasmic RNA Separation Assay. The diagnostic efficiency of hsa_tsr016141 was analyzed through receiver operating characteristic.

Results

The expression level of hsa_tsr016141 in GC tissues and serum was significantly increased. The serum expression level showed a gradient change between GC patients, gastritis patients, and healthy donors and was positively correlated with the degree of lymph node metastasis and tumor grade. ROC analysis showed that the serum expression level of hsa_tsr016141 could significantly distinguish GC patients from healthy donors or gastritis patients. Besides, the expression level of hsa_tsr016141 in GC patients decreased significantly after the operation (P<0.0001).

Conclusions

Serum hsa_tsr016141 has good stability and specificity and can be used for dynamic monitoring of GC patients, suggesting that serum hsa_tsr016141 can be a novel biomarker for GC diagnosis and postoperative monitoring.

Clinical diagnostic values of transfer RNA-derived fragment tRF-19-3L7L73JD and its effects on the growth of gastric cancer cells

Background and aim: Medicine has made great progress, but gastric cancer is still one of the most common malignant tumors worldwide. tRNA-derived fragments (tRFs), a type of small non-coding RNA, have been found to play important roles in cancers. Due to an abundance of modifications, tRFs have the potential to serve as cancer biomarkers. However, the relationship between tRFs and gastric cancer is still largely unclear. We have identified a new tRF, tRF-19-3L7L73JD, found to be expressed at a lower level in gastric cancer patients than healthy controls. Our study aims to explore the diagnostic value of tRF-19-3L7L73JD screening in gastric cancer and to investigate its effects on the growth of gastric cancer cells.

Methods: Using quantitative reverse transcription-polymerase chain reaction, we identified tRF-3L7L73JD as differentially expressed in plasma from gastric cancer patients compared to healthy controls. We measured tRF-3L7L73JD levels in plasma from 40 gastric cancer patients and healthy controls. Furthermore, we tested another cohort containing 89 gastric cancer patients and 98 healthy controls to validate our findings. Next, we analyzed the relationship between levels of tRF-19-3L7L73JD in plasma and clinicopathological data of gastric cancer patients, and then evaluated the effects of tRF-19-3L7L73JD on gastric cancer cell growth. Cell proliferation was measured by the Cell Counting Kit‐8 and clone formation experiments after transfer with tRF-19-3L7L73JD mimics. The changes in cell migration ability were explored through the scratch and Transwell experiments. Finally, we explored changes in apoptosis and cell cycle by flow cytometry.

Results: tRF-19-3L7L73JD showed lower expression in the tested gastric cancer patients. In the validation cohort tRF-19-3L7L73JD was also expressed at low levels in the pre-operative plasma group compared with healthy plasma and post-operative plasma groups. Additionally, a comparison of gastric cancer cell lines with normal gastric epithelial cell lines produced the same result. We found that tRF-19-3L7L73JD expression in patients was related to tumor size. The area under the curve (AUC) was 0.6230, with sensitivity and specificity of 0.4045 and 0.7959, respectively. Cellular function studies revealed that tRF-19-3L7L73JD inhibited cell proliferation and migration, induced apoptosis, and arrested cells at G₀/G₁ phases, suggesting it may suppress the development of gastric cancer.

Conclusion: The results suggest that tRF-19-3L7L73JD may be useful as a biomarker of gastric cancer.