Gastric juice piR-1245: A promising prognostic biomarker for gastric cancer

piR-38,736 promotes gastric cancer cell proliferation by downregulating SMAD4 expression

PIWI-interacting RNAs (piRNAs) play an important role in cancer development and progression. Although recent studies had advanced our understanding of the functions of various piRNAs in cancer, the specific role of piR-38736 in gastric cancer remained poorly understood. This study aimed to investigate the clinical significance and underlying mechanisms of piR-38736 in gastric cancer. This study found that piR-38736 was significantly upregulated in gastric cancer cells and tissues. Positive piR-38736 expression was closely correlated with larger tumor size and medium to poor differentiation. Survival analysis revealed that patients with positive piR-38736 expression had significantly shorter survival times compared to those with negative expression. Knockdown of piR-38736 markedly inhibited cell proliferation and tumor growth in gastric cancer. Furthermore, piR-38736 was found to directly bind to the 3' untranslated region (UTR) of SMAD4 mRNA, resulting in significant downregulation of SMAD4 at both the mRNA and protein levels upon overexpression of piR-38,736. In conclusion, these findings indicate that piR-38,736 promotes cell proliferation and tumor growth in gastric cancer by downregulating SMAD4 expression. piR-38,736 may serve as a prognostic biomarker and a potential therapeutic target for gastric cancer. Further studies are required to fully elucidate the underlying mechanisms of piR-38,736 and explore its clinical implications in gastric cancer management.

Circulating non-coding RNAs as a tool for liquid biopsy in solid tumors

Solid tumors are significant causes of global mortality and morbidity. Recent research has primarily concentrated on finding pathology-specific molecules that can be acquired non-invasively and that can change as the disease progresses or in response to treatment. The focus of research has moved to RNA molecules that are either freely circulating in body fluids or bundled in microvesicles and exosomes because of their great stability in challenging environments, ease of accessibility, and changes in level in response to therapy. In this context, there are many non-coding RNAs that can be used for this purpose in liquid biopsies. Out of these, microRNAs have been extensively studied. However, there has been an increase of interest in studying long non-coding RNAs, piwi interacting RNAs, circular RNAs, and other small non-coding RNAs. In this article, an overview of the most researched circulating non-coding RNAs in solid tumors will be reviewed, along with a discussion of the significance of these molecules for early diagnosis, prognosis, and therapeutic targets. The publications analyzed were extracted from the PubMed database between 2008 and June 2024.

PIWI-interacting RNA biomarkers in gastrointestinal disease

Detection and diagnosis of neoplastic and inflammatory gastrointestinal (GI) diseases are typically based on endoscopic and pathologic examination. In GI neoplastic diseases, diagnosis can be delayed due to the expense and invasive nature of this approach. Recently, PIWI-interacting RNAs (piRNAs), a group of small non-coding RNA molecules containing 24-31 nucleotides, have been thought to serve as biomarkers in many disease processes. For example, piRNAs are differentially expressed in GI cancer but their biologic role remains unclear. Using next-generation sequencing and microarray analyses, researchers have suggested that monitoring piRNAs could facilitate diagnosis and prognosis in GI disease. Herein, we reviewed the use of piRNAs in neoplastic, inflammatory, functional, and other diseases of the digestive system, which could shed new light on cancer screening, early detection, and personalized treatment.

Somatic piRNA and PIWI-mediated post-transcriptional gene regulation in stem cells and disease

PIWI-interacting RNAs (piRNAs) are small non-coding RNAs that bind to the PIWI subclass of the Argonaute protein family and are essential for maintaining germline integrity. Initially discovered in Drosophila, PIWI proteins safeguard piRNAs, forming ribonucleoprotein (RNP) complexes, crucial for regulating gene expression and genome stability, by suppressing transposable elements (TEs). Recent insights revealed that piRNAs and PIWI proteins, known for their roles in germline maintenance, significantly influence mRNA stability, translation and retrotransposon silencing in both stem cells and bodily tissues. In the current review, we explore the multifaceted roles of piRNAs and PIWI proteins in numerous biological contexts, emphasizing their involvement in stem cell maintenance, differentiation, and the development of human diseases. Additionally, we discussed the up-and-coming animal models, beyond the classical fruit fly and earthworm systems, for studying piRNA-PIWIs in self-renewal and cell differentiation. Further, our review offers new insights and discusses the emerging roles of piRNA-dependent and independent functions of PIWI proteins in the soma, especially the mRNA regulation at the post-transcriptional level, governing stem cell characteristics, tumor development, and cardiovascular and neurodegenerative diseases.

PIWI-interacting RNAs (PiRNAs) as emerging biomarkers and therapeutic targets in biliary tract cancers: A comprehensive review

Cancers affecting the biliary tract, such as gallbladder cancer and cholangiocarcinoma, make up a small percentage of adult gastrointestinal malignancies, but their incidence is on the rise. Due to the lack of dependable molecular biomarkers for diagnosis and prognosis, these cancers are often not detected until later stages and have limited treatment options. Piwi-interacting RNAs (piRNAs) are a type of small noncoding RNA that interacts with Piwi proteins and has been linked to various diseases, especially cancer. Manipulation of piRNA expression has the potential to serve as an important biomarker and target for therapy. This review uncovers the relationship between PIWI-interacting RNA (piRNA) and a variety of gastrointestinal cancers, including biliary tract cancer (BTC). It is evident that piRNAs have the ability to impact gene expression and regulate key genes and pathways related to the advancement of digestive cancers. Abnormal expression of piRNAs plays a significant role in the development and progression of digestive-related malignancies. The potential of piRNAs as potential biomarkers for diagnosis and prognosis, as well as therapeutic targets in BTC, is noteworthy. Nevertheless, there are obstacles and limitations that require further exploration to fully comprehend piRNAs' role in BTC and to devise effective diagnostic and therapeutic approaches using piRNAs. In summary, this review underscores the value of piRNAs as valuable biomarkers and promising targets for treating BTC, as we delve into the association between piRNAs and various gastrointestinal cancers, including BTC, and how piRNAs can impact gene expression and control essential pathways for digestive cancer advancement. The present research consists of a thorough evaluation presented in a storytelling style. The databases utilized to locate original sources were PubMed, MEDLINE, and Google Scholar, and the search was conducted using the designated keywords.

The role of piRNAs in predicting and prognosing in cancer: a focus on piRNA-823 (a systematic review and meta-analysis)

INTRODUCTION

This article examines the potential of using liquid biopsy with piRNAs to study cancer survival outcomes. While previous studies have explored the relationship between piRNA expression and cancer patient outcomes, a comprehensive investigation is still lacking. To address this gap, we conducted a systematic review and meta-analysis of existing literature.

METHODS

We searched major online databases up to February 2024 to identify articles reporting on the role of piRNA in cancer patient survival outcomes. Our meta-analysis used a random-effects model to pool hazard ratios with 95% confidence intervals (CI) and assess the prognostic value of deregulated piRNA-823. For survival analysis, the Kaplan-Meier method and COX analysis were used.

RESULTS

Out of 6104 articles screened, 20 met our inclusion criteria. Our analysis revealed that dysregulated piRNA expression is associated with cancer patient survival outcomes. Specifically, our meta-analysis found that overexpression of piR-823 is significantly linked with poorer overall survival in patients with colorectal cancer and renal cell cancer (HR: 3.82, 95% CI = [1.81, 8.04], I2 = 70%).

CONCLUSION

Our findings suggest that various piRNAs may play a role in cancer survival outcomes and that piRNA-823 in particular holds promise as a prognostic biomarker for multiple human cancers.

IMPLICATIONS FOR CANCER SURVIVORS

Our systematic review and meta-analysis of piRNA-823 has important implications for cancer survivors. Our findings suggest that piRNA-823 can be used as a prognostic biomarker for predicting cancer recurrence and survival rates. This information can help clinicians develop personalized treatment plans for cancer survivors, which can improve their quality of life and reduce the risk of recurrence.

Liquid Biopsy: An Emerging Diagnostic, Prognostic, and Predictive Tool in Gastric Cancer

Liquid biopsy, a minimally invasive procedure that causes minimal pain and complication risks to patients, has been extensively studied for cancer diagnosis and treatment. Moreover, it facilitates comprehensive quantification and serial assessment of the whole-body tumor burden. Several biosources obtained through liquid biopsy have been studied as important biomarkers for establishing early diagnosis, monitoring minimal residual disease, and predicting the prognosis and response to treatment in patients with cancer. Although the clinical application of liquid biopsy in gastric cancer is not as robust as that in other cancers, biomarker studies using liquid biopsy are being actively conducted in patients with gastric cancer. Herein, we aimed to review the role of various biosources that can be obtained from patients with gastric cancer through liquid biopsies, such as blood, saliva, gastric juice, urine, stool, peritoneal lavage fluid, and ascites, by dividing them into cellular and acellular components. In addition, we reviewed previous studies on the diagnostic, prognostic, and predictive biomarkers for gastric cancer using liquid biopsy and discussed the limitations of liquid biopsy and the challenges to overcome these limitations in patients with gastric cancer.

The potential of piR-823 as a diagnostic biomarker in oncology: A systematic review

BACKGROUND

Emerging evidence has demonstrated that PIWI-interacting RNAs (piRNAs) play important roles in various physiological processes and contribute to cancer progression. Moreover, piRNAs and PIWI protein levels are associated with the prognosis and chemoresistance of various cancers. The limitations of biomarkers challenge early detection and monitoring of chemoresistance and cancer relapse.

METHODS

To evaluate the potential of piRNA as a diagnostic biomarker in oncology, we systematically reviewed previous studies on the subject. PubMed, Embase, and Cochrane databases were searched to evaluate the diagnostic relevance of piRNAs in cancer. Eighteen studies (2,352 patients) were included. The quality of each study was evaluated with AMSTAR and QUADAS-2 tool.

RESULTS & CONCLUSIONS

The area under the curve (AUC) values of 26 piRNAs in patients with cancer ranged from 0.624 to 0.978, with piR-9491 showing the highest value (0.978). The sensitivity of the total of 21 piRNAs in cancer patients was between 42.86 and 100, with piR-9491 showing the highest sensitivity (100). The specificity of these 21 piRNAs ranged from 60.10 to 96.67 (with piR-018569 showing the highest specificity (96.67)). Their odds ratios were between 1.61 and 44.67, and piR-12488 showed the highest odds ratio (44.67). Generally, the piRNAs in this review showed better sensitivity and AUC values than current clinical diagnostic biomarkers, although current biomarkers appear to be more specific. Reviewed piRNAs showed better diagnostic performance than currently used clinical biomarkers. Notably, piR-823 showed a significant diagnostic performance in four types of cancer (colorectal, esophageal, gastric, and renal cell cancer). However, all 18 studies included in this review were a case-control study. So, further prospective studies are required for their validation.

Pan-cancer landscape of immunology PIWI-interacting RNAs

PIWI-interacting RNAs (piRNAs), an emergent type of non-coding RNAs during oncogenesis, play critical roles in regulating tumor microenvironment. Systematic analysis of piRNAs' roles in modulating immune pathways is important for tumor immunotherapy. In this study, in-depth analysis of piRNAs was performed to develop an integrated computational algorithm, the immunology piRNA (ImmPI) pipeline, for uncovering the global expression landscape of piRNAs and identifying their regulatory roles in immune pathways. The immunology piRNAs show a tendency towards overexpression patterns in immune cells, causing perturbations in tumors, being significantly associated with infiltration of immune cells, and having prognostic value. The ImmPI score can contribute to prioritizing tumor-related piRNAs and distinguish two subtypes of SKCM (immune-cold and hot phenotypes), as characterized by different prognoses, immunogenicity and antitumor immunity. Finally, we developed an interactive web resource (ImmPI portal: http://www.hbpding.com/ImmPi) for the biomedical research community, with several useful modules to browse, visualize, and download the results of immunology piRNAs analysis. Overall, our work provides a comprehensive landscape of piRNAs across multiple cancer types and sheds light on their regulatory and functional roles in tumor immunity. These findings pave the way for future research and development of piRNA-based immunotherapies for cancer treatment.

Roles of circRNA dysregulation in esophageal squamous cell carcinoma tumor microenvironment

Esophageal squamous cell carcinoma (ESCC) is the most prevalent histological esophageal cancer characterized by advanced diagnosis, metastasis, resistance to treatment, and frequent recurrence. In recent years, numerous human disorders such as ESCC, have been linked to abnormal expression of circular RNAs (circRNAs), suggesting that they are fundamental to the intricate system of gene regulation that governs ESCC formation. The tumor microenvironment (TME), referring to the area surrounding the tumor cells, is composed of multiple components, including stromal cells, immune cells, the vascular system, extracellular matrix (ECM), and numerous signaling molecules. In this review, we briefly described the biological purposes and mechanisms of aberrant circRNA expression in the TME of ESCC, including the immune microenvironment, angiogenesis, epithelial-to-mesenchymal transition, hypoxia, metabolism, and radiotherapy resistance. As in-depth research into the processes of circRNAs in the TME of ESCC continues, circRNAs are promising therapeutic targets or delivery systems for cancer therapy and diagnostic and prognostic indicators for ESCC.

PiRNA Obtained through Liquid Biopsy as a Possible Cancer Biomarker

In recent years PIWI-interacting RNAs (piRNAs) have gained the interest of scientists, mainly because of their possible implications in cancer. Many kinds of research showed how their expression can be linked to malignant diseases. However, most of them evaluated the expression of piRNAs in tumor tissues. It was shown how these non-coding RNAs can interfere with many signaling pathways involved in the regulation of proliferation or apoptosis. A comparison of piRNA expression in tumor tissue and adjacent healthy tissues has demonstrated they can be used as biomarkers. However, this way of obtaining samples has a significant drawback, which is the invasiveness of such a procedure. Liquid biopsy is an alternative for acquiring biological material with little to no harm to a patient. Several different piRNAs in various types of cancer were shown to be expressed in bodily fluids such as blood or urine. Furthermore, their expression significantly differed between cancer patients and healthy individuals. Hence, this review aimed to assess the possible use of liquid biopsy for cancer diagnosis with piRNAs as biomarkers.

The Human Gastric Juice: A Promising Source for Gastric Cancer Biomarkers

Gastric cancer (GC) is a major public health problem worldwide, with high mortality rates due to late diagnosis and limited treatment options. Biomarker research is essential to improve the early detection of GC. Technological advances and research methodologies have improved diagnostic tools, identifying several potential biomarkers for GC, including microRNA, DNA methylation markers, and protein-based biomarkers. Although most studies have focused on identifying biomarkers in biofluids, the low specificity of these markers has limited their use in clinical practice. This is because many cancers share similar alterations and biomarkers, so obtaining them from the site of disease origin could yield more specific results. As a result, recent research efforts have shifted towards exploring gastric juice (GJ) as an alternative source for biomarker identification. Since GJ is a waste product during a gastroscopic examination, it could provide a "liquid biopsy" enriched with disease-specific biomarkers generated directly at the damaged site. Furthermore, as it contains secretions from the stomach lining, it could reflect changes associated with the developmental stage of GC. This narrative review describes some potential biomarkers for gastric cancer screening identified in gastric juice.

PIWI-interacting RNAs: Critical roles and therapeutic targets in cancer

P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) are a novel class of small regulatory RNAs (approximately 24-31 nucleotides in length) that often bind to members of the PIWI protein family. piRNAs regulate transposons in animal germ cells; piRNAs are also specifically expressed in many human tissues and regulate pivotal signaling pathways. Additionally, the abnormal expression of piRNAs and PIWI proteins has been associated with various malignant tumours, and multiple mechanisms of piRNA-mediated target gene dysregulation are involved in tumourigenesis and progression, suggesting that they have the potential to serve as new biomarkers and therapeutic targets for tumours. However, the functions and potential mechanisms of action of piRNAs in cancer have not yet been elucidated. This review summarises the current findings on the biogenesis, function, and mechanisms of piRNAs and PIWI proteins in cancer. We also discuss the clinical significance of piRNAs as diagnostic or prognostic biomarkers and therapeutic tools for cancer. Finally, we present some critical questions regarding piRNA research that need to be addressed to provide insight into the future development of the field.

Identification and validation of anoikis-associated gene SNCG as a prognostic biomarker in gastric cancer

Anoikis is a newly discovered form of apoptosis that was originally identified in the extracellular matrix (ECM). Recent studies have reported that anoikis is central to cancer metastasis. Here, SNCG was identified as hub anoikis-associated gene in GC and associated with prognosis of patients with GC. To screen the hub anoikis-associated genes connected to GC, the database of Cancer Genome Atlas (TCGA) was employed. For further validating these identified genes, the Gene Expression Omnibus (GEO) dataset was applied, and Western blotting and quantitative Real-Time PCR were carried out. To identify hub genes, we conducted the analyses of univariate Cox regression, differential expression, and weighted gene co-expression network analysis (WGCNA). According to the identified hub genes, we constructed a model of prognosis. Following complex analysis, SNCG was finally identified as hub anoikis-associated gene in GC. Indeed, K-M and receiver operating characteristic analyses suggested that the expression patterns of SNCG can be used as prognostic factors for GC survival. The expression and survival trends of SNCG were verified in the validation cohort and in vitro experimental analyses. The analysis of immune cell infiltration showed that the infiltrated immune cells varied among patients with GC and gene SNCG. Furthermore, due to the significant association of the constructed risk signature with patient age and survival, this risk signature can be used to predict the prognosis of GC. We suggest that SNCG was served as hub anoikis-associated gene in GC. Meanwhile, SNCG may have prognostic potential for overall patient survival.

Gastric cancer detection by non-blood-based liquid biopsies: A systematic review looking into the last decade of research

Gastric cancer (GC) screening is arguable in most Western countries. Liquid biopsies are a great promise to answer the unmet need for less invasive diagnostic biomarkers in GC. Thus, we aimed at systematically reviewing the current knowledge on liquid biopsy-based biomarkers in GC screening. A systematic search on PubMed/MEDLINE and Scopus databases was performed on published articles reporting the use of non-blood specimen (saliva, gastric juice [GJ], urine and stool) on GC diagnosis. 3208 records were retrieved by June 2022. After removal of duplicate records, 2379 abstracts were screened, and 84 full texts included in this systematic review. More than 90% of studies were reported on Asian populations. Overall, 9 studies explored stool-, 12 saliva-, and 29 urine-derived biomarkers for GC detection. Additionally, 37 studies, representing the majority, analyzed GJ, focusing on nucleic acid molecules. Several miRNAs and lncRNA molecules have been associated with GC risk, particularly miR-21 (area under the curve [AUC] = 0.97, 95% CI: 0.94-1.00). Considering salivary biomarkers, the best described model in validation sets included the soybean agglutinin and Vicia villosa agglutinin lectins (AUC = 0.89, 95% CI: 0.80-0.99). Most studies in urine carried out metabolomic approaches, with two discriminatory models presenting AUC values superior to 0.97. This systematic review emphasizes the potential role of non-blood-based biomarkers, although further validation, particularly in Western countries, is mandatory, namely for non-invasive screening and/or monitoring, as well as the use of GJ as a tool to enhance upper gastrointestinal endoscopy accuracy.

PIWI-interacting RNAs in cancer: Biogenesis, function, and clinical significance

PIWI-interacting RNAs (piRNAs) are a less-studied class of small non-coding RNAs approximately 24–31 nucleotides in length. They express in germline and somatic cells and form complexes with PIWI proteins to exert regulatory effects. New studies show that piRNAs are aberrantly expressed in various cancers. In this review, we focus on those piRNAs that are associated with cancer hallmarks such as proliferation, invasion, and chemoresistance and discuss their potential as biomarkers for cancer diagnosis and prognosis.

A new biomarker for the early diagnosis of gastric cancer: gastric juice- and serum-derived SNCG

Aim: To explore the possibility of gastric juice (GJ)- and serum-derived SNCG as a potential biomarker for the early diagnosis of gastric cancer (GC). Materials & methods: GJ and serum samples were collected from 87 patients with GC, 38 patients with gastric precancerous lesions and 44 healthy volunteers. The levels of SNCG in GJ and serum samples were detected by ELISA. Results: The levels of SNCG in GJ and serum were significantly higher in the GC group when compared with the GPL group or the control group. The expression of SNCG in GJ and serum was associated with tumor node metastasis stage, lymph node metastasis, tumor size and drinking, and it is important for the diagnosis and prognosis of GC (p < 0.05). Conclusion: The findings highlight the significance of SNCG in GC diagnosis and prognosis and implicate SNCG as a promising candidate for GC treatment.

Emerging roles of PIWI-interacting RNAs (piRNAs) and PIWI proteins in head and neck cancer and their potential clinical implications

Head and neck squamous cell carcinoma (HNSCC) are among the well-known neoplasms originating in the oral cavity, pharynx, and larynx. Despite advancements in chemotherapy, radiotherapy, and surgery, the survival rates of the patients are low, which has posed a major therapeutic challenge. A growing number of non-coding RNAs (ncRNAs), for instance, microRNAs, have been identified whose abnormal expression patterns have been implicated in HNSCC. However, more recently, several seminal research has shown that piwi-interacting RNAs (piRNAs), a promising and young class of small ncRNA, are linked to the emergence and progression of cancer. They can regulate transposable elements (TE) and gene expression through multiple mechanisms, making them potentially more powerful regulators than miRNAs. Hence, they can be more promising ncRNAs candidates for cancer therapeutic intervention. Here, we surveyed the roles and clinical implications of piRNAs and their PIWI proteins partners in tumorigenesis and associated molecular processes of cancer, with a particular focus on HNSCC, to offer a new avenue for diagnosis, prognosis, and therapeutic interventions for the malignancy, improving patient's outcomes.

piRNA: A promising biomarker in early detection of gastrointestinal cancer

Gastrointestinal (GI) cancer has become the primary concern of today's society due to its aggressive nature and poor prognosis. PIWI-interacting RNAs (piRNAs), a subgroup of non-coding RNAs, are mainly expressed in the germline and have emerged as a critical regulator in gene expression and the epigenetic silencing of DNA transposable elements by interacting with PIWI proteins. piRNAs' dysregulations were reported to promote or suppress the initiation and development of different malignancies, especially gastrointestinal cancers. Recently, several studies suggested the use of piRNAs as potential cancer biomarkers associated with the progression and chemoresistance of GI cancer. Hence, this review article aims to focus on the role of piRNAs in GI cancer progression, metastasis, and their molecular mechanisms as therapeutic markers for GI cancer patients.

Identification and validation of PGLS as a metabolic target for early screening and prognostic monitoring of gastric cancer

BACKGROUND

Gastric cancer is the third leading cause of cancer-related death in the world. The purpose of the present study is to investigate the expression and prognostic significance of 6-phosphogluconolactonase (PGLS) in gastric cancer.

METHODS

The protein extracted from a panel of four pairs of gastric cancer tissues and adjacent tissues, labeled with iTRAQ (8-plex) reagents, and followed by LC-ESI-MS/MS. The expressions of proteins were further validated by immunohistochemistry analysis. The expression levels of mRNA were analyzed and validated in the Oncomine database. The correlations of PGLS with prognostic outcomes were evaluated with Kaplan-Meier plotter database.

RESULTS

The present study found that PGLS was significantly up-regulated in gastric cancer by using iTRAQ-based proteomics and immunohistochemistry analysis. The sensitivity of PGLS in gastric cancer was 72.9%. The high expression of PGLS was significantly correlated with TNM staging in gastric cancer (p = 0.02). The overexpression of PGLS predicts worse overall survival (OS) and post-progression survival (PPS) for gastric cancer (OS, HR = 1.48, p = 2.1e-05; PPS, HR = 1.35, p = 0.015). Specifically, the high PGLS expression predicts poor OS, PPS in male gastric cancer patients, in patients with lymph node metastasis and in patients with Her-2 (-).

CONCLUSIONS

These findings suggested that PGLS was aberrantly expressed in gastric cancer and predicts poor overall survival, post-progression survival for gastric cancer patients. The present study collectively supported that PGLS is an important target for early determining and follow-up monitoring for gastric cancer.

PIWI interacting RNAs perspectives: a new avenues in future cancer investigations

As a currently identified small non-coding RNAs (ncRNAs) category, the PIWI-interacting RNAs (piRNAs) are crucial mediators of cell biology. The human genome comprises over 30.000 piRNA genes. Although considered a new field in cancer research, the piRNA pathway is shown by the existing evidence as an active pathway in a variety of different types of cancers with critical impacts on main aspects of cancer progression. Among the regulatory molecules that contribute to maintaining the dynamics of cancer cells, the P-element Induced WImpy testis (PIWI) proteins and piRNAs, as new players, have not been broadly studied so far. Therefore, the identification of cancer-related piRNAs and the assessment of target genes of piRNAs may lead to better cancer prevention and therapy strategies. This review articleaimed to highlight the role and function of piRNAs based on existing data. Understanding the role of piRNA in cancer may provide perspectives on their applications as particular biomarker signature in diagnosis in early stage, prognosis and therapeutic strategies.

Biomarkers for Gastric Cancer Screening and Early Diagnosis

Gastric cancer is one of the most common cancers worldwide, with a bad prognosis associated with late-stage diagnosis, significantly decreasing the overall survival. This highlights the importance of early detection to improve the clinical course of these patients. Although screening programs, based on endoscopic or radiologic approaches, have been useful in countries with high incidence, they are not cost-effective in low-incidence populations as a massive screening strategy. Additionally, current biomarkers used in daily routine are not specific and sensitive enough, and most of them are obtained invasively. Thus, it is imperative to discover new noninvasive biomarkers able to diagnose early-stage gastric cancer. In this context, liquid biopsy is a promising strategy. In this review, we briefly discuss some of the potential biomarkers for gastric cancer screening and diagnosis identified in blood, saliva, urine, stool, and gastric juice.

Piwi-interacting RNA-651 promotes cell proliferation and migration and inhibits apoptosis in breast cancer by facilitating DNMT1-mediated PTEN promoter methylation

Piwi-interacting RNAs (piRNAs/piRs) are small non-coding RNAs that play important roles in stablizing genome through silencing transposable genetic elements. The piR-651 was reported to be dysregulated in several human solid cancer tissues, such as gastric and lung cancers. However, the role of piRNA-651 in carcinogenesis of breast cancer has not been defined. We found that piR-651 was highly expressed in breast cancer tissues and cell lines. Overexpression of piR-651 facilitated cell proliferation and invasion, restrained cell apoptosis and the percentage of arrested cells in G0/G1 phase, accompanied by upregulated expression of oncogenes (MDM2, CDK4 and Cyclin D1), whereas piR-651 downregulation showed the opposite effects. Additionally, piR-651 could promote phosphatase and tensin homolog (PTEN) methylation and its downregulated expression by recruiting DNA methyltransferase 1 (DNMT1) to the PTEN promoter region through complex formation with PIWIL2. PTEN overexpression reversed the effects of upregulated piR-651 on cell functions. This study reveals that piR-651 promotes proliferation and migration and induces apoptosis of breast cancer cells by facilitating DNMT1-mediated PTEN promoter methylation, which may provide a potential therapeutic mechanism for breast cancer.

The Regulation and Role of piRNAs and PIWI Proteins in Cancer

P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) are regulatory small non-coding RNAs that participate in transposon inactivation, chromatin regulation, and endogenous gene regulation. Numerous genetic and epigenetic factors regulate cell proliferation and tumor metastasis. PIWI proteins and piRNAs have been revealed to function in regulating upstream or downstream of oncogenes or tumor-suppressor genes in cancer tissues. In the present review, we summarize major recent findings in uncovering the regulation and role of PIWI proteins and piRNAs in tumorigenesis and highlight some of the promising applications of specific piRNAs in cancer therapeutics and as cancer biomarkers.

The biogenesis and biological function of PIWI-interacting RNA in cancer

Small non-coding RNAs (ncRNAs) are vital regulators of biological activities, and aberrant levels of small ncRNAs are commonly found in precancerous lesions and cancer. PIWI-interacting RNAs (piRNAs) are a novel type of small ncRNA initially discovered in germ cells that have a specific length (24-31 nucleotides), bind to PIWI proteins, and show 2'-O-methyl modification at the 3'-end. Numerous studies have revealed that piRNAs can play important roles in tumorigenesis via multiple biological regulatory mechanisms, including silencing transcriptional and posttranscriptional gene processes and accelerating multiprotein interactions. piRNAs are emerging players in the malignant transformation of normal cells and participate in the regulation of cancer hallmarks. Most of the specific cancer hallmarks regulated by piRNAs are involved in sustaining proliferative signaling, resistance to cell death or apoptosis, and activation of invasion and metastasis. Additionally, piRNAs have been used as biomarkers for cancer diagnosis and prognosis and have great potential for clinical utility. However, research on the underlying mechanisms of piRNAs in cancer is limited. Here, we systematically reviewed recent advances in the biogenesis and biological functions of piRNAs and relevant bioinformatics databases with the aim of providing insights into cancer diagnosis and clinical applications. We also focused on some cancer hallmarks rarely reported to be related to piRNAs, which can promote in-depth research of piRNAs in molecular biology and facilitate their clinical translation into cancer treatment.

Emerging functions of piwi-interacting RNAs in diseases

PIWI‐interacting RNAs (piRNAs) are recently discovered small non‐coding RNAs consisting of 24‐35 nucleotides, usually including a characteristic 5‐terminal uridine and an adenosine at position 10. PIWI proteins can specifically bind to the unique structure of the 3′ end of piRNAs. In the past, it was thought that piRNAs existed only in the reproductive system, but recently, it was reported that piRNAs are also expressed in several other human tissues with tissue specificity. Growing evidence shows that piRNAs and PIWI proteins are abnormally expressed in various diseases, including cancers, neurodegenerative diseases and ageing, and may be potential biomarkers and therapeutic targets. This review aims to discuss the current research status regarding piRNA biogenetic processes, functions, mechanisms and emerging roles in various diseases.

Combined Analysis of Intragastric Malignant Exfoliation and Ca 72.4 Concentration in Stomach Adenocarcinoma: The "GL1 Ca 72.4" Parameter

INTRODUCTION/OBJECTIVE

Differently from other digestive malignancies, gastric cancer (GC) pathobiology is still little known and understood. Recently, cytopathology and molecular biology on gastric juice/gastric lavage (GJ/GL) of GC patients have provided novel and interesting results in terms of screening, diagnosis, prognosis, and therapy. However, entertaining cytologic examination and molecular test as a unified solo-run test is previously unreported. Our aim was to assess the new parameter "GL Ca 72.4" for GC patients.

METHODS

Between April 2012 and July 2013, GJ/GL obtained from 37 surgical GC patients were tested for the presence/absence (GL1/GL0) of exfoliated malignant cells along with the intragastric concentration of Ca 72.4 (normal value <6.49 ng/mL: Ca 72.4n; elevated level ≥6.49 ng/mL: Ca 72.4+).

RESULTS

At a median follow-up of 79.3 months, all the GC alive patients were "GL0 Ca 72.4n." The "GL1 Ca 72.4+" parameter, in comparison with GL0 Ca 72.4n, strongly correlated with deeper tumor invasion (p = 0.027), severe nodal metastasis (p = 0.012), worst metastatic node ratio (p = 0.041), higher number of metastatic lymph nodes (30 vs. 20 nodes, p = 0.014), angiolymphatic invasion (p = 0.044), advanced stage (p = 0.034), and adjuvant therapy (p = 0.044). The Kaplan-Meier model showed that GL1 Ca 72.4+ subjects had shorter overall survival (OS) than GL0 Ca 72.4n cases (9.7 vs. 43.2 months, respectively, p = 0.042). At univariate analysis, the GL1 Ca 72.4+ parameter resulted a significant prognostic factor for OS (p = 0.023).

CONCLUSIONS

The combined cyto-molecular parameter "GL1 Ca 72.4+" appears to be a strong indicator of aggressive tumor behavior and a significant prognostic factor of poor survival for GC patients.

Gastric juice piR-1245: A promising prognostic biomarker for gastric cancer

Background

Emerging reports demonstrated that PIWI‐interacting RNAs (piRNAs) played an indispensable role in tumorigenesis. However, it still remains elusive whether piR‐1245 in gastric juice specific in stomach could be employed as a biomarker for gastric cancer (GC). The present work is aiming at exploring the possibility of piR‐1245 in gastric juice as a potential marker to judge for diagnosis and prognosis of gastric cancer.

Methods

Gastric juice was collected from 66 GC patients and 66 healthy individuals. Quantitative real‐time reverse transcriptase polymerase chain reaction (qRT‐PCR) was employed to measure the levels of piR‐1245 expression. Then, the pattern of piR‐1245 expression in gastric juice was determined between GC patients and healthy individuals. A receiver operating characteristic (ROC) curve was constructed for distinguishing GC from healthy individuals.

Results

Gastric juice piR‐1245 levels in GC were higher than those of controls (P < .0001). The value of area under ROC (AUC) was 0.885 (sensitivity, 90.9%; specificity, 74.2%; 95% confidence interval, 0.8286 to 0.9414). High gastric juice piR‐1245 expression was signally correlated with tumor size (P = .013) and TNM stage (P = .001). GC patients with high piR‐1245 expression in gastric juice exerted a poorer overall survival (OS) (P = .0152) and progression‐free survival (PFS) (P = .013). COX regression analysis verified that gastric juice piR‐1245 expression was an independent prognostic risk variable for OS (P < .05).

Conclusions

The current study suggested that piR‐1245 in gastric juice had the potential to be a useful biomarker for GC detection and prognosis prediction.