Non-Coding RNAs in Gastric Cancer: From Malignant Hallmarks to Clinical Applications

The role of lncRNA SNHG14 in gastric cancer: enhancing tumor cell proliferation and migration, and mechanisms of CDH2 expression

LncRNAs are a class of non-coding RNAs that play an important role in regulating gene expression. However, their specific molecular mechanisms in gastric carcinogenesis and metastasis need further exploration. TCGA data showed that the expression of MFGE8, which was closely related to survival, was significantly positively correlated with lncRNA SNHG14. And moreover, the results of high-throughput sequencing and qRT-PCR showed that lncRNA SNHG14 was significantly elevated in gastric cancer. Further, in vitro functional realization showed that lncRNA SNHG14 overexpression significantly increased gastric cancer's proliferation, invasion and migration. Animal experiments also showed that lncRNA SNHG14 overexpression promoted tumorigenesis and metastasis in vivo. Mechanistically, MFGE8 activates the expression of lncRNA SNHG14, which activates the cellular EMT by stabilizing CDH2. Our study suggests that lncRNA SNHG14 could be a potential target for gastric cancer therapy.

RP11-789C1.1 inhibits gastric cancer cell proliferation and accelerates apoptosis via the ATR/CHK1 signaling pathway

BACKGROUND

Long non-coding RNAs (lncRNAs) plays an important role in the progression of gastric cancer (GC). Their involvement ranges from genetic regulation to cancer progression. However, the mechanistic roles of RP11-789C1.1 in GC are not fully understood.

METHODS

We identified the expression of lncRNA RP11-789C1.1 in GC tissues and cell lines by real-time fluorescent quantitative polymerase chain reaction. A series of functional experiments revealed the effect of RP11-789C1.1 on the proliferation of GC cells. In vivo experiments verified the effect of RP11-789C1.1 on the biological behavior of a GC cell line. RNA pull-down unveiled RP11-789C1.1 interacting proteins. Western blot analysis indicated the downstream pathway changes of RP11-789C1.1, and an oxaliplatin dosing experiment disclosed the influence of RP11-789C1.1 on the drug sensitivity of oxaliplatin.

RESULTS

Our results demonstrated that RP11-789C1.1 inhibited the proliferation of GC cells and promoted the apoptosis of GC cells. Mechanistically, RP11-789C1.1 inhibited checkpoint kinase 1 (CHK1) phosphorylation by binding ataxia-telangiectasia mutated and Rad3 related (ATR), a serine/threonine-specific protein kinase, promoted GC apoptosis, and mediated oxaliplatin sensitivity.

CONCLUSION

In general, we discovered a tumor suppressor molecule RP11-789C1.1 and confirmed its mechanism of action, providing a theoretical basis for targeted GC therapy.

Metastasis-associated lung adenocarcinoma transcript 1 molecular mechanisms in gastric cancer progression

Gastric cancer (GC) remains among the most common cancers worldwide with a high mortality-to-incidence ratio. Accumulated evidence suggests that long noncoding RNAs (lncRNAs) are involved in gastric carcinogenesis. These transcripts are longer than 200 nucleotides and modulate gene expression at multiple molecular levels, inducing or inhibiting biological processes and diseases. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is one of the best-studied lncRNAs with comprehensive actions contributing to cancer progression. This lncRNA regulates gene expression at the transcriptional and posttranscriptional levels through interactions with microRNAs and proteins. In the present review, we discussed the molecular mechanism of MALAT1 and summarized the current knowledge of its expression in GC. Moreover, we highlighted the potential use of MALAT1 as a biomarker, including liquid biopsy.

LncRNA NORAD mediates KMT2D expression by targeting miR-204-5p and affects the growth of gastric cancer

BACKGROUND

Long non-coding ribonucleic acids (lncRNAs) are a class of non-coding RNAs implicated in the development of many malignancies, including gastric cancer (GC). In this study, we investigated the functions and molecular mechanisms of non-coding RNA activated by deoxyribonucleic acid damage (NORAD) in GC.

METHODS

NORAD expression at the messenger RNA levels was determined by quantitative reverse transcriptase (RT)-polymerase chain reaction assays. Cell proliferation, migration, and invasion were detected by Cell Counting Kit-8 assays, in-vivo tumor formation assays, and Transwell assays. Cell-cycle distribution was detected by a flow cytometry analysis. NORAD location was detected by nucleocytoplasmic fractionation assays. The interaction between NORAD and the microRNA-204-5p (miR-204-5p)/Lysine Methyltransferase 2D (KMT2D) axis was verified by dual-luciferase reporter gene assays and RNA binding protein immunoprecipitation (RIP) assays. Western blot was used to study the phosphatase and tensin homolog (PTEN)/phosphoinositide 3-kinases (PI3K)/protein kinase B (AKT) signaling pathway.

RESULTS

NORAD was upregulated in the GC tissues and cell lines. The silencing of NORAD repressed cell proliferation and the Growth 2 (G2)/Mitosis (M) cell-cycle transition in GC. NORAD also regulated KMT2D expression by targeting miR-204-5p and mediated PTEN/PI3K/AKT signaling in GC.

CONCLUSIONS

We found that NORAD acts as an oncogene in GC. Our findings might provide a novel therapeutic target for GC.

Research Progress for Targeting Deubiquitinases in Gastric Cancers

Gastric cancers (GCs) are malignant tumors with a high incidence that threaten global public health. Despite advances in GC diagnosis and treatment, the prognosis remains poor. Therefore, the mechanisms underlying GC progression need to be identified to develop prognostic biomarkers and therapeutic targets. Ubiquitination, a post-translational modification that regulates the stability, activity, localization, and interactions of target proteins, can be reversed by deubiquitinases (DUBs), which can remove ubiquitin monomers or polymers from modified proteins. The dysfunction of DUBs has been closely linked to tumorigenesis in various cancer types, and targeting certain DUBs may provide a potential option for cancer therapy. Multiple DUBs have been demonstrated to function as oncogenes or tumor suppressors in GC. In this review, we summarize the DUBs involved in GC and their associated upstream regulation and downstream mechanisms and present the benefits of targeting DUBs for GC treatment, which could provide new insights for GC diagnosis and therapy.

[CircPCSK5 is highly expressed in gastric cancer and promotes cancer cell proliferation, invasion and epithelial-mesenchymal transition]

OBJECTIVE

To investigate the expression of circPCSK5 in gastric cancer (GC) and its role in regulation of the proliferation, invasion and epithelial-mesenchymal transition (EMT) of GC cells.

METHODS

High-throughput sequencing was performed in 3 pairs of GC and adjacent gastric mucosa tissues to obtain the differential expression profile of circRNA. The expression of circPCSK5 was detected in 62 patients undergoing radical surgery for GC using RT-qPCR, and the correlation between circPCSK5 expression level and clinicopathological data of the patients was analyzed. The overall survival and disease-free survival of the patients were assessed with Kaplan-Meier survival analysis, and the independent risk factors affecting the patients' prognosis were analyzed using Cox proportional hazards regression model. The stability and subcellular localization of circPCSK5 were assessed using RNase R and actinomycin D assays, fluorescence in situ hybridization and nucleocytoplasmic separation assay. CCK-8 assay, EdU assay and Transwell assay were employed to examine the changes in proliferation, migration and invasion of GC cells with circPCSK5 knockdown or overexpression; Western blotting and RT-qPCR assays were used to detect the expression levels of EMT markers in the transfected cells.

RESULTS

The expression of circPCSK5 was significantly upregulated in GC tissues and cells (P < 0.001, P < 0.01). The expression level of circPCSK5 was positively correlated with tumor size, vascular invasion, lymph node metastasis and AJCC stage of GC (P < 0.05). The overall survival and disease-free survival were significantly lower in GC patients with high circPCSK5 expression than in those with low circPCSK5 expression (P < 0.001). High circPCSK5 expression was an independent risk factor for a poor prognosis of GC patients (P < 0.05). Knockdown of circPCSK5 significantly inhibited the proliferation, migration and invasion of HGC27 cells (P < 0.01), increased the expressions of E-cadherin, and decreased the expression of N-cadherin and vimentin (P < 0.01). CircPCSK5 overexpression promoted the proliferation, migration and invasion of MKN45 cells (P < 0.01), reduced E-cadherin expression and increased N-cadherin and vimentin expressions (P < 0.01).

CONCLUSION

CircPCSK5 is highly expressed in GC and promotes the proliferation, invasion and EMT of GC cells, suggesting its potential as a prognostic biomarker and therapeutic target for GC.

Differential Expression of Tissular miRNA-155 in Pediatric Gastritis

BACKGROUND

MicroRNA molecules, among them the intensely studied miRNA-155 (miR-155), are regarded as potential biomarkers of chronic gastric inflammation and premalignant lesion progression. However, literature data are scarce in terms of pediatric studies and in the evaluation of the predictive role of miRNA in early gastric inflammation. This study aims to assess the differential expression of miR-155 in relation to pediatric gastritis.

METHODS

The present research was conducted on 192 patients with chronic dyspeptic symptoms who underwent upper digestive endoscopy. Bioptic samples were harvested for histopathological analysis and tissue miR-155 depiction. MiR-155 expression analysis was carried out through quantitative real-time polymerase chain reaction (qRT-PCR). The study population was divided into two groups: controls (93 patients) and study group (99 patients) with inflammatory modifications.

RESULTS

MiR-155 expression was augmented in patients with gastritis but did not differ significantly from controls (p = 0.16). An increase in miR-155 expression was noted in relation to chronic gastritis, H. pylori infection, or increase in gastritis severity, but these variations were not important (p = 0.30, p = 0.44, and p = 0.45, respectively).

CONCLUSIONS

According to our study, pediatric gastritis increases, but does not greatly influence, miR-155 expression. Dynamic evaluation of miR-155 might enlighten its prognostic role in pediatric gastritis.

LINC01232 Promotes Metastasis and EMT by Regulating miR-506-5p/PAK1 Axis in Gastric Cancer

Background

Long non-coding RNA LINC01232 plays an important role in the progression of metastasis in several cancers. However, the function of LINC01232 in gastric cancer is limited. Authors aimed to investigate the role and mechanism of LINC01232 in the metastasis of gastric cancer.

Methods

The expression levels and correlation of LINC01232, miR-506-5p, and PAK1 were analyzed by GEPIA or ENCORI, and the abundance of LINC01232 and miR-506-5p was measured in tissues and cells via qRT-PCR, the location of LINC01232 in gastric cells was analyzed by nuclear and cytoplasmic fractionation, while the protein levels of PAK1, E-cadherin and vimentin were additionally quantified by Western blotting. Interactions between LINC01232, miR-506-5p, and PAK1 were detected through luciferase reporter assays, qRT-PCR and Western blotting. Cellular viability was evaluated through CCK8 assays, migration ability was measured by transwell assays, invasion ability was tested by wound healing experiment.

Results

LINC01232 was overexpressed in gastric cancer tissues and cells, and mainly located in nucleus. The inhibition of LINC01232 could suppress migration, invasion and EMT of gastric cancer cells. MiR-506-5p was downregulated in gastric cancer tissues and cells. LINC01232 sponged miR-506-5p to accelerate migration and EMT. PAK1 was certified to be a target of miR-506-5p, inhibition of PAK1 could interrupt LINC01232 overexpression-induced migration of gastric cancer cells.

Conclusion

The LINC01232/miR-506-5p/PAK1 axis promotes metastasis of gastric cancer cells.

Contribution of MicroRNAs in Chemoresistance to Cisplatin in the Top Five Deadliest Cancer: An Updated Review

Cisplatin (DDP) is a well-known anticancer drug used for the treatment of numerous human cancers in solid organs, including bladder, breast, cervical, head and neck squamous cell, ovarian, among others. Its most important mode of action is the DNA-platinum adducts formation, inducing DNA damage response, silencing or activating several genes to induce apoptosis; these mechanisms result in genetics and epigenetics modifications. The ability of DDP to induce tumor cell death is often challenged by the presence of anti-apoptotic regulators, leading to chemoresistance, wherein many patients who have or will develop DDP-resistance. Cancer cells resist the apoptotic effect of chemotherapy, being a problem that severely restricts the successful results of treatment for many human cancers. In the last 30 years, researchers have discovered there are several types of RNAs, and among the most important are non-coding RNAs (ncRNAs), a class of RNAs that are not involved in protein production, but they are implicated in gene expression regulation, and representing the 98% of the human genome non-translated. Some ncRNAs of great interest are long ncRNAs, circular RNAs, and microRNAs (miRs). Accumulating studies reveal that aberrant miRs expression can affect the development of chemotherapy drug resistance, by modulating the expression of relevant target proteins. Thus, identifying molecular mechanisms underlying chemoresistance development is fundamental for setting strategies to improve the prognosis of patients with different types of cancer. Therefore, this review aimed to identify and summarize miRs that modulate chemoresistance in DDP-resistant in the top five deadliest cancer, both in vitro and in vivo human models.

Comprehensive analysis of competitive endogenous RNAs network: Identification and validation of prediction model composed of mRNA signature and miRNA signature in gastric cancer

Gastric cancer (GC), one of the most lethal malignant tumors, is highly aggressive with a poor prognosis, while the molecular mechanisms underlying it remain largely unknown. Although advanced imaging techniques and comprehensive treatment facilitate the diagnosis and survival of some GC patients, the precise diagnosis and prognosis are still a challenge. The present study used publicly available gene expression profiles from The Cancer Genome Atlas and Gene Expression Omnibus datasets including mRNA, micro (mi)RNA and circular (circ)RNA of GC to establish a competing endogenous RNA network (ceRNA). Further, the present study performed least absolute shrinkage and selector operator regression analysis on the hub RNAs to establish a prediction model with mRNA and miRNA. The ceRNA network contained 109 edges and 56 nodes and the visible network contains 13 miRNAs, 9 circRNAs and 34 mRNAs. The five mRNA-based signature were CTF1, FKBP5, RNF128, GSTM2 and ADAMTS1. The area under curve (AUC) value of the diagnosis training cohort was 0.9975. The prognosis of the high-risk group (RiskScore >4.664) was worse compared with that of the low-risk group (RiskScore ≤4.664; P<0.05) in the training cohort. The five miRNA-based signature were miR-145-5p, miR-615-3p, miR-6507-5p, miR-937-3p and miR-99a-3p. The AUC value of the diagnosis training cohort was 0.9975. The prognosis of the high-risk group (RiskScore >1.621) was worse compared with that of the low-risk group (RiskScore ≤1.621; P<0.05) in the training cohort. The validation cohorts indicated that both five mRNA and five miRNA-based signatures had strong predictive power in diagnosis and prognosis for GC. In conclusion, a ceRNA network was established for GC and a five mRNA-based signature and a five miRNA-based signature was identified that enabled diagnosis and prognosis of GC by assigning patient to a high-risk group or low-risk group.

Long Non-Coding RNA in Gastric Cancer: Mechanisms and Clinical Implications for Drug Resistance

Gastric cancer (GC) is the third leading cause of cancer-related deaths worldwide, with high recurrence and mortality rate. Chemotherapy, including 5-fluorouracil (5-FU), adriamycin (ADR), vincristine (VCR), paclitaxel (PTX), and platinum drugs, remains one of the fundamental methods of GC treatment and has efficiently improved patients’ prognosis. However, most patients eventually develop resistance to chemotherapeutic agents, leading to the failure of clinical treatment and patients’ death. Recent studies suggest that long non-coding RNAs (lncRNAs) are involved in the drug resistance of GC by modulating the expression of drug resistance-related genes via sponging microRNAs (miRNAs). Moreover, lncRNAs also play crucial roles in GC drug resistance via a variety of mechanisms, such as the regulation of the oncogenic signaling pathways, inhibition of apoptosis, induction of autophagy, modulation of cancer stem cells (CSCs), and promotion of the epithelial-to-mesenchymal transition (EMT) process. Some of lncRNAs exhibit great potential as diagnostic and prognostic biomarkers, as well as therapeutic targets for GC patients. Therefore, understanding the role of lncRNAs and their mechanisms in GC drug resistance may provide us with novel insights for developing strategies for individual diagnosis and therapy. In this review, we summarize the recent findings on the mechanisms underlying GC drug resistance regulated by lncRNAs. We also discuss the potential clinical applications of lncRNAs as biomarkers and therapeutic targets in GC.