MiR-548d-3p Promotes Gastric Cancer by Targeting RSK4

Exosome-mediated miR-200a delivery into TGF-β-treated AGS cells abolished epithelial-mesenchymal transition with normalization of ZEB1, vimentin and Snail1 expression

Exosomes are small extracellular vesicles that can be derived from human cells such as mesenchymal stem cells (MSCs). The size of exosomes is at nano-scale range and owing to their biocompatibility and other characteristics, they have been promising candidates for delivery of bioactive compounds and genetic materials in disease therapy, especially cancer therapy. Gastric cancer (GC) is a leading cause of death among patients and this malignant disease affects gastrointestinal tract that its invasiveness and abnormal migration mediate poor prognosis of patients. Metastasis is an increasing challenge in GC and microRNAs (miRNAs) are potential regulators of metastasis and related molecular pathways, especially epithelial-to-mesenchymal transition (EMT). In the present study, our aim was to explore role of exosomes in miRNA-200a delivery for suppressing EMT-mediated GC metastasis. Exosomes were isolated from MSCs via size exclusion chromatography. The synthetic miRNA-200a mimics were transfected into exosomes via electroporation. AGS cell line exposed to TGF-β for EMT induction and then, these cells cultured with miRNA-200a-loaded exosomes. The transwell assays performed to evaluate GC migration and expression levels of ZEB1, Snail1 and vimentin measured. Exosomes demonstrated loading efficiency of 5.92 ± 4.6%. The TGF-β treatment transformed AGS cells into fibroblast-like cells expressing two stemness markers, CD44 (45.28%) and CD133 (50.79%) and stimulated EMT. Exosomes induced a 14.89-fold increase in miRNA-200a expression in AGS cells. Mechanistically, miRNA-200a enhances E-cadherin levels (P < 0.01), while it decreases expression levels of β-catenin (P < 0.05), vimentin (P < 0.01), ZEB1 (P < 0.0001) and Snail1 (P < 0.01). Leading to EMT inhibition in GC cells. This pre-clinical experiment introduces a new strategy for miRNA-200a delivery that is of importance for preventing migration and invasion of GC cells.

P90 ribosomal S6 kinases: A bona fide target for novel targeted anticancer therapies?

The 90 kDa ribosomal S6 kinase (RSK) family of proteins is a group of highly conserved Ser/Thr kinases. They are downstream effectors of the Ras/ERK/MAPK signaling cascade. ERK1/2 activation directly results in the phosphorylation of RSKs, which further, through interaction with a variety of different downstream substrates, activate various signaling events. In this context, they have been shown to mediate diverse cellular processes like cell survival, growth, proliferation, EMT, invasion, and metastasis. Interestingly, increased expression of RSKs has also been demonstrated in various cancers, such as breast, prostate, and lung cancer. This review aims to present the most recent advances in the field of RSK signaling that have occurred, such as biological insights, function, and mechanisms associated with carcinogenesis. We additionally present and discuss the recent advances but also the limitations in the development of pharmacological inhibitors of RSKs, in the context of the use of these kinases as putative, more efficient targets for novel anticancer therapeutic approaches.

Raltitrexed regulates proliferation and apoptosis of HGC-27 cells by upregulating RSK4

Background

Raltitrexed is a specific inhibitor of thymidylate synthase and a potential chemotherapeutic agent for the treatment of advanced gastric cancer. In this study, we investigated the effect of raltitrexed on the proliferation of HGC-27 human gastric cancer cells and its potential underlying molecular mechanism(s).

Methods

RT-qPCR and western blotting were used to quantify RSK4 levels. Colony formation and flow cytometry assays were used to assess HGC-27 cell proliferation, cell cycle progression, mitochondrial membrane potential, and apoptosis. The expression of cell cycle and apoptosis markers were determined by western blotting.

Results

Our results demonstrate that raltitrexed upregulated RSK4 mRNA and protein levels in HGC-27 cells. Moreover, raltitrexed significantly inhibited tumor cell colony formation, arrested the cell cycle, decreased the mitochondrial membrane potential, and induced apoptosis. We observed that raltitrexed was capable of upregulating the expression of Bax, cyclin A1, and CDK3, and downregulating the expression of Bcl-2 and cleaved caspase-3. Importantly, siRNA-mediated RSK4 knockdown significantly reduced the inhibitory effect of raltitrexed on cell proliferation and its promotion of cell apoptosis. Moreover, silencing of RSK4 inhibited the raltitrexed-induced upregulation of cytochrome C. In addition, the changes in molecular markers related to the cell cycle and apoptosis induced by raltitrexed were reduced upon RSK4 depletion.

Conclusion

Our study shows that RSK4 is a key target of raltitrexed in the regulation of gastric cancer cell proliferation, cell cycle progression, and apoptosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40360-022-00605-2.

miR-548d-3p inhibits the invasion and migration of gastric cancer cells by targeting GKN1

Background

The aim of this study was to explore the function and mechanism of GKN1 in gastric cancer (GC) progression.

Methods

Firstly, we used GEO2R to perform differential gene analysis on GSE26942 and GSE79973 and constructed the protein–protein interaction network of differential genes by STRING. Next, the cytoHubba, Mcode plugins, and GEPIA were used to obtain our follow‐up research object GKN1. Then, the function of GKN1 in GC was verified by scratch and transwell assay in GC cells. We further analyzed the genes related to GKN1 through LinkedOmics, and exported top 100 genes positively or negatively correlated with GKN1. Meanwhile, Metascape was performed on these genes. Finally, we analyzed the miRNAs that bind to GKN1 through the miRDB and verified the correlation between miR‐548d‐3p and GKN1 using dual‐fluorescence and quantitative PCR experiments.

Results

Bioinformatics analysis showed that there were 52 differential genes on GSE26942 and GSE79973. In addition, the results of functional assays indicated that overexpressed GKN1 can inhibit GC cell migration and invasion, while GKN1 knockdown demonstrated the opposite effect. Additionally, Metascape analysis results showed that the 3′‐UTR region of mRNA is rich in AU sequences, based on which we infer that mRNA may be regulated by miRNA. Dual‐fluorescence and quantitative PCR assays clarified that miR‐548d‐3p may be one of the target miRNAs of GKN1, which was up‐regulated in GC tissues.

Conclusions

In summary, we clarified that miR‐548d‐3p regulates GKN1 to participate in GC cell migration and invasion, and provides a possible target for the prognostic diagnosis and treatment of GC.

miR-133a-5p suppresses gastric cancer through TCF4 down-regulation

Background

The effect of microRNAs (miRNA) on cancer regulations has received a considerable amount of attention recently. MiR-133a-5p has been identified as an anti-tumor miRNA in several types of cancers. However, the effect of miR-133a-5p on gastric cancer (GC) have not been uncovered. In this study, we sought to evaluate the regulation of TCF4 expression by miR-133-5p and the role of the miR-25-3p/TCF4 axis in the progression of GC, with the aim of identifying a potential therapeutic target for GC.

Methods

TCGA (The Cancer Genome Atlas), GTEx (The Genotype-Tissue Expression) and GEO (Gene Expression Omnibus) database were used to analyze the expression and prognosis. We performed MTT and EdU assays to elucidate the effect on cell replication. Apoptotic cells were stained with annexin V-fluorescein isothiocyanate and propidium iodide to stain, and then analyzed by flow cytometry. The effect on cell metastasis was investigated in wound healing and transwell assays. A dual-luciferase reporter assay was used to check for the direct targeting of TCF4 by miR-133a-5p. Bioinformatic analysis of the relationship of TCF4 with tumor microenvironment and the signaling cascade of TCF4 was finally performed.

Results

We found that the level of miR-133a-5p was decreased in both tumor tissues and GC cell lines. MiR-133a-5p inhibited cell growth and metastasis, but promoted cell apoptosis. MiR-133a-5p directly targeted TCF4 and downregulated its expression. TCF4 was highly expressed in tumor and higher level of TCF4 indicated poorer prognosis. Moreover, TCF4 overexpression reversed the aforementioned anti-tumor activity of miR-133a-5p. The expression level of TCF4 was significantly correlated with tumor-infiltrating immune cells.

Conclusions

Our findings altogether reveal that miR-133a-5p can serve as a tumor suppressor in gastric cancer via the miR-133a-5p/TCF4 pathway.