Novel Insights into Gastric Cancer: Methylation of R-spondins and Regulation of LGR5 by SP1

RSPO2-associated mitochondrial metabolism defines molecular subtypes with distinct clinical and immune features in esophageal cancer

BACKGROUND

Esophageal cancer is a highly aggressive malignancy with limited treatment options and poor prognosis. The identification of novel molecular subtypes and therapeutic targets is crucial for improving clinical outcomes.

METHOD

In this study, we investigated the role of R-spondin 2 (RSPO2) in esophageal cancer and its association with mitochondrial metabolism. Using bioinformatics analysis of publicly available datasets, we identified a panel of RSPO2-related mitochondrial metabolism genes and their expression patterns in esophageal cancer. Based on these genes, we stratified esophageal cancer patients into distinct molecular subtypes with different survival rates, immune cell infiltration profiles, and drug sensitivities.

RESULTS

Our findings suggest that RSPO2-related mitochondrial metabolism genes may serve as potential therapeutic targets and prognostic markers for esophageal cancer. These genes play an important role in the prognosis, immune cell infiltration and drug sensitivity of esophageal cancer.

CONCLUSION

The identified molecular subtypes provide valuable insights into the underlying molecular mechanisms of esophageal cancer and could guide personalized treatment strategies in the future.

Multiomics data identifies RSPO2 as a prognostic biomarker in human tumors associated with pan-cancer

RSPO2 protein may provide valuable insights into the mechanism underlying various types of tumorigenesis. The role of RSPO2 in pan-cancer has not been reported so far. Therefore, this study aimed to provide a comprehensive analysis of RSPO2 from a pan-cancer perspective employing multiomics data. The expression profile and function of RSPO2 across different tumors were investigated using various web-based tools UALCAN, GEPIA, TIMER, Human Protein Atlas, cBioPortal, TISIDB, STRING, and Metascape to interpret the expression profile, promoter methylation status, genomic alterations, survival analysis, protein-protein interaction, correlation with immune cell subtypes, tumor immune microenvironment and enrichment analysis. Comprehensive pan-cancer analysis indicated that RSPO2 was significantly downregulated in eleven and upregulated in five tumor types compared to normal tissues, validation results further suggest RSPO2 was downregulated in most of the tumors. The protein level expression of RSPO2 was mostly low in malignant tissues. We found that RSPO2 was significantly related to individual pathological stages in BLCA, COAD, LUAD and LUSC. Prognostic analysis indicates that the high RSPO2 expression was significantly correlated with the poor prognosis in BRCA, KICH, KIRP, READ, and UCES. Furthermore, RSPO2 is frequently amplified, exhibits hypermethylated promoter in most cancers, and is associated with immune subtypes, molecular subtypes and immune cell infiltration. Finally, enrichment analysis showed that RSPO2 is involved in the regulation of the canonical Wnt pathway and neuronal development. The overall comprehensive pan-cancer analysis affirms that RSPO2 could be a promising diagnostic and prognostic biomarker and latent therapy target in the future.

Specificity Proteins (Sp) and Cancer

The specificity protein (Sp) transcription factors (TFs) Sp1, Sp2, Sp3 and Sp4 exhibit structural and functional similarities in cancer cells and extensive studies of Sp1 show that it is a negative prognostic factor for patients with multiple tumor types. In this review, the role of Sp1, Sp3 and Sp4 in the development of cancer and their regulation of pro-oncogenic factors and pathways is reviewed. In addition, interactions with non-coding RNAs and the development of agents that target Sp transcription factors are also discussed. Studies on normal cell transformation into cancer cell lines show that this transformation process is accompanied by increased levels of Sp1 in most cell models, and in the transformation of muscle cells into rhabdomyosarcoma, both Sp1 and Sp3, but not Sp4, are increased. The pro-oncogenic functions of Sp1, Sp3 and Sp4 in cancer cell lines were studied in knockdown studies where silencing of each individual Sp TF decreased cancer growth, invasion and induced apoptosis. Silencing of an individual Sp TF was not compensated for by the other two and it was concluded that Sp1, Sp3 and Sp4 are examples of non-oncogene addicted genes. This conclusion was strengthened by the results of Sp TF interactions with non-coding microRNAs and long non-coding RNAs where Sp1 contributed to pro-oncogenic functions of Sp/non-coding RNAs. There are now many examples of anticancer agents and pharmaceuticals that induce downregulation/degradation of Sp1, Sp3 and Sp4, yet clinical applications of drugs specifically targeting Sp TFs are not being used. The application of agents targeting Sp TFs in combination therapies should be considered for their potential to enhance treatment efficacy and decrease toxic side effects.

miR-138-5p inhibits the progression of colorectal cancer via regulating SP1/LGR5 axis

Colorectal cancer (CRC) is one of the main malignancies that seriously threaten human health. Considering the high mortality and morbidity associated with this disease, even surgical resection and chemotherapy may not be sufficient in certain cases. This study aimed to explore the molecular mechanisms of miR-138-5p in regulating CRC progression. Quantitative reverse transcriptase polymerase chain reaction and western blot were performed to assess the levels of mRNA and proteins, including miR-138-5p, leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5), SP1, β-catenin, cyclin D1, and c-myc. The bioactivities of LoVo and HCT116 cells were assessed via MTT assay, flow cytometry, and transwell assay. StarBase was used to identify the downstream targets of genes. Double luciferase reporter and RIP assays revealed the direct binding of miR-138-5p to SP1 and of SP1 to LGR5. Our results illustrated that miR-138-5p was downregulated in CRC and its knockdown accelerated CRC progression. Conversely, SP1 was upregulated in CRC and its knockdown inhibited CRC progression. SP1 is also targeted by miR-138-5p and binds to LGR5. This study showed that miR-138-5p inhibits LoVo and HCT116 cell proliferation, migration, and invasion. Overall, miR-138-5p regulates CRC progression and promotes apoptosis via the SP1/LGR5 axis. This study indicates that miR-138-5p is involved in regulating CRC progression.

The origin of gastric cancer stem cells and their effects on gastric cancer: Novel therapeutic targets for gastric cancer

Gastric cancer (GC) is one of the most prevalent malignancies and the most common causes of cancer-related mortality worldwide. Furthermore, the prognosis of advanced GC remains poor even after surgery combined with chemoradiotherapy. As a small group of cells with unlimited differentiation and self-renewal ability in GC, accumulating evidence shows that GC stem cells (GCSCs) are closely associated with the refractory characteristics of GC, such as drug resistance, recurrence, and metastasis. With the extensive development of research on GCSCs, GCSCs seem to be promising therapeutic targets for GC. However, the relationship between GCSCs and GC is profound and intricate, and its mechanism of action is still under exploration. In this review, we elaborate on the source and key concepts of GCSCs, systematically summarize the role of GCSCs in GC and their underlying mechanisms. Finally, we review the latest information available on the treatment of GC by targeting GCSCs. Thus, this article may provide a theoretical basis for the future development of the novel targets based on GCSCs for the treatment of GC.

Effects of the Wnt/β-Catenin Signaling Pathway on Proliferation and Apoptosis of Gastric Cancer Cells

Objective

To explore the effect of the Wnt/β-catenin signaling pathway on the proliferation and apoptosis of gastric cancer cells.

Methods

An MTT colorimetric assay was used to detect the inhibitory effect of the Wnt/β-catenin signaling pathway inhibitor FH535 on the proliferation of MKN45 gastric cancer cells. The cell proliferation index (PI) and apoptosis index (AI) were measured by flow cytometry. The expression levels of β-catenin, c-myc, and cleaved caspase-3 in MKN45 gastric cancer cells were detected.

Results

After using the Wnt/β-catenin signaling pathway inhibitor FH535, MKN45 gastric cancer cells showed obvious shrinkage, death, and cell density decrease. MTT showed that the A value of MKN45 gastric cancer cells in FH535 group was significantly lower than that in the control group (P < 0.05). The survival rate of MKN45 gastric cancer cells in FH535 group was significantly lower than that in the control group (P < 0.05). The cell cycle of gastric cancer was arrested in G0/G1 phase. The expression levels of β-catenin and c-myc protein in MKN45 gastric cancer cells in FH535 group decreased significantly (P < 0.05), while the expression level of cleaved caspase-3 protein increased significantly (P < 0.05).

Conclusion

The Wnt/β-catenin signal molecule can maintain the proliferation of gastric cancer cells. Inhibition of the Wnt/β-catenin signaling pathway can inhibit the proliferation of gastric cancer cells and promote the apoptosis of MKN45 gastric cancer cells.

A novel mechanism for C1GALT1 in the regulation of gastric cancer progression

Background

Gastric cancer (GC) is a highly aggressive and lethal disease around the world. High expression of core 1 β 1, 3-galactosyltransferase 1 (C1GALT1), the primary enzyme responsible for protein O-glycosylation, plays a critical role in gastric carcinogenesis. However, proteins that can be O-glycosylated by C1GALT1 in GC have not been completely elucidated. Also, the mechanism leading to its upregulation in GC is currently unknown.

Results

Using public databases and our patient samples, we confirmed that C1GALT1 expression was upregulated at both the mRNA and protein levels in GC tissues. Elevated expression of C1GALT1 protein was closely associated with advanced TNM stage, lymph node metastasis, tumor recurrence, and poor overall survival. With gain- and loss-of-function approaches, we demonstrated that C1GALT1 promoted GC cell proliferation, migration, and invasion. By employing lectin pull-down assay and mass spectrometry, integrin α5 was identified as a new downstream target of C1GALT1 in GC. C1GALT1 was able to modify O-linked glycosylation on integrin α5 and thereby modulate the activation of the PI3K/AKT pathway. Functional experiments indicated that integrin α5 inhibition could reverse C1GALT1-mediated tumor growth and metastasis both in vitro and in vivo. Moreover, transcription factor SP1 was found to bind to the C1GALT1 promoter region and activated its expression. Further investigation proved that miR-152 negatively regulated C1GALT1 expression by directly binding to its 3′ -UTR.

Conclusions

Our findings uncover a novel mechanism for C1GALT1 in the regulation of GC progression. Thus, C1GALT1 may serve as a promising target for the diagnosis and treatment of GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00678-2.

DNA methylation mediated RSPO2 to promote follicular development in mammals

In female mammals, the proliferation, apoptosis, and estradiol-17β (E2) secretion of granulosa cells (GCs) have come to decide the fate of follicles. DNA methylation and RSPO2 gene of Wnt signaling pathway have been reported to involve in the survival of GCs and follicular development. However, the molecular mechanisms for how DNA methylation regulates the expression of RSPO2 and participates in the follicular development are not clear. In this study, we found that the mRNA and protein levels of RSPO2 significantly increased during follicular development, but the DNA methylation level of RSPO2 promoter decreased gradually. Inhibition of DNA methylation or DNMT1 knockdown could decrease the methylation level of CpG island (CGI) in RSPO2 promoter and upregulate the expression level of RSPO2 in porcine GCs. The hypomethylation of -758/-749 and -563/-553 regions in RSPO2 promoter facilitated the occupancy of transcription factor E2F1 and promoted the transcriptional activity of RSPO2. Moreover, RSPO2 promoted the proliferation of GCs with increasing the expression level of PCNA, CDK1, and CCND1 and promoted the E2 secretion of GCs with increasing the expression level of CYP19A1 and HSD17B1 and inhibited the apoptosis of GCs with decreasing the expression level of Caspase3, cleaved Caspase3, cleaved Caspase8, cleaved Caspase9, cleaved PARP, and BAX. In addition, RSPO2 knockdown promoted the apoptosis of GCs, blocked the development of follicles, and delayed the onset of puberty with decreasing the expression level of Wnt signaling pathway-related genes (LGR4 and CTNNB1) in vivo. Taken together, the hypomethylation of -758/-749 and -563/-553 regions in RSPO2 promoter facilitated the occupancy of E2F1 and enhanced the transcription of RSPO2, which further promoted the proliferation and E2 secretion of GCs, inhibited the apoptosis of GCs, and ultimately ameliorated the development of follicles through Wnt signaling pathway. This study will provide useful information for further exploration on DNA-methylation-mediated RSPO2 pathway during follicular development.

The Long Noncoding RNA D63785 Regulates Chemotherapy Sensitivity in Human Gastric Cancer by Targeting miR-422a

Gastric cancer is one of the most prevalent tumor types in the world. Chemotherapy is the most common choice for cancer treatment. However, chemotherapy resistance and adverse side effects limit its clinical applications. Aberrant expression of long noncoding RNAs (lncRNAs) has been found in various stages of gastric cancer development and progression. In this study, we identified that an oncogenic lncRNA, long intergenic non-protein-coding RNA D63785 (lncR-D63785), is highly expressed in gastric cancer tissues and cells. Silencing of lncR-D63785 inhibited cell proliferation, cell migration and invasion in gastric cancer cell lines and reduced tumor volume and size in mice. We found that the expression of lncR-D63785 was inversely correlated with microRNA 422a (miR-422a) expression, which was involved in the downregulation of expression of myocyte enhancer factor-2D (MEF2D) and drug sensitivity. Knockdown of lncR-D63785 increased the expression of miR-422a and the sensitivity of gastric cancer cells to apoptosis induced by the anticancer drug doxorubicin (DOX). This indicates that lncR-D63785 acts as a competitive endogenous RNA (ceRNA) of miR-422a and promotes chemoresistance by blocking miR-422-dependent suppression of MEF2D. Together, our results suggest that the therapeutic suppression of lncR-D63785 alone or in combination with chemotherapeutic agents may be a promising strategy for treating gastric cancer.

Wnt Signalling in Gastrointestinal Epithelial Stem Cells

Wnt signalling regulates several cellular functions including proliferation, differentiation, apoptosis and migration, and is critical for embryonic development. Stem cells are defined by their ability for self-renewal and the ability to be able to give rise to differentiated progeny. Consequently, they are essential for the homeostasis of many organs including the gastrointestinal tract. This review will describe the huge advances in our understanding of how stem cell functions in the gastrointestinal tract are regulated by Wnt signalling, including how deregulated Wnt signalling can hijack these functions to transform cells and lead to cancer.

Stromal R-spondin orchestrates gastric epithelial stem cells and gland homeostasis

The constant regeneration of stomach epithelium is driven by long-lived stem cells, but the mechanism that regulates their turnover is not well understood. We have recently found that the gastric pathogen Helicobacter pylori can activate gastric stem cells and increase epithelial turnover, while Wnt signalling is known to be important for stem cell identity and epithelial regeneration in several tissues. Here we find that antral Wnt signalling, marked by the classic Wnt target gene Axin2, is limited to the base and lower isthmus of gastric glands, where the stem cells reside. Axin2 is expressed by Lgr5⁺ cells, as well as adjacent, highly proliferative Lgr5^- cells that are able to repopulate entire glands, including the base, upon depletion of the Lgr5⁺ population. Expression of both Axin2 and Lgr5 requires stroma-derived R-spondin 3 produced by gastric myofibroblasts proximal to the stem cell compartment. Exogenous R-spondin administration expands and accelerates proliferation of Axin2⁺/Lgr5^- but not Lgr5⁺ cells. Consistent with these observations, H. pylori infection increases stromal R-spondin 3 expression and expands the Axin2⁺ cell pool to cause hyperproliferation and gland hyperplasia. The ability of stromal niche cells to control and adapt epithelial stem cell dynamics constitutes a sophisticated mechanism that orchestrates epithelial regeneration and maintenance of tissue integrity.