SPHK1-induced autophagy in peritoneal mesothelial cell enhances gastric cancer peritoneal dissemination

Dysregulation of autophagy in gastric carcinoma: Pathways to tumor progression and resistance to therapy

The considerable death rates and lack of symptoms in early stages of gastric cancer (GC) make it a major health problem worldwide. One of the most prominent risk factors is infection with Helicobacter pylori. Many biological processes, including those linked with cell death, are disrupted in GC. The cellular "self-digestion" mechanism necessary for regular balance maintenance, autophagy, is at the center of this disturbance. Misregulation of autophagy, however, plays a role in the development of GC. In this review, we will examine how autophagy interacts with other cell death processes, such as apoptosis and ferroptosis, and how it affects the progression of GC. In addition to wonderful its role in the epithelial-mesenchymal transition, it is engaged in GC metastasis. The role of autophagy in GC in promoting drug resistance stands out. There is growing interest in modulating autophagy for GC treatment, with research focusing on natural compounds, small-molecule inhibitors, and nanoparticles. These approaches could lead to breakthroughs in GC therapy, offering new hope in the fight against this challenging disease.

SPHK1 potentiates colorectal cancer progression and metastasis via regulating autophagy mediated by TRAF6-induced ULK1 ubiquitination

A sphingolipid metabolite regulator, sphingosine kinase 1 (SPHK1), plays a critical role in the development of colorectal cancer (CRC). Studies have demonstrated that invasion and metastasis of CRC are promoted by SPHK1-driven autophagy. However, the exact mechanism of SPHK1 drives autophagy to promote tumor progression remains unclear. Here, immunohistochemical detection showed the expression of SPHK1 and tumor necrosis factor receptor-associated factor-6 (TRAF6) in human CRC tissues was stronger than in adjacent normal tissues, they were both associated with distance metastasis. It was discovered that knockdown of SPHK1 reduced the expression of TRAF6, inhibited autophagy, and inhibited the growth and metastasis of CRC cells in vitro. Moreover, the effects of SPHK1-downregulating were reversed by overexpression of TRAF6 in CRC cells transfected by double-gene. Overexpression of SPHK1 and TRAF6 promoted the expression of autophagy protein LC3 and Vimentin, while downregulated the expression of autophagy protein P62 and E-cadherin. The expression of autophagy-related ubiquitination protein ULK1 and Ubiquitin protein were significantly upregulated in TRAF6-overexpressed CRC cells. In addition, autophagy inhibitor 3-methyladenine (3MA) significantly inhibited the metastasis-promoting effect of SPHK1 and TRAF6, suppressed the expression of LC3 and Vimentin, and promoted the expression of P62 and E-cadherin, in CRC cells. Immunofluorescence staining showed SPHK1 and TRAF6 were co-localized in HT29 CRC cell membrane and cytoplasm. Immunoprecipitation detection showed SPHK1 was efficiently combined with the endogenous TRAF6, and the interaction was also detected reciprocally. Additionally, proteasome inhibitor MG132 treatment upregulated the expression of TRAF6 and the level of Ubiquitin protein, in SPHK1-downregulating CRC cells. These results reveal that SPHK1 potentiates CRC progression and metastasis via regulating autophagy mediated by TRAF6-induced ULK1 ubiquitination. SPHK1-TRAF6-ULK1 signaling axis is critical to the progression of CRC and provides a new strategy for the therapeutic control of CRC.

FN1 mRNA 3'-UTR supersedes traditional fibronectin 1 in facilitating the invasion and metastasis of gastric cancer through the FN1 3'-UTR-let-7i-5p-THBS1 axis

Background: Current clinical treatments for gastric cancer (GC), particularly advanced GC, lack infallible therapeutic targets. The 3'-untranslated region (3'-UTR) has attracted increasing attention as a drug target. Methods: In vitro and in vivo experiments were conducted to determine the function of FN1 3'-UTR and FN1 protein in invasion and metastasis. RNA pull-down assay and high-throughput sequencing were used to screen the factors regulated by FN1 3'-UTR and construct the regulatory network. Western blotting and polymerase chain reaction were used to examine the correlation of intermolecular expression levels. RNA-binding protein immunoprecipitation was used to verify the correlation between FN1 3'-UTR and target mRNAs. Results: The FN1 3'-UTR may have stronger prognostic implications than the FN1 protein in GC patients. Upregulation of FN1 3'-UTR significantly promoted the invasive and metastatic abilities of GC cells to a greater extent than FN1 protein in vitro and in vivo. A novel regulatory network was constructed based on the FN1 3'-UTR-let-7i-5p-THBS1 axis, wherein FN1 3'-UTR displayed stronger oncogenic effects than the FN1 protein. Conclusions: FN1 3'-UTR may be a better therapeutic target for constructing targeted drugs in GC than the FN1 protein.

PUM1 Promotes Tumor Progression by Activating DEPTOR-Meditated Glycolysis in Gastric Cancer

RNA-binding proteins (RBPs) play essential roles in tumorigenesis and progression, but their functions in gastric cancer (GC) remain largely elusive. Here, it is reported that Pumilio 1 (PUM1), an RBP, induces metabolic reprogramming through post-transcriptional regulation of DEP domain-containing mammalian target of rapamycin (mTOR)-interacting protein (DEPTOR) in GC. In clinical samples, elevated expression of PUM1 is associated with recurrence, metastasis, and poor survival. In vitro and in vivo experiments demonstrate that knockdown of PUM1 inhibits the proliferation and metastasis of GC cells. In addition, RNA-sequencing and bioinformatics analyses show that PUM1 is enriched in the glycolysis gene signature. Metabolomics studies confirm that PUM1 deficiency suppresses glycolytic metabolism. Mechanistically, PUM1 binds directly to DEPTOR mRNA pumilio response element to maintain the stability of the transcript and prevent DEPTOR degradation through post-transcriptional pathway. PUM1-mediated DEPTOR upregulation inhibits mTORC1 and alleviates the inhibitory feedback signal transmitted from mTORC1 to PI3K under normal conditions, thus activating the PI3K-Akt signal and glycolysis continuously. Collectively, these results reveal the critical epigenetic role of PUM1 in modulating DEPTOR-dependent GC progression. These conclusions support further clinical investigation of PUM1 inhibitors as a metabolic-targeting treatment strategy for GC.

Regulation of Autophagy via Carbohydrate and Lipid Metabolism in Cancer

Metabolic changes are an important component of tumor cell progression. Tumor cells adapt to environmental stresses via changes to carbohydrate and lipid metabolism. Autophagy, a physiological process in mammalian cells that digests damaged organelles and misfolded proteins via lysosomal degradation, is closely associated with metabolism in mammalian cells, acting as a meter of cellular ATP levels. In this review, we discuss the changes in glycolytic and lipid biosynthetic pathways in mammalian cells and their impact on carcinogenesis via the autophagy pathway. In addition, we discuss the impact of these metabolic pathways on autophagy in lung cancer.

HOXC11 drives lung adenocarcinoma progression through transcriptional regulation of SPHK1

Lung adenocarcinoma (LUAD) is a fatal threat to human health, while the mechanism remains unclear, and the therapy brings limited therapeutic effects. Transcription factor Homeobox C11 (HOXC11) was previously proved to be related to hind limbs and metanephric development during the embryonic phase, and its role in tumors has been gradually recognized. Our study found that HOXC11 overexpressed in LUAD and was associated with worse overall survival. Moreover, its expression in lung cancer was regulated by IκB kinase α (IKKα), a pivotal kinase in NF-κB signaling, which was related to the ubiquitination of HOXC11. We further proved that HOXC11 could enhance the ability of proliferation, migration, invasion, colony formation, and the progression of the cell cycle in LUAD cells. Meanwhile, it also accelerated the formation of subcutaneous and lung metastases tumors. In contrast, loss of HOXC11 in LUAD cells significantly inhibited these malignant phenotypes. At the same time, HOXC11 regulated the expression of sphingosine kinase 1 (SPHK1) by directly binding to its promoter region. Therefore, we conclude that HOXC11 impacts the development of LUAD and facilitates lung cancer progression by promoting the expression of SPHK1.

Sphk1-induced autophagy in microglia promotes neuronal injury following cerebral ischaemia-reperfusion

Microglial hyperactivation mediated by sphingosine kinase 1/sphingosine-1-phosphate (SphK1/S1P) signalling and the consequent inflammatory mediator production serve as the key drivers of cerebral ischaemia-reperfusion injury (CIRI). Although SphK1 reportedly controls autophagy and microglial activation, it remains uncertain as to whether SphK1 is similarly capable of regulating damage mediated by CIRI-activated microglia. In the current study, we adopted both in vitro oxygen-glucose deprivation reperfusion (OGDR) models and in vivo rat models of focal CIRI to ascertain this possibility. It was found that CIRI upregulated SphK1 and induced autophagy in microglia, while inhibiting these changes significantly impaired to prevented neuronal apoptosis. Results of mechanistic investigation revealed that SphK1 promoted autophagy via the tumour necrosis factor receptor associated factor 2 (TRAF2) pathway. Altogether, our findings unfolded to reveal a novel mechanism, whereby SphK1-induced autophagy in microglia contributed to the pathogenesis of CIRI, potentially highlighting novel avenues for future therapeutic intervention in ischaemic stroke patients.

Inhibition of SphK1/S1P Signaling Pathway Alleviates Fibrosis and Inflammation of Rat Myocardium after Myocardial Infarction

Objective

The sphingosine kinase 1 (SphK1)/sphingosine-1-phosphate (S1P) signaling pathway is involved in fibrosis and inflammatory responses of myocardial tissue after myocardial infarction (MI). The purpose of our study was to explore the role of SphK1/S1P signaling pathway in myocardial injury after MI.

Materials and Methods

We used Sprague-Dawley (SD) rats to make MI models and detected the changes of SphK1 and S1P in rats at 1, 7, and 14 days after MI. SphK1 inhibitor PF543 was used to treat MI rats, and we detected the changes in myocardial function and structure in rats by cardiac function test, 2,3,5-triphenyl tetrazolium staining, and histological staining. In addition, we used H₂O₂ to induce H9c2 cell injury to investigate the effect of PF543 on the viability of myocardial cells.

Results

Myocardial tissue lesions and fibrosis were observed at 7 and 14 days after MI, and the expressions of SphK1 and S1P in the injured myocardial tissues increased significantly in day 7 and day 14 in comparison to the control group. After treatment of MI rats with PF543, the structure of rat myocardial tissue was significantly improved and the degree of fibrosis was reduced. After MI, the expression of α-SMA and collagen I in the myocardium of rats was significantly increased while PF543 decreased their expression. PF543 also improved the cardiac function of MI rats and reduced the expression of IL-1β, IL-6, and TNF-α in the serum. PF543 also increased the viability of H9c2 cells in vitro.

Conclusions

The inhibition of the SphK1/S1P signaling pathway contributed to the relief of myocardial injury in MI rats. PF543 improved the myocardial structure and function of MI rats and reduced the level of fibrosis and inflammation in MI rats.

LMOD1, an oncogene associated with Lauren classification, regulates the metastasis of gastric cancer cells through the FAK-AKT/mTOR pathway

Background

The Lauren classification of gastric tumors strongly correlates with prognosis. The purpose of this study was to explore the specific molecular mechanism of Lauren classification of gastric cancer and provide a possible theoretical basis for the treatment of gastric cancer.

Methods

We standardized the gene expression data of five Gene Expression Omnibus gastric cancer databases and constructed a Weighted Co-expression Network Analysis (WGCNA) model based on clinicopathological information. The overall survival (OS) and disease-free survival (DFS) curves were extracted from the Cancer Genome Atlas (TCGA) and GSE62254 databases. Western blotting was used to measure protein expression in cells and tissues. Scratch and transwell experiments were used to test the migration ability of tumor cells. Immunohistochemistry was used to measure tissue protein expression in clinical tissue samples to correlate to survival data.

Results

The WGCNA model demonstrated that blue cyan was highly correlated with the Lauren classification of the tumor (r = 0.24, P = 7 × 10¹⁶). A protein-protein interaction network was used to visualize the genes in the blue cyan module. The OS and PFS TCGA analysis revealed that LMOD1 was a gene of interest. The proportion of diffuse gastric cancer patients with high expression of LMOD1 was significantly higher than that of intestinal type patients. LMOD1 promoted the migration of gastric cancer cells by regulating the FAK-Akt/mTOR pathway in vitro. Additionally, a Gene Set Enrichment Analysis using the TCGA and GSE62254 databases, and western blot data, showed that LMOD1 could promote an epithelial-mesenchymal transition (EMT), thus potentially affecting the occurrence of peritoneal metastasis of gastric cancer. Immunohistochemistry showed that LMOD1 was highly expressed in cancer tissues, and the prognosis of patients with high LMOD1 expression was poor.

Conclusion

LMOD1 is an oncogene associated with diffuse gastric cancer and can affect the occurrence and development of EMT by regulating the FAK-Akt/mTOR pathway. LMOD1 can therefore promote peritoneal metastasis of gastric cancer cells and can be used as a novel therapeutic target for gastric cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09541-0.

Increased Sphingosine Kinase 1 Expression Is Associated with Poor Prognosis in Human Solid Tumors: A Meta-Analysis

Methods

PubMed, Web of Science, Embase, CNKI, and Wanfang databases were thoroughly searched for eligible studies, in which the relationship between SPHK1 expression and cancer prognosis was evaluated. Hazard ratios (HRs) and 95% confidence intervals (CIs) were pooled to estimate the impact of SPHK1 expression on cancer patients' survival. Odds ratios (ORs) and 95% CIs were combined to assess the association between SPHK1 expression and clinicopathological characteristics of cancer patients. The certainty of evidence was evaluated by Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) criteria.

Results

Thirty studies comprising 32 cohorts with 5965 patients were included in this meta-analysis. The outcomes indicated that elevated SPHK1 expression was associated with worse overall survival (OS) (HR = 1.71, 95% CI: 1.45-2.01, P < 0.001) and disease-free survival (DFS) (HR = 1.34, 95% CI: 1.13-1.59, P = 0.001). What is more, SPHK1 overexpression was significantly correlated with certain phenotypes of tumor aggressiveness, such as clinical stage (OR = 2.07, 95% CI: 1.39-3.09, P < 0.001), tumor invasion (OR = 2.16, 95% CI: 1.47-3.18, P < 0.001), lymph node metastasis (OR = 2.04, 95% CI: 1.71-2.44, P < 0.001), and distant metastasis (OR = 3.16, 95% CI: 2.44-4.09, P < 0.001). The quality of the evidence for both OS and DFS was low.

Conclusions

Increased SPHK1 expression is related to poor prognosis in human cancers and may serve as a promising prognostic marker and therapeutic target for malignant patients. However, conclusions need to be treated with caution because of lack of high quality of evidence.

Decreased exosome-delivered miR-486-5p is responsible for the peritoneal metastasis of gastric cancer cells by promoting EMT progress

Background

The present study aims to investigate the preliminary mechanism underlying the peritoneal metastasis of gastric cancer cells.

Methods

Exosomes from GC9811 cells (Con-Exo) and from GC9811-P cells (PM-Exo) were extracted by ultracentrifugation, which were identified with transmission electron microscopy (TEM) and nanoparticle trafficking analysis, as well as the expression of CD9, CD63, and CD81 detected by Western blot assay. α-SMA expression was determined by immunofluorescence assay and Western blot assay. The levels of Snail1, E-cadherin, and Actin-related protein 3 (ACTR3) were evaluated by Western blot assay. MiRNA array was performed on exosomes to screen the differentially expressed miRNAs. The expressions of miRNAs, SMAD2, CDK4, and ACTR3 were determined by QRT-PCR. The delivery of miR-486-5p was confirmed by laser confocal detection.

Results

Firstly, TEM, nanoparticle trafficking analysis, and Western blot assays were used to confirm the successful extraction of Con-Exo and PM-Exo. The incubation of Con-Exo and PM-Exo could decrease E-cadherin expression and increase of α-SMA respectively in HMrSV5 cells, with the increased proportion of fusiform cells. More significant changes were observed in PM-Exo-treated HMrSV5 cells. Secondary, compared to Con-Exo, miR-486-5p and miR-132-3p were found downregulated, and miR-132-5p was found upregulated in PM-Exo. The transfection of miR-486-5p and miR-132-3p was observed to suppress EMT, and the transfection of miR-132-3p was observed to induce EMT. Laser confocal detection confirmed the delivery of miR-486-5p from gastric cancer cells to HMrSV5 cells through exosomes. Lastly, the expression of Mothers against decapentaplegic homolog 2 (SMAD2), cyclin-dependent kinase 4 (CDK4), and ACTR3 was found to be downregulated via miR-486-5p.

Conclusion

Decreased delivery of miR-486-5p via exosomes might be responsible for the peritoneal metastasis of gastric cancer cells by promoting epithelial-mesenchymal transition progress.

Integrative analysis-based identification and validation of a prognostic immune cell infiltration-based model for patients with advanced gastric cancer

BACKGROUNDS

Advanced gastric cancer (GC) remains difficult to conduct individualized prognostic evaluations owing to the highly heterogeneous nature and the low level of immune cell infiltration (ICI) within GC tumors. This study thus sought to develop a model capable of classifying GC patients according to the degree of tumor ICI and gauging prognosis.

METHODS

The degree of ICI in GC patients from the GSE15459, GSE57303, and GSE62254 datasets were estimated, and these values were used to group patients via an unsupervised clustering approach, after which ICI cluster-related genes were identified the association with prognosis through Cox and LASSO regression analyses. The primary risk genes were then verified by immunohistochemical staining of GC tumor tissue samples.

RESULTS

570 patients were clustered into three clusters and 289 ICI cluster-related genes were identified. A prognostic model based on the expression of six crucial ICI risk genes (CXCL11, RBPMS2, LOC400043, JCHAIN, CT83, and ORM1) wa constructed. Patients identified as being high risk based upon the model have poorer clinical features and survival outcomes compared to the other patients. Adjuvant intervention was found to be more beneficial for patients expressing high levels of RBPMS2, JCHAIN, or ORM1. Furthermore, patients expressing low levels of JCHAIN or CT83 in GC tumor tissues were verified to exhibit a significantly better prognosis in a CMU cohort.

CONCLUSION

Advanced GC patients were successfully grouped into clusters based on the degree of intratumoral ICI, and a prognostic evaluation model based on 6 ICI risk genes was developed and validated.

SphK1-driven autophagy potentiates focal adhesion paxillin-mediated metastasis in colorectal cancer

Invasion and metastasis are the main causes of colorectal cancer (CRC)‐related death. Accumulating evidence suggested that sphingosine kinase 1 (SphK1) promoted the metastasis of CRC and autophagy played an important role in SphK1 promoting the metastasis of malignancy. However, the mechanism by which SphK1‐driven autophagy promotes invasion and metastasis in CRC remains to be clarified. In the present study, immunohistochemical detection showed the expression of SphK1 and paxillin was higher in human CRC tissues than those of normal colorectal mucosal tissues, they were both associated with TNM staging, lymphatic, and distance metastasis. In addition, study of in situ tumor transplantation model in nude mice showed that the suppression of SphK1 inhibited the growth of colonic orthotopic implantation tumors and the expression of paxillin, p‐paxillin, LC3 in the tumor. So, SphK1 may promote CRC metastasis via inducing the expression of paxillin expression and its phosphorylation, in vivo. Furthermore, results of CCK8 assay, transwell and wound healing assays showed that SphK1 promoted the viability, invasion, and metastasis of CRC cells. Transmission electron microscopy detection showed that SphK1 is the key factor in autophagy induction in CRC cells. Moreover, western blot examination indicated that the expression of LC3Ⅱ/Ⅰ, paxillin, p‐paxillin, MMP‐2, and vimentin was enhanced in SphK1‐overexpressed CRC cells and suppressed in SphK1 knockdown CRC cells, meanwhile, the expression of E‐cadherin was suppressed in SphK1‐overexpressed CRC cells and enhanced in SphK1 knockdown CRC cells. Suppression of autophagy by 3MA reversed the expression of paxillin and its phosphorylation in SphK1‐overexpressed CRC cells, indicated that SphK1‐driven autophagy induced the expression of paxillin and its phosphorylation in CRC cells. Together, these findings reveal that SphK1‐driven autophagy may promote the invasion and metastasis of CRC via promoting the expression of focal adhesion paxillin and its phosphorylation.

Targeting the Sphingosine Kinase/Sphingosine-1-Phosphate Signaling Axis in Drug Discovery for Cancer Therapy

Sphingolipid metabolites have emerged as critical players in the regulation of various physiological processes. Ceramide and sphingosine induce cell growth arrest and apoptosis, whereas sphingosine-1-phosphate (S1P) promotes cell proliferation and survival. Here, we present an overview of sphingolipid metabolism and the compartmentalization of various sphingolipid metabolites. In addition, the sphingolipid rheostat, a fine metabolic balance between ceramide and S1P, is discussed. Sphingosine kinase (SphK) catalyzes the synthesis of S1P from sphingosine and modulates several cellular processes and is found to be essentially involved in various pathophysiological conditions. The regulation and biological functions of SphK isoforms are discussed. The functions of S1P, along with its receptors, are further highlighted. The up-regulation of SphK is observed in various cancer types and is also linked to radio- and chemoresistance and poor prognosis in cancer patients. Implications of the SphK/S1P signaling axis in human pathologies and its inhibition are discussed in detail. Overall, this review highlights current findings on the SphK/S1P signaling axis from multiple angles, including their functional role, mechanism of activation, involvement in various human malignancies, and inhibitor molecules that may be used in cancer therapy.

High expression of COL5A2, a member of COL5 family, indicates the poor survival and facilitates cell migration in gastric cancer

Background: Gastric cancer (GC) metastasis determines the prognosis of patients, and exploring the molecular mechanism of GC metastasis is expected to provide a theoretical basis for clinical treatment. Recent studies have shown that extracellular matrix protein is closely related to GC metastasis. The present study aimed to explore the expression profile and role of COL5A2, as an extracellular matrix protein, in GC.

Methods: The expression, overall survival, and progression-free survival data of COL5 family members were extracted from The Cancer Genome Atlas (TCGA) database, respectively. Weighted gene co-expression network analysis of the GSE62229 database was performed out to identify modules and associated genes.

Results: COL5A2 was selected as our research target in the TCGA database, and was also verified in the GSE62229 and GSE15459 datasets. COL5A2 was up-regulated in GC tissues by paraffin immunohistochemistry and RT-qPCR. The prognosis of patients with low COL5A2 expression was better than that of patients with high COL5A2 expression. Scratch and migration experiments showed that knockdown of COL5A2 decreased the migration ability of gastric cancer cells compared with the control group. In vivo, mice with tail vein injection COL5A2 knockdown had fewer and smaller metastatic nodules in liver. GSEA results showed that the TCGA and GSE62229 samples were significantly enriched in several well-known cancer-related pathways, such as the TGF-β, MAPK, and JAK2 signaling pathways.

Conclusion: COL5A2 was most closely related to advanced GC among COL5 family members. High COL5A2 expression is associated with a poor prognosis, and may be a novel therapeutic target for GC.

A Weighted Gene Co-Expression Network Analysis-Derived Prognostic Model for Predicting Prognosis and Immune Infiltration in Gastric Cancer

Background

Gastric cancer (GC) is a major public health problem worldwide. In recent decades, the treatment of gastric cancer has improved greatly, but basic research and clinical application of gastric cancer remain challenges due to the high heterogeneity. Here, we provide new insights for identifying prognostic models of GC.

Methods

We obtained the gene expression profiles of GSE62254 containing 300 samples for training. GSE15459 and TCGA-STAD for validation, which contain 200 and 375 samples, respectively. Weighted gene co-expression network analysis (WGCNA) was used to identify gene modules. We performed Lasso regression and Cox regression analyses to identify the most significant five genes to develop a novel prognostic model. And we selected two representative genes within the model for immunohistochemistry staining with 105 GC specimens from our hospital to verify the prediction efficiency. Moreover, we estimated the correlation coefficient between our model and immune infiltration using the CIBERSORT algorithm. The data from GSE15459 and TCGA cohort validated the robustness and predictive accuracy of this prognostic model.

Results

Of the 12 gene modules identified, 1,198 green-yellow module genes were selected for further analysis. Multivariate Cox analysis was performed on genes from univariate Cox regression and Lasso regression analysis using the Cox proportional hazards regression model. Finally, we constructed a five gene prognostic model: Risk Score = [(-0.7547) * Expression (ARHGAP32)] + [(-0.8272) * Expression (KLF5)] + [1.09 * Expression (MAMLD1)] + [0.5174 * Expression (MATN3)] + [1.66 * Expression (NES)]. The prognosis of samples in the high-risk group was significantly poorer than that of samples in the low-risk group (p = 6.503e-11). The risk model was also regarded as an independent predictor of prognosis (HR, 1.678, p < 0.001). The observed correlation with immune cells suggested that this risk model could potentially predict immune infiltration.

Conclusion

This study identified a potential risk model for prognosis and immune infiltration prediction in GC using WGCNA and Cox regression analysis.

Hypoxia-autophagy axis induces VEGFA by peritoneal mesothelial cells to promote gastric cancer peritoneal metastasis through an integrin α5-fibronectin pathway

BACKGROUND

Peritoneal metastasis (PM) is an important pathological process in the progression of gastric cancer (GC). The metastatic potential of tumor and stromal cells is governed by hypoxia, which is a key molecular feature of the tumor microenvironment. Mesothelial cells also participate in this complex and dynamic process. However, the molecular mechanisms underlying the hypoxia-driven mesothelial-tumor interactions that promote peritoneal metastasis of GC remain unclear.

METHODS

We determined the hypoxic microenvironment in PM of nude mice by immunohistochemical analysis and screened VEGFA by human growth factor array kit. The crosstalk mediated by VEGFA between peritoneal mesothelial cells (PMCs) and GC cells was determined in GC cells incubated with conditioned medium prepared from hypoxia-treated PMCs. The association between VEGFR1 and integrin α5 and fibronectin in GC cells was enriched using Gene Set Enrichment Analysis and KEGG pathway enrichment analysis. In vitro and xenograft mouse models were used to evaluate the impact of VEGFA/VEGFR1 on gastric cancer peritoneal metastasis. Confocal microscopy and immunoprecipitation were performed to determine the effect of hypoxia-induced autophagy.

RESULTS

Here we report that in the PMCs of the hypoxic microenvironment, SIRT1 is degraded via the autophagic lysosomal pathway, leading to increased acetylation of HIF-1α and secretion of VEGFA. Under hypoxic conditions, VEGFA derived from PMCs acts on VEGFR1 of GC cells, resulting in p-ERK/p-JNK pathway activation, increased integrin α5 and fibronectin expression, and promotion of PM.

CONCLUSIONS

Our findings have elucidated the mechanisms by which PMCs promote PM in GC in hypoxic environments. This study also provides a theoretical basis for considering autophagic pathways or VEGFA as potential therapeutic targets to treat PM in GC.

Relationship between Sphk1/S1P and microRNAs in human cancers

Sphingosine kinases type 1 (SphK1) is a key enzyme in the phosphorylation of sphingosine to sphingosine 1-phosphate (S1P). Different abnormalities in SphK1 functions may correspond with poor prognosis in various cancers. Additionally, upregulated SphK1/S1P could promote cancer cell proliferation, angiogenesis, mobility, invasion, and metastasis. MicroRNAs as conserved small noncoding RNAs play major roles in cancer initiation, progression, metastasis, etc. Their posttranscriptionally mechanisms could affect the development of cancer growth or tumorigenesis suppression. The growing number of studies has described that various microRNAs can be regulated by SphK1, and its expression level can also be regulated by microRNAs. In this review, the relationship of SphK1 and microRNA functions and their interaction in human malignancies have been discussed. Based on them novel treatment strategies can be introduced.

Peroxisomicine A1, a potential antineoplastic agent, causes micropexophagy in addition to macropexophagy

Peroxisomicine A1 (PA1) is a potential antineoplastic agent with high and selective toxicity toward peroxisomes of tumor cells. Pexophagy is a selective autophagy process that degrades damaged peroxisomes; this process has been studied mainly in methylotrophic yeasts. There are two main modes of pexophagy in yeast: macropexophagy and micropexophagy. Previous studies showed that peroxisomes damaged by a prolonged exposition to PA1 are eliminated by macropexophagy. In this work, Candida boidinii was grown in methanol-containing media, and PA1 was added to the cultures at 2 µg/mL after they reached the mid-exponential growth phase. Samples were taken at 5, 10, 15, 20, and 25 min after the addition of PA1 and processed for ultrastructural analysis. Typical morphological characteristics of micropexophagy were observed: the direct engulfment of peroxisomes by the vacuolar membrane and the presence of the micropexophagic membrane apparatus (MIPA), which mediates the fusion between the opposing tips of the vacuole to complete sequestration of peroxisomes from the cytosol. In conclusion, here we report that, in addition to macropexophagy, peroxisomes damaged by PA1 can be eliminated by micropexophagy. This information is useful to deepen the knowledge of the mechanism of action of PA1 and of that of pexophagy per se.

The Therapeutic Effect of Melatonin on GC by Inducing Cell Apoptosis and Autophagy Induced by Endoplasmic Reticulum Stress

Background

Gastric cancer (GC) is the main malignancy affecting a large population worldwide. Lack of effective enough treatment is one of the leading factors contributing to the high mortality rate. Melatonin, a naturally occurring compound, has been proven to exert cytotoxic and antiproliferative effects on human gastric cancers. Nevertheless, the mechanisms of anti-gastric cancer of melatonin remain elucidated. It is believed that endoplasmic reticulum (ER) stress and its resultant unfolded protein response (UPR) are connected to the survival, progression, and chemoresistance of various tumor cells via multiple cellular procedures, such as autophagy. In this study, the effects of melatonin on human gastric cancer cell lines AGS and SGC-7901 was assessed to reveal the interaction between melatonin, endoplasmic reticulum stress, and autophagy in gastric cancer.

Methods

CCK-8, the wound healing analysis, colony formation assay, immunofluorescence analysis, Western blotting, flow cytometry, and animal models were used in the current study.

Results

The data demonstrated that melatonin could inhibit GC growth, proliferation, and invasion both in vivo and in vitro. Apoptosis and autophagy induced in a concentration-dependent manner is response to melatonin-induced ER stress. Melatonin induced the expression of apoptotic and autophagy-related proteins, which was markedly attenuated by the ER stress inhibitor 4-PBA and autophagy inhibitor 3-MA. In addition, we used the specific IRE1 inhibitor STF 083010, finding that inhibiting IRE1 could considerably relieve ER stress-induced autophagy activity, as revealed by the reduction of LC3-II and Beclin-1.

Conclusion

This study confirmed that melatonin-induced inhibition of GC cell proliferation is mediated by the activation of the IRE/JNK/Beclin1 signaling.

SPHK1-induced autophagy in peritoneal mesothelial cell enhances gastric cancer peritoneal dissemination

Gastric cancer peritoneal dissemination (GCPD) has been recognized as the most common form of metastasis in advanced gastric cancer (GC), and the survival is pessimistic. The injury of mesothelial cells plays an important role in GCPD. However, its molecular mechanism is not entirely clear. Here, we focused on the sphingosine kinase 1 (SPHK1) in human peritoneal mesothelial cells (HPMCs) which regulates HPMCs autophagy in GCPD progression. Initially, we analyzed SPHK1 expression immunohistochemically in 120 GC peritoneal tissues, and found high SPHK1 expression to be significantly associated with LC3B expression and peritoneal recurrence, leading to poor prognosis. Using a coculture system, we observed that GC cells promoted HPMCs autophagy and this process was inhibited by blocking TGF-β1 secreted from GC cells. Autophagic HPMCs induced adhesion and invasion of GC cells. We also confirmed that knockdown of SPHK1 expression in HPMCs inhibited TGF-β1-induced autophagy. In addition, SPHK1-driven autophagy of HPMCs accelerated GC cells occurrence of GCPD in vitro and in vivo. Moreover, we explored the relationship between autophagy and fibrosis in HPMCs, observing that overexpression of SPHK1 induced HPMCs fibrosis, while the inhibition of autophagy weakened HPMCs fibrosis. Taken together, our results provided new insights for understanding the mechanisms of GCPD and established SPHK1 as a novel target for GCPD.