Reduced group IVA phospholipase A2 expression is associated with unfavorable outcome for patients with gastric cancer

PLA2G4A and ACHE modulate lipid profiles via glycerophospholipid metabolism in platinum-resistant gastric cancer

BACKGROUND

Bioactive lipids involved in the progression of various diseases. Nevertheless, there is still a lack of biomarkers and relative regulatory targets. The lipidomic analysis of the samples from platinum-resistant in gastric cancer patients is expected to help us further improve our understanding of it.

METHODS

We employed LC-MS based untargeted lipidomic analysis to search for potential candidate biomarkers for platinum resistance in GC patients. Partial least squares discriminant analysis (PLS-DA) and variable importance in projection (VIP) analysis were used to identify differential lipids. The possible molecular mechanisms and targets were obtained by metabolite set enrichment analysis and potential gene network screened. Finally, verified them by immunohistochemical of a tissue microarray.

RESULTS

There were 71 differential lipid metabolites identified in GC samples between the chemotherapy-sensitivity group and the chemotherapy resistance group. According to Foldchange (FC) value, VIP value, P values (FC > 2, VIP > 1.5, p < 0.05), a total of 15 potential biomarkers were obtained, including MGDG(43:11)-H, Cer(d18:1/24:0) + HCOO, PI(18:0/18:1)-H, PE(16:1/18:1)-H, PE(36:2) + H, PE(34:2p)-H, Cer(d18:1 + hO/24:0) + HCOO, Cer(d18:1/23:0) + HCOO, PC(34:2e) + H, SM(d34:0) + H, LPC(18:2) + HCOO, PI(18:1/22:5)-H, PG(18:1/18:1)-H, Cer(d18:1/24:0) + H and PC(35:2) + H. Furthermore, we obtained five potential key targets (PLA2G4A, PLA2G3, DGKA, ACHE, and CHKA), and a metabolite-reaction-enzyme-gene interaction network was built to reveal the biological process of how they could disorder the endogenous lipid profile of platinum resistance in GC patients through the glycerophospholipid metabolism pathway. Finally, we further identified PLA2G4A and ACHE as core targets of the process by correlation analysis and tissue microarray immunohistochemical verification.

CONCLUSION

PLA2G4A and ACHE regulated endogenous lipid profile in the platinum resistance in GC patients through the glycerophospholipid metabolism pathway. The screening of lipid biomarkers will facilitate earlier precision medicine interventions for chemotherapy-resistant gastric cancer. The development of therapies targeting PLA2G4A and ACHE could enhance platinum chemotherapy effectiveness.

Cystathionine-β-synthase is essential for AKT-induced senescence and suppresses the development of gastric cancers with PI3K/AKT activation

Hyperactivation of oncogenic pathways downstream of RAS and PI3K/AKT in normal cells induces a senescence-like phenotype that acts as a tumor-suppressive mechanism that must be overcome during transformation. We previously demonstrated that AKT-induced senescence (AIS) is associated with profound transcriptional and metabolic changes. Here, we demonstrate that human fibroblasts undergoing AIS display upregulated cystathionine-β-synthase (CBS) expression and enhanced uptake of exogenous cysteine, which lead to increased hydrogen sulfide (H₂S) and glutathione (GSH) production, consequently protecting senescent cells from oxidative stress-induced cell death. CBS depletion allows AIS cells to escape senescence and re-enter the cell cycle, indicating the importance of CBS activity in maintaining AIS. Mechanistically, we show this restoration of proliferation is mediated through suppressing mitochondrial respiration and reactive oxygen species (ROS) production by reducing mitochondrial localized CBS while retaining antioxidant capacity of transsulfuration pathway. These findings implicate a potential tumor-suppressive role for CBS in cells with aberrant PI3K/AKT pathway activation. Consistent with this concept, in human gastric cancer cells with activated PI3K/AKT signaling, we demonstrate that CBS expression is suppressed due to promoter hypermethylation. CBS loss cooperates with activated PI3K/AKT signaling in promoting anchorage-independent growth of gastric epithelial cells, while CBS restoration suppresses the growth of gastric tumors in vivo. Taken together, we find that CBS is a novel regulator of AIS and a potential tumor suppressor in PI3K/AKT-driven gastric cancers, providing a new exploitable metabolic vulnerability in these cancers.

Protein dynamics analysis identifies candidate cancer driver genes and mutations in TCGA data

Recently, it has been showed that cancer missense mutations selectively target the neighborhood of hinge residues, which are key sites in protein dynamics. Here, we show that this approach can be extended to find previously unknown candidate mutations and genes. To this aim, we developed a computational pipeline to detect significantly enriched three-dimensional (3D) clustering of missense mutations around hinge residues. The hinge residues were detected by applying a Gaussian network model. By systematically analyzing the PanCancer compendium of somatic mutations in nearly 10 000 tumors from the Cancer Genome Atlas, we identified candidate genes and mutations in addition to well known ones. For instance, we found significantly enriched 3D clustering of missense mutations in known cancer genes including CDK4, CDKN2A, TCL1A, and MAPK1. Beside these known genes, we also identified significantly enriched 3D clustering of missense mutations around hinge residues in PLA2G4A, which may lead to excessive phosphorylation of the extracellular signal-regulated kinases. Furthermore, we demonstrated that hinge-based features improves pathogenicity prediction for missense mutations. Our results show that the consideration of clustering around hinge residues can help us explain the functional role of the mutations in known cancer genes and identify candidate genes.

Multi-Omics Characterization of Inflammatory Bowel Disease-Induced Hyperplasia/Dysplasia in the Rag2-/-/Il10-/- Mouse Model

Epigenetic dysregulation is hypothesized to play a role in the observed association between inflammatory bowel disease (IBD) and colon tumor development. In the present work, DNA methylome, hydroxymethylome, and transcriptome analyses were conducted in proximal colon tissues harvested from the Helicobacter hepaticus (H. hepaticus)-infected murine model of IBD. Reduced representation bisulfite sequencing (RRBS) and oxidative RRBS (oxRRBS) analyses identified 1606 differentially methylated regions (DMR) and 3011 differentially hydroxymethylated regions (DhMR). These DMR/DhMR overlapped with genes that are associated with gastrointestinal disease, inflammatory disease, and cancer. RNA-seq revealed pronounced expression changes of a number of genes associated with inflammation and cancer. Several genes including Duox2, Tgm2, Cdhr5, and Hk2 exhibited changes in both DNA methylation/hydroxymethylation and gene expression levels. Overall, our results suggest that chronic inflammation triggers changes in methylation and hydroxymethylation patterns in the genome, altering the expression of key tumorigenesis genes and potentially contributing to the initiation of colorectal cancer.

Supplementation with omega fatty acids increases the mRNA expression level of PLA2G4A in patients with gastric cancer

Background

Many lines of evidence suggest that arachidonic acid (AA)-based eicosanoid signaling pathway involved in development and progression of human cancers. Cytosolic phospholipase A2-α (cPLA2α) encoded by the PLA2G4A gene acts as an upstream regulator of eicosanoid signaling pathway through providing intracellular AA. The current study aimed to evaluate the effect of omega fatty acids on mRNA expression level of PLA2G4A in patients with gastric cancer (GC) and to assess the possible relation between its expression and clinicopathological features.

Methods

According to treatment strategy, 34 chemotherapy-naive patients were randomly divided into two groups including, treatment group I (17 subjects received cisplatin alone) and treatment group II (17 individuals received cisplatin plus omega fatty acids) in a double-blind manner. The gastric biopsies specimens were taken from subjects before and after treatment and then mRNA expression level of PLA2G4A was evaluated by quantitative real-time PCR procedure.

Results

The expression of the PLA2G4A gene at the protein level in the gastric biopsies samples was also determined by immunohistochemistry. Our findings revealed a significantly up-regulated expression of PLA2G4A mRNA in treatment group II after receiving cisplatin plus omega fatty acid compared to before treatment (P=0.003). In treatment group I, there was no significant difference in mRNA expression levels of PLA2G4A before and after treatment (P=0.790). We also found that mRNA expression of PLA2G4A in treatment group II was significantly associated with tumor size (P=0.007) and familial history (P=0.006).

Conclusions

This study provides evidence that supplementation with omega fatty acids increases the mRNA expression level of PLA2G4A in patients with GC and may be crucial in guarding the cell from transformation and carcinogenesis.

cPLA2α mediates TGF-β-induced epithelial-mesenchymal transition in breast cancer through PI3k/Akt signaling

A high incidence of tumor recurrence and metastasis has been reported in breast cancer patients; nevertheless, the underlying molecular mechanisms are largely unknown. Epithelial–mesenchymal transition (EMT), which is induced by transforming growth factor-β (TGF-β), has been implicated in tumorigenesis and breast cancer metastasis. EMT events are now directly associated with tumor metastasis, and this progress is dependent on the inflammatory microenvironment. Cytosolic phospholipase A2α (cPLA2α) has been shown to participate in a series of biological processes including inflammation and cancer development. However, the role and molecular mechanism of cPLA2α in breast cancer EMT and metastasis remain enigmatic. In this study, we found that cPLA2α was commonly overexpressed in most human breast cancer tissues and significantly correlated with a poor prognosis for human breast cancer. Functional studies demonstrated that cPLA2α overexpression was significantly associated with elevated migration and invasion in MDA-MB-231 and T47D cells. Conversely, reduced cPLA2α expression strongly attenuated metastasis and the EMT program of MDA-MB-231 cells. Further study found that knockdown of cPLA2α in MDA-MB-231 cells inhibited TGF-β-induced EMT through the PI3K/Akt signaling pathway. Animal experiments revealed that cPLA2α downregulation in MDA-MB-231 cells markedly restrained tumorigenesis and metastasis in vivo. This study indicates the potential role of cPLA2α in breast cancer metastasis and indicates that this molecule is a promising therapeutic target for breast cancer.

New Insights on COX-2 in Chronic Inflammation Driving Breast Cancer Growth and Metastasis

The medicinal use of aspirin stretches back to ancient times, before it was manufactured in its pure form in the late 19th century. Its accepted mechanistic target, cyclooxygenase (COX), was discovered in the 1970s and since this landmark discovery, the therapeutic application of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has increased dramatically. The most significant benefits of NSAIDs are in conditions involving chronic inflammation (CI). Given the recognized role of CI in cancer development, the use of long-term NSAID treatment in the prevention of cancer is an enticing possibility. COX-2 is a key driver of CI, and here we review COX-2 expression as a predictor of survival in various cancer types, including breast. Obesity and post-partum involution are natural inflammatory states that are associated with increased breast cancer risk. We outline the COX-2 mediated mechanisms contributing to the growth of cancers. We dissect the cellular mechanism of epithelial-mesenchymal transition (EMT) and how COX-2 may induce this to facilitate tumor progression. Finally we examine the potential regulation of COX-2 by c-Myb, and the possible interplay between c-Myb/COX-2 in proliferation, and hypoxia inducible factor-1 alpha (HIF1α)/COX-2 in invasive pathways in breast cancer.

Screening of alternative drugs to the tumor suppressor miR-375 in esophageal squamous cell carcinoma using the connectivity map

OBJECTIVE

The aim of this study was to identify alternative compounds to the tumor suppressor miR-375 using the connectivity map (CMAP) and to validate the antitumor effects of the identified drugs in esophageal squamous cell carcinoma (ESCC).

METHODS

Gene profiling of miR-375-treated TE2 and T.Tn cells was applied in order to search the CMAP database. Among the compounds identified using the CMAP, we focused on 8 drugs [(-)-epigallocatechin-3-gallate, metformin, rosiglitazone among others], excluding 2 drugs among the top 10 compounds. We evaluated whether these compounds possess tumor-suppressive functions in ESCC.

RESULTS

A cytotoxicity assay showed that the sensitivity of TE2 and T.Tn cells treated with the 8 compounds was evaluated based on IC50 values of 42.9 µM to 3.8 mM. A cell cycle analysis revealed that the percentage of TE2 and T.Tn cells incubated with 6 compounds in the G0/G1 phase or the G2/M phase increased by approximately 40-80%. A TUNEL assay showed that the percentages of apoptotic cells treated with almost all compounds were significantly increased (p < 0.05) compared with the control cells.

CONCLUSION

The CMAP database is a useful tool for identifying compounds affecting the same molecular pathways, particularly products that are difficult to apply via practical approaches, such as microRNAs.

Cyclooxygenase-2 expression is associated with poor overall survival of patients with gastric cancer: a meta-analysis

BACKGROUND

Cyclooxygenase-2 (COX-2) is believed to be involved in gastric carcinogenesis. However, it is still controversial whether COX-2 expression can be regarded as a prognostic factor for gastric cancer patients.

AIM

To obtain a more accurate relationship between COX-2 overexpression and prognosis in gastric cancer by meta-analysis.

METHOD

Relevant articles published up to May 2013 were searched by use of several keywords in electronic databases. Separate hazard ratio (HR) estimates and 95 % confidence intervals (95 % CI) for COX-2 overexpression and overall survival (OS) and disease-free survival (DFS) with gastric cancer were extracted. Combined HR with 95 % CI was calculated by use of Stata11.0 software to estimate the size of the effect. Publication bias testing and sensitivity analysis were also performed.

RESULTS

A total of 27 studies which included 3,891 gastric cancer patients were combined in the final analysis. Combined results suggested that COX-2 overexpression was associated with an unfavorable OS (HR 1.58, 95 % CI 1.36-1.84) but not DFS (HR 1.15, 95 % CI 0.93-1.43) among patients with gastric cancer. Publication bias was absent. Sensitivity analysis suggested that the results of this meta-analysis were robust.

CONCLUSIONS

The results of this meta-analysis suggest that high COX-2 expression may be an independent risk factor for poor OS of patients with gastric cancer. More large prospective studies are now needed to further clarify the prognostic value of COX-2 expression for DFS in gastric cancer.

Expression of group IIA phospholipase A2 is an independent predictor of favorable outcome for patients with gastric cancer

Growing evidence suggests that phospholipase A2 (PLA2) plays a pivotal role in tumorigenesis in human gastrointestinal cancer. One of the well-studied isoforms of PLA2, group IIA PLA2 (PLA2G2A), appears to exert its protumorigenic or antitumorigenic effects in a tissue-specific manner. The present study was designed to determine the expression profile and prognostic value of PLA2G2A in gastric cancer in a large Chinese cohort. By using real-time polymerase chain reaction, the amount of PLA2G2A messenger RNA in 60 pairs of fresh gastric tumors and adjacent noncancerous mucosa was measured. The immunostaining of PLA2G2A in 866 gastric cancers with paired noncancerous tissues was assayed. No expression of PLA2G2A was found in normal gastric mucosa, and focal expression of PLA2G2A was noticed in intestinal metaplasia, whereas significantly increased expression of PLA2G2A was observed in the cytoplasm of gastric cancer cells. Furthermore, the extent of PLA2G2A expression was associated with tumor size (P < .001), tumor differentiation (P = .001), T class (P < .001), N class (P < .001), and TNM stage (P < .001) of gastric cancer. Multivariate analysis showed that PLA2G2A expression was an independent predictor of survival for patients with gastric cancer (P = .024). Expression of PLA2G2A seems to be protective for patients with gastric cancer (hazard ratio, 1.423; 95% confidence interval, 1.047-1.935), and it may be a target for achieving better treatment outcomes.