Gastric cancer (GC) has a clear predilection for metastasis toward the omentum which is primarily composed of adipose tissue, indicating that fatty acids may contribute to this phenomenon. However their function remains poorly understood in GC. In this study, we investigated the role of palmitate acid (PA) and its cellular receptor CD36 in the progression of GC. Immunohistochemical (IHC) staining was performed to detect CD36 expression in GC tissues and its clinical significance was determined statistically. CD36 over-expression and knock-down expression cell models were developed and tested in vitro. Wound-healing assays, migration assays, and invasion assays were performed and peritoneal implants into nude mice were done to assess the biological effects of PA and CD36. The underlying mechanisms were investigated using western blot, immunofluorescence (IF), quantitative real-time PCR (qRT-PCR) and antibody blocking assays. PA promoted the metastasis of GC by phosphorylation of AKT, which facilitated the nuclear localization of β-catenin through inactivation of GSK-3β via phosphorylation. This tumor-promoting effect of PA was mediated by CD36, a cell surface receptor of fatty acids (FAs). The higher the CD36 expression levels in GC tissues correlated with the poorer the prognosis of patients according to the TCGA database, the GEO database and our own clinical data. Our experiments established CD36 as a key mediator of FA-induced metastasis of GC via the AKT/GSK-3β/β-catenin signaling pathway. CD36 might, therefore, constitute a potential therapeutic target for clinical intervention in GC.

Long noncoding RNA UCA1 has emerged as a novel regulator in cancer initiation and progression of various cancers. However, function and underlying mechanism of UCA1 in the progression of gastric cancer (GC) remain unclear. In the present study, we report that UCA1 expressed highly in GC tissues and GC cells, which was partly induced by SP1. UCA1 promoted GC cell proliferation and G1/S transition in vitro and in vivo. Moreover, UCA1 exerted its function through interacting with EZH2, promoting direct interaction with cyclin D1 promoter to activate the translation of cyclin D1. Furthermore, AKT/GSK-3B/cyclin D1 axis was activated to upregulate cyclin D1 due to overexpression of UCA1. In addition, EZH2 and phosphorylated AKT induced by UCA1 could impact each other to form a positive feedback to promote cyclin D1 expression. This study demonstrated that UCA1 as a critical regulator involved in GC proliferation and cell cycle progression by promoting cyclin D1 expression, which indicates that it may be clinically a potential therapeutic target in GC.

Gastric cancer (GC) is one of the most malignant tumors and the second leading cause of cancer-related deaths in the world. Luteolin, a flavonoid present in many fruits and green plants, suppresses cancer progression. The effects of luteolin on GC cells and their underlying mechanisms remain unclear. Effects of luteolin on cell proliferation, migration, invasion, and apoptosis were examined in vitro and in vivo by cell counting kit-8 (CCK-8), transwell assays, and flow cytometry, respectively. Real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blots were performed to evaluate Notch1 signaling and activation of epithelial-mesenchymal transition (EMT) in GC cells treated with or without luteolin. Immunohistochemistry was performed to examine proliferation and Notch1 expression in xenograft tumors. Luteolin significantly inhibited cell proliferation, invasion, and migration in a dose-dependent and time-dependent manner and promoted cell apoptosis. Luteolin reversed EMT by shrinking the cytoskeleton and by inducing the expression of epithelial biomarker E-cadherin and downregulating the mesenchymal biomarkers N-cadherin, vimentin and Snail. Furthermore, Notch1 signaling was inhibited by luteolin, and downregulation of Notch1 had similar effects as luteolin treatment on cell proliferation, migration, and apoptosis. In addition, luteolin suppressed tumor growth in vivo. A higher expression of Notch1 correlated with a poor overall survival and a poor time to first progression. Furthermore, co-immunoprecipitation analysis revealed that activated Notch1 and β-catenin formed a complex and regulated cell proliferation, migration, and invasion. In this study, GC progression was inhibited by luteolin through suppressing Notch1 signaling and reversing EMT, suggesting that luteolin may serve as an effective anti-tumor drug in GC treatment.

Neoadjuvant chemotherapy with docetaxel, oxaliplatin, fluorouracil, and leucovorin (FLOT regimen) has shown promising results in terms of pathological response and survival rate in patients with locally advanced resectable gastric cancer (LAGC). However, tegafur gimeracil oteracil potassium capsule (S-1) plus oxaliplatin (SOX regimen) is the preferred chemotherapy regimen in Eastern countries. Here, we conduct an open label, two-arm, phase II randomized interventional clinical trial (Dragon III; ClinicalTrials.gov: NCT03636893) to evaluate the safety and efficacy of both regimens. Patients with LAGC are randomly assigned to receive either 4 cycles of the neoadjuvant FLOT regimen (40 patients) or 3 cycles of the SOX regimen (34 patients) before gastrectomy. The primary endpoint is the comparison of complete (TRG1a) or subtotal (TRG1b) tumor regression grading in the primary tumor. There are no significant differences in adverse effects or postoperative morbidity and mortality between the two groups. No significant differences in the proportion of tumor regression grading between the FLOT group and the SOX group are found. Complete or subtotal TRG is 20.0% in the FLOT group versus 32.4% in the SOX group. Therefore, our study does not find statistically significant differences between neoadjuvant FLOT and SOX regimens for the primary outcomes reported here in locally advanced gastric cancer.

Elevated MELK expression is featured in multiple tumors and correlated with tumorigenesis and tumor development. This study is aimed to investigate the mechanisms of MELK-mediated development of gastric cancer. MELK expression levels in human gastric cancer were determined by quantitative-PCR and immunohistochemistry. The effect of MELK on cell activity was explored by knockdown and overexpression experiments. Cell growth was measured using the CCK-8 assay. Apoptosis and cell cycle distributions were analyzed by flow cytometry. Migration and invasion were tested using a transwell migration assay. Cytoskeletal changes were analyzed by immunofluorescence. To explore the molecular mechanism and effect of MELK on migration and invasion, Western blotting was used to analyze the FAK/Paxillin pathway and pull down assays for the activity of small Rho GTPases. In vivo tumorigenicity and peritoneal metastasis experiments were performed by tumor cell engraftment into nude mice. MELK mRNA and protein expression were both elevated in human gastric cancer, and this was associated with chemoresistance to 5-fluorouracil (5-FU). Knockdown of MELK significantly suppressed cell proliferation, migration and invasion of gastric cancer both in vitro and in vivo, decreased the percentages of cells in the G1/G0 phase and increased those in the G2/M and S phases. Moreover, knockdown of MELK decreased the amount of actin stress fibers and inhibited RhoA activity. Finally, knockdown of MELK decreased the phosphorylation of the FAK and paxillin, and prevented gastrin-stimulated FAK/paxillin phosphorylation. By contrast, MELK overexpression had the opposite effect. MELK promotes cell migration and invasion via the FAK/Paxillin pathway, and plays an important role in the occurrence and development of gastric cancer. MELK may be a potential target for treatment against gastric cancer.

Background: Many studies showed that long non-coding RNA MALAT1 is served as an oncogene. However, the specific role of MALAT1 in gastric cancer is not fully elucidated. The aim of this study is to elucidate the regulatory effects of MALAT1 on tumor development and cisplatin resistance in gastric cancer. Methods: TCGA database was applied to investigate the expression levels of MALAT1 in GC tissues and normal gastric tissues and its correlation with GC patients’ survival. Univariate and multivariate analysis were performed to investigate whether MALAT1 expression is an independent risk for overall survival of gastric cancer patients. The expression of MALAT1 was detected by Quantitative real-time PCR. After knockdown or overexpression of MALAT1, the cellular functions of GC cells were detected by cell-proliferation, flow cytometry, transwell assay and colony formation assays, respectively. Western blot analysis was performed to detect the protein levels of Bcl-2 and key genes in the PI3K/AKT pathway in GC cells. Finally, CCK-8 assay was performed to explore the effect of MALAT1 on cisplatin resistance of GC cells. Results: Higher expression of MALAT1 was detected in GC tissues than that of adjacent normal tissues, high MALAT1 expression is an independent risk for overall survival of gastric cancer patients. Knockdown of MALAT1 inhibited proliferation, migration and invasion of GC cells, while overexpression of MALAT1 Overexpression of MALAT1 yielded opposite results. Western blot results showed that protein expressions of p-PI3K, p-AKT and p-STAT3 were downregulated after MALAT1 knockdown in GC cells, while these proteins were upregulated after MALAT1 overexpression. Additionally, the IC₅₀ in MGC803/CDDP cells transfected with si-MALAT1 was lower than in those transfected with si-NC. The apoptotic rate in MGC803 cells transfected with pcDNA-MALAT1 was remarkably lower than those transfected with NC. Conclusion: We demonstrated that MALAT1 is highly expressed in GC, high MALAT1 expression is an independent risk factor for OS among GC patients. Moreover, MALAT1 promotes malignant progression of GC and contributes to cisplatin resistance of GC cells, indicating MALAT1 may serve as a biological hallmark for predicting the prognosis of GC.