α-Mangostin suppresses human gastric adenocarcinoma cells in vitro via blockade of Stat3 signaling pathway.

AIM: To investigate the anti-tumor effects of α-mangostin, a major xanthone identified in the pericarp of mangosteen (Garcinia mangostana Linn), against human gastric adenocarcinoma cells in vitro, and the mechanisms of the effects. METHODS: Human gastric adenocarcinoma cell lines BGC-823 and SGC-7901 were treated with α-mangostin. The cell viability was measured with MTT assay, and cell apoptosis was examined using flow cytometry and TUNEL assay. The expression of the relevant proteins was detected using Western blot. RESULTS: Treatment with α-mangostin (3-10 µg/mL) inhibited the viability of both BGC-823 and SGC-7901 cells in dose- and time-manners. Furthermore, α-mangostin (7 µg/mL) time-dependently increased the apoptosis index of the cancer cells, reduced the mitochondrial membrane potential of the cancer cells, and significantly increased the release of cytochrome c and AIF into cytoplasm. Moreover, the α-mangostin treatment markedly suppressed the constitutive Stat3 protein activation, and Stat3-regulated Bcl-xL and Mcl-1 protein levels in the cancer cells. CONCLUSION: The anti-tumor effects of α-mangostin against human gastric adenocarcinoma cells in vitro can be partly attributed to blockade of Stat3 signaling pathway.

Conversion of epithelial-to-mesenchymal transition to mesenchymal-to-epithelial transition is mediated by oxygen concentration in pancreatic cancer cells.

[This retracts the article DOI: 10.3892/ol.2018.8219.].

Expression of microRNA-184 in glioma.

The aim of the present study was to examine the expression of microRNA (miRNA)-184 in gliomas with different pathological grades, and its effect on survival prognosis. For the present study, 40 participants were selected with different pathological grades of glioma tissues with grade I (n=10), grade II (n=8), grade III (n=16), and grade IV (n=6). In addition, 10 cases of normal brain tissue (obtained by decompression because of traumatic brain injury) were selected. RT-PCR and immunohistochemical techniques were used to detect the expression level and intensity of miRNA-184 in different grades of glioma tissues. The length of survival of miRNA-184-positive patients was analyzed. miRNA-184 mRNA expression was found in normal tissues and tumor tissues, and the expression in tumor tissues was significant (P<0.05). Statistically significant differences of miRNA-184 expression were observed among different grades (P<0.05). miRNA-184 expression increased with the increase of grade level. The differences in expression across grade levels was statistically significant (P<0.05). A positive expression was not related to the pathological types of glioma cells. The median survival time of patients with miRNA-184-positive expression was significantly shorter than that of the negative expression group (P<0.05). miRNA-184 is highly expressed in gliomas, which is positively correlated with pathological grade, and is not correlated with pathological type, and negatively correlated with survival time. Thus, miRNA-184 is a potentially important molecular marker for glioma.

E2F1 induces LSINCT5 transcriptional activity and promotes gastric cancer progression by affecting the epithelial-mesenchymal transition.

BACKGROUND: Long noncoding RNAs (lncRNAs) have been shown to play important regulatory roles in human cancer. We previously verified that the lncRNA long stress-induced noncoding transcript 5 (LSINCT5) is overexpressed in gastric cancer (GC) cells and closely correlated with cell proliferation and patient prognosis. However, whether aberrant LSINCT5 expression has an important effect on GC progression is unclear, and the potential mechanisms remain unknown. In GC, E2F1 expression is also aberrant, but the biological functions of E2F1 are controversial, and the correlation between E2F1 and lncRNAs remains unknown. MATERIALS AND METHODS: Expression of LSINCT5 was analyzed in metastatic GC tissues compared with nonmetastatic tissues using quantitative real-time PCR (qRT-PCR) assays. Gain and loss of function approaches were used to investigate the biological role of LSINCT5 in GC cell migration and invasion. A computational screen of LSINCT5 promoter was conducted to search for transcription factor-binding sites. LSINCT5 promoter activities were examined by ChIP and luciferase reporter assays. qRT-PCR and western blotting assays were performed to detect the expression of multiple EMT markers in cells in which LSINCT5 was overexpressed or knocked down. RESULTS: An integrated quantitative analysis revealed that LSINCT5 was significantly over-expressed in metastatic GC tissues. Forced LSINCT5 expression promoted cell migration and invasion, whereas loss of LSINCT5 function decreased cell migration and invasion. Mechanistic investigations showed that LSINCT5 is a direct transcriptional target of E2F1. Moreover, LSINCT5 overexpression was found to play an important role in the epithelial-to-mesenchymal transition by regulating the expression of E-cadherin, N-cadherin, vimentin, and matrix metalloproteinase-2. CONCLUSION: These data suggest that E2F1-mediated activation of LSINCT5, a regulator of cell migration and invasion, constitute the mechanistic link between the E2F1-mediated pathway and lncRNA that regulates cell migration and invasion. Thus, LSINCT5 may be a target for new GC therapies.

Conversion of epithelial-to-mesenchymal transition to mesenchymal-to-epithelial transition is mediated by oxygen concentration in pancreatic cancer cells.

Tumor metastasis is accompanied by a two-stage process of epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET). Currently, the exact mechanisms underlying EMT-MET conversion are unclear. In the present study, the mechanisms by which primary sites (hypoxic) and homing sites (normoxic or hyperoxic) participate in EMT-MET conversion were evaluated. Pancreatic cancer cells were grown under different oxygenation conditions. Cell morphology and epithelial (E)-cadherin and vimentin expression were examined. Transwell chambers were used to examine tumor invasiveness, and scratch assays were performed to examine cell migration. Reverse transcription-polymerase chain reaction and western blot analysis were used to quantitate the mRNA and protein expression of E-cadherin, vimentin, Snail and hypoxia-inducible factor (HIF)-1α. BxPc-3 and Panc-1 cells grown under hypoxic conditions demonstrated increased partial EMT, reduced E-cadherin expression, and increased vimentin expression, compared with cells grown under normoxic or hyperoxic conditions. Cells grown under hypoxic conditions also indicated increased migration and invasiveness. HIF-1α mRNA and protein expression was increased in cells grown under hypoxic conditions. These changes were reversed when a specific inhibitor of the HIF-1α receptor was used to block HIF-1α signaling. Differences in oxygen concentration at primary sites and homing sites are important in the EMT-MET process, and the underlying mechanism may involve HIF-1α-Snail signaling.

Prometastatic mechanisms of CAF-mediated EMT regulation in pancreatic cancer cells.

Tumor metastasis are accompanied by the EMT (epithelial-mesenchymal transition)-MET (mesenchymal-epithelial transition) two-step process. In this study, we investigated the importance of cancer associated fibroblasts (CAF) in the process. First, the primary cultures of isolated pancreatic CAF, fibroblasts of normal pancreatic tissues (NF), and normal hepatic stellate cells (HSF) were identified and verified via the expression of α-SMA and vimentin. Using an indirect three-dimensional co-culture model, the morphological changes were observed by light microscopy and laser scanning confocal microscopy. The invasive and migration capacity of pancreatic cancer cells was determined by Transwell chamber migration assay or scratch assay. The mRNA and protein expression levels of E-cadherin, vimentin, and Gli1 were determined by RT-PCR and western blotting. Primary cultures of isolated CAF, NF, HSF showed satisfactory growth with active proliferation. Indirect co-culture with CAF, BxPc-3 and Panc-1 cells showed significant partial EMT, reduced E-cadherin expression, and enhanced vimentin expression as compared with the single culture and NF/HSF co-culture groups, with corresponding increases in migratory and invasive capacities. PCR and western blotting results showed that mRNA and protein expression levels of Gli1 in CAF and Snail in cancer cells were increased. This process could be reversed by inhibition of hedgehog (HH) signaling in CAF. In the tumor microenvironment, activation of CAF is the key event in mediating partial EMT, and its mechanism may be associated with paracrine action after activation of HH signaling in CAF.

Cancer-associated fibroblasts enhance pancreatic cancer cell invasion by remodeling the metabolic conversion mechanism.

We investigated the mechanism of cancer-associated fibroblasts (CAFs) in promoting the invasion and metastasis of pancreatic cancer cells in a non-vascular manner. We verified the original generation of isolated cultured CAFs and normal fibroblasts (NFs) based on the expression of α-SMA and vimentin, and we examined the cell glycolysis level through glucose consumption and lactate production experiments. The mRNA and protein expression of CAF glycolytic enzymes, lactate dehydrogenase and pyruvate kinase m2, were examined by RT-PCR and western blotting, respectively. In vitro culture first-generation pancreatic CAFs were collected and cultured together with pancreas cancer BxPc-3 and Panc-1 cells. Cell invasion and migration were assessed using a Transwell assay and scratch test, respectively. Mitochondrial activity was assessed by experimentally determining oxidative phosphorylation (OP) activity. The aerobic oxidation index of cancer cells was also examined. Succinate dehydrogenase, fumarate hydratase (FH), and monocarboxylate transporter 1 (MCT1) expression were examined using an MCT1-specific inhibitor to remove 'tumor-stromal' metabolic coupling to observe the influence of cell interstices on pancreas cancer progression. First-generation isolated cultured CAFs and NFs both grew well, and showed active proliferation. Glucose absorption and lactate production were significantly enhanced in CAFs compared with that in NFs. PCR and western blotting showed that the lactate dehydrogenase and pyruvate kinase m2 mRNA and protein expression levels were increased in the CAFs. After indirect co-culture, OP was increased in the BxPc-3 and Panc-1 cells; correspondingly, succinate dehydrogenase, FH and MCT expression were increased. After the MCT1-specific inhibitor removed 'tumor-stromal' metabolic coupling, the migration and invasion abilities of the pancreatic cancer cells were decreased. Pancreatic CAFs can alter metabolism as well as communicate with and respond to cancer cell migration and invasion. This may be an important mechanism for promoting tumor progression in a non-vascular manner in the tumor microenvironment. The mechanism by which CAFs reshape metabolic transition requires further analysis.