MIAT shuttled by tumor-secreted exosomes promotes paclitaxel resistance in esophageal cancer cells by activating the TAF1/SREBF1 axis

Chemoresistance remains a major obstacle to the treatment of esophageal cancer (EC). Exosome-mediated transfer of long noncoding RNAs (lncRNAs) has recently been unveiled to correlate with the regulation of drug resistance in EC. This study aimed to investigate the physiological mechanisms by which exosome-encapsulated lncRNA myocardial infarction-associated transcript (MIAT) derived from tumor cells might mediate the paclitaxel (PTX) resistance of EC cells. First, MIAT was experimentally determined to be upregulated in PTX nonresponders and PTX-resistant EC cells. Silencing of MIAT in PTX-resistant EC cells decreased cell viability and enhanced apoptosis, corresponding to a reduced half-maximal inhibitory concentration (IC50 ) value. Next, exosomes were isolated from EC109 and EC109/T cells, and EC109 cells were cocultured with EC109/T-cell-derived exosomes. Accordingly, MIAT was revealed to be transmitted through exosomes from EC109/T cells to EC109 cells. Tumor-derived exosomes carrying MIAT increased the IC50 value of PTX and suppressed apoptosis in EC109 cells to promote PTX resistance. Furthermore, MIAT promoted the enrichment of TATA-box binding protein-associated Factor 1 (TAF1) in the promoter region of sterol regulatory element binding transcription factor 1 (SREBF1), as shown by a chromatin immunoprecipitation assay. This might be the mechanism by which MIAT could promote PTX resistance. Finally, in vivo experiments further confirmed that the knockdown of MIAT attenuated the resistance of EC cells to PTX. Collectively, these results indicate that tumor-derived exosome-loaded MIAT activates the TAF1/SREBF1 axis to induce PTX resistance in EC cells, providing a potential therapeutic target for overcoming PTX resistance in EC.

Trichostatin A enhances radiosensitivity and radiation-induced DNA damage of esophageal cancer cells

Background

Trichostatin A (TSA) is emerging as a potential component of anticancer therapy. In this study, we aimed to identify the radiosensitizing effects of TSA in esophageal squamous carcinoma cell lines and identify the genomic alteration of histone acetylation associated with TSA treatment.

Methods

EC109 and KYSE450 cells were pretreated with TSA (0.1 µM) for 12 hours prior to irradiation, and the cell viability, flow cytometry, and comet assays were performed to analyze cell growth, cell apoptosis, and DNA damage, respectively. Chromatin immunoprecipitation sequencing (ChIP-Seq) was performed to identify the acetylation sites of histone H3 lysine 9 (H3K9), which was altered by TSA.

Results

Our data showed that TSA could sensitize esophageal cancer cells to radiation by inducing cell cycle arrest and increasing cell apoptosis. DNA damage induced by radiation was enhanced by TSA treatment. In addition, a total of 105 differential peak-related genes were found to be associated with TSA treatment, which was identified using ChIP-Seq with specific antibodies against acetylated histone H3K9.

Conclusions

Our data suggest that pretreatment with TSA can enhance ionizing radiation-induced DNA damage of esophageal cancer cells, which was associated with the altered histone modification of whole genome. TSA has potential implications for clinical use in increasing the anticancer efficacy of radiation.

CFTR inhibits the invasion and growth of esophageal cancer cells by inhibiting the expression of NF-κB

Our study aimed to explore the function of cystic fibrosis transmembrane conductance regulator (CFTR) in esophageal cancer. Twenty patients with esophageal squamous cell carcinoma (ESCC) and 20 patients with esophageal adenocarcinoma (EA) were enrolled in this study. The levels of CFTR and NF-κB in tumor tissues and adjacent normal tissues were detected, respectively. The expression of CFTR were detected by qRT-PCR and Western blot in normal esophageal cell line, esophagus squamous cell, carcinoma cell lines, and EA cell lines, respectively. Effects of CFTR silencing and overexpression on NF-κB protein expression were detected by Western blot. Transwell assay was performed to detect cell invasion. Mouse tumor model was established and the effect of CFTR inhibitor on tumor growth was examined. The expression of CFTR was downregulated in tumor tissues and cancer cell lines. CFTR silencing promoted the expression of NF-κB-p65 and NF-κB-p50, and the results of CFTR overexpression were reversed. In addition, CFTR silencing promoted the invasion of cancer cells and tumor growth in mice. Besides that, NF-κB inhibitor reduced the enhancing effects of CFTR silencing on esophageal cell invasion. We conclude that CFTR inhibits the growth and migration of esophageal cancer cells by downregulating of the NF-κB protein expression.

Effect of galectin-3 on vasculogenic mimicry in esophageal cancer cells

Galectin-3 is a multifunctional β-galactoside binding lectin associated with tumor progression. Previous studies confirmed the roles of galecin-3 overexpression and silencing in the biological behavior of Eca109 human esophageal cancer (EC) cells; galectin-3 may serve a critical role in the vasculogenic mimicry (VM) of tumors. Therefore, the present study examined the effects of galectin-3 knockdown using lentivirus vectors on VM in EC. Eca109 and EC9706 EC cells were transfected with a lentiviral vector to inhibit galectin-3 expression, or a control vector. VM formation in vitro was evaluated via 3D culture. Western blotting was used to detect the expression level of galectin-3 following galectin-3 silencing and the expression levels of VE-cadherin, ephrin type-A receptor 2 precursor (EphA2) and matrix metalloproteinase 2 (MMP-2). According to the results of western blot analysis, the Eca109/galectin-3 and EC9706/galectin-3 cells exhibited effective galectin-3 silencing (P<0.05). Eca109 and EC9706 cells formed typical tubular networks; the number of tubular networks markedly decreased subsequent to galectin-3 knockdown. The expression levels of MMP-2 and EphA2 proteins in Eca109/galectin-3 and EC9706/galectin-3 cells were lower compared with those in Eca109, EC9706, and control vector-transfected Eca109 and EC9706 cells (P<0.05); however, there was no significant difference in the expression of VE-cadherin proteins. These results indicated that galectin-3 may modulate VM in EC by regulating the EphA2 expression level, which affects VM formation via MMP-2.