X-linked inhibitor of apoptosis protein accelerates migration by inducing epithelial-mesenchymal transition through TGF-β signaling pathway in esophageal cancer cells

Background

The prognosis of esophageal cancer is still dismal because of its high probability of metastasis that is likely related to the cellular process of epithelial–mesenchymal transition (EMT). Recent studies have shown a novel role of X-linked inhibitor of apoptosis protein (XIAP) in regulating the migration process of cancer cells and, therefore, linking to progression and poor prognosis of cancer.

Methods

The expression of XIAP in esophageal squamous cell cancer (ESCC) tissues was determined by immunohistochemistry assay. Cell migration was analyzed by wound healing assay and Transwell assay. The expression of EMT markers (E-cadherin, N-cadherin and Vimentin) was revealed by immunofluorescence assay. Quantitative real‑time PCR analysis and Western blot analysis were used to detect the expression of XIAP and EMT markers as well as transforming growth factor-β (TGF-β) at mRNA and protein level, respectively.

Results

We found that the expression of XIAP closely correlated to the probability of lymphatic metastasis in patients and that ESCC patients with the high XIAP expression were associated with worse overall survival (OS). Univariate and multivariate analysis also revealed XIAP as an independent prognostic factor for overall survival in ESCC patients. In both EC9706 and TE13 cell lines, knockdown of XIAP decreased the migration of cancer cells by inhibiting EMT process through regulating the TGF-β signaling pathway, pinpointing a regulatory role of XIAP in migratory process upon TGF-β activation.

Conclusions

Taken together, our results suggest XIAP as a important prognostic and regulative factor in ESCC patients. XIAP may promote migration of esophageal cancer cells through the activation of TGF-β mediated EMT.

Expression of miR-944 in esophageal squamous cell carcinoma and its role in cell proliferation and invasion in human esophageal carcinoma cell line Eca109

AIM

To detect the expression of miRNA-944 in esophageal squamous cell carcinoma (ESCC), and to explore its role in cell proliferation and migration in human esophageal cancer cell line Eca109.

METHODS

ESCC and matched tumor adjacent noncancerous tissue samples were obtained from 36 patients who underwent surgical treatment and were pathologically diagnosed with ESCC. Real-time quantitative PCR (qRT-PCR) was used to detect the expression levels of miRNA-944, and the relationship between miRNA-944 and clinical and pathological parameters were then analyzed. Eca109 cells were transfected with miR-944 mimic, inhibitor and negative control using LipofectamineTM2000, and then the expression level of miR-944 was detected by qRT-PCR. Cell proliferation and invasion were assessed by MTT assay and transwell assay, respectively.

RESULTS

The expression level of miR-944 in ESCC tissues was significantly higher than that in tumor adjacent non-cancerous tissues (P < 0.01).The up-regulation of miR-944 expression in ESCC was correlated with advanced TNM stage (P < 0.01) and lymph node metastasis (P < 0.01). Compared to control cells, transfection of miR-944 mimic and inhibitor up- and down-regulated miR-944 expression in Eca109 cells, respectively (P < 0.01). Furthermore, transfection of miR-944 mimic enhanced cell proliferation and invasion, while transfection of miR-944 inhibitor inhibited cell proliferation and invasion (P < 0.01).

CONCLUSION

The expression of miR-944 is up-regulated in ESCC and associated with TNM stage and lymph node metastasis, indicating that miR-944 may facilitate ESCC occurrence possibly by promoting the proliferation and invasion of ESCC cells.

β-Carotene synergistically enhances the anti-tumor effect of 5-fluorouracil on esophageal squamous cell carcinoma in vivo and in vitro

Recently, we reported that β-carotene exhibited anticancer activity against human esophageal squamous cell carcinoma cells in vitro. In the present study, we examined a novel therapeutic strategy by combining β-carotene with 5-fluorouracil (5-FU) in human esophageal cancer in vitro and in vivo, and elucidated the underlying mechanisms. We found that the combination of 5-FU and β-carotene displayed greater growth inhibitory effects than did either compound alone in esophageal squamous cell carcinoma (ESCC) cells. In addition, the combination of 5-FU and β-carotene displayed greater tumor growth inhibition in an Eca109 xenograft mouse model than did a single agent with low systemic toxicity. β-Carotene enhanced 5-FU-induced apoptosis. TUNEL staining revealed that the rate of TUNEL-positive cells was markedly increased in tumor tissues after treatment with 5-FU and β-carotene. Western blotting and immunohistochemistry revealed the down-regulation of Bcl-2 and PCNA and the up-regulation of Bax and caspase-3 in tumor tissues. Further studies demonstrated that the combined administration of 5-FU and β-carotene significantly down-regulated the protein levels of Cav-1, p-AKT, p-NF-κB, p-mTOR and p-p70S6K in Eca109 cells more effectively than did 5-FU alone. These data suggested that the combined therapy of 5-FU and β-carotene exerted synergistic antitumor effects in vivo and in vitro and could constitute a novel therapeutic treatment for ESCC.

Subcellular localization of EGFR in esophageal carcinoma cell lines

BACKGROUND

The EGF receptor is a therapeutic target in cancer cells, whereby mutations of EGFR and/or signalling members act as predictive markers. EGFR however also exhibits dynamic changes of subcellular localization, leading to STAT5 complex formation, nuclear translocation and induction of Aurora-A expression in squamous cancer cells. We previously described high EGFR and Aurora-A expression in esophageal cancer cells. Here, we investigated subcellular localization of EGFR and STAT5 in esophageal cancer cells.

RESULTS

Quantitative immunofluorescence analyses of four esophageal cancer cell lines reflecting esophageal squamous cell carcinomas (ESCC) and esophageal adenocarcinomas (EAC) revealed that the subcellular localization of EGFR was shifted from a membranous to cytoplasmic localization upon EGF-stimulation in OE21 (ESCC) cells. Thereby, EGFR in part co-localized with E-Cadherin. In parallel, phosphorylated STAT5-Tyr694 appeared to increase in the nucleus and to decrease at the cell membrane. In three additional cell lines, EGFR was only marginally (Kyse-410/ESCC; OE19/EAC) and weakly (OE33, EAC) detectable at the cell membrane. Partial co-localization of EGFR and E-Cadherin occurred in OE33 cells. Post EGF-stimulation, EGFR was detected in the cytoplasm, resembling endosomal compartments. Furthermore, OE19 and OE33 exhibited nuclear STAT5-Tyr694 phosphorylation upon EGF-stimulation. None of the four cell lines showed nuclear EGFR expression and localization.

CONCLUSION

In contrast to other (squamous) cancer cells, activation of EGFR in esophageal squamous cancer cells does not result in nuclear translocation of EGFR. Still, the subcellular localization of EGFR may influence STAT5-associated signaling pathways in esophageal cancer cells and hence possibly also the responses to ErbB, respective EGFR-targeted therapies.

Overexpression of miR-451 inhibits cell proliferation and invasion and promotes apoptosis in human esophageal carcinoma cell line EC9706

AIM: To explore the effect of overexpression of miR-451 on cell proliferation, apoptosis and invasion in human esophageal carcinoma cell line EC9706.

METHODS: MiR-451 mimics were constructed and transfected into EC9706 cells using LipofectamineTM2000. EC9706 cells transfected with Scramble-miR, empty liposomes or negative miR-451 were used as controls. Forty-eight hours after transfection, the expression of miR-451 was detected by RT-PCR, and the expression of Bcl-2, AKT and phosphorylated AKT proteins were detected by Western blot. Cell apoptosis, invasion and proliferation were assessed by flow cytometry, transwell assay and MTT assay, respectively.

RESULTS: Compared to control cells, the expression of miR-451 was significantly up-regulated (P < 0.01, F = 69.26); the expression of Bcl-2, AKT and phosphorylated AKT proteins was significantly down-regulated (P < 0.05, F = 5.83); cell apoptosis rate significantly increased (P < 0.01, F = 26.72); the average number of cells penetrating Matrigel membrane significantly decreased (P < 0.01, F = 34.55); and cell proliferation was significantly suppressed in a time-dependent manner (P < 0.05, F = 5.95) in EC9706 cells transfected with miR-451 mimics.

CONCLUSION: Over-expression of miR-451 induces apoptosis and suppresses cell proliferation and invasion in human esophageal carcinoma cell line EC9706.

Bile salts inhibit growth and induce apoptosis of human esophageal cancer cell line

AIM: To explore the effect of six bile salts, including glycoc-holate (GC), glycochenodeoxycholate (GCDC), glycodeoxy-cholate (GDC), taurocholate (TC), taurochenodeoxycholate (TCDC), taurodeoxycholate (TDC), and two bile acids including cholic acid (CA) and deoxycholic acid (DCA) on esophageal cancer Eca109 cell line.

METHODS: Eca109 cells were exposed to six bile salts, two bile acids and the mixed bile salts at different concentrations for 24-72 h. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay was used to detect the cell proliferation. Apoptotic morphology was observed by phase-contrast video microscopy and deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Sub-G1 DNA fragmentations and early apoptosis cells were assayed by flow cytometry (FCM) with propidium iodide (PI) staining and annexin V-FITC conjugated with PI staining. Apoptosis DNA ladders on agarose were observed. Activation of caspase-3 was assayed by FCM with FITC-conjugated monoclonal rabbit anti-active caspase-3 antibody and expressions of Bcl-2 and Bax proteins were examined immunocytochemically in 500 μmol/L-TC-induced apoptosis cells.

RESULTS: Five bile salts except for GC, and two bile acids and the mixed bile salts could initiate growth inhibition of Eca109 cells in a dose- and time-dependent manner. TUNEL, FCM, and DNA ladder assays all demonstrated apoptosis induced by bile salts and bile acids at 500 μmol/L, except for GC. Early apoptosis cell percentages in Eca109 cells treated with GCDC, GDC, TC, TCDC, TDC, CA at 500 μmol/L for 12 h, DCA at 500 μmol/L for 6 h, and mixed bile salts at 1 000 μmol/L for 12 h were 7.5%, 8.7%, 14.8%, 8.9%, 7.8%, 9.3%, 22.6% and 12.5%, respectively, all were significantly higher than that in control (1.9%). About 22% of the cell population treated with TC at 500 μmol/L for 24 h had detectable active caspase-3, and were higher than that in the control (1%). Immunocytochemical assay suggested that TC down-regulated Bcl-2 protein level and up-regulated Bax protein level.

CONCLUSION: GCDC, GDC, TC, TCDC, TDC, CA and DCA, except for GC, can inhibit growth and induce apoptosis of esophageal cancer Eca109 cells. Activation of caspase-3, decreased Bcl-2 protein and increased Bax protein are involved in TC-induced apoptosis of Eca109 cells.