Overexpression of angiopoietin 2 promotes the formation of oral squamous cell carcinoma by increasing epithelial–mesenchymal transition-induced angiogenesis

Abstract

Oral squamous cell carcinoma (OSCC) is the most common cancer of the head and neck and is associated with a high rate of lymph node metastasis. The initial step in the metastasis and transition of tumors is epithelial–mesenchymal transition (EMT)-induced angiogenesis, which can be mediated by angiopoietin 2 (ANG2), a key regulatory factor in angiogenesis. In the present study, immunohistochemistry and real-time quantitative reverse transcriptase (qRT-PCR) were used to measure the expression of ANG2 in OSCC tissues. Plasmids encoding ANG2 mRNA were used for increased ANG2 expression in the OSCC cell line TCA8113. The short interfering RNA (siRNA)-targeting ANG2 mRNA sequences were used to inhibit ANG2 expression in TCA8113 cells. Subsequently, transwell assays were performed to examine the effects of ANG2 on TCA8113 cell migration and invasion. Furthermore, in vivo assays were performed to assess the effect of ANG2 on tumor growth. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays and immunohistochemistry were used to examine cell apoptosis and angiogenesis in tumor tissues, respectively. Finally, western blot analysis was performed to evaluate tumor formation-related proteins in OSCC tissues. We found that protein expression of ANG2 was remarkably upregulated in OSCC tissues. Overexpression of ANG2 increased the migration and invasion of TCA8113 cells by regulating EMT. Further investigations showed that overexpression of ANG2 increased tumor growth in nude mice, and angiogenesis of OSCC tissues increased in the presence of ANG2 overexpression. Overexpression of ANG2 also reduced cell apoptosis in tumor tissue cells. Finally, we found that overexpression of ANG2 resulted in changes in the expression of tumor formation-related proteins including vimentin, E-cadherin, Bim, PUMA, Bcl-2, Bax, Cyclin D1, PCNA and CD31. Our findings show that ANG2 has an important role in the migration and invasion of OSCC. More importantly, further investigations suggested that overexpression of ANG2 might increase OSCC metastasis by promoting angiogenesis in nude mice. This stimulatory effect could be achieved by inducing abnormal EMT and by reducing apoptosis and increasing proliferation of cells.

RNA interference: new mechanistic and biochemical insights with application in oral cancer therapy

“…RNA interference: new mechanistic and biochemical insights would present a reduction in their capacity to invade and migrate through the EMT process. 90 The same pattern was observed in the case of siRNA inhibition of superoxide dismutase 2 in SACC-LM that led to E-cadherin increased levels as well as the decreased expression of migration-associated genes Vimentin, Slug, Snail, p-ERK, and MMP-2. 91 Aberrant Notch4 expression has an essential function in OSCC tumorigenesis and promotes metastasis by perineural spread, 92 becoming an important prognosis marker and therapeutic target.…”

Potential suppressive effects of theophylline on human rectal cancer SW480 cells in�vitro by inhibiting YKL-40 expression

“…Angiopoietin-2 caninduce anarchical blood vessel organization during cancer progression and enhance the effect of vascular endothelial growth factor during active neovascularization (38,39). Additionally, angiopoietin-2 serves a notable role in the migration and invasion of a malignancy, and is partly responsible for inducing abnormal epithelial-mesenchymal transition (40). Upregulation of angiopoietin-2 expression was observed in diverse human malignant tumors, but notable expression does not occur in healthy individuals, meaning it may represent a novel mechanistically directed target for antitumor therapy.…”

Stage-dependent angiopoietin-Tie2 and nitric oxide signaling of erythrocytes in response to surgical trauma in head and neck cancer

“…27,28 The expression of angiopoietin-2 is upregulated at sites of tumor angiogenesis in multiple types of cancer, and overexpression of angiopoietin-2 promoted angiogenesis and tumor growth in experimental models. 8,29,30 Importantly, overexpression of angiopoietin 2 accelerated the carcinogenesis of oral squamous cell carcinoma through promoting epithelial-mesenchymal transition-induced angiogenesis. 8 Angiopoietin-2 has been proposed as a potential target for antiangiogenic drug development.…”

“…6 Animal study reported that overexpression of angiopoietin-2 has also been shown to promote the growth and metastasis of oral SCC. 8 Besides, experimental study demonstrated the distinct expressions of angiopoietin-1 and angiopoietin-2 in tumor samples of human oral SCC. 9 However, the dynamic changes of these angiogenic factors in the setting of tumor resection remains unclear.…”