High Glucose Promotes Epithelial-Mesenchymal Transition of Uterus Endometrial Cancer Cells by Increasing ER/GLUT4-Mediated VEGF Secretion

BACKGROUND/AIMS: Uterus endometrial cancer (UEC) is the common malignancy among gynecologic cancers, and most of them are type I estrogen-dependent UEC. Diabetes is well-known risk factor for the development of UEC. However, the underlying link between high glucose (HG) and the estrogen receptor in UEC remains unclear. Epithelial-mesenchymal transition (EMT) has also been shown to occur during the initiation of metastasis in cancer progression. The aim of this study was to determine the relationships and roles of HG, estrogen receptor and EMT in the growth and migration of UEC. METHODS: The expression of glucose transport protein 4 (GLUT4) in the control endometrium and UEC tissues was detected by immunohistochemistry (IHC); the cell viability and invasion were analyzed through CCK-8 and Matrigel invasion assays; the transcriptional level of EMT-related genes was evaluated through real-time PCR; and the effect of HG and / or GLUT4 on estrogen receptors, vascular endothelial growth factor (VEGF) and its receptor VEGFR was analyzed through western blotting, ELISA and flow cytometry (FCM) assay, respectively. In addition, Ishikawa-xenografted nude mice were constructed and were used to analyze the effect of estrogen and GLUT4 on the growth of UEC in vivo. RESULTS: Here, we found that exposure to HG led to a high level of viability and invasion of UEC cell lines (UECC, Ishikawa and RL95-2 cells). Compared with the normal endometrium, a higher level of GLUT4 was observed in UEC tissues. Silencing GLUT4 obviously inhibited the HG-promoted viability, invasion and expression of EMT-related genes (TWIST, SNAIL and CTNNB1) of UECC promoted by HG. Further analysis showed that HG and GLUT4 promoted the secretion of VEGF and expression of VEGFR in UECC. Treatment with HG led to the increase of estrogen receptor α (ERα) and β (ERβ) in UECC, blocking ERα or ERβ resulted in the decreases in GLUT4 expression, TWIST, SNAIL and CTNNB1 transcription, and VEGF and VEGFR expression in UECC. Treatment with anti-human VEGF neutralizing antibody restricted the viability and invasion of UECC that was induced by HG and estrogen. Exposure to estrogen accelerated growth, VEGF production, and TWIST and CTNNB1 expression in UEC in Ishikawa-xenografted nude mice, and silencing GLUT4 restricted these effects. CONCLUSION: These data suggest that HG increases GLUT4 and VEGF/VEGFR expression, further promotes EMT process and accelerates the development of UEC by up-regulating ER.