5460

POU5F1

The stem cell-related transcription factor Oct4 regulates tumor proliferation and apoptosis, but its role in tumor migration and invasion is still undefined. Here, we compared Oct4 expression in MCF-7 and MDA-MB-231 cells, two breast cancer cell lines with similar epithelial origins, but distinct invasive and metastatic characteristics. We found MCF-7 cells to express very high levels of Oct4, while no obvious expression was detected in MDA-MB-231 cells. We then downregulated Oct4 expression using small interfering RNA (siRNA) to explore its effects on migration and invasion. Transwell assays showed that silencing Oct4 in MCF-7 cells improved their migration and invasion capabilities. Reverse-transcriptase PCR and western blots showed that E-cadherin expression decreased, and alpha-smooth muscle actin expression increased with Oct4 downregulation, which suggests that epithelial-to-mesenchymal transition (EMT) occurred. A potent EMT stimulus, TGF-beta1, significantly inhibited Oct4 expression in both dose- and time course-dependent manners. Silencing Oct4 also upregulated expression of two major components of store-operated Ca(2+) entry channels (SOCs), STIM1 and Orai1, and enhanced SOC-directed Ca(2+) influx. Silencing STIM1 blocked the Ca(2+) influx and rescued the EMT initiated by Oct4 downregulation. In conclusion, silencing Oct4 promotes invasion and metastasis in breast cancer cells by inducing EMT. This effect may be related to SOCs-directed enhancement of Ca(2+) influx.CI - Copyright (c) 2011 Elsevier Inc. All rights reserved.

Octamer-binding transcription factor 4 (OCT4) has been implicated in cancer metastasis. In this study, we investigated whether OCT4 promotes colorectal cancer (CRC) metastasis through the epithelial-mesenchymal transition (EMT) process. We designed our experiment as a loss-of-function study. Western blot analysis was used to measure the extent and stability of OCT4 knockdown. We evaluated the metastatic phenotype of OCT4-silenced SW620 cells using standard migration and invasion assays in vitro and the commonly used mouse model for experimental metastases in vivo. We found that OCT4 knockdown inhibited colorectal cancer cell motility and invasion (in vitro) and decreased hepatic colonization (in vivo). It also induced changes in EMT characteristic cell morphology and marker gene expression. In addition, its knockdown decreased WNT pathway activity. Finally, in human primary colorectal cancers, the frequency of upregulated OCT4 expression in cases with liver metastasis was statistically higher than that in cases without liver metastasis. These results indicate that OCT4 may contribute to CRC cell metastasis through EMT and serves as a promising biomarker for identifying CRC patients at high risk for liver metastases.

BACKGROUND: Overexpression of Oct4, an important transcription factor of embryonic stem cells (ESC), has been reported in several cancers. The aim of this study was to determine the emerging role of Oct4 in oral squamous cell carcinoma (OSCC) both in vitro and in vivo. METHODOLOGY/PRINCIPAL FINDING: tumourigenic activity and molecular mechanisms of Oct4 overexpression or knockdown by lentiviral infection in OSCC was investigated in vitro and in vivo. Initially, we demonstrated that Oct4 expression was increased in OSCC cell lines as compared to a normal oral epithelial cell line SG. Overexpression of Oct4 was demonstrated to enhance cell proliferation, invasiveness, anchorage-independent growth and xenotransplantation tumourigenicity. These findings were coupled with epithelial-mesenchymal transition (EMT) transformation in OSCCs. In contrast, the silence of Oct4 significantly blocked the xenograft tumorigenesis of OSCC-derived cancer stem cells (OSCC-CSCs) and significantly improved the recipient survival. Clinically, the level of Oct4 expression was higher in recurrent and metastatic OSCC specimens but lower in primary OSCC specimens. CONCLUSION/SIGNIFICANCE: Our results suggest that Oct4-mediated tumorigenecity is associated with the regulation of EMT. Oct4 might be a therapeutic target for OSCC.

Oct-4 and Nanog in regulating the epithelial-mesenchymal transition (EMT) and metastasis of breast cancer has not been clarified. We found that both Oct-4 and Nanog expression were significantly associated with tumor pathology and poor prognosis in 126 breast cancer patients. Characterization of CD44+CD24-cancer stem cell(CSC) derived from breast cancer cells indicated that CSC rapidly formed mammospheres and had potent tumorigenicity in vivo. Furthermore, TGF-beta up-regulated the expression of Oct-4, Nanog, N-cadherin, vimentin, Slug, and Snail, but down-regulated E-cadherin and cytokeratin 18 expression, demonstrating that CSC underwent EMT. Knockdown of both Oct-4 and Nanog expression inhibited spontaneous changes in the expression of EMT-related genes, while induction of both Oct-4 and Nanog over-expression enhanced spontaneous changes in the expression of EMT-related genes in CSC. However, perturbing alternation of Oct-4 and Nanog expression also modulated TGF-beta-induced EMT-related gene expression in CSC. Induction of Oct-4 and Nanog over-expression enhanced the invasiveness of CSC, but knockdown of both Oct-4 and Nanog inhibited the migration of CSC in vitro. Our data suggest that both Oct-4 and Nanog may serve as biomarkers for evaluating breast cancer prognosis. Our findings indicate that Oct-4 and Nanog positively regulate the EMT process, contributing to breast cancer metastasis.

BACKGROUND: Oct4 and Nanog are key regulatory genes that maintain the pluripotency and self-renewal properties of embryonic stem cells. We previously reported that the two stemness markers were tightly associated with cancer progression and poor outcomes of hepatocellular carcinoma. In this study, we demonstrate that coexpression of Oct4/Nanog modulates activation of signal transducer and activator of transcription 3 (Stat3), an oncogenic transcription factor that is activated in many human malignancies including hepatocellular carcinoma (HCC), as well as the expression of Snail, a key regulator implicated in epithelial-mesenchymal transition and tumor metastasis. METHODS: Oct4 and Nanog were ectopic expressed in MHCC97-L cell lines via lentiviral gene transfection. The stemness characteristics including self-renewal, proliferation, chemoresistance, and tumorigenicity were assessed. The effect of coexpression of Oct4 and Nanog on epithelial-mesenchymal transition change, and the underlying molecular signaling was investigated. RESULTS: Ectopic coexpression of Oct4 and Nanog empowered MHCC97-L cells with cancer stem cell (CSC) properties, including self-renewal, extensive proliferation, drug resistance, and high tumorigenic capacity. Significantly, Oct4 and Nanog encouraged epithelial-mesenchymal transition change contributing to tumor migration, invasion/metastasis in vitro and in vivo. Following molecular mechanism investigation indicated Oct4/Nanog-regulated epithelial-mesenchymal transition change through Stat3-dependent Snail activation. Moreover, silencing Stat3 abrogates Oct4/Nanog-mediated epithelial-mesenchymal transition (EMT) change and invasion/metastasis in HCC. CONCLUSIONS: We delineate Oct4 and Nanog initiate stem cell characteristics in hepatocellular carcinoma and promote epithelial-mesenchymal transition through activation of Stat3/Snail signaling. Our findings propose Stat3/Snail pathway as a novel therapeutic target for the treatment of progression and metastasis of HCC with CSC-like signatures and epithelial-mesenchymal transition phenotype.

Our previous study showed that Octamer-binding transcription factor 4 (OCT4) expression was upregulated and significantly associated with histological grade through the analysis of OCT4 expression in 159 ovarian cancer tissue samples, and OCT4 mediated follicle-stimulating hormone (FSH)-induced anti-apoptosis in epithelial ovarian cancer. Nevertheless, whether OCT4 participates in FSH-induced invasion in ovarian cancer is still unknown. Therefore, the present study aimed to define whether FSH-induced ovarian cancer invasion is mediated by OCT4. In present study, we showed that FSH induced not only the epithelial-mesenchymal transition (EMT) and invasive phenotype but also the upregulation of OCT4 expression in a dose- and time-dependent manner in epithelial ovarian cancer cells. In addition, the expression of FSH receptor (FSHR) was upregulated by FSH induction, and knockdown of FSHR inhibited FSH-stimulated OCT4 expression. ERK1/2 signaling pathway participated in the enhanced expression of OCT4 and Snail induced by FSH. We further showed that the activated expression of Snail and N-cadherin, the suppressed expression of E-cadherin and the morphological change of the cells stimulated by FSH were blocked by OCT4-specific small interfering RNA. Moreover, our results showed that OCT4 mediated the increase in invasive capacity induced by FSH in ovarian cancer cells. Taken together, our work reveals that OCT4 is an essential mediator in FSH-induced EMT and invasion in epithelial ovarian cancer and may act as a potential therapeutic target.CI - Copyright (c) 2015 Elsevier Inc. All rights reserved.

Although the Oct4/Sox2 complex is crucial for maintaining the pluripotency of stem cells, the molecular basis underlying its regulation during lineage-specific differentiation remains unknown. Here, we revealed that the highly conserved Oct4/Lys-156 is important for maintaining the stability of the Oct4 protein and the intermolecular salt bridge between Oct4/Lys-151 and Sox2/Asp-107 that contributes to the Oct4/Sox2 interaction. Post-translational modifications at Lys-156 and K156N, a somatic mutation detected in bladder cancer patients, both impaired the Lys-151-Asp-107 salt bridge and the Oct4/Sox2 interaction. When produced as a recombinant protein or overexpressed in pluripotent stem cells, Oct4/K156N, with reduced binding to Sox2, significantly down-regulated the stemness genes that are cooperatively controlled by the Oct4/Sox2 complex and specifically up-regulated the mesendodermal genes and the SNAIL family genes that promote the epithelial-mesenchymal transition. Thus, we conclude that Oct4/Lys-156-modulated Oct4/Sox2 interaction coordinately controls the epithelial-mesenchymal transition and mesendoderm specification induced by specific differentiation signals.CI - (c) 2016 by The American Society for Biochemistry and Molecular Biology, Inc.