Aibin Liu

Downregulation of miR-138 Sustains NF-κB Activation and Promotes Lipid Raft Formation in Esophageal Squamous Cell Carcinoma

Purpose: Constitutive activation of NF-κB signaling plays vital roles in esophageal squamous cell carcinoma (ESCC) progression. The aim of this study was to evaluate the effect of miR-138 on NF-κB activation and ESCC progression. Experimental Design: Expression of miR-138 in ESCC cell lines, ESCC tissues, and 205 archived ESSC specimens was determined using real-time PCR analysis. Anchorage-independent growth, chicken chorioallantoic membrane, Transwell matrix invasion and Annexin V–binding assays, and a xenograft tumor model were used to determine the role of miR-138 in ESCC progression. The effect of miR-138 on NF-κB activation was investigated using IKK in vitro kinase, electrophoretic mobility shift, lipid raft isolation, and luciferase reporter assays. Results: miR-138 was downregulated and inversely correlated with tumor progression and patient survival in ESCCs. Downregulation of miR-138 enhanced, whereas upregulation of miR-138 reduced, the aggressive phenotype of ESCC cells both in vitro and in vivo. Silencing miR-138 promoted K63-linked polyubiquitination of the NF-κB signaling intermediaries TRAF2 and RIP1 and sustained NF-κB activation. Furthermore, downregulation of miR-138 induced lipid raft formation via upregulating multiple components of lipid rafts, including FLOT1, FLOT2, and caveolin-1. Importantly, the in vitro analysis was consistent with a significant inverse correlation between miR-138 expression and NF-κB hyperactivation in a cohort of human ESCC specimens. Conclusion: Our results show that miR-138 functions as a tumor-suppressive miRNA and that downregulation of miR-138 contributes to constitutive NF-κB activation and ESCC progression. Clin Cancer Res; 19(5); 1083–93. ©2013 AACR.

TBL1XR1 promotes lymphangiogenesis and lymphatic metastasis in esophageal squamous cell carcinoma

Objective Transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) plays an important role in controlling the precisely regulated switch between gene repression and gene activation in transcriptional regulation. We investigated its biological function and clinical significance in esophageal squamous cell carcinoma (ESCC). Design Immunoblotting and immunochemistry were used to determine TBL1XR1 expression in ESCC cell lines, ESCC clinical tissues and 230 clinicopathologically characterised ESCC specimens. The role of TBL1XR1 in lymphangiogenesis and lymphatic metastasis was examined by tube formation, cell invasion and wound-healing assays in vitro, and by a popliteal lymph node metastasis model in vivo. The molecular mechanism by which TBL1XR1 upregulates vascular endothelial growth factor C (VEGF-C) expression was explored using real-time PCR, ELISA, luciferase reporter assay and chromatin immunoprecipitation. Results TBL1XR1 expression was significantly upregulated in ESCC, positively correlated with disease stage and patient survival, and identified as an independent prognostic factor for patient outcome. We found that TBL1XR1 overexpression promoted lymphangiogenesis and lymphatic metastasis in ESCC in vitro and in vivo, whereas TBL1XR1 silencing had the converse effect. We demonstrated that TBL1XR1 induced VEGF-C expression by binding to the VEGF-C promoter. We confirmed the correlation between TBL1XR1 and VEGF-C expression in a large cohort of clinical ESCC samples and through analysis of published datasets in gastric, colorectal and breast cancer. Conclusions Our results demonstrated that TBL1XR1 induced lymphangiogenesis and lymphatic metastasis in ESCC via upregulation of VEGF-C, and may represent a novel prognostic biomarker and therapeutic target for patients with ESCC.

Acylglycerol kinase promotes cell proliferation and tumorigenicity in breast cancer via suppression of the FOXO1 transcription factor

BackgroundAcylglycerol kinase (AGK) is reported to be overexpressed in multiple cancers. The clinical significance and biological role of AGK in breast cancer, however, remain to be established.MethodsAGK expression in breast cancer cell lines, paired patient tissues were determined using immunoblotting and Real-time PCR. 203 human breast cancer tissue samples were analyzed by immunochemistry (IHC) to investigate the relationship between AGK expression and the clinicopathological features of breast cancer. Functional assays, such as colony formation, anchorage-independent growth and BrdU assay, and a xenograft tumor model were used to determine the oncogenic role of AGK in human breast cancer progression. The effect of AGK on FOXO1 transactivity was further investigated using the luciferase reporter assays, and by detection of the FOXO1 downstream genes.ResultsHerein, we report that AGK was markedly overexpressed in breast cancer cells and clinical tissues. Immunohistochemical analysis showed that the expression of AGK significantly correlated with patients’ clinicopathologic characteristics, including clinical stage and tumor-nodule-metastasis (TNM) classification. Breast cancer patients with higher levels of AGK expression had shorter overall survival compared to patients with lower AGK levels. We gained valuable insights into the mechanism of AGK expression in breast cancer cells by demonstrating that overexpressing AGK significantly enhanced, whereas silencing endogenous AGK inhibited, the proliferation and tumorigenicity of breast cancer cells both in vitro and in vivo. Furthermore, overexpression of AGK enhanced G1-S phase transition in breast cancer cells, which was associated with activation of AKT, suppression of FOXO1 transactivity, downregulation of cyclin-dependent kinase inhibitors p21Cip1 and p27Kip1 and upregulation of the cell cycle regulator cyclin D1.ConclusionsTaken together, these findings provide new evidence that AGK plays an important role in promoting proliferation and tumorigenesis in human breast cancer and may serve as a novel prognostic biomarker and therapeutic target in this disease.

Nkx2-8 Downregulation Promotes Angiogenesis and Activates NF-κB in Esophageal Cancer

Angiogenesis is a major clinical feature of esophageal squamous cell carcinoma (ESCC), an aggressive disease of increasing incidence in developed countries. In ESCCs, the proangiogenic factor VEGF-C is an independent prognostic factor for ESCC, where understanding the mechanisms of VEGF-C upregulation may cue possible therapeutic insights. Here, we report that expression of the transcription factor Nkx2-8 is downregulated in ESCCs where it inversely correlates with progression and VEGF-C upregulation. Patients with ESCCs with lower Nkx2-8 expression exhibited reduced overall survival. Modulating expression of Nkx2-8 up or down inhibited or enhanced, respectively, proangiogenic activity in vitro and in vivo. Mechanistic investigations showed that Nkx2-8 repressed NF-κB activity by restraining nuclear localization of NF-κB p65 via downregulation of AKIP1, a NF-κB p65 binding partner, and also by directly targeting the AKIP1 promoter. We confirmed evidence for the importance of the Nkx2-8/AKIP1/NF-κB axis identified in ESCC cell models through an immunohistochemical analysis of a large cohort of human ESCC specimens. Taken together, our results showed that Nkx2-8 functions as a tumor suppressor in ESCCs, the downregulation of which contributes to NF-κB activation and ESCC angiogenesis.

miR-508 sustains phosphoinositide signalling and promotes aggressive phenotype of oesophageal squamous cell carcinoma.

The strength and duration of phosphoinositide signalling from phosphatidylinositol-3-kinase (PI3K) activation to Akt is tightly balanced by phosphoinositide kinases and phosphatases. However, how phosphatase-mediated negative regulatory effects are concomitantly disrupted in cancers, which commonly exhibit constitutively activated PI3K/Akt signalling, remains undefined. Here we report that miR-508 directly suppresses multiple phosphatases, including inositol polyphosphate-5-phosphatase J (INPP5J), phosphatase and tensin homologue (PTEN) and inositol polyphosphate 4-phosphatase type I (INPP4A), resulting in constitutive activation of PI3K/Akt signalling. Furthermore, we find that overexpressing miR-508 promotes, while silencing miR-508 impairs, the aggressive phenotype of oesophageal squamous cell carcinoma (ESCC) both in vitro and in vivo. Importantly, the level of miR-508 correlates with poor survival and activated PI3K/Akt signalling in a large cohort of ESCC specimens. These findings uncover a mechanism for constitutive PI3K/Akt activation in ESCC, and support a functionally and clinically relevant epigenetic mechanism in cancer progression.

Overexpression of AKIP1 promotes angiogenesis and lymphangiogenesis in human esophageal squamous cell carcinoma

A-kinase-interacting protein 1 (AKIP1) is found to be overexpressed in breast and prostate cancers, suggesting that AKIP1 might act as a potent oncogenic protein. However, the clinical significance and biological role of AKIP1 in cancer progression remain largely unknown. Herein, we report that AKIP1 is markedly overexpressed in esophageal squamous cell carcinoma (ESCC) cell lines and clinical ESCC samples. AKIP1 expression significantly correlates with ESCC progression and patients’ shorter survival time. Furthermore, we find that overexpressing AKIP1 induces, whereas silencing AKIP1 reduces, ESCC angiogenesis and lymphangiogenesis both in vitro and in vivo. Moreover, we demonstrate that AKIP1 transcriptionally upregulates vascular endothelial growth factor-C (VEGF-C) via interaction with its promoter through cooperation with multiple transcriptional factors, including SP1, AP2 and nuclear factor-κB (NF-κB). Importantly, significant correlation between levels of AKIP1 and VEGF-C is observed in a cohort of human ESCC, as well as in non-small cell lung cancer, hepatocellular carcinoma and ovarian cancer. Hence, these findings indicate an important role for AKIP1 in ESCC angiogenesis and lymphangiogenesis, and uncover a novel mechanism for the upregulation of VEGF-C in cancers.

miR-892b Silencing Activates NF-κB and Promotes Aggressiveness in Breast Cancer

The strength and duration of NF-κB signaling is tightly controlled at multiple levels under physiologic conditions, but the mechanism underlying constitutive activation of the NF-κB pathway in cancer remains unclear. In this study, we investigated miRNA-mediated regulation of the NF-κB cascade in breast cancer. We report that miR-892b expression was significantly downregulated in human breast cancer specimens and correlated with poor patient survival. Overexpression of miR-892b in breast cancer cells significantly decreased tumor growth, metastatic capacity, and the ability to induce angiogenesis, whereas miR-892b depletion enhanced these properties, in vitro and in vivo. Furthermore, we demonstrate that miR-892b attenuated NF-κB signaling by directly targeting and suppressing multiple mediators of NF-κB, including TRAF2, TAK1, and TAB3, and thus, miR-892b silencing in breast cancer cells sustains NF-κB activity. Moreover, miR-892b downregulation was attributed to aberrant hypermethylation of its promoter. Taken together, our results provide insight into a new mechanism by which NF-κB signaling becomes constitutively activated in breast cancer and suggest a tumor-suppressive role for miR-829b, prompting further investigation into miRNA mimics for cancer therapy.

MiR-1207 overexpression promotes cancer stem cell-like traits in ovarian cancer by activating the Wnt/β-catenin signaling pathway.

Wnt/β-catenin signaling pathway is strictly controlled by multiple negative regulators. However, how tumor cells override the negative regulatory effects to maintain constitutive activation of Wnt/β-catenin signaling, which is commonly observed in various cancers, remains puzzling. In current study, we reported that overexpression of miR-1207 in ovarian cancer activated Wnt/β-catenin signaling by directly targeting and suppressing secreted Frizzled-related protein 1 (SFRP1), AXIN2 and inhibitor of β-catenin and TCF-4 (ICAT), which are vital negative regulators of the Wnt/β-catenin pathway. We found that the expression of miR-1207 was ubiquitously upregulated in both ovarian cancer tissues and cells, which inversely correlated with patient overall survival. Furthermore, overexpression of miR-1207 enhanced, while silencing miR-1207 reduced, stem cell-like traits of ovarian cancer cells in vitro and in vivo, including tumor sphere formation capability and proportion of SP+ and CD133+ cells. Importantly, upregulating miR-1207 promoted, while silencing miR-1207 inhibited, the tumorigenicity of ovarian cancer cells. Hence, our results suggest that miR-1207 plays a vital role in promoting the cancer stem cell-like phenotype in ovarian cancer and might represent a potential target for anti-ovarian cancer therapy.

Antagonizing miR-455-3p inhibits chemoresistance and aggressiveness in esophageal squamous cell carcinoma

BackgroundThe plasticity of cancer stem cells (CSCs)/tumor-initiating cells (T-ICs) suggests that multiple CSC/T-IC subpopulations exist within a tumor and that multiple oncogenic pathways collaborate to maintain the CSC/T-IC state. Here, we aimed to identify potential therapeutic targets that concomitantly regulate multiple T-IC subpopulations and CSC/T-IC-associated pathways.MethodsA chemoresistant patient-derived xenograft (PDX) model of human esophageal squamous cell carcinoma (ESCC) was employed to identify microRNAs that contribute to ESCC aggressiveness. The oncogenic effects of microRNA-455-3p (miR-455-3p) on ESCC chemoresistance and tumorigenesis were examined by in vivo and in vitro chemoresistance, tumorsphere formation, side-population, and in vivo limiting dilution assays. The roles of miR-455-3p in activation of the Wnt/β-catenin and transforming growth factor-β (TGF-β)/Smad pathways were determined by luciferase and RNA immunoprecipitation assays.ResultsWe found that miR-455-3p played essential roles in ESCC chemoresistance and tumorigenesis. Treatment with a miR-455-3p antagomir dramatically chemosensitized ESCC cells and reduced the subpopulations of CD90+ and CD271+ T-ICs via deactivation of multiple stemness-associated pathways, including Wnt/β-catenin and TGF-β signaling. Importantly, miR-455-3p exhibited aberrant upregulation in various human cancer types, and was significantly associated with decreased overall survival of cancer patients.ConclusionsOur results demonstrate that miR-455-3p functions as an oncomiR in ESCC progression and may provide a potential therapeutic target to achieve better clinical outcomes in cancer patients.