TNF-α-induced miR-450a mediates TMEM182 expression to promote oral squamous cell carcinoma motility

Distant metastasis leads oral cancer patients into a poor survival rate and a high recurrence stage. During tumor progression, dysregulated microRNAs (miRNAs) have been reported to involve tumor initiation and modulate oral cancer malignancy. MiR-450a was significantly upregulated in oral squamous cell carcinoma (OSCC) patients without functional reports. This study was attempted to uncover the molecular mechanism of novel miR-450a in OSCC. Mir-450a expression was examined by quantitative RT-PCR, both in OSCC cell lines and patients. Specific target of miR-450a was determined by software prediction, luciferase reporter assay, and correlation with target protein expression. The functions of miR-450a and TMEM182 were accessed by adhesion and transwell invasion analyses. Determination of the expression and cellular localization of TMEM182 was examined by RT-PCR and by immunofluorescence staining. The signaling pathways involved in regulation of miR-450a were investigated using the kinase inhibitors. Overexpression of miR-450a in OSCC cells impaired cell adhesion ability and induced invasiveness, which demonstrated the functional role of miR-450a as an onco-miRNA. Interestingly, tumor necrosis factor alpha (TNF-α)-mediated expression of TMEM182 was regulated by miR-450a induction. MiR-450a-reduced cellular adhesion was abolished by TMEM182 restoration. Furthermore, the oncogenic activity of TNF-α/miR-450a/TMEM182 axis was primarily through activating extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. ERK1/2 inhibitor prevented the TNF-α-induced miR-450a expression and enhanced adhesion ability. Our data suggested that TNF-α-induced ERK1/2-dependent miR-450a against TMEM182 expression exerted a great influence on increasing OSCC motility. Overall, our results provide novel molecular insights into how TNF-α contributes to oral carcinogenesis through miR-450a that targets TMEM182.

Abstract 1475: miRNA-450a suppresses adhesion but promotes invasion through targeting of TMEM182 in oral squamous cell carcinoma

Our microRNA (miRNA) expression signatures of oral squamous cell carcinoma (OSCC) revealed that miR-450a was significantly increased in cancer tissues compared with normal epithelium. In this study, we focused on the functional significance of miR-450a in cancer cells and identification of miR-450a-regulated novel targets in OSCC. Overexpression of miR-450a in DOK and SAS cells showed significant inhibition of cell adhesion and induction of cell invasiveness, suggesting that miR-450a functions as an onco-miRNA. We performed genome-wide gene expression analysis to search for miR-450a-regulated molecular targets. Gene expression data and luciferase reporter assays revealed that TMEM182 was directly targeted by miR-450a. The miR-450a-reduced cellular adhesion was blocked by TMEM182 restoration, suggesting that miR-450a exhibits its oncogenic activity through negatively regulating TMEM182 level. Furthermore, miR-450a expression could be induced by the cytokine TNF-α primarily through activating extracellular signal-regulated kinase (ERK) signaling pathway. ERK inhibitor prevented the TNF-α-induced miR-450a expression and enhanced adhesion ability. Taken together, these data indicate that TNF-α/ERK-dependent expression of miR-450a plays an important role in mediating cellular adhesion and invasiveness, and scavenging miR-450a function using antagomir may have therapeutic potential for the treatment of OSCC. (The study was supported by the following grants: MOST 103-2320-B-006-036-MY3 and MOST 105-2325-B-400-001 from the Ministry of Science and Technology of Taiwan, ROC)

Citation Format: En-Wei Hsing, Shine-Gwo Shiah, Ching-Chuan Kuo, Jang-Yang Chang. miRNA-450a suppresses adhesion but promotes invasion through targeting of TMEM182 in oral squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1475. doi:10.1158/1538-7445.AM2017-1475

Protein phosphatase 4 is an essential positive regulator for Treg development, function, and protective gut immunity

BACKGROUND

Protein phosphates 4 (PP4), encoded by the ppp4c gene, is a ubiquitously expressed phosphatase that has been implicated in the regulation of cytokine signaling and lymphocyte survival; recent reports suggest that PP4 may be involved in pre-TCR signaling and B cell development. However, whether PP4 also modulates the functions of peripheral T cells has not been investigated due to the lack of a suitable in vivo model. Treg cells are a specialized subset of CD4 helper T cells that can suppress the proliferation of activated effector T cells. In the absence of this negative regulation, autoimmune syndromes and inflammatory diseases, such as human Crohn's disease, will arise.

RESULTS

In this report, we generated mice with T cell-specific ablation of the ppp4c gene (CD4cre:PP4(f/f)) and a Foxp3-GFP reporter gene to examine the roles of PP4 in Treg development and function. Characterizations of the CD4cre:PP4(f/f) mice showed that PP4 deficiency induced partial αβ T lymphopenia and T cell hypo-proliferation. Further analyses revealed significant reductions in the numbers of thymic and peripheral Treg cells, as well as in the efficiency of in vitro Treg polarization. In addition, PP4-deficient Treg cells exhibited reduced suppressor functions that were associated with decreased IL-10, CTLA4, GITR and CD103 expression. More interestingly, the CD4cre:PP4(f/f) mice developed spontaneous rectal prolapse and colitis with symptoms similar to human Crohn's disease. The pathogenesis of colitis required the presence of commensal bacteria, and was correlated with reduced Treg cells in the gut. Nevertheless, PP4-deficient Treg cells were still capable of suppressing experimental colitis, suggesting that multiple factors contributed to the onset of the spontaneous colitis.

CONCLUSIONS

While the molecular mechanisms remain to be investigated, our results clearly show that PP4 plays a non-redundant role for the differentiation, suppressor activity and gut homeostasis of Treg cells. The onset of spontaneous colitis in the CD4cre:PP4(f/f) mice further suggests that PP4 is essential for the maintenance of protective gut immunity. The CD4cre:PP4(f/f) mice thus may serve as a good model for studying the interactions between Treg cells and gut commensal bacteria for the regulation of mucosal immunity.

TBK1-associated protein in endolysosomes (TAPE)/CC2D1A is a key regulator linking RIG-I-like receptors to antiviral immunity

Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are key RNA viral sensors for triggering antiviral immunity. The underlying mechanisms for RLRs to trigger antiviral immunity have yet to be explored. Here we report the identification of TAPE (TBK1-associated protein in endolysosomes) as a novel regulator of the RLR pathways. TAPE functionally and physically interacts with RIG-I, MDA5, and IPS-1 to activate the IFN-β promoter. TAPE knockdown impairs IFN-β activation induced by RLRs but not IPS-1. TAPE-deficient cells are defective in cytokine production upon RLR ligand stimulation. During RNA virus infection, TAPE knockdown or deficiency diminishes cytokine production and antiviral responses. Our data demonstrate a critical role for TAPE in linking RLRs to antiviral immunity.

14-3-3σ regulates β-catenin-mediated mouse embryonic stem cell proliferation by sequestering GSK-3β

BACKGROUND

Pluripotent embryonic stem cells are considered to be an unlimited cell source for tissue regeneration and cell-based therapy. Investigating the molecular mechanism underlying the regulation of embryonic stem cell expansion is thus important. 14-3-3 proteins are implicated in controlling cell division, signaling transduction and survival by interacting with various regulatory proteins. However, the function of 14-3-3 in embryonic stem cell proliferation remains unclear.

METHODOLOGY AND PRINCIPAL FINDINGS

In this study, we show that all seven 14-3-3 isoforms were detected in mouse embryonic stem cells. Retinoid acid suppressed selectively the expression of 14-3-3σ isoform. Knockdown of 14-3-3σ with siRNA reduced embryonic stem cell proliferation, while only 14-3-3σ transfection increased cell growth and partially rescued retinoid acid-induced growth arrest. Since the growth-enhancing action of 14-3-3σ was abrogated by β-catenin knockdown, we investigated the influence of 14-3-3σ overexpression on β-catenin/GSK-3β. 14-3-3σ bound GSK-3β and increased GSK-3β phosphorylation in a PI-3K/Akt-dependent manner. It disrupted β-catenin binding by the multiprotein destruction complex. 14-3-3σ overexpression attenuated β-catenin phosphorylation and rescued the decline of β-catenin induced by retinoid acid. Furthermore, 14-3-3σ enhanced Wnt3a-induced β-catenin level and GSK-3β phosphorylation. DKK, an inhibitor of Wnt signaling, abolished Wnt3a-induced effect but did not interfere GSK-3β/14-3-3σ binding.

SIGNIFICANCE

Our findings show for the first time that 14-3-3σ plays an important role in regulating mouse embryonic stem cell proliferation by binding and sequestering phosphorylated GSK-3β and enhancing Wnt-signaled GSK-3β inactivation. 14-3-3σ is a novel target for embryonic stem cell expansion.

Defective regulatory T cells function and spontaneous colitis induced by protein phosphatase 4-deficiency (120.14)

Protein phosphatase 4 (PP4) is essential during early T cells development. To assess the function of PP4 in peripheral T cells, we generated conditional PP4 knockout mice with CD4-cre transgene (CD4cre-PP4f/f). In these mice a partial block of thymocyte development was manifested as a ~40-60% reduction of peripheral T cells. Further studies showed that PP4 deletion resulted in poor T cell proliferation, inefficient Treg polarization, decreased Treg cell number and reduced Treg suppression activity. In vivo, CD4cre-PP4f/f mice exhibited defective T-dependent antibody production. More interestingly, by 5-month old ~50% of the CD4cre-PP4f/f mice developed spontaneous colitis with wasting syndrome, and showed increased percentages of IFNgamma+, IL-6+, or IL-17A+-producing cells in intra-epithelial lymphocytes and lamina propria lymphocytes. When investigating the pathogenesis of colitis, we found that transferring PP4-deficient CD4+CD45RBhigh cells failed to induce colitis in RAG-/- recipients, whereas antibiotics treatment could reverse the wasting syndrome. Combined with the defects in Treg and antibody production, these results are consistent with the possibility that PP4 deficiency reduced the efficiency of mucosal immunity against commensal bacteria, causing uncontrolled gut inflammation that eventually develop into colitis. The spontaneous colitis in CD4cre-PP4f/f mice may thus serve as an unique model for studying the pathogenesis of human inflammatory bowel disease.

Rho kinases regulate the renewal and neural differentiation of embryonic stem cells in a cell plating density-dependent manner

Background

Rho kinases (ROCKs) mediate cell contraction, local adhesion, and cell motility, which are considered to be important in cell differentiation. We postulated that ROCKs are involved in controlling embryonic stem (ES) cell renewal and differentiation.

Methodology/Principal Findings

CCE, a murine ES cell, was treated with Y-27632 for 48 to 96 hours and colony formation was evaluated. Y-27632 blocked CCE colony formation and induced CCE to grow as individual cells, regardless of the initial seeding cell density either at 10⁴/cm² (“high” seeding density) or 2×10³/cm² (“low” density). However, at high seeding density, Y-27632–treated cells exhibited reduction of alkaline phosphatase (AP) staining and Oct3/4 expression. They expressed SOX-1, nestin, and MAP2c, but not βIII-tubulin or NG-2. They did not express endoderm or mesoderm lineage markers. After removal of Y-27632, the cells failed to form colonies or regain undifferentiated state. Silencing of ROCK-1 or ROCK-2 with selective small interference RNA induced CCE morphological changes similar to Y-27632. Silencing of ROCK-1 or ROCK-2 individually was sufficient to cause reduction of AP and Oct3/4, and expression of SOX-1, nestin, and MAP2c; and combined silencing of both ROCKs did not augment the effects exerted by individual ROCK siRNA. Y-27632–treated CCE cells seeded at 2×10³ or 6.6×10³ cells/cm² did not lose renewal factors or express differentiation markers. Furthermore, they were able to form AP-positive colonies after removal of Y-27632 and reseeding. Similar to ROCK inhibition by Y-27632, silencing of ROCK-1 or ROCK-2 in cells seeded at 2×10³/cm² did not change renewal factors.

Conclusions/Significance

We conclude that ROCKs promote ES cell colony formation, maintain them at undifferentiated state, and prevent them from neural differentiation at high seeding density. ROCK inhibition represents a new strategy for preparing large numbers of neural progenitor cells.