TAZ induces growth factor-independent proliferation through activation of EGFR ligand amphiregulin

The Hippo signaling pathway regulates cellular proliferation and survival, thus exerting profound effects on normal cell fate and tumorigenesis. We previously showed that the pivotal effector of this pathway, YAP, is amplified in tumors and promotes epithelial-to-mesenchymal transition (EMT) and malignant transformation. Here, we report that overexpression of TAZ, a paralog of YAP, in human mammary epithelial cells promotes EMT and, in particular, some invasive structures in 3D cultures. TAZ also leads to cell migration and anchorage-independent growth in soft agar. Furthermore, we identified amphiregulin (AREG), an epidermal growth factor receptor (EGFR) ligand, as a target of TAZ. We show that AREG functions in a non-cell-autonomous manner to mediate EGF-independent growth and malignant behavior of mammary epithelial cells. In addition, ablation of TEAD binding completely abolishes the TAZ-induced phenotype. Last, analysis of breast cancer patient samples reveals a positive correlation between TAZ and AREG in vivo. In summary, TAZ-dependent secretion of AREG indicates that activation of the EGFR signaling is an important non-cell-autonomous effector of the Hippo pathway, and TAZ as well as its targets may play significant roles in breast tumorigenesis and metastasis.     

TAZ induces growth factor-independent proliferation through activation of EGFR ligand amphiregulin

The Hippo signaling pathway regulates cellular proliferation and survival, thus exerting profound effects on normal cell fate and tumorigenesis. We previously showed that the pivotal effector of this pathway, YAP, is amplified in tumors and promotes epithelial-to-mesenchymal transition (EMT) and malignant transformation. Here, we report that overexpression of TAZ, a paralog of YAP, in human mammary epithelial cells promotes EMT and, in particular, some invasive structures in 3D cultures. TAZ also leads to cell migration and anchorage-independent growth in soft agar. Furthermore, we identified amphiregulin (AREG), an epidermal growth factor receptor (EGFR) ligand, as a target of TAZ. We show that AREG functions in a non-cell-autonomous manner to mediate EGF-independent growth and malignant behavior of mammary epithelial cells. In addition, ablation of TEAD binding completely abolishes the TAZ-induced phenotype. Last, analysis of breast cancer patient samples reveals a positive correlation between TAZ and AREG in vivo. In summary, TAZ-dependent secretion of AREG indicates that activation of the EGFR signaling is an important non-cell-autonomous effector of the Hippo pathway, and TAZ as well as its targets may play significant roles in breast tumorigenesis and metastasis.     

长非编码 RNA ILF3-AS1 通过调控 miR-130a-3p/PTEN轴抑制宫颈癌细胞的增殖

ILF3反义 RNA 1(ILF3 antisense RNA 1,ILF3-AS1)是一条定位于染色体 19p13.2的lncRNA,它是白介素增强子结合因子3(interleukin enhancer binding factor 3,ILF3)的反义 RNA.ILF3-AS1在多种肿瘤发生发展中发挥关键作用,但其...     

Tolfenamic acid negatively regulates YAP and TAZ expression in human cancer cells

Several diseases are associated with improper regulation of the Hippo pathway, which plays an important role in cell proliferation and cancer metastasis. Overactivation of the YAP and TAZ proteins accelerates cell proliferation, invasion, and migration during tumorigenesis. Tolfenamic acid (TA) is a non-steroidal anti-inflammatory drug (NSAID) that exhibits activity against various types of cancer. In this study, we observed that TA decreased YAP and TAZ protein levels in cancer cells. TA increased the phosphorylation of YAP and TAZ, leading to the degradation of YAP and TAZ in the cytoplasm and nucleus. TA predominantly affected multiple phosphodegron sites in the YAP and TAZ and lowered 14-3-3β protein expression, causing YAP and TAZ to enter the ubiquitination pathway. Proteins that affect YAP and TAZ regulation, such as NAG-1 and several YAP/TAZ E3 ligases, were not involved in TA-mediated YAP/TAZ degradation. In summary, our results indicate that TA affects phosphodegron sites on YAP/TAZ, demonstrating a novel effect of TA in tumorigenesis.     

A Cdc2-related protein kinase hPFTAIRE1 from human brain interacting with 14-3-3 proteins

hPFTAIRE1 （PFTK1）, a Cdc2-related protein kinase, is highly expressed in human brain. It exhibits cytoplasmic distribution in Hela cells, although it contains two nuclear localization signals （NLSs） in its N-terminus. To search for its substrates and regulatory components, we screened a two-hybrid library by using the full-length hPFTAIRE1 as a bait. Four 14-3-3 isoforms （β,ε,η,τ） were identified interacting with the hPFTAIRE1. We found a putative 14-3-3 binding consensus motif（RHSSPSS） in the hPFTAIRE 1, which overlapped with its second NLS. Deletion of the RHSSPSS motif or substitution of Ser^119 gwithAla in the conserved binding motif abolished the specific interaction between the hPFTAIRE 1 and the 14-3 -3 proteins. The mutant S 120A hPFTAIRE1 also showed a weak interaction to the 14-3-3 proteins. The results suggested that the Ser^119 is crucial for the interaction between hPFTAIREI and the 14-3-3 proteins. All the hPFTAIRE1 mutants distributed in cytoplasm of Hela cells and human neuroblastoma cells （SH-SY5Y） when fused to the C-terminus of a green fluorescent protein （GFP）, indicating that binding with the 14-3-3 proteins does not contribute to the subcellular localization of the hPFTAIRE1, although the binding may be involved in its signaling regulation.     

UHRF1 is regulated by miR-124-3p and promotes cell proliferation in intrahepatic cholangiocarcinoma

Ubiquitin-like with PHD and ring finger domains 1 (UHRF1) is abnormally overexpressed in multiple cancers and closely correlated with tumor-promoting effects, such as high proliferation. However, how UHRF1 functions in intrahepatic cholangiocarcinoma (ICC) has not yet been determined. Herein, we found that UHRF1 is overexpressed in ICC tissues. Downregulated UHRF1 attenuated the transition of the G1/S cell cycle and then suppressed cell proliferation in vitro and tumor growth in vivo. Moreover, upstream regulators of the UHRF1 expression were predicted, and we found that direct binding of miR-124-3p inhibited the UHRF1 expression. Elevated miR-124-3p suppressed proliferation and led to the arrest of the cell cycle. Furthermore, the expression of UHRF1 was positively correlated with PCNA. Clinically, we showed that elevated UHRF1 was associated with poor prognosis, and served as an independent prognostic factor in ICC patients. Together, these findings demonstrate that UHRF1, regulated by miR-124-3p, acts as a tumor promoter by promoting cell proliferation in ICC.     

Estrogen-responsive RING finger protein controls breast cancer growth

Most of the breast cancers initially respond to endocrine therapy that reduces the levels of estrogens or competes with estrogen for binding to its receptor. Most of the patients, however, acquire resistance to endocrine therapy with tamoxifen and aromatase inhibitors later. We assumed that identification of estrogen-responsive genes those regulate the growth of breast cancer is indispensable to develop new strategies targeting the genes and overcome the resistance to current endocrine therapy. Estrogen-responsive finger protein (Efp) is one of the estrogen receptor (ER)-target genes we have cloned using genomic binding site cloning. Efp features a structure of the RING-finger B-box coiled-coil (RBCC) motif. We postulated that Efp is a critical factor in proliferation of breast tumors. In a model system using MCF7 cells grown in xenografts, we showed that inhibition of Efp expression by antisense oligonucleotide reduced the tumor growth. MCF7 cells overexpressing Efp formed tumors in xenografts even in estrogen deprivation environment. By yeast two-hybrid screen, we identified that Efp interacts with 14-3-3σ, which is known as a cell cycle brake that causes G2 arrest and expressed in normal mammary glands. In vitro studies have revealed that Efp functions as a ubiquitin-protein ligase (E3) that targets 14-3-3σ. These data suggest that Efp controls breast cancer growth through ubiquitin-dependent proteolysis of 14-3-3σ. Future studies may provide a new therapy to block breast tumor proliferation by targeting Efp.     

LINC00052 functions as a tumor suppressor through negatively modulating miR-330-3p in pancreatic cancer

Pancreatic cancer is a serious solid malignant tumor worldwide. Increasing evidence has pointed out that abnormal expressions of long noncoding RNAs are involved in various tumors. Meanwhile, LINC00052 is reported as a famous tumor regulator in several cancers. Nevertheless, the biological role of LINC00052 in pancreatic cancer progression is still unknown. Our study was to explore the specific mechanism of LINC00052 in pancreatic cancer. First, we observed that the LINC00052 was obviously downregulated in several pancreatic cancer cell lines. Overexpression of LINC00052 greatly repressed AsPC-1 and SW1990 cell proliferation, triggered the apoptosis and prevented cell cycle in the G1 phase. For another, AsPC-1 and SW1990 cell migration and invasion capacity were also obviously repressed by LINC00052 upregulation. Moreover, miR-330-3p was elevated in pancreatic cancer cells and can function as a target of LINC00052 confirmed by luciferase reporter and RNA Immunoprecipitation (RIP) experiments. Inhibition of miR-330-3p could depress pancreatic cancer progression while overexpressed miR-330-3p exhibited an opposite process. Finally, our data indicated that the LINC00052 also remarkably suppressed pancreatic tumor growth via modulating miR-330-3p in vivo. To conclude, our study revealed that the LINC00052 might provide a new perspective for pancreatic cancer therapy.     

远端上游元件结合蛋白1的生物学功能

远端上游元件结合蛋白1（far upstream element binding protein 1, FUBP1）通过特异性结合远端上游元件（upstream element, FUSE）调控原癌基因c-Myc的转录。FUBP家族包括FUBP1、FUBP2、FUBP3及FUBP4,其序列具有高度同源性,但功能各不相同。FUBP1蛋白由3个结构域构成,具有两亲性螺旋结构的N端、富含酪氨酸的C端以及1个DNA结合区域。生理状态下,FUBP1蛋白定位于细胞核。除了调控c-Myc转录外,FUBP1还可结合RNA,参与调控mRNA稳定性、病毒复制及RNA的剪接。     

Phosphorylation-dependent C-terminal binding of 14-3-3 proteins promotes cell surface expression of HIV co-receptor GPR15

Membrane trafficking is dictated by dynamic molecular interactions involving discrete determinants in the cargo proteins and the intracellular transport machineries. We have previously reported that cell surface expression of GPR15, a G protein-coupled receptor (GPCR) that serves as a co-receptor for HIV, is correlated with the mode III binding of 14-3-3 proteins to the receptor C terminus. Here we provide a mechanistic basis for the role of 14-3-3 in promoting the cell surface expression of GPR15. The Ala mutation of penultimate phospho-Ser (S359A) that abolishes 14-3-3 binding resulted in substantially reduced O-glycosylation and the cell surface expression of GPR15. The surface membrane protein CD8 fused with the C-terminal tail of GPR15(S359A) mutant was re-localized in the endoplasmic reticulum (ER). In the context of S359A mutation, the additional mutations in the upstream stretch of basic residues (RXR motif) restored O-glycosylation and the cell surface expression. The RXR motif was responsible for the interaction with coatomer protein I (COPI), which was inversely correlated with the 14-3-3 binding and cell surface expression. These results suggest that 14-3-3 binding promotes cell surface expression of GPR15 by releasing the receptor from ER retrieval/retention pathway that is mediated by the interaction of RXR motif and COPI. Moreover, 14-3-3 binding substantially increased the stability of GPR15 protein. Thus 14-3-3 proteins play multiple roles in biogenesis and trafficking of an HIV co-receptor GPR15 to control its cell surface density in response to the phosphorylation signal.