Search

Ovarian cancer (OC) is the fifth most common cancer of female cancer death and leading cause of lethal gynecological cancers. High‐grade serous ovarian carcinoma (HGSOC) is an aggressive malignancy that is rapidly fatal. Many cases of OC show amplification of the 8q24 chromosomal region, which contains the well‐known oncogene MYC. Although MYC amplification is more frequently observed in OCs than in other tumor types, due to the large size of the 8q24 amplicon, the functions of the vast majority of the genes it contains are still unknown. The TIGD5 gene is located at 8q24.3 and encodes a nuclear protein with a DNA‐binding motif, but its precise role is obscure. We show here that TIGD5 often co‐amplifies with MYC in OCs, and that OC patients with high TIGD5 mRNA expression have a poor prognosis. However, we also found that TIGD5 overexpression in ovarian cancer cell lines unexpectedly suppressed their growth, adhesion, and invasion in vitro, and also reduced tumor growth in xenografted nude mice in vivo. Thus, our work suggests that TIGD5 may in fact operate as a tumor suppressor in OCs rather than as an oncogene. [ABSTRACT FROM AUTHOR]

Bladder cancer (BlC) is the fourth most common cancer in males worldwide, but few systemic chemotherapy options for its effective treatment exist. The development of new molecularly‐targeted agents against BlC is therefore an urgent issue. The Hippo signaling pathway, with its upstream LATS kinases and downstream transcriptional co‐activators YAP1 and TAZ, plays a pivotal role in diverse cell functions, including cell proliferation. Recent studies have shown that overexpression of YAP1 occurs in advanced BlCs and is associated with poor patient prognosis. Accessing data from our previous screening of a chemical library of compounds targeting the Hippo pathway, we identified DMPCA (N‐(3,4‐dimethoxyphenethyl)‐6‐methyl‐2,3,4,9‐tetrahydro‐1H‐carbazol‐1‐amine) as an agent able to induce the phosphorylation of LATS1 and YAP1/TAZ in BlC cells, thereby suppressing their viability both in vitro and in mouse xenografts. Our data indicate that DMPCA has a potent anti‐tumor effect, and raise the possibility that this agent may represent a new and effective therapeutic option for BlC. [ABSTRACT FROM AUTHOR]

There are currently no treatments for salivary gland diseases, making it vital to understand signaling mechanisms operating in acinar and ductal cells so as to develop regenerative therapies. To date, little work has focused on elucidating the signaling cascades controlling the differentiation of these cell types in adult mammals. To analyze the function of the Hippo‐TAZ/YAP1 pathway in adult mouse salivary glands, we generated adMOB1DKO mice in which both MOB1A and MOB1B were TAM‐inducibly deleted when the animals were adults. Three weeks after TAM treatment, adMOB1DKO mice exhibited smaller submandibular glands (SMGs) than controls with a decreased number of acinar cells and an increased number of immature dysplastic ductal cells. The mutants suffered from reduced saliva production accompanied by mild inflammatory cell infiltration and fibrosis in SMGs, similar to the Sjogren's syndrome. MOB1‐deficient acinar cells showed normal proliferation and apoptosis but decreased differentiation, leading to an increase in acinar/ductal bilineage progenitor cells. These changes were TAZ‐dependent but YAP1‐independent. Biochemically, MOB1‐deficient salivary epithelial cells showed activation of the TAZ/YAP1 and β‐catenin in ductal cells, but reduced SOX2 and SOX10 expression in acinar cells. Thus, Hippo‐TAZ signaling is critical for proper ductal and acinar cell differentiation and function in adult mice. [ABSTRACT FROM AUTHOR]

Cell competition is a biological process by which unfit cells are eliminated from "cell society." We previously showed that cultured mammalian epithelial Madin‐Darby canine kidney (MDCK) cells expressing constitutively active YAP were eliminated by apical extrusion when surrounded by "normal" MDCK cells. However, the molecular mechanism underlying the elimination of active YAP‐expressing cells was unknown. Here, we used high‐throughput chemical compound screening to identify cyclooxygenase‐2 (COX‐2) as a key molecule triggering cell competition. Our work shows that COX‐2‐mediated PGE2 secretion engages its receptor EP2 on abnormal and nearby normal cells. This engagement of EP2 triggers downstream signaling via an adenylyl cyclase‐cyclic AMP‐PKA pathway that, in the presence of active YAP, induces E‐cadherin internalization leading to apical extrusion. Thus, COX‐2‐induced PGE2 appears a warning signal to both abnormal and surrounding normal cells to drive cell competition. [ABSTRACT FROM AUTHOR]

Mammalian STE20‐like protein kinase 1/2 (MST1/2) and nuclear Dbf2‐related kinase 1/2 (NDR1/2) are core components of Hippo signaling that are also known to be important regulators of lymphocyte trafficking. However, little is understood about the roles of other Hippo pathway molecules in these cells. Here, we present the first analysis of the function of Mps one binder kinase activator‐1 (MOB1) in T lymphocytes in vivo. T‐cell‐specific double knockout (DKO) of MOB1A/B in mice [tMob1 DKO mice] reduces the number of naïve T cells in both the circulation and secondary lymphoid organs, but leads to an accumulation of CD4+CD8− and CD4−CD8+ single‐positive (SP) cells in the thymus. In vitro, naïve MOB1A/B‐deficient T cells show increased apoptosis and display impaired trafficking capacity in response to the chemokine CCL19. These defects are linked to suppression of the activation of MST and NDR kinases, but are independent of the downstream transcriptional co‐activator Yes‐associated protein 1 (YAP1). Thus, MOB1 proteins play an important role in thymic egress and T‐cell survival that is mediated by a pathway other than conventional Hippo‐YAP1 signaling. [ABSTRACT FROM AUTHOR]

FEAT, the protein encoded by methyltransferase‐like 13 (METTL13), is aberrantly upregulated in most human cancers and potently drives tumorigenesis in vivo; however, its role in normal tissues remains elusive. Immunoblotting has displayed weak FEAT expression in normal human tissues, including the testis. Here, we found that FEAT is expressed in fetal and adult Leydig cells in the testis. FEAT knockdown using siRNA increased primary cilia formation in MA‐10 Leydig tumor cells, accompanied by enhanced 5′ adenosine monophosphate‐activated protein kinase (AMPK) activation. Immunofluorescence analyses of FEAT‐silenced MA‐10 cells showed diminished insulin‐like factor 3 (INSL3) expression. A male Mettl13+/− mouse developed bilateral intraabdominal cryptorchidism, suggesting defective INSL3 production by fetal Leydig cells. Leydig cells from the mouse showed markedly decreased INSL3 protein by immunohistochemistry. Together, these results suggest that FEAT facilitates the INSL3 production in testicular Leydig cells that is essential for transabdominal testis migration. FEAT (METTL13) is expressed in fetal and adult Leydig cells in the testis. FEAT‐silenced MA‐10 Leydig cells showed diminished INSL3 protein. A male Mettl13+/− mouse exhibited bilateral intraabdominal cryptorchidism and markedly decreased INSL3 expression in Leydig cells. [ABSTRACT FROM AUTHOR]

The Hippo signaling pathway is a vital suppressor of tumorigenesis that is often inactivated in human cancers. In normal cells, the Hippo pathway is triggered by external forces such as cell crowding, or changes to the extracellular matrix or cell polarity. Once activated, Hippo signaling down-regulates transcription supported by the paralogous cofactors YAP1 and TAZ. The Hippo pathway's functions in normal and cancer biology have been dissected by studies of mutant mice with null or conditional tissue-specific mutations of Hippo signaling elements. In this review, we attempt to systematically summarize results that have been gleaned from detailed in vivo characterizations of these mutants. Our goal is to describe the physiological roles of Hippo signaling in several normal organ systems, as well as to emphasize how disruption of the Hippo pathway, and particularly hyperactivation of YAP1/ TAZ, can be oncogenic. [ABSTRACT FROM AUTHOR]