102 research outputs found
Modeling WWOX Loss of Function in vivo: What Have We Learned?
The WW domain–containing oxidoreductase (WWOX) gene encompasses a common fragile sites (CFS) known as FRA16D, and is implicated in cancer. WWOX encodes a 46kDa adaptor protein, which contains two N-terminal WW–domains and a catalytic domain at its C–terminus homologous to short–chain dehydrogenase/reductase (SDR) family proteins. A high sequence conservation of WWOX orthologues from insects to rodents and ultimately humans suggest its significant role in physiology and homeostasis. Indeed, data obtained from several animal models including flies, fish, and rodents demonstrate WWOX in vivo requirement and that its deregulation results in severe pathological consequences including growth retardation, post–natal lethality, neuropathy, metabolic disorders, and tumorigenesis. Altogether, these findings set WWOX as an essential protein that is necessary to maintain normal cellular/physiological homeostasis. Here, we review and discuss lessons and outcomes learned from modeling loss of WWOX expression in vivo
The ubiquitin E3 ligase ITCH enhances breast tumor progression by inhibiting the Hippo tumor suppressor pathway
The Hippo kinase pathway is emerging as a conserved signaling pathway that is
essential for organ growth and tumorigenesis. Recently, we reported that the ubiquitin
E3 ligase ITCH negatively regulates LATS1, thereby increasing YAP activity, which
leads to increased cell proliferation and decreased apoptosis. Here, we investigated
the role of ITCH in breast tumorigenesis. In particular, we show that ITCH enhances
epithelial-to-mesenchymal transition (EMT) through boosting YAP oncogenic function.
By contrast, a point mutation in the catalytic domain or WW1 domain of ITCH abolished
its EMT-mediated effects. Furthermore, while overexpression of ITCH expression in
breast cells is associated with increased incidence of mammary tumor formation and
progression, its knockdown inhibited breast cancer cell tumorigenicity and metastasis.
Importantly, YAP knockdown was able to attenuate ITCH pro-tumorigenic functions.
Lastly, we found that ITCH expression is significantly upregulated in invasive and
metastatic breast cancer cases and is associated with worse survival. Together, our
results reveal that ITCH pro-tumorigenic functions in breast cancer are mediated, at
least in part, through inactivation of the Hippo tumor suppressor pathway.We would like to thank all the Aqeilan lab members
for fruitful discussion and technical help. This work
was supported by grant funds from the Israel Science
Foundation (ISF 12-0542) to R.I.A
MicroRNAs: New Players in Multiple Myeloma
MicroRNAs (miRNAs) are short non-coding RNAs that play critical roles in numerous cellular processes through post-transcriptional regulating functions. The aberrant role of miRNAs has been reported in a number of hematopoietic malignancies including multiple myeloma (MM). In this review we summarize the current knowledge on roles of miRNAs in the pathogenesis of MM
NEDD4 E3 ligase inhibits the activity of the Hippo pathway by targeting LATS1 for degradation
Proper regulation of cell proliferation, cell apoptosis, and cell death are vital for the development and survival of living
organisms. Failure or dysfunction of any of these processes can have devastating effects, including cancer. The Hippo
pathway, first discovered in Drosophila, has been found to be a major growth-regulatory signaling pathway that controls
these crucial processes and has been implicated in cell-progress regulation and organ size determination. Abnormal regulation
of this pathway has been found in several cancer types. However, the mechanisms that regulate the pathway and
its core members yet have to be elucidated. One of the main core components of this pathway is LATS1, a serine/threonine
kinase. Therefore, understanding how LATS1 activity is regulated is expected to shed light on new mechanisms that
regulate the Hippo pathway. In the current work, we identified several potential LATS1 regulators and proved that NEDD4
E3 ubiquitin ligase controls LATS1 stability. We demonstrate that NEDD4 directly interacts with LATS1, leading to ubiquitination
and decreased levels of LATS1 and, thus, increased YAP localization in the nucleus, which subsequently increases
the transcriptional activity of YAP. As such, we show that NEDD4 acts as an additional regulator of the Hippo pathway on
the protein level via interactions between WW domain-containing and PP xY motif-containing proteins. These findings
might be applied in the development of new therapeutic approaches through the activation of LATS1
Characterization of WWOX Inactivation in Murine Mammary Gland Development
The WW domain-containing oxidoreductase (WWOX) is commonly inactivated in multiple human cancers, including breast cancer. Wwox null mice die prematurely precluding adult tumor analysis. Nevertheless, aging Wwox-heterozygous mice at C3H genetic background develop higher incidence of mammary tumors. We recently generated a Wwox conditional knockout mouse in which loxp sites flank exon 1 in the Wwox allele and showed that total ablation of WWOX in these mice resembles that of conventional targeting of Wwox. Here, we report the characterization of WWOX ablation in mouse mammary gland using MMTV-Cre transgenic line. We demonstrated that WWOX ablation leads to impaired mammary ductal growth. Moreover, targeted deletion of WWOX is associated with increased levels of fibronectin, a component of the extracellular matrix. In addition, we showed that shRNA knockdown of WWOX in MCF10A breast epithelial cells dramatically increased fibronectin and is associated with enhanced cell survival and impaired growth in three-dimensional culture Matrigel assay. Taken together our results are consistent with a critical role for WWOX in normal breast development and tumorigenesis.Authors are grateful to Norma Qidees for technical help in
histology and for Sara Del-Mare, Mohammad Abu-Odeh, and
Ella Abaktekov for technical assistance. This work was
supported by the Israeli Science Foundation grant (ISF #08-
1331), EU-FP7 Marie Curie Re-integration grant to R.I.A. and
Israeli Cancer Research Funds (ICRF) to Z.S. and NIH R01
DK079217 from NIDDK
WWOX, the common fragile site FRA16D gene product, regulates ATM activation and the DNA damage response
Genomic instability is a hallmark of cancer. The WW domaincontaining
oxidoreductase (WWOX) is a tumor suppressor spanning
the common chromosomal fragile site FRA16D. Here, we report a
direct role ofWWOXin DNA damage response (DDR) and DNA repair.
We show that Wwox deficiency results in reduced activation of the
ataxia telangiectasia-mutated (ATM) checkpoint kinase, inefficient
induction and maintenance of γ-H2AX foci, and impaired DNA repair.
Mechanistically, we show that, upon DNA damage, WWOX accumulates
in the cell nucleus, where it interacts with ATM and enhances its
activation. Nuclear accumulation of WWOX is regulated by its K63-
linked ubiquitination at lysine residue 274, which is mediated by the
E3 ubiquitin ligase ITCH. These findings identify a novel role for the
tumor suppressor WWOX and show that loss of WWOX expression
may drive genomic instabilityWe thank Dr. Eugenio Gaudio and Dr. Sonja Matt for
technical help, Dr. Yossi Shiloh for the ataxia telangiectasia-mutated inhibitor,
and Dr. Kay Huebner for the rabbit polyclonal WW domaincontaining
oxidoreductase antibody. This study was supported by a German
Israeli Foundation Joint Grant (to T.G.H. and R.I.A.), Israeli Cancer Research
Funds (to Z.S. and R.I.A.), Deutsche Forschungsgemeinschaft Grant SFB1036
(to T.G.H.), and the Deutsche Krebshilfe (T.G.H.)
Common Fragile Site Tumor Suppressor Genes and Corresponding Mouse Models of Cancer
Chromosomal common fragile sites (CFSs) are specific mammalian genomic regions that show an increased frequency of gaps and breaks when cells are exposed to replication stress in vitro. CFSs are also consistently involved in chromosomal abnormalities in vivo related to cancer. Interestingly, several CFSs contain one or more tumor suppressor genes whose structure and function are often affected by chromosomal fragility. The two most active fragile sites in the human genome are FRA3B and FRA16D where the tumor suppressor genes FHIT and WWOX are located, respectively. The best approach to study tumorigenic effects of altered tumor suppressors located at CFSs in vivo is to generate mouse models in which these genes are inactivated. This paper summarizes our present knowledge on mouse models of cancer generated by knocking out tumor suppressors of CFS
MiR-16-1* and miR-16-2* possess strong tumor suppressive and anti-metastatic properties in osteosarcoma
Osteosarcoma (OS) is an aggressive malignancy affecting mostly children and adolescents. MicroRNAs (miRNAs) play important roles in OS development and progression. Here we found that miR-16-1* and miR-16-2* “passenger” strands as well as the “lead” miR-16 strand possess strong tumor suppressive functions in human OS. We report different although strongly overlapping functions for miR-16-1* and miR-16-2* in OS cells. Ectopic expression of these miRNAs affected primary tumor growth, metastasis seeding, and chemoresistance and invasiveness of human OS cells. Loss-of-function experiments verified tumor suppressive functions of these miRNAs at endogenous levels of expression. Using RNA immunoprecipitation (RIP) assays, we identify direct targets of miR-16-1* and miR-16-2* in OS cells. Furthermore, validation experiments identified FGFR2 as a direct target for miR-16-1* and miR-16-2*. Overall, our findings underscore the importance of passenger strand miRNAs in osteosarcomagenesis
RBM6 splicing factor promotes homologous recombination repair of double-strand breaks and modulates sensitivity to chemotherapeutic drugs
RNA-binding proteins regulate mRNA processing and translation and are often aberrantly expressed in cancer. The RNA-binding motif protein 6, RBM6, is a known alternative splicing factor that harbors tumor suppressor activity and is frequently mutated in human cancer. Here, we identify RBM6 as a novel regulator of homologous recombination (HR) repair of DNA double-strand breaks (DSBs). Mechanistically, we show that RBM6 regulates alternative splicing-coupled nonstop-decay of a positive HR regulator, Fe65/APBB1. RBM6 knockdown leads to a severe reduction in Fe65 protein levels and consequently impairs HR of DSBs. Accordingly, RBM6-deficient cancer cells are vulnerable to ATM and PARP inhibition and show remarkable sensitivity to cisplatin. Concordantly, cisplatin administration inhibits the growth of breast tumor devoid of RBM6 in mouse xenograft model. Furthermore, we observe that RBM6 protein is significantly lost in metastatic breast tumors compared with primary tumors, thus suggesting RBM6 as a potential therapeutic target of advanced breast cancer. Collectively, our results elucidate the link between the multifaceted roles of RBM6 in regulating alternative splicing and HR of DSBs that may contribute to tumorigenesis, and pave the way for new avenues of therapy for RBM6-deficient tumors
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