ATM-mediated stabilization of ZEB1 promotes DNA damage response and radioresistance through CHK1

Newberg

Proc. Natl. Acad. Sci. U.S.A.

et al. 2016

Epithelial-mesenchymal transition (EMT) is thought to contribute to metastasis and chemoresistance in patients with hepatocellular carcinoma (HCC), leading to their poor prognosis. The genes driving EMT in HCC are not yet fully understood, however. Here, we show that mobilization of Sleeping Beauty (SB) transposons in immortalized mouse hepatoblasts induces mesenchymal liver tumors on transplantation to nude mice. These tumors show significant down-regulation of epithelial markers, along with up-regulation of mesenchymal markers and EMT-related transcription factors (EMTTFs). Sequencing of transposon insertion sites from tumors identified 233 candidate cancer genes (CCGs) that were enriched for genes and cellular processes driving EMT. Subsequent trunk driver analysis identified 23 CCGs that are predicted to function early in tumorigenesis and whose mutation or alteration in patients with HCC is correlated with poor patient survival. Validation of the top trunk drivers identified in the screen, including MET (MET proto-oncogene, receptor tyrosine kinase), GRB2-associated binding protein 1 (GAB1), HECT, UBA, and WWE domain containing 1 (HUWE1), lysine-specific demethylase 6A (KDM6A), and protein-tyrosine phosphatase, nonreceptor-type 12 (PTPN12), showed that deregulation of these genes activates an EMT program in human HCC cells that enhances tumor cell migration. Finally, deregulation of these genes in human HCC was found to confer sorafenib resistance through apoptotic tolerance and reduced proliferation, consistent with recent studies showing that EMT contributes to the chemoresistance of tumor cells. Our unique cell-based transposon mutagenesis screen appears to be an excellent resource for discovering genes involved in EMT in human HCC and potentially for identifying new drug targets.H CC is the sixth most common cancer and the third-leading cause of cancer-related deaths worldwide (1). In the United States, the incidence of HCC is increasing, and overall 5-y survival is now <12%, despite recent progress in diagnostic and therapeutic modalities (2). This high mortality rate is related mainly to a high recurrence rate and associated intrahepatic or extrahepatic metastases (1). Patients with HCC who develop metastasis are no longer eligible for liver transplantation therapy and have very limited therapeutic options. Currently, sorafenib is the sole systemic antineoplastic agent for HCC described in the National Comprehensive Cancer Network (NCCN) guideline (3); however, its clinical benefit is limited (4), and alternative effective treatments are needed for these patients.Epithelial-mesenchymal transition (EMT) is a complex differentiation process whereby epithelial cells lose their identity and acquire mesenchymal characteristics (5). EMT is observed routinely in developmental processes, but is also believed to play an important role in the migration, invasion, and metastasis of various cancers (6-9). It also promotes the generation of cancer stem cells, thereby contributing to tumor recurrence and metastasis...

Section: Discussionmentioning

confidence: 99%

Transposon mutagenesis identifies genes and cellular processes driving epithelial-mesenchymal transition in hepatocellular carcinoma

Newberg

Proc. Natl. Acad. Sci. U.S.A.

et al. 2016

“…Phosphorylation at Ser 100 stabilize Snail as well as promote invasion and cancer metastasis, which is important for cell survival in response to ionizing irradiation [29,30]. The identification of ZEB1 as another ATM substrate for phosphorylation and the mechanism behind further confirmed the association between radioresistance and EMT process [31].…”

Section: Phosphorylation Of Snailmentioning

confidence: 51%

“…Taken together, with improved understanding of the regulatory mechanism behind PTMs-mediated EMT process, it would be worth to determine whether manipulation via HATs or kinases pathways help to control [31] cancer metastasis. More importantly, the molecular basis of tumor development requires to be comprehensively investigated owing to the opposite effects of PTMs on various cancer cells.…”

Section: Resultsmentioning

confidence: 99%

Post-translational modifications of EMT transcriptional factors in cancer metastasis

2016

Metastasis is an important reason for death of cancer patients which characterized as the formation of secondary cancers at distant sites. Epithelial– mesenchymal transition (EMT) is a dynamic process that appear to facilitate tumor metastasis in various cancers by switching epithelial cells into mesenchymal properties. Although previous investigation suggested a key role of EMT transcriptional factors in suppression of E-cadherin, the association of these factors with other cellular regulators in cancer metastasis need to be fully elucidated. Post-translational modifications (PTMs), such as acetylation and phosphorylation, have emerged as an important mechanism to modulate biological behavior of substrate proteins. In this review, we summarized protein modification and subsequent function changes of Snail, Twist and ZEB, as well as their influence on tumor progression. Acetylation of EMT transcriptional factors usually cause nuclear localization and/or protein stabilization thus contribute to E-cadherin repression. Besides, Twist and ZEB were phosphorylated by diverse kinases to promote metastasis in many cancers, while Snail was negatively regulated by phosphorylation to degradation. Then, the potential of therapy for metastasis by targeting PTMs-involved regulation of EMT transcriptional factors were discussed.

“…The group of Gomez-Casal et al (2013) observed EMT changes (decreased E-cadherin and increased N-cadherin and vimentin levels) and activation of Snail1, the major transcription factor involved in the EMT, in surviving irradiated NSCLC cells. In an another study, the up-regulation of ZEB1 has been suggested to play a key role in the accelerated DNA damage response and radioresistance of breast cancer cells (Zhang et al, 2014). According to our hypothesis a possible step of α-particles-induced lung cancer is an EMT transformation of the targeted epithelial cells.…”

Section: Discussionmentioning

confidence: 99%

“…The EMT hallmarks include loss of apicobasal orientation, decreased expression of adhesion molecules, matrix degradation and increased expression of mesenchymal markers (Lee and Nelson, 2012). There has been previously reported a connection between the EMT-inducing transcription factors twist, snail and zeb1 activation and the promotion of radioresistance in both non-small cell lung cancer (NSCLC) and breast cancer cells (Gomez-Casal et al, 2013;Zhang et al, 2014). Exposure of cells to IR is regarded as a sensitising factor for cells to undergo the TGF-β-induced EMT.…”

Section: Introductionmentioning

confidence: 99%

Lack of epithelial-to-mesenchymal transition induction in two bronchial epithelial cell lines after alpha and gamma irradiation

Acheva

Eklund

Lemola

et al. 2015

IJLR

Abstract:The induction of epithelial-to-mesenchymal transition (EMT) in human lung epithelial cell lines was investigated after α-particle and γ-radiation exposures. We applied TGF-β treatment of cells as positive EMT-controls and tested in parallel if radiation has a potentiating effect on the EMT induction. BEAS-2B and HBEC-3KT cells were irradiated with 5.4 MeV α-particles or γ-rays ( 60 Co, 1.13-1.15 Gy/min) with or without of TGF-β. The cells were harvested three days post treatment and the EMT markers vimentin, fibronectin and E-cadherin were analysed by immunofluorescence staining and Western blotting. The TGF-β treatment-induced EMT in both cell lines in the applied concentrations. We could not prove any clear EMT induction with low or moderate doses of α-particles and γ-rays. No significant additive effect with radiation and TGF-β was observed. We suggest that there might be a different mechanism induced by radiation in bronchial cells after radon and medical exposures that does not involve direct EMT changes.