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Defining the role of ZEB1 in the pathogenesis of lung cancer

ABSTRACT: Using an in vitro model for malignant transformation of human bronchial epithelial cells (HBECs) we have found epithelial-to-mesenchymal transition (EMT) and expression of the EMT-transcription factor ZEB1 are early and critical events. Specifically, we found preexisting oncogenic mutations in TP53 and KRAS were required for HBECs to engage EMT machinery in response to microenvironmental (serum/TGFβ) or specific oncogenetic (MYC) EMT-inducing factors, which induce EMT through distinct TGFβ-dependent and vitamin D receptor (VDR)-dependent pathways, respectively, with both requiring ZEB1. Functional studies demonstrated ZEB1 causally promotes the malignant progression of HBECs and tumorigenicity of NSCLC and small cell lung cancer (SCLC) lines. Mechanistically ZEB1 directly represses ESRP1 leading to increased mesenchymal splicing of CD44, which drives a switch to CD44hi status and defines a highly transformed subpopulation. This was supported by finding ZEB1 is expressed in early-stage primary non-small cell lung cancers (NSCLC), as early as stage IB tumors, and its expression correlates with TNM stage. We conclude that: ZEB1-induced EMT and associated ESRP1 and CD44 molecular changes are important biomarkers for lung cancer pathogenesis; TGFβ and VDR are EMT chemoprevention targets; and as such, ZEB1 represents an important therapeutic target in NSCLC and SCLC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE77925 | GEO | 2016/08/31

SECONDARY ACCESSION(S): PRJNA312112

REPOSITORIES: GEO

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Project description:We have developed cdk4/hTERT-immortalized normal human bronchial epithelial cells (HBECs) to study lung cancer pathogenesis. By studying the oncogenic effect of common lung cancer alterations (p53, KRAS, and c-MYC) we demonstrate the ability of this model to characterize the stepwise transformation of bronchial epithelial cells to full malignancy. Using HBECs derived from multiple individuals we found: 1) the combination of five genetic alterations (p53, KRASV12, c-MYC, CDK4 and hTERT) is sufficient for full tumorigenic conversion of HBECs; 2) high levels of KRASV12 are required for full malignant transformation of HBECs, however these levels also stimulate oncogene-induced senescence; 3) RAS-induced senescence is largely bypassed with loss of p53 function; 4) over-expression of c-MYC greatly enhances malignancy but only in the context of sh-p53+KRASV12; 5) HBECs from different individuals vary in their sensitivity to transformation by these oncogenic manipulations; 6) serum-induced epithelial-to-mesenchymal transition (EMT) increases in vivo tumorigenicity; 7) genetically-identical clones of transformed HBECs exhibit pronounced differences in tumor growth, histology, and differentiation as well as sensitivity to standard platinum-based chemotherapies; and 8) an mRNA signature derived from tumorigenic and non-tumorigenic clones is predictive of outcome in lung cancer patients. Collectively, we demonstrate this HBEC model system can be used to study the effect of oncogenic mutations on malignant progression, oncogene-induced senescence, and EMT along with clinically translatable applications such as development of prognostic signatures and drug response phenotypes. Human bronchial epithelial cells (HBECs) immortalized with cdk4 and hTERT were transformed with p53 knockdown, KrasV12 and cMYC over-expression and profiled on Illumina HumanHT-12 V4.0 expression beadchips. Transformed HBECs were grown in two different growth media: KSFM (defined, serum-free medium) or R10 (RPMI with 10% FBS) as indicated. Clones were isolated from HBECs with sh-p53 + KrasV12 and sh-p53 + KrasV12 + cMYC.

Project description:Importance of growth factor (GF) signaling in cancer progression is widely acknowledged. Transforming growth factor beta (TGFβ) and and hepa- tocyte growth factor (HGF) are known to play a key role in epithelial-to- mesenchymal transition (EMT) and metastatic cell transformation that are characterized by distinctive alterations in cell mechanical architecture and behavior towards a more robust and motile single cell phenotype. How- ever, molecular mechanisms mediating cancer type specific enhancement of cell mechanical properties in response to growth factors remain unlighted. Here, we combine high-throughput mechanical cell phenotyping, microarray analysis and gene-silencing to dissect molecular mediators of GF-induces cell mechanical enhancement in non-small-cell lung adenocarcinoma (NSCLC). Our experimental results show that both growth factors elevate cell rigidity, size and migratory activity, however, effects of TGFβ stimulation on cell mechanical phenotype and differential gene expression turn out to be significantly stronger. Our microarray analysis reveals that TGFβ-treated NSCLC cells exhibit upregulation of migration-, adhesion-related and down- regulation of cytokinesis-related groups of genes. In addition to vimentin, a canonical marker of EMT, a large number of cytoskeletal and motor proteins including previously reported MYL9, MYLK, TMP1 but also less-known un- conventional myosins are overexpressed in lung adenocarcenoma cells upon treatment with TGFβ. Selective probing of gene-silenced cells lead to identi- fication of unconventional myosin MYH15 as a novel mediator of elevated cell rigidity and invasiveness in TGFβ-stimulated NSCLC cells. In comparison to TGFβ, HGF-treated NSCLC cells respond with upregulation of a relatively small number of genes that are related to actin cyskeleton, microtubules and caveolae. Our results provide insights into phenotypic effects and molecular mechanisms of TGFβ- and HGF-induced mesenchymal cell transformation in NSCLC, and suggest that mediators of cell mechanical enhancement such as unconventional cytoskeletal and motor proteins represent promising phar- maceutical targets for restraining invasive spread of lung cancer.

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Defining the role of ZEB1 in the pathogenesis of lung cancer

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