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CUX1

Idiopathic pulmonary fibrosis (IPF) is a refractory and lethal interstitial lung disease characterized by alveolar epithelial cells apoptosis, fibroblast proliferation and extra-cellular matrix protein deposition. EBV, localised to alveolar epithelial cells of pulmonary fibrosis patients is associated with a poor prognosis. A strategy based on microarray-differential gene expression analysis to identify molecular drivers of EBV-associated lung fibrosis was utilized. Alveolar epithelial cells were infected with EBV to identify genes whose expression was altered following TGFbeta1-mediated lytic phase. EBV lytic reactivation by TGFbeta1 drives a selective alteration in CUX1 variant (a) (NCBI accession number NM_181552) expression, inducing activation of non-canonical Wnt pathway mediators, implicating it in epithelial mesenchymal transition (EMT), the molecular event underpinning scar production in tissue fibrosis. The role of EBV in EMT can be attenuated by antiviral strategies and inhibition of Wnt signaling by using All-Trans Retinoic Acids (ATRA). Activation of non-canonical Wnt signaling pathway by EBV in epithelial cells suggests a novel mechanism of EMT via CUX1 signaling. These data present a framework for further description of the link between infectious agents and fibrosis, a significant disease burden.

The epithelial mesenchymal transition (EMT) promotes tumor migration and invasion by downregulating epithelial markers such as E-cadherin and upregulating mesenchymal markers such as vimentin. Cathepsin L (Cat L) is a cysteine protease that can proteolytically activate CCAAT displacement protein/cut homeobox transcription factor (CUX1). We hypothesized that nuclear Cat L may promote EMT via CUX1 and that this could be antagonized with the Cat L-specific inhibitor Z-FY-CHO. mesenchymal prostate (ARCaP-M and ARCaP-E overexpressing Snail) and breast (MDA-MB-468, MDA-MB-231, and MCF-7 overexpressing Snail) cancer cells expressed lower E-cadherin activity, higher Snail, vimentin, and Cat L activity, and a p110/p90 active CUX1 form, compared to epithelial prostate (ARCaP-E and ARCaP-Neo) and breast (MCF-7 and MCF-7 Neo) cancer cells. There was increased binding of CUX1 to Snail and the E-cadherin promoter in mesenchymal cells compared to epithelial prostate and breast cells. Treatment of mesenchymal cells with the Cat L inhibitor Z-FY-CHO led to nuclear-to-cytoplasmic relocalization of Cat L, decreased binding of CUX1 to Snail and the E-cadherin promoter, reversed EMT, and decreased cell migration/invasion. Overall, our novel data suggest that a positive feedback loop between Snail-nuclear Cat L-CUX1 drives EMT, which can be antagonized by Z-FY-CHO. Therefore, Z-FY-CHO may be an important therapeutic tool to antagonize EMT and cancer progression.CI - Copyright (c) 2017 American Society for Microbiology.

The homeobox transcription factor CUTL1 has been associated with cellular proliferation and cell cycle progression, and CUTL1 functions as an oncogene. The aim of the present study was to investigate whether CUTL1 participates in epithelial-mesenchymal transition (EMT). The expression levels of CUTL1, E-cadherin, N-cadherin and Snail were determined by immunohistochemistry assay, immunofluorescence assay or real-time quantitative reverse transcription PCR. Their roles in non-small cell lung cancer (NSCLC) were assessed by functional analyses. Protein expression was detected by western blot analysis. The CUTL1 expression levels are higher in non-small cell lung cancer (NSCLC) tissues. High CUTL1 expression in NSCLC is associated with the mesenchymal-like phenotype. Mechanistically, CUTL1 upregulates transforming growth factor beta receptor I (TbetaR-I) expression, and the TbetaR-I inhibitor SB431542 abolishes EMT elicited by ectopic CUTL1 expression. Transforming growth factor beta (TGF-beta) signaling is essential for CUTL1-induced EMT in NSCLC cells. CUTL1 is downstream of TGF-beta signaling and CUTL1 is involved in the expression of the TbetaR-I. This study indicates that CUTL1 may be a potential target for anti-lung cancer therapy.

K-ras mutation is involved in cancer progression including invasion and migration, but the underlying mechanism is not yet clear. Cathepsin L is a lysosomal cysteine protease and has recently been associated with invasion and migration in human cancers when it is overexpressed. Our recent studies have shown that ionizing radiation (IR) enhanced expression of cathepsin L and increased invasion and migration of tumor cells, but the molecular mechanism is still unclear. In the present study, the effects of K-ras mutation and IR induced invasion and migration of lung cancer as well as the underlying mechanisms were investigated both in vitro and in vivo. Firstly, the levels of cathepsin L and epithelial mesenchymal transition (EMT) marker proteins remarkably changed in A549 (K-ras mutant) after irradiation compared with H1299 (K-ras wild), thereby promoting invasion and migration. Additionally, cathepsin L and its downstream transcription factor CUX1/p110 were increased after irradiation in A549 transfected with CUX1/p200, and the proteolytic processing of CUX1 by cathepsin L was remarkably increased after co-transfection of CUX1/p200 and cathepsin L-lentivirus in H1299. In addition, delivery of a mutant K-ras (V12) into HEK 293 cells stimulated EMT after irradiation due to the accumulation of cathepsin L. Moreover, mutated K-ras was associated with IR-induced cathepsin L and EMT in BALB/c nude mice. Finally, the level of cathepsin L expression was higher in samples carrying a K-ras mutation than in wild-type K-ras samples and the mesenchymal markers were upregulated in the samples of mutant K-ras, whereas the epithelial marker E-cadherin was downregulated in non-small cell lung cancers tissues. In conclusion, the findings demonstrated that mutated K-ras promotes cathepsin L expression and plays a pivotal role in EMT of human lung cancer. The regulatory effect of IR-induced cathepsin L on lung cancer invasion and migration was partially attributed to the Cathepsin L /CUX1-mediated EMT signaling pathway. This study will provide cathepsin L as a potential target for tumor therapy.CI - Copyright (c) 2017 Elsevier Inc. All rights reserved.