DUOX1 silencing in lung cancer promotes EMT, cancer stem cell characteristics and invasive properties

Abstract

Dual oxidase 1 (DUOX1) is an oxidant-generating enzyme within the airway epithelium that participates in innate airway host defense and epithelial homeostasis. Recent studies indicate that DUOX1 is suppressed in lung cancers by epigenetic silencing, although the importance of DUOX1 silencing in lung cancer development or progression is unknown. Here we show that loss of DUOX1 expression in a panel of lung cancer cell lines is strongly associated with loss of the epithelial marker E-cadherin. Moreover, RNAi-mediated DUOX1 silencing in lung epithelial cells and the cancer cell line NCI-H292 was found to result in loss of epithelial characteristics/molecular features (altered morphology, reduced barrier function and loss of E-cadherin) and increased mesenchymal features (increased migration, anchorage-independent growth and gain of vimentin/collagen), suggesting a direct contribution of DUOX1 silencing to epithelial-to-mesenchymal transition (EMT), an important feature of metastatic cancer. Conversely, overexpression of DUOX1 in A549 cells was capable of reversing EMT features. DUOX1 silencing in H292 cells also led to enhanced resistance to epidermal growth factor receptor tyrosine kinase inhibitors such as erlotinib, and enhanced levels of cancer stem cell (CSC) markers CD133 and ALDH1. Furthermore, acquired resistance of H292 cells to erlotinib resulted in enhanced EMT and CSC features, as well as loss of DUOX1. Finally, compared with control H292 cells, H292-shDUOX1 cells displayed enhanced invasive features in vitro and in vivo. Collectively, our findings indicate that DUOX1 silencing in lung epithelial cancer cells promotes features of EMT, and may be strongly associated with invasive and metastatic lung cancer.

Paradoxical roles of dual oxidases in cancer biology

“…Other subsequently developed DNMT inhibitors such as zebularine also displays similar cytotoxic side effects, thus limiting their use therapeutically[186]. As might be expected, DNMT inhibition was found to be capable of restoring expression of DUOX1 in lung cancer cells[52, 54, 111], and suggest that the beneficial actions of DNMT inhibition might be related to recovering DUOX1 activity. Importantly, DNA hypermethylation in cancer is not unique to DUOX genes, but is also observed in other NOX isoforms such as NOX5[47].…”

“…Conversely, DNA methylation is often suppressed in oncogenes and thereby permit their expression to promote cellular transformation[175, 176]. The intergenic promoter regions of DUOX1/DUOXA1 and DUOX2/DUOXA2 were found to be rich in CpG islands, and their hypermethylation in cancer results in reduced expression[52, 54, 111, 177], likely due to interference with binding of transcription factors such as Sp1 and Sp3[178, 179]. Therefore, DUOX1 has been considered to function as a tumor suppressor [52].…”

“…Indeed, our recent studies demonstrated that loss of DUOX1 in a panel lung cancer cell lines strongly corresponded to loss of the epithelial marker E-cadherin[54]. Subsequent studies showed that persistent silencing of DUOX1 using RNAi strategies, in normal epithelial cells or in the lung cancer cell line H292 (which maintains epithelial characteristics and expresses DUOX1), results in progressive loss of epithelial characteristics and acquisition of features representative of epithelial-to-mesenchymal transition (EMT)[54]. The process of EMT involves the loss of epithelial cell-cell contacts and epithelial molecular signatures (such as E-cadherin) and the gradual acquisition of a more motile, mesenchymal cell phenotype and expression of characteristic mesenchymal markers (e.g.…”

“…Moreover, as will be discussed in more detail in this review, some NOX homologs also appear to be downregulated in cancer cells, primarily due to epigenetic mechanisms [47]. This applies in particular to the dual oxidases DUOX1 and DUOX2, which are normally expressed in the thyroid and in epithelia of mucosal tissues[48–51], and are frequently suppressed in many epithelia-derived cancers[52–54], primarily through hypermethylation of its promoter[13, 52]. This review will first briefly discuss the known contributions of NOX enzymes to cancer biology and then focus specifically on the biological functions of the DUOX proteins in epithelial biology, and the functional implications of altered expression of DUOX1 and DUOX2 in various cancers.…”

Avaliação do efeito antiproliferativo da apocinina e diapocinina em células de osteossarcoma humano

“…Também foi demonstrado que a perda da expressão de Duox1 em células de câncer de pulmão está fortemente associada com a perda do marcador epitelial E-caderina e que o silenciamento do Duox1 promove a transição de célula epitelial para mesenquimal (EMT), uma importante característica do câncer metastático (LITTLE et al, 2016).…”