Abstract
The mechanism underlying increased concentrations of cancer stem cell (CSC)-associated factors in non-small cell lung cancer (NSCLC) cells treated with transforming growth factor β1 (TGFβ1) and tumor necrosis factor α (TNFα), is still not clear. The purpose of this study was to investigate the possible role of CD44 in the regulation of CSC-associated genes, by analyzing the effect of CD44 knockdown on their expression. A549, a NSCLC cell line that expresses CD44 antigen, was treated with TGFβ1 and TNFα. Small-interfering ribonucleic acid (siRNA) that specifically targets the CD44 gene was used to knockdown the expression of CD44 in A549. The gene expressions of CD44, CXCR4, POU5F1 (octamer-binding transcription factor 4 [Oct4]), PROM1, NANOG, c-Myc, KLF4, and SOX2, as well as of CDH1 (E-cadherin), CDH2 (N-cadherin), VIM (vimentin), and FN1 (fibronectin) were analyzed in A549 cells by quantitative reverse transcription polymerase chain reaction (RT-qPCR). Cell morphology was observed using light microscopy. After TGFβ1/TNFα treatment, increased expressions of CXCR4 and POU5F1 were detected. Silencing of CD44 gene expression was confirmed by RT-qPCR. The knockdown of CD44 decreased the CXCR4 and POU5F1 gene expressions in TGFβ1/TNFα-treated A549 cells. However, the silencing of CD44 did not affect the morphology of TGFβ1/TNFα-treated A549 cells nor it reversed epithelial-mesenchymal transition (EMT) gene signature induced by TGFβ1/TNFα in A549 cells. Our preliminary findings suggest that the CD44 gene may have a role in regulating CXCR4 and POU5F1 gene expressions, independently of the EMT signaling pathway.
Highlights
Cancer stem cells (CSCs) are a minor population of tumor cells that have the ability to self-renew
Our results showed upregulated expression of CXCR4 and POU5F1 in transforming growth factor β1 (TGFβ1)/tumor necrosis factor α (TNFα)-treated A549 cells (Figure 1), no increase was observed in the expression of CD133, NANOG, c-Myc, KLF4, and SOX2 genes
Knockdown of CD44 reduced the expression of CXCR4 and POU5F1 in TGFβ1/TNFα-treated A549 cells
Summary
Cancer stem cells (CSCs) are a minor population of tumor cells that have the ability to self-renew. Dysregulation of this stem cell self-renewal process is likely a basis for the development of cancer [1]. CSC markers have been reported in different cancer types, including CD44 [4,5,6], C-X-C chemokine receptor type 4 (CXCR4) [7], and octamer-binding transcription factor 4 (Oct4) [8]. CD44 was first reported as a CSC marker by Al-Hajj et al in 2003 [6], and since has been extensively investigated in cancers of various organs. In non-small cell lung cancer (NSCLC) it was reported that the cells expressing CD44 have stem cell-like characteristics [9]. We previously reported that the interaction between CD44 and its ligand hyaluronate in NSCLC cells in which CD44 was reintroduced
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