TGF‐β1 induces amoeboid‐to‐mesenchymal transition of CD44 high oral squamous cell carcinoma cells via miR‐422a downregulation through ERK activation and Cofilin‐1 phosphorylation

Abstract Background The objective of this study was to clarify the molecular mechanism of amoeboid‐to‐mesenchymal transition (AMT) of CD44 high oral squamous cell carcinoma (OSCC) cells. Methods Morphology and expression of mesenchymal genes were investigated in CD44 high OSCC cells (CD44 high OM‐1 cells) cultured on laminin‐coated soft silicone gel. Additionally, microarray analysis was performed to investigate microRNA (miRNA) expression inhibited by transforming growth factor‐β1 (TGF‐β1) in CD44 high OM‐1 cells. Results When CD44 high OM‐1 cells were cultured on 2.0‐kPa laminin‐coated silicone gel, the cells exhibited an amoeboid‐like round morphology. Cofilin‐1 expression was found in the nucleus and cytoplasm of amoeboid‐like CD44 high OM‐1 cells. The invasive capacity was significantly reduced after Cofilin‐1 knockdown. Additionally, Cofilin‐1 knockdown cells had an irregularly extended shape. Phosphorylated Cofilin‐1 was significantly upregulated by TGF‐β1. Additionally, TGF‐β1 enhanced N‐cadherin and Snail mRNA expression and induced a spindle‐shaped morphology. ERK1/2 phosphorylation was induced by TGF‐β1. Microarray analysis revealed that miR‐422a exhibited the greatest downregulation (fold change: 0.22) in the presence of TGF‐β1. Importantly, TGF‐β1‐inhibited miR‐422a expression was recovered by the ERK inhibitor or ERK1/2 knockdown. Additionally, miR‐422a inhibitor‐transfected CD44 high OM‐1 cells exhibited high N‐cadherin and Snail mRNA expression. Furthermore, Cofilin‐1 knockdown and miR‐422a inhibition induced a spindle cell morphology. Conclusion Cofilin‐1 is involved in the invasive ability of CD44 high OSCC cells. TGF‐β1 contributes to AMT by downregulation of miR‐422a via ERK activation and Cofilin‐1 phosphorylation. Our findings suggest that miR‐422a and Cofilin‐1 play major roles in the maintenance of amoeboid‐like CD44 high cells.