Effects of miR‐224‐5p‐enhanced downregulation of pannexin‐1 on docetaxel‐induced apoptosis in amoeboid‐like CD44<sup>high</sup> oral cancer cells
Sho Yokoyama, Hideo Shigeishi, Hiroshi Murodumi, Miyuki Sakuma, Shigehiro Ono, Kei Tobiume, Kouji Ohta, Masaaki Takechi
Abstract
Abstract We previously found that microRNAs play major roles in the maintenance of amoeboid‐like oral squamous cell carcinoma (OSCC) cells with high expression of CD44 (CD44 high ). However, the roles of microRNAs in chemotherapeutic resistance exhibited by CD44 high amoeboid‐like OSCC cells are unclear. Here, docetaxel‐induced apoptosis was examined in CD44 high OSCC cells (CD44 high OM‐1 cells) cultured on laminin‐coated silicone gel. Amoeboid‐like CD44 high OSCC cells exhibited robust resistance to docetaxel‐induced apoptosis and significant upregulation of miR‐224‐5p expression compared with epithelial‐like CD44 high OSCC cells and mesenchymal‐like CD44 high OSCC cells. The expression of pannexin‐1 (PANX1), a channel‐forming protein that regulates the release of ATP, was significantly upregulated following transfection of amoeboid‐like CD44 high OSCC cells with an miR‐224‐5p inhibitor. These results suggest that miR‐224‐5p inhibits PANX1 expression. Furthermore, miR‐224‐5p inhibitor‐transfected amoeboid‐like CD44 high OSCC cells exhibited significant enhancement of the proportion of apoptotic cells; however, this effect was significantly inhibited by knockdown of PANX1 with PANX1 small interfering RNA. Additionally, the miR‐224‐5p inhibitor‐enhanced extracellular ATP levels were significantly reduced by PANX1 knockdown. These findings imply that miR‐224‐5p plays a vital role in the resistance to docetaxel‐induced apoptosis by attenuating PANX1‐induced ATP discharge. Moreover, amoeboid‐like CD44 high OSCC cells may be involved in chemotherapeutic resistance of OSCC.