BECN1 Is Involved in Spheroid Formation and Resistance to 5‐FU‐Induced Cytotoxicity in CD44^high Oral Cancer Cells

ABSTRACT Aim Beclin‐1 (BECN1) is an autophagy‐related protein, and its expression is related to prognosis of several human cancers. Whether autophagy is involved in the cancer stem cell character of oral cancer cells has not been clear. The objective of this study was to investigate the involvement of BECN1 in cancer stem cell characteristics in CD44 high oral cancer cells. Methods CD44 high oral cancer cells (OM‐1 cells) were cultured on laminin 332–coated silicone gel. The impact of BECN1 siRNA knockdown on spheroid formation and 5‐Fluorouracil (5‐FU)‐induced cell death was investigated. A lactate dehydrogenase cytotoxicity assay was performed to assess 5‐FU‐induced cell death. MicroRNAs (miRNAs) that target BECN1 were examined using Target Scan. Results CD44 high OM‐1 cells cultured on soft silicone gel exhibited a round cell body, indicating an amoeboid‐like cell phenotype. BECN1 knockdown inhibited mRNA expression of stem cell markers (i.e., BMI1 , OCT4 , KLF4 , CD44 , and ALDH1 ) and spheroid formation in CD44 high OM‐1 cells. Furthermore, BECN1 knockdown enhanced 5‐FU‐induced cell death. miR‐506‐3p was found to be a potential miRNA that regulates BECN1 expression. miR‐506‐3p overexpression significantly reduced BECN1 mRNA expression and enhanced 5‐FU‐induced cell death. Furthermore, BECN1 knockdown significantly enhanced miR‐506‐3p inhibitor–attenuated 5‐FU‐induced cell death. These results suggest that miR‐506‐3p is involved in the inhibition of chemotherapy resistance in CD44 high cells by attenuating BECN1 . Conclusions BECN1 is importantly involved in the maintenance of cancer stem cell characteristics in CD44 high oral cancer cells.