MicroRNA-200c attenuates tumour growth and metastasis of presumptive head and neck squamous cell carcinoma stem cells.

MicroRNA-200c (miR200c) is emerging as an important regulator of tumourigenicity and cancer metastasis with a strong capacity for inducing epithelial-mesenchymal transitions. However, the role of miR200c in head and neck squamous cell carcinoma (HNSCC) and HNSCC-associated cancer stem cells (HNSCC-CSCs) is unknown. In this study, the expression of miR200c in the regional metastatic lymph node of HNSCC tissues was significantly decreased, but BMI1 expression was increased as compared to parental tumours. Importantly, site-directed mutagenesis with a luciferase reporter assay showed that miR200c targeted the 3' UTR of BMI1 in HNSCC cells. Isolated HNSCC-derived ALDH1(+) /CD44(+) cells displayed CSC-like tumour initiating and radio-resistant properties. The expression levels of miR200c were significantly down-regulated while BMI1 was increased in HNSCC-ALDH1(+) /CD44(+) compared to the other subsets of HNSCC cells. Furthermore, increased miR200c expression or knockdown of BMI1 could significantly inhibit the malignant CSC-like properties of ALDH1(+) /CD44(+) cells. miR200c over-expression further down-regulated the expressions of ZEB1, Snail and N-cadherin, but up-regulated E-cadherin expression in ALDH1(+) /CD44(+) cells. Finally, a xenotransplantion study confirmed that over-expression of miR200c or BMI1 knockdown effectively inhibited the lung metastatic ability and prolonged the survival rate of ALDH1(+) /CD44(+) -transplanted mice. In summary, miR200c negatively modulates the expression of BMI1 but also significantly inhibits the metastatic capability of epithelial-mesenchymal transitions in malignant HNSCC by reducing the expression of BMI1/ZEB1. Restoration of miR200c in HNSCC and CSCs may be a promising therapeutic approach.