The mRNA expression of FaDu-Ctrl, FaDu-ARID3B cells

Microarray analyses for the identification of differences in gene expression patterns have increased our understanding of the molecular mechanism of ARID3B in HNSCC.We used gene expression analysis data from FaDu-ARID3B and FaDu-pCDH to identify differentially expressed probes. The expression of the embryonic stem cell (ESC) signature in cancer cells indicates the coordinated regulation of the stemness genes in cancer stem cells, which are responsible for cancer initiation and dissemination. let-7 family microRNAs are crucial regulators for stem cell differentiation. In cancer cells, let-7 suppresses cancer stemness through targeting different oncogenes such as c-Myc, RAS, and HMGA2. However, most let-7 target genes are oncogenes rather than stemness factors, and the mechanism of let-7-repressed stemness is unclear. Here we demonstrate that let-7 supresses the formation of AT-rich interacting domain 3B (ARID3B) complex through targeting the expression of ARID3B, the interacting partner ARID3A, and importin 9. ARID3B complex recruits histone demethylase 4C (KDM4C) to the regulatory region of stemness genes for reducing histone 3 lysine 9 trimethylation, resulting in an open configuration of the chromatin of stemness genes. In cancer tissues, ARID3B expression correlates with the nuclear ARID3A expression and a worse prognosis. This result highlights the role of let-7 in regulating stemness through histone modifications. The plasmids pCMVΔR8.9, pDVsVg (from the National RNAi Core Facility, Taiwan) and expression lentivectors (pCDH-GFP, pCDH-ARID3B) were co-transfected into 293T cells for virus packaging. The virus-containing supernatant was collected at 48 and 72 hours after transfection. While virus transduction, FaDu cells were infected with 10-fold virus concentrates supplemented with 8 μg/ml polybrene. pCDH-GFP as vector control.