Lin28B/Let-7 Regulates Expression of Oct4 and Sox2 and Reprograms Oral Squamous Cell Carcinoma Cells to a Stem-like State.

Chian-Shiu Chien,Wen-Liang Lo,Pin-I Huang,Yi-Wei Chen,Yuh-Lih Chang,Yi-Yen Lee,Yuan-Tzu Lan,Wei-Hsiu Liu,Pen-Yuan Chu,Mong-Lien Wang,Cheng-Chia Yu,Shih-Hwa Chiou

doi:10.1158/0008-5472.can-14-2215

Abstract

Lin28, a key factor for cellular reprogramming and generation of induced pluripotent stem cell (iPSC), makes a critical contribution to tumorigenicity by suppressing Let-7. However, it is unclear whether Lin28 is involved in regulating cancer stem-like cells (CSC), including in oral squamous carcinoma cells (OSCC). In this study, we demonstrate a correlation between high levels of Lin28B, Oct4, and Sox2, and a high percentage of CD44(+)ALDH1(+) CSC in OSCC. Ectopic Lin28B expression in CD44(-)ALDH1(-)/OSCC cells was sufficient to enhance Oct4/Sox2 expression and CSC properties, whereas Let7 co-overexpression effectively reversed these phenomena. We identified ARID3B and HMGA2 as downstream effectors of Lin28B/Let7 signaling in regulating endogenous Oct4 and Sox2 expression. Let7 targeted the 3' untranslated region of ARID3B and HMGA2 and suppressed their expression, whereas ARID3B and HMGA2 increased the transcription of Oct4 and Sox2, respectively, through promoter binding. Chromatin immunoprecipitation assays revealed a direct association between ARID3B and a specific ARID3B-binding sequence in the Oct4 promoter. Notably, by modulating Oct4/Sox2 expression, the Lin28B-Let7 pathway not only regulated stemness properties in OSCC but also determined the efficiency by which normal human oral keratinocytes could be reprogrammed to iPSC. Clinically, a Lin28B(high)-Let7(low) expression pattern was highly correlated with high levels of ARID3B, HMGA2, OCT4, and SOX2 expression in OSCC specimens. Taken together, our results show how Lin28B/Let7 regulates key cancer stem-like properties in oral squamous cancers.

Highlights

Head and neck squamous cell carcinoma (HNSCC), including oral squamous cell carcinoma (OSCC), is the sixth most prevalent malignancy worldwide [1, 2]
Elevated Lin28B in high-grade and cancer stem–like cells (CSC)-like OSCC cells were correlated with increased Oct4, Sox2, and sphere formation
Because Oct4 and Sox2 mediate the Embryonic stem cell (ESC)/stemness-acquisition, we aimed to investigate the roles of Lin28B–Let7 signaling in cellular reprogramming in Normal human oral keratocyte (NHOK) primary cells [21] and OSCC cells using a reprogramming protocol as described in the Supplementary Data

Summary

Introduction

Head and neck squamous cell carcinoma (HNSCC), including oral squamous cell carcinoma (OSCC), is the sixth most prevalent malignancy worldwide [1, 2]. Recent reports showed that the Lin28–Let pathway plays a critical role in regulating the stemness, self-renewal, tumor initiation, and epithelial–mesenchymal transition–derived metastasis in malignant tumors and cancer stem–like cells We reported that the Lin28B–Let pathway positively regulates Oct and Sox expression, inducing a reprogramming-like phenomenon, switching non-CSCs to CSCs with tumor-initiating and self-renewal properties in oral CSC. We identified the AT-rich interaction domain molecule 3B (ARID3B) and HMGA2 as direct targets of Let, mediating Oct and Sox expression by direct regulation of Oct and Sox promoter activity, respectively These data suggested that the Lin28B–Let pathway serves as a driver mechanism to promote ESC-stemness properties through inducing a reprogramminglike mechanism in OSCC cells

Materials and Methods

Results

D2 length

Discussion

Disclosure of Potential Conflicts of Interest