Patients with oral squamous cell carcinoma (OSCC) generally have an elevated expression of homeobox C6 (HOXC6) gene. We found that HOXC6 was the significantly upregulated gene in hypopharyngeal squamous cell carcinoma (FaDu) cells using RNA-seq analysis. However, it remains unclear whether HOXC6 plays a role in tumor process mechanism. Our study aimed to explore the potential oncogenic role and the detailed molecular mechanism of HOXC6 in FaDu cells. In this study, Sirt1 was validated to be overexpressed in FaDu cells and associated with HOXC6 expression. Overexpression of HOXC6 promoted the cell colony formation, whereas inhibition of Sirt1 by Sirt1 inhibitor EX527 reduced cell proliferation/colony formation and migration, and induced apoptosis in HOXC6 overexpressed FaDu cells. Interestingly, mechanistic study showed that EX527 mediated Sirt1 suppression led to decreased HOXC6 expression and upregulation of Sirt1 significantly increased the expression of HOXC6. HOXC6 was shown to cooperate with Sirt1 to enhance cell survival. We propose that HOXC6 promotes cell growth/colony formation, and that the HOXC6 may be a progression of hypopharyngeal carcinoma by activating Sirt1 pathways.

Abstract
Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHOD
    1. Cell culture and Reagent
    2. Bioinformatics Analysis
    3. Microarray data and Analysis
    4. Construction of the pGL3-Sirt1 Promoter
    5. Luciferase Reporter Assay
    6. Transfection of the pcDNA4-HOXC6 andpCMV5-Sirt1 Plasmid
    7. Western Blotting Analysis
    8. Reverse transcription quantitative PCR(RT-qPCR) analysis
    9. Cell proliferation assay
    10. Wound-healing assay
    11. Cell apoptosis assay
    12. Colony formation
    13. Statistical analysis
Ⅲ. RESULT
    1. HOXC6 up-regulated in Heck and NeckSquamous cell carcinoma
    2. Up-regulation of HOXC6 induces Sirt1expression through transcription regulation
    3. Sirt1 inhibitor EX527 suppress invasion andproliferation of oral cancer cell lines
    4. EX527 inhibits HOXC6-induced cell growthand proliferation
    5. Sirt1 Positively regulates HOXC6 Expression
Ⅳ. DISCUSSION
ACKNOWLEDGMENT
REFERENCES

• 원옥튀띠엔(조선대학교 치과대학 병리학교실) | Tien Nguyen Ngoc Thuy (Department of Pathology, School of Dentistry, Chosun University)
• 정연수(조선대학교 치과대학 병리학교실) | Yun-Soo Jeong (Department of Pathology, School of Dentistry, Chosun University)
• 응웬 칸 톤(조선대학교 치과대학 병리학교실) | Nguyen Khanh Toan (Department of Pathology, School of Dentistry, Chosun University)
• 안상건(조선대학교 치과대학 병리학교실) | Sang-Gun Ahn (Department of Pathology, School of Dentistry, Chosun University) Corresponding Author