| Introduction: Barrett's esophagus is a squamous-to-columnar epithelial metaplasia caused by GERD. The molecular mechanisms underlying this metaplasia are not well understood. SOX2 is a putative regulator of ΔNp63 expression in squamous epithelial cells. Now, we explored whether SOX2 might regulate proliferation and esophageal expression of CK5 and CK14 through ΔNp63 in human esophageal squamous and in Barrett's columnar cells. Methods: Telomerase-immortalized Barrett's and esophageal squamous epithelial cell lines were evaluated by Western blot, qPCR, and ChIP following transfection with SOX2, ΔNp63, or TAp63-expressing plasmids, or with siRNAs targeting SOX2 or total p63. We evaluated effects of SOX2 and p63 expression on cell viability and proliferation by MTS and BrdU assays. Results: In both cell lines, overexpression of SOX2 or ΔNp63 significantly upregulated CK5 and CK14 expression; this was associated with increased proliferation in squamous cells, and decreased proliferation in Barrett's cells. ChIP demonstrated SOX2 binding to the ΔNp63 promoter, which increased following SOX2 overexpression. In addition, we found that ΔNp63 bound to a known p63 binding site on the CK5 and CK14 promoters, and this binding increased after SOX2 or ΔNp63 overexpression. Furthermore, esophageal squamous cells transfected with siRNA for SOX2 or for total p63 showed decreased CK5 and CK14 expression, and a significant decrease in cell growth. Conclusion: In both cells, SOX2 and ΔNp63 upregulate expression of squamous cytokeratins, supporting a role for SOX2 and ΔNp63 in esophageal squamous cell differentiation. We speculate that downregulation of SOX2 and ΔNp63 in the esophagus plays a role in Barrett's pathogenesis. |
