SOX2 and p63 colocalize at genetic loci in squamous cell carcinomas
Hideo Watanabe, … , Matthew Meyerson, Adam J. Bass
Hideo Watanabe, … , Matthew Meyerson, Adam J. Bass
Published March 3, 2014
Citation Information: J Clin Invest. 2014;124(4):1636-1645. https://doi.org/10.1172/JCI71545.
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Research Article Oncology

SOX2 and p63 colocalize at genetic loci in squamous cell carcinomas

Abstract

The transcription factor SOX2 is an essential regulator of pluripotent stem cells and promotes development and maintenance of squamous epithelia. We previously reported that SOX2 is an oncogene and subject to highly recurrent genomic amplification in squamous cell carcinomas (SCCs). Here, we have further characterized the function of SOX2 in SCC. Using ChIP-seq analysis, we compared SOX2-regulated gene profiles in multiple SCC cell lines to ES cell profiles and determined that SOX2 binds to distinct genomic loci in SCCs. In SCCs, SOX2 preferentially interacts with the transcription factor p63, as opposed to the transcription factor OCT4, which is the preferred SOX2 binding partner in ES cells. SOX2 and p63 exhibited overlapping genomic occupancy at a large number of loci in SCCs; however, coordinate binding of SOX2 and p63 was absent in ES cells. We further demonstrated that SOX2 and p63 jointly regulate gene expression, including the oncogene ETV4, which was essential for SOX2-amplified SCC cell survival. Together, these findings demonstrate that the action of SOX2 in SCC differs substantially from its role in pluripotency. The identification of the SCC-associated interaction between SOX2 and p63 will enable deeper characterization the downstream targets of this interaction in SCC and normal squamous epithelial physiology.

Authors

Hideo Watanabe, Qiuping Ma, Shouyong Peng, Guillaume Adelmant, Danielle Swain, Wenyu Song, Cameron Fox, Joshua M. Francis, Chandra Sekhar Pedamallu, David S. DeLuca, Angela N. Brooks, Su Wang, Jianwen Que, Anil K. Rustgi, Kwok-kin Wong, Keith L. Ligon, X. Shirley Liu, Jarrod A. Marto, Matthew Meyerson, Adam J. Bass

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Figure 2

Identification of SOX2 interacting proteins in SCCs.

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Identification of SOX2 interacting proteins in SCCs. (A) Strategy used t...
(A) Strategy used to identify binding partners of SOX2 in SCC. Stable expression of FLAG-HA-SOX2 in SCCs was achieved by retroviral transduction. Chromatin prepared from the nuclear fraction was solubilized using micrococcal nuclease digestion. SOX2 complexes were purified from solubilized chromatin by TAP and identified by LC-MS/MS (see Supplemental Table 1 for the complete list). The Venn diagram shows the number of proteins identified in each of the 3 SCC cell lines and highlights the subset of 45 SOX2 binding partners found across all 3 cell lines. Proteins in this common subset were further classified based on their association with regulators of stem cell pluripotency. Among the 26 SCC-specific SOX2 partners, 14 transcriptional regulators were identified. The number of peptides for each of those factors, and their relative abundance with each purification, is indicated for each cell line. (B) Expression of ectopic FLAG-HA-SOX2 and endogenous SOX2 in parental and FLAG-HA-SOX2–expressing TT cells, determined by immunofluorescence with anti-FLAG (green) and anti-SOX2 (red) antibodies, respectively. DAPI staining (nuclei; blue) and merged images are also shown. Original magnification, ×200.