SOX2 expression is regulated by BRAF and contributes to poor patient prognosis in colorectal cancer

PLoS One. 2014 Jul 10;9(7):e101957. doi: 10.1371/journal.pone.0101957. eCollection 2014.

Abstract

Sporadic colorectal cancer (CRC) is a common malignancy and also one of the main causes of cancer deaths worldwide. Aberrant expression of the transcription factor SOX2 has recently been observed in several cancer types, but its role in CRC has not been fully elucidated. Here we studied the expression of SOX2 in 441 CRC patients by immunohistochemistry and related the expression to clinicopathological and molecular variables and patient prognosis. SOX2 was expressed in 11% of the tumors and was significantly associated to BRAFV600E mutation, but not to KRAS mutations (codon 12 and 13). SOX2 positivity was correlated to poor patient survival, especially in BRAFV600E mutated cases. In vitro studies showed that cells expressing the constitutively active BRAFV600E had increased SOX2 expression, a finding not found in cells expressing KRASG12V. Furthermore, blocking downstream BRAF signalling using a MEK-inhibitor resulted in a decreased expression of SOX2. Since SOX2 overexpression has been correlated to increased migration and invasion, we investigated the SOX2 expression in human CRC liver metastasis and found that a SOX2 positive primary CRC also had SOX2 expression in corresponding liver metastases. Finally we found that cells overexpressing SOX2 in vitro showed enhanced expression of FGFR1, which has been reported to correlate with liver metastasis in CRC. Our novel findings suggest that SOX2 expression is partly regulated by BRAF signalling, and an increased SOX2 expression may promote CRC metastasis and mediate a poor patient prognosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Cell Line, Tumor
  • Colorectal Neoplasms / diagnosis*
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / pathology
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Liver Neoplasms / secondary
  • Male
  • Middle Aged
  • Mutation
  • Neoplasm Grading
  • Neoplasm Staging
  • Prognosis
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / metabolism*
  • Receptor, Fibroblast Growth Factor, Type 1 / genetics
  • SOXB1 Transcription Factors / genetics*
  • Survival Analysis

Substances

  • SOXB1 Transcription Factors
  • Receptor, Fibroblast Growth Factor, Type 1
  • Proto-Oncogene Proteins B-raf

Grants and funding

This study was supported by grants from The Cancer Research Foundation in Northern Sweden, OE and Edla Johanssons foundation, Petrus and Augusta Hedlunds Foundation, Magn Bergvall Foundation, The Swedish Cancer Society, The Swedish Research Council and Umeå University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.