Up-regulation of c-MYC and SIRT1 expression correlates with malignant transformation in the serrated route to colorectal cancer

Oncotarget. 2012 Oct;3(10):1182-93. doi: 10.18632/oncotarget.628.

Abstract

Approximately 7.5% of all colorectal cancers are considered to originate from the alternative, serrated route. Here, we investigate the expression of the c-MYC oncogene and the SIRT1 protein deacetylase by immunohistochemical staining in subgroups of colorectal serrated lesions that were characterized by different molecular alterations. The expression of c-MYC and SIRT1 correlated with the presence of KRAS and BRAF mutations and high expression of c-MYC and SIRT1 was strongly associated with higher grades of malignancy. In contrast, in the majority of serrated lesions without KRAS or BRAF mutations, c-MYC and SIRT1 expression was not found increased. In this group only a subset of mostly high grade intraepithelial neoplasia and carcinoma was characterized by elevated c-MYC and SIRT1 expression. This was associated with nuclear localization of beta-catenin, indicating that Wnt pathway activation may confer transcriptional induction of c-MYC. In summary, we established a link between oncogenic K-Ras and B-Raf, suggesting post-transcriptional regulation of c-MYC through MAPK/ERK1/2 pathway activation, as well as for Wnt signalling to the activation of the c-MYC oncogene, and consequently of SIRT1 in the serrated route. The increasing expressions with higher grades of malignancy suggest crucial functions for c-MYC and SIRT1 in the progression of serrated lesions to colorectal cancer. These functions may include antagonizing of apoptosis and senescence, which are characteristic features of serrated lesions.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoma / metabolism
  • Adenoma / pathology*
  • Adult
  • Aged
  • Aged, 80 and over
  • Cell Transformation, Neoplastic / metabolism
  • Cell Transformation, Neoplastic / pathology*
  • Colonic Polyps / metabolism
  • Colonic Polyps / pathology*
  • Colorectal Neoplasms / metabolism
  • Colorectal Neoplasms / pathology*
  • DNA, Neoplasm / genetics
  • Female
  • Humans
  • Immunoenzyme Techniques
  • Male
  • Middle Aged
  • Mutation / genetics
  • Neoplasm Grading
  • Neoplasm Invasiveness
  • Polymerase Chain Reaction
  • Precancerous Conditions / metabolism
  • Precancerous Conditions / pathology*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins c-myb / metabolism*
  • Proto-Oncogene Proteins p21(ras)
  • Sirtuin 1 / metabolism*
  • ras Proteins / genetics

Substances

  • DNA, Neoplasm
  • KRAS protein, human
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-myb
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • SIRT1 protein, human
  • Sirtuin 1
  • Proto-Oncogene Proteins p21(ras)
  • ras Proteins