Raf-1 kinase, epidermal growth factor receptors, and mutant Ras proteins in colonic carcinomas

Dig Dis Sci. 1996 Jun;41(6):1069-75. doi: 10.1007/BF02088221.


Epidermal growth factor receptors (EGFR) and ras mutations are known to play a significant role in controlling cell growth and tumor promotion. Both of them transmit mitogenic signals to the nucleus by activation of Raf-1 kinase. In this study, the expression of EGFR and mutant Ras proteins, and, for the first time, the expression, phosphorylation and kinase activity of Raf-1 kinase have been determined in paired samples of colorectal cancer and mucosa. The tumor and mucosa samples did not differ significantly with regard to Raf-1 kinase content and activity. A major difference between tumors and mucosa was found, however, in the phosphorylation of Raf-1. Most of the mucosa samples (13/20), but only 1/20 of the cancer samples, contained hyperphosphorylated Raf-1. EGFR were significantly (p = 0.0025) decreased in the tumors. The decreased phosphorylation of Raf-1 in colonic carcinomas could be the result of activation of Raf-1 phosphatases or inactivation of kinases phosphorylating Raf-1. New forms of treatment based on EGFR overexpression do not seem to be suitable for the majority of colonic cancers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / metabolism*
  • Aged
  • Aged, 80 and over
  • Blotting, Western
  • Colorectal Neoplasms / metabolism*
  • Enzyme-Linked Immunosorbent Assay
  • ErbB Receptors / analysis*
  • Female
  • Humans
  • Intestinal Mucosa / metabolism
  • Male
  • Middle Aged
  • Phosphorylation
  • Point Mutation
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-raf
  • ras Proteins / analysis*
  • ras Proteins / genetics


  • Proto-Oncogene Proteins
  • ErbB Receptors
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-raf
  • ras Proteins