Rebecca S Sippel1, Herbert Chen. 1. Department of Surgery, The University of Wisconsin Medical School, H4/750 Clinical Science Center, 600 Highland Avenue, Madison, WI 53792, USA.
Abstract
BACKGROUND: Recent studies of neuroendocrine tumor cell lines suggest that ras/raf-1 activation could be detrimental to tumorigenesis. The mechanism by which it alters neuroendocrine tumor cells is unclear. We hypothesize that activation of the ras/raf signal transduction pathway may alter gastrointestinal carcinoid cells by inducing morphologic transdifferentiation. METHODS: Pancreatic carcinoid (BON) cells were transduced in a stable manner with an estrogen inducible raf-1 fusion protein (creating "BON-raf cells"). BON and BON-raf cells were then treated with either control or 1 micromol/L estradiol (E2). Western blots were used to confirm the phosphorylation of extracellular signal-regulated kinase 1/2. Morphologic changes were evaluated using light and electron microscopy. RESULTS: Western blots using antibodies against phosphorylated and unphosphorylated extracellular signal-regulated kinase 1/2. confirmed that phosphorylation was only present in the BON-raf E2 cells. BON cells treated with control and E2 and BON-raf cells treated with control all looked identical in culture. After treatment with E2 to induce raf-1, the BON-raf cells underwent dramatic morphologic changes. Under light and electron microscopy the cells became flatter and developed much sharper cellular borders mimicking cellular differentiation. CONCLUSIONS: Activation of the ras/raf-1 signal transduction pathway leads to prominent phenotypic changes that resemble differentiation of gastrointestinal carcinoid cells in vitro.
BACKGROUND: Recent studies of neuroendocrine tumor cell lines suggest that ras/raf-1 activation could be detrimental to tumorigenesis. The mechanism by which it alters neuroendocrine tumor cells is unclear. We hypothesize that activation of the ras/raf signal transduction pathway may alter gastrointestinal carcinoid cells by inducing morphologic transdifferentiation. METHODS:Pancreatic carcinoid (BON) cells were transduced in a stable manner with an estrogen inducible raf-1 fusion protein (creating "BON-raf cells"). BON and BON-raf cells were then treated with either control or 1 micromol/L estradiol (E2). Western blots were used to confirm the phosphorylation of extracellular signal-regulated kinase 1/2. Morphologic changes were evaluated using light and electron microscopy. RESULTS: Western blots using antibodies against phosphorylated and unphosphorylated extracellular signal-regulated kinase 1/2. confirmed that phosphorylation was only present in the BON-raf E2 cells. BON cells treated with control and E2 and BON-raf cells treated with control all looked identical in culture. After treatment with E2 to induce raf-1, the BON-raf cells underwent dramatic morphologic changes. Under light and electron microscopy the cells became flatter and developed much sharper cellular borders mimicking cellular differentiation. CONCLUSIONS: Activation of the ras/raf-1 signal transduction pathway leads to prominent phenotypic changes that resemble differentiation of gastrointestinal carcinoid cells in vitro.
Authors: Jan Liman; Sundar Ganesan; Christoph P Dohm; Stan Krajewski; John C Reed; Mathias Bähr; Fred S Wouters; Pawel Kermer Journal: Mol Cell Biol Date: 2005-05 Impact factor: 4.272