Epidermal growth factor receptor signaling is up-regulated in human colonic aberrant crypt foci.
Aberrant crypt foci (ACF) are collections of abnormal colonic crypts with heterogeneous molecular and pathologic characteristics. Large and dysplastic ACF are putative precursors of colon cancer with neoplastic risk related to increased proliferation. In this study, we examined the role of epidermal growth factor receptor (EGFR) signaling in regulating ACF proliferation. Using magnification chromoendoscopy, we collected large ACF with endoscopic features of dysplasia and separately biopsied adjacent mucosa. Transcript levels were measured by real-time PCR, proteins were assessed by Western blotting, and levels were expressed as fold changes of adjacent mucosa. K-ras and B-Raf mutations were assessed by PCR and Ras activation by the ratio Ras-GTP / (Ras-GTP + Ras-GDP). At the RNA level, 38% of ACF were hyperproliferative, with proliferating cell nuclear antigen (PCNA) mRNA >/=2-fold of adjacent mucosa. Hyperproliferative ACF had significantly increased mRNA levels of EGFR (6.0 +/- 1.7-fold), transforming growth factor-alpha (14.4 +/- 5.0-fold), heparin-binding EGF-like growth factor (4.5 +/- 1.4-fold), cyclin D1 (4.6 +/- 0.7-fold), and cyclooxygenase-2 (COX-2; 9.3 +/- 4.2-fold; P < 0.05). At the protein level, 46% of ACF were hyperproliferative (PCNA, 3.2 +/- 1.2-fold). In hyperproliferative ACF, 44% possessed significant increases in four EGFR signaling components: EGFR (9.5 +/- 1.3-fold), phosphoactive ErbB2 (2.6 +/- 0.4-fold), phosphoactive extracellular signal-regulated kinase (3.7 +/- 1.1-fold), and cyclin D1 (3.4 +/- 0.8-fold; P < 0.05). Ras was activated in 46% of ACF (3.2 +/- 0.4-fold; P < 0.05), but K-ras mutations were present in only 7% of ACF. In contrast to COX-2 mRNA, the protein was not increased in hyperproliferative ACF. In summary, we have shown that ACF with up-regulated PCNA possess increased EGFR signaling components that likely contribute to the enhanced proliferative state of dysplastic-appearing ACF.
Cohen
Greg
G
Department of Medicine, University of Chicago, Illinois, USA.
Mustafi
Reba
R
Chumsangsri
Anusara
A
Little
Nathaniel
N
Nathanson
Jeff
J
Cerda
Sonia
S
Jagadeeswaran
Sujatha
S
Dougherty
Urszula
U
Joseph
Loren
L
Hart
John
J
Yerian
Lisa
L
Tretiakova
Maria
M
Yuan
Weihua
W
Obara
Piotr
P
Khare
Sharad
S
Sinicrope
Frank A
FA
Fichera
Alessandro
A
Boss
Gerry R
GR
Carroll
Robert
R
Bissonnette
Marc
M
D048708:Cell Growth Processes / Q000502:physiology; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics; D051546:Cyclooxygenase 2 / Q000096:biosynthesis / Q000235:genetics; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D011905:Genes, ras; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D011230:Precancerous Conditions / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018809:Proliferating Cell Nuclear Antigen / Q000096:biosynthesis / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D015854:Up-Regulation
D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; D019938:Cyclin D1; D051546:Cyclooxygenase 2; D066246:ErbB Receptors; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf