Differential Notch and TGFbeta signaling in primary colorectal tumors and their corresponding metastases.
BACKGROUND
Loss of epithelial morphology and the acquisition of mesenchymal characteristics may contribute to metastasis formation during colorectal tumorigenesis. The Wnt, Notch and TGFbeta signaling pathways control tissue homeostasis and tumor development in the gut. The relationship between the activity of these pathways and the expression of epithelial and mesenchymal markers was investigated in a series of primary colorectal tumors and their corresponding metastases.


METHODS
Tissue samples of primary colorectal tumors, normal colonic mucosa, and regional and systemic metastases were processed for immunohistochemistry in a tissue microarray format. The expression of mesenchymal (vimentin, fibronectin) and epithelial (E-cadherin) markers was related to markers of Wnt (beta-catenin), Notch (HES1) and TGFbeta (phospho-SMAD2) signalling. In addition, the KRAS mutation status was assessed.


RESULTS
When compared to normal mucosa, primary colorectal tumors showed a marked increase in the levels of cytoplasmic vimentin and nuclear beta-catenin, phospho-SMAD2 and HES1. Increased vimentin expression correlated with the presence of oncogenic KRAS and with nuclear beta-catenin. The corresponding liver, lymph node, brain and lung metastases did not express vimentin and displayed significantly lower levels of nuclear phospho-SMAD2 and HES1, while retaining nuclear beta-catenin.


CONCLUSIONS
Primary colorectal carcinomas display aberrant expression of vimentin, and have activated Notch and TGFbeta signaling pathways. Surprisingly, many regional and distant metastases have lost nuclear HES1 and pSMAD2, suggesting that the activity of the Notch and TGFbeta pathways is reduced in secondary colorectal tumors.
Veenendaal
Liesbeth M
LM
Department of Surgery, University Medical Center Utrecht, The Netherlands.
Kranenburg
Onno
O
Smakman
Niels
N
Klomp
Annemarie
A
Borel Rinkes
Inne H M
IH
van Diest
Paul J
PJ
D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000556:secondary; D015820:Cadherins / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000556:secondary; D008175:Lung Neoplasms / Q000556:secondary; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras); D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction; D046888:Tissue Array Analysis; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014746:Vimentin / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
D015820:Cadherins; D005353:Fibronectins; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D051880:Receptors, Notch; D016212:Transforming Growth Factor beta; D014746:Vimentin; D051153:Wnt Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins