Smad7 induces hepatic metastasis in colorectal cancer.

Halder SK, Rachakonda G, Deane NG, Datta PK
Br J Cancer. 2008 99 (6): 957-65

PMID: 18781153 · PMCID: PMC2538763 · DOI:10.1038/sj.bjc.6604562

Although Smad signalling is known to play a tumour suppressor role, it has been shown to play a prometastatic function also in breast cancer and melanoma metastasis to bone. In contrast, mutation or reduced level of Smad4 in colorectal cancer is directly correlated to poor survival and increased metastasis. However, the functional role of Smad signalling in metastasis of colorectal cancer has not been elucidated. We previously reported that overexpression of Smad7 in colon adenocarcinoma (FET) cells induces tumorigenicity by blocking TGF-beta-induced growth inhibition and apoptosis. Here, we have observed that abrogation of Smad signalling by Smad7 induces liver metastasis in a splenic injection model. Polymerase chain reaction with genomic DNA from liver metastases indicates that cells expressing Smad7 migrated to the liver. Increased expression of TGF-beta type II receptor in liver metastases is associated with phosphorylation and nuclear accumulation of Smad2. Immunohistochemical analyses have suggested poorly differentiated spindle cell morphology and higher cell proliferation in Smad7-induced liver metastases. Interestingly, we have observed increased expression and junctional staining of Claudin-1, Claudin-4 and E-cadherin in liver metastases. Therefore, this report demonstrates, for the first time, that blockade of TGF-beta/Smad pathway in colon cancer cells induces metastasis, thus supporting an important role of Smad signalling in inhibiting colon cancer metastasis.

MeSH Terms (26)

Adenocarcinoma Animals Biomarkers, Tumor Blotting, Western Cadherins Cell Proliferation Claudin-1 Claudin-4 Colorectal Neoplasms Gene Expression Regulation, Neoplastic Humans Liver Neoplasms Membrane Proteins Mice Mice, Nude Phosphorylation Polymerase Chain Reaction Protein-Serine-Threonine Kinases Receptor, Transforming Growth Factor-beta Type II Receptors, Transforming Growth Factor beta Signal Transduction Smad2 Protein Smad3 Protein Smad7 Protein Transforming Growth Factor beta Tumor Cells, Cultured

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