TY - JOUR
T1 - Tiam1 regulates cell adhesion, migration and apoptosis in colon tumor cells
AU - Minard, Meghan E.
AU - Ellis, Lee M.
AU - Gallick, Gary E.
N1 - Funding Information:
Acknowledgements We thank Nila U. Parikh for excellent technical assistance. This work was supported by the Rosalie B. Hite Fellowship and the Andrew Sowell-Wade Huggins Scholarship to MEM. MEM was the T.C. Hsu Memorial Scholar in Cell Biology.
PY - 2006/11
Y1 - 2006/11
N2 - The guanine nucleotide exchange factor Tiam1 regulates numerous biologic properties including migration and invasion. We demonstrated previously that colon tumor cells biologically selected for increased migration were increased in Tiam1 expression. Cells selected for increased Tiam1 expression or that ectopically overexpress Tiam1 were increased in metastatic potential. Here, we demonstrate that Tiam1 regulates additional functions associated with metastasis, including reduced cellular adhesion and resistance to anoikis. Tiam1 effects on cellular migration are mediated through its downstream substrate, Rac. Increased Tiam1 expression also leads to anoikis-resistance, whereas decreasing Tiam1 expression by siRNA sensitizes cells to this form of apoptosis; however, Tiam1's regulation of anoikis is Rac-independent. Staurosporine sensitivity is also Rac-independent, suggesting Tiam1's effects on apoptosis require other effectors. As many of the observed phenotypes are characteristic of a transition of transformed epithelial cells to a mesenchymal-like phenotype, we also examined biochemical properties associated with an EMT. We demonstrate an increase in vimentin expression in cell lines that overexpress Tiam1 and have a more metastatic phenotype. Concomitant with this increase, we observe a decrease in E-cadherin expression in these cells. Lastly, we stained a panel of human colorectal specimens and adjacent normal tissue, and demonstrate that Tiam1 is overexpressed in a subset of human colorectal tumors. In summary, in colon tumor cells, Tiam1 affects multiple properties associated with acquisition of the metastatic phenotype, and may represent a marker of colon tumor progression and metastasis in a subset of tumors.
AB - The guanine nucleotide exchange factor Tiam1 regulates numerous biologic properties including migration and invasion. We demonstrated previously that colon tumor cells biologically selected for increased migration were increased in Tiam1 expression. Cells selected for increased Tiam1 expression or that ectopically overexpress Tiam1 were increased in metastatic potential. Here, we demonstrate that Tiam1 regulates additional functions associated with metastasis, including reduced cellular adhesion and resistance to anoikis. Tiam1 effects on cellular migration are mediated through its downstream substrate, Rac. Increased Tiam1 expression also leads to anoikis-resistance, whereas decreasing Tiam1 expression by siRNA sensitizes cells to this form of apoptosis; however, Tiam1's regulation of anoikis is Rac-independent. Staurosporine sensitivity is also Rac-independent, suggesting Tiam1's effects on apoptosis require other effectors. As many of the observed phenotypes are characteristic of a transition of transformed epithelial cells to a mesenchymal-like phenotype, we also examined biochemical properties associated with an EMT. We demonstrate an increase in vimentin expression in cell lines that overexpress Tiam1 and have a more metastatic phenotype. Concomitant with this increase, we observe a decrease in E-cadherin expression in these cells. Lastly, we stained a panel of human colorectal specimens and adjacent normal tissue, and demonstrate that Tiam1 is overexpressed in a subset of human colorectal tumors. In summary, in colon tumor cells, Tiam1 affects multiple properties associated with acquisition of the metastatic phenotype, and may represent a marker of colon tumor progression and metastasis in a subset of tumors.
KW - Anoikis
KW - Colorectal carcinoma
KW - EMT
KW - Metastasis
KW - Tiam1
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U2 - 10.1007/s10585-006-9040-z
DO - 10.1007/s10585-006-9040-z
M3 - Article
C2 - 17086355
AN - SCOPUS:33751198483
SN - 0262-0898
VL - 23
SP - 301
EP - 313
JO - Clinical and Experimental Metastasis
JF - Clinical and Experimental Metastasis
IS - 5-6
ER -