Activin A induces phosphorylation of Smad2 but not complex formation of Smad2 with Smad4 in human colon cancer cell line HT-29.

Western blotting coupled with immunoprecipitation showed that activin A treatment induced phosphorylation of Smad2 but not complex formation of Smad2/4 in human colon cancer-derived HT-29 cells. Because HT-29 cells expressed neither Smad4 mRNA nor Smad4 protein, it is suggested that deletion of Smad4 leads to a defect of formation of Smad2/4 complex upon activin A stimulation in HT-29 cells.

Upregulation of activin A gene by butyrate in human colon cancer cell lines.

Activin A has been reported to play a role in the progression of colorectal cancer. Because dietary fiber protects against colorectal cancer, we hypothesized that butyrate, a fermentation product of dietary fiber, may affect the expression of activin A in colon cancer cells. Semiquantitative RT-PCR demonstrated that the activin A gene was upregulated by sodium butyrate in the human colon cancer cell lines HT-29 and Caco-2 in a concentration- and time-dependent manner.