SMAD4 and adenoma: The time-dependent TGF-β1 on gene expression used a fixed concentration of 390 pM which exceeds the TGF-β1 IC50 of Smad4+/+ adenoma, resulted in differential expression of genes that were Smad4 and TGF-β1 dependent, with the most significant being decreased expression of Id1. Id1 codes for a non-DNA binding inhibitor of basic-helix-loop-helix (bHLH) transcription factors (e.g. GATA4) to inhibit multiple cell processes including differentiation.