The MAP3K19 inhibitor, Compound A, can block phosphorylated R-Smad nuclear accumulation, whereas pirfenidone has a negligible effect, following TGF-β1 stimulation.

<p>HeLa cells were cultured overnight on glass cover slips and pretreated with vehicle (DMSO), Compound A (1 μM) or pirfenidone (1 μM) for 30 minutes and treated with TGF-β1 (1 ng/ml) for one hour, prior to fixation and staining with anti-MAP3K19 (green staining, RabK19 polyclonal antibody) and anti-phospho-Smad2/3 (red staining). The cells were counterstained with DAPI nuclear stain. This experiment was repeated two independent times, and a representative experiment is shown. Similar results were observed with the A549 lung epithelial cell line.