FURIN and hepatocellular carcinoma: In recent SARS-CoV-2 research, Mezger and colleagues reported that activation of the Smad pathway via TGF-β1 or ALK5 agonists led to increased expression of furin, a protease that cleaves the spike protein of SARS-CoV-2, in a broad spectrum of cells including Huh-7 (a permanent cell line established from male hepatoma tissue), and Calu-3 cells (epithelial cells isolated from lung tissue derived from a male patient with lung adenocarcinoma), which enhanced susceptibility to SARS-CoV-2 infection in these cells [256].