cancers Article The Cancer Stem Cell Inhibitor Napabucasin (BBI608) Shows General Cytotoxicity in Biliary Tract Cancer Cells and Reduces Cancer Stem Cell Characteristics Marlena Beyreis 1, Martin Gaisberger 1,2,3 , Martin Jakab 1, Daniel Neureiter 4,5, Katharina Helm 3,4,5, Markus Ritter 1,...