NOX4 and cholangiocarcinoma: For the staining of NOX4 we used an antibody previously manufactured and validated for IHC.31 Indeed, our analysis revealed that NOX4 shows an intense and specific localization in stromal areas of iCCA where α-SMA and Picro Sirius red signals are also strong, indicating NOX4 expression in CAF, while no expression was found in CCA tumour cells (Fig. 4c).