Studies have shown that levels of both the iron storage protein ferritin and the iron exporter ferroportin (FPN) are decreased in cholangiocarcinoma CSCs and ovarian CSCs.112, 118 In addition, low H ferritin levels and high TFRC expression were detected in cholangiocarcinoma cells when grown in monolayers; however, when the same cell lines formed tumour spheres, there were high H ferritin levels and low TFR1 expression levels. Here, SLC40A1 is linked to cholangiocarcinoma.