Vaquero et al. generated erlotinib-resistant CCA cells by escalating exposure to erlotinib from 1 to 20 μM and found that resistant CCA lines, including Mz-ChA-1, HuCCT1, and SK-ChA-1 cells, expressed higher levels of IGF-2 and IGF-1R as well as insulin receptor (IR) [63]. Here, IGF2 is linked to cholangiocarcinoma.