EGFR and cholangiocarcinoma: In cholangiocarcinoma cells, upregulation of the epidermal growth factor receptor (EGFR) and the consequent activation of the Signal Transducer and Activator of Transcription 3 (STAT3) and extracellular signal-regulated kinases (Erk) signaling pathways increased ALDH1A3 expression and resulted in gemcitabine resistance [79].