 Further evidence for the essential contribution of EGFR-signalling comes from studies with IL-6 Blechacz and Gores 2008. IL-6 is a key cytokine in the pathogenesis of CCA. IL-6 is produced at high levels by CCA cells, and elevated IL-6 serum concentrations have been reported in CCA patients. It has been shown that there is a cross-communication between IL-6 and EGFR resulting in IL-6 mediated overexpression of EGFR. 