Human cholangiocarcinoma development is associated with dysregulation of opioidergic modulation of cholangiocyte growth

Background/Aims: Incidence of cholangiocarcinoma is increasing worldwide, yet remaining highly aggressive and with poor prognosis. The mechanisms that drive cholangiocyte transition towards malignant phenotype are obscure. Cholangiocyte benign proliferation is subjected to a self-limiting mechanism based on the autocrine release of endogenous opioid peptides. Despite the presence of both, ligands interact with δ opioid receptor (OR), but not with μOR, with the consequent inhibition of cell growth. We aimed to verify whether cholangiocarcinoma growth is associated with failure of opioidergic regulation of growth control. Methods: We evaluated the effects of OR selective agonists on cholangiocarcinoma cell proliferation, migration and apoptosis. Intracellular signals were also characterised. Results: Activation of μOR, but not δOR, increases cholangiocarcinoma cell growth. Such an effect is mediated by ERK1/2, PI3K and Ca²⁺-CamKIIα cascades, but not by cAMP/PKA and PKCα. μOR activation also enhances cholangiocarcinoma cell migration and reduces death by apoptosis. The anti-apoptotic effect of μOR was PI3K dependent. Conclusions: Our data indicate that cholangiocarcinoma growth is associated with altered opioidergic regulation of cholangiocyte biology, thus opening new scenarios for future surveillance or early diagnostic strategies for cholangiocarcinoma.