VIP and intrahepatic cholangiocarcinoma: To test whether the effect of VIP on ICCs is dependent on the NO–cGMP–PKG pathway, we used VIP together with a nonselective NOS inhibitor (L‐NA), PKG inhibitors (KT‐5823 and RP‐8CPT‐cGMPS), and a guanylate cyclase inhibitor (ODQ) to treat ICC cells.