Targeted inhibition of the c-Jun N-terminal
kinases (JNKs) has shown therapeutic potential in
intrahepatic cholangiocarcinoma (CCA)-related
tumorigenesis. However, the cell-type-specific role and mechanisms triggered by JNK in liver parenchymal cells during CCA remain largely unknown. Here, we aimed to investigate the relevance of JNK1 and JNK2 function in hepatocytes in two different models of experimental
carcinogenesis, the dethylnitrosamine (DEN) model and in
nuclear factor kappa B essential modulator (NEMO)hepatocyte-specific knockout (Δhepa) mice, focusing on liver damage, cell death, compensatory proliferation, fibrogenesis, and
tumor development. Moreover, regulation of essential genes was assessed by reverse transcription polymerase chain reaction, immunoblottings, and immunostainings. Additionally, specific Jnk2 inhibition in hepatocytes of NEMOΔhepa/JNK1Δhepa mice was performed using small interfering (si)
RNA (siJnk2) nanodelivery. Finally, active signaling pathways were blocked using specific inhibitors. Compound deletion of Jnk1 and Jnk2 in hepatocytes diminished
hepatocellular carcinoma (HCC) in both the DEN model and in NEMOΔhepa mice but in contrast caused massive proliferation of the biliary ducts. Indeed, Jnk1/2 deficiency in hepatocytes of NEMOΔhepa (NEMOΔhepa/JNKΔhepa) animals caused elevated
fibrosis, increased apoptosis, increased compensatory proliferation, and elevated inflammatory
cytokines expression but reduced HCC. Furthermore, siJnk2 treatment in NEMOΔhepa/JNK1Δhepa mice recapitulated the phenotype of NEMOΔhepa/JNKΔhepa mice. Next, we sought to investigate the impact of molecular pathways in response to compound JNK deficiency in NEMOΔhepa mice. We found that NEMOΔhepa/JNKΔhepa livers exhibited overexpression of the
interleukin-6/
signal transducer and activator of transcription 3 pathway in addition to
epidermal growth factor receptor (EGFR)-rapidly accelerated
fibrosarcoma (Raf)-
mitogen-activated protein kinase kinase (
MEK)-
extracellular signal-regulated kinase (ERK) cascade. The functional relevance was tested by administering
lapatinib, which is a dual
tyrosine kinase inhibitor of erythroblastic oncogene B-2 (ErbB2) and EGFR signaling, to NEMOΔhepa/JNKΔhepa mice.
Lapatinib effectively inhibited cystogenesis, improved
transaminases, and effectively blocked EGFR-Raf-
MEK-ERK signaling. Conclusion: We define a novel function of JNK1/2 in cholangiocyte hyperproliferation. This opens new therapeutic avenues devised to inhibit pathways of cholangiocarcinogenesis.