The Hedgehog Pathway Promotes Monocytes Infiltration Through <scp>CCL20</scp> – <scp>CCR6</scp> Axis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading cancers worldwide, and its development is strongly associated with the tumour microenvironment, particularly fibrosis and chronic inflammation. This study aims to investigate the role of the Hedgehog (Hh) pathway, a key signalling pathway in HCC progression, in the interaction between HCC cells and monocytes, which are central players in inflammation. Using a transwell migration assay, GLI1, the downstream transcriptional effector of the Hh pathway in HCC cells, was found to promote the migration of THP-1 monocyte cells. Among the cytokines regulated by the Hh pathway in HCC cells, CCL20 was identified as a crucial factor that interacts with CCR6 in THP-1 cells to facilitate migration. Next, using a luciferase reporter assay and chromatin immunoprecipitation, GLI1 binding sites within the CCL20 promoter region were confirmed. In a xenograft tumour mouse model, tumour growth and monocyte infiltration were inhibited in GLI1 or CCL20 knockout PLC5 cells. Moreover, mRNA expressions of GLI1 and CCL20 were positively correlated in clinical samples, with patients exhibiting high CCL20 expression showing poorer overall survival. Overall, our findings highlight that the Hh pathway in HCC contributes to monocyte infiltration via the CCL20-CCR6 axis, providing potential insights for future therapeutic strategies.