<scp>KGF</scp> secreted from <scp>HSCs</scp> activates <scp>PAK4</scp>/<scp>BMI1</scp>, promotes <scp>HCC</scp> stemness through <scp>PI3K</scp>/<scp>AKT</scp> pathway

In our present study, we investigated the interaction between HSCs and HCC, also explored the molecular mechanism. Clinical samples were collected from HCC and adjacent tissue with different degree of liver fibrosis. HCC cells were co-cultured with LX-2 cell by Transwell system or cultured with conditioned medium (CM), which was collected from LX-2. The tumor spheroid growth and colony formation analyses were performed to evaluate the cell stemness. Flow cytometry analysis was conducted on cell apoptosis after 5-Fu treatment. Co-immunoprecipitation assay confirmed the interaction between BMI1 and PAK4. Our results showed that BMI1 was highly expressed in HCC and was correlated with HCC liver fibrosis. Both co-cultured with LX-2 and cultured with CM promoted HCC stemness, also increased KGF level and BMI1 expression. KGF treatment had a similar effect with co-culture with LX-2 on HCC. BMI1 overexpression promoted HCC stemness and activated PI3K/AKT pathway, which was reversed by PI3K inhibition. PAK4 was activated by KGF, then phosphorylated S315 site and promoted protein stability of BMI1, therefore enhanced HCC stemness. BMI1 also had a promote effect on liver fibrosis. In summary, we found that KGF secreted by HSCs activated PAK4, which phosphorylated S315 and promoted protein stability of BMI1, and further promoted liver fibrosis and HCC stemness through the PI3K/AKT signaling pathway. Our present study deeply studied the interaction and mechanism between HSCs and HCC, which might provide a new insight for HCC therapy.