Exosomal FOSL1 From Cancer-associated Fibroblasts Drives the Progression and Pro-tumorigenic M2 Macrophage Polarization of Hepatocellular Carcinoma By Activating PLAU Transcription

Exosomes derived from cancer-associated fibroblasts (CAFs) play a crucial role in Cancer development. Fos-like antigen 1 (FOSL1) exhibits oncogenic properties across various malignancies. However, the specific role of FOSL1 in CAFs-derived exosomes (CAFs-EXO) in hepatocellular carcinoma (HCC) has not been previously explored. This study aimed to investigate whether CAFs-EXO transfer FOSL1 to HCC cells and to examine the functional consequences of this transfer. HCC-related CAFs and their exosomes were used to incubate HCC cells. Cell proliferation and migration/invasion were assessed. The percentage of CD11b⁺CD206⁺ macrophages was measured. The FOSL1/PLAU relationship was validated by chromatin immunoprecipitation (ChIP) and luciferase assays. FOSL1 expression was increased in CAFs-EXO compared with normal controls (3.36 ± 0.25 vs. 1.00 ± 0.04, P < 0.001). CAFs-EXO transmitted FOSL1 into HCC cells, promoting HCC cell proliferation (Huh-7 cells: 63.93 ± 2.68 vs. 54.37 ± 0.8, P < 0.01; Hep3B: 63.27 ± 5.13 vs. 51.9 ± 1.75, P < 0.01). CAFs-EXO enhanced cell migration (Huh-7 cells: 197.33 ± 12.06 vs. 153.0 ± 6.25, P < 0.05; Hep3B: 215.33 ± 29.14 vs. 143.0 ± 7.55, P < 0.01) and invasion (Huh-7 cells: 176.67 ± 19.86 vs. 130.33 ± 8.62, P < 0.01; Hep3B: 191.0 ± 8.19 vs. 121.0 ± 7.0, P < 0.001). CAFs-EXO increased pro-tumorigenic M2 macrophage polarization by transmitting FOSL1. Moreover, CAFs-EXO affected the in vivo growth and metastasis of HCC cells through FOSL1. Mechanistically, FOSL1 activated PLAU transcription. FOSL1 promoted HCC cell malignant phenotypes and pro-tumorigenic M2 macrophage polarization by upregulating PLAU. Additionally, PLAU depletion suppressed HCC malignant phenotypes and decreased pro-tumorigenic M2 macrophage polarization. This study provides the first evidence that CAFs-EXO transport FOSL1 into HCC cells, thereby influencing HCC progression through the activation of PLAU transcription. These findings highlight the FOSL1/PLAU axis as a previously unrecognized therapeutic target in HCC.