Effect of HepG2-Derived Exosome with PDGF-D Knockdown on Transformation of Normal Fibroblasts into Tumor-Associated Fibroblasts in Liver Cancer.

Background: It is known that the transformation of liver cancer-mediated fibroblasts into cancer-related fibroblasts (CAFs) is beneficial to the development of liver cancer. However, the specific mechanism is still unclear.

Methods: Human hepatocarcinoma (HepG2) cells were treated with short hairpin RNA (shRNA) of platelet-derived growth factor-D (shPDGF-D) vector, and the exosomes secreted by the cells were separated using ultracentrifugation and identified by using nanoparticle tracking analysis, transmission electron microscope, and western blot analysis. Exosomes were co-cultured with mouse primary fibroblasts, and then the activity, proliferation, cell cycle, migration, epithelial-mesenchymal transition- (EMT-) and CAF marker-related protein expression levels of fibroblasts were determined by cell counting kit-8 (CCK-8), immunofluorescence, flow cytometry, wound healing, real-time reverse transcription-PCR, and western blotting assays, respectively. Co-cultured fibroblasts were mixed with HepG2 cells and injected subcutaneously into mice to construct animal models. The size and weight of xenograft tumor and the expression of epithelial-mesenchymal transition- (EMT-), angiogenesis- and CAFs marker-related proteins were detected.

Results: The exosomes inhibited the proliferation, migration, EMT, and induced cell cycle arrest, as well as decreased the expression of α-SMA, FAP, MMP-9, and VEGF in fibroblasts. In vivo, sh-PDGF-D inhibited tumor growth, reduced the expressions of CD31, vimentin, α-SMA, FAP, MMP9, and VEGF, and promoted the expression of E-cadherin.

Conclusions: Exosomes derived from HepG2 cells transfected with shPDGF-D prevent normal fibroblasts from transforming into CAFs, thus inhibiting angiogenesis and EMT of liver cancer.