Abstract: Objective To investigate the level of somatostatin (SST) in liver cancer-associated fibroblasts (CAFs) and its association with the prognosis of hepatocellular carcinoma (HCC) patients, as well as the underling mechanism. Methods Eight-three HCC patients underwent operation were randomly collected in this study. The levels of α-smooth muscle actin (α-SMA), vimentin and SST in isolated CAFs and normal fibroblasts (NFs) from the HCC and adjacent non-cancerous tissues respectively were detected using quantitative reverse transcription PCR (RT-qPCR). The relationship between SST and clinicopathological parameters and the prognosis of HCC patients was analyzed. After transfection of CAFs with SST overexpression plasmid, the supernatant was taken to co-culture with Huh7, a hepatoma cell line. Cell proliferation, invasion and Wnt/β-catenin pathway-related protein levels of Huh7 cells were determined with CCK-8 assay, Transwell assay, and Western blot, respectively. Enzyme-linked immunosorbent assay (ELISA) was conducted to detect the content of chemokines in the supernatant of CAFs-cultured Huh7 cells medium. Kaplan-Meier method was used to evaluate the association of SST with the survival rate of the HCC patients. Results Compared with NFs, the expression of α-SMA (2.87±0.091) and Vimentin (2.93±0.085) were significantly increased in CAFs, while the level of SST (0.328±0.073) was significantly decreased (t=26.441, P=0.001; t=30.886, P=0.001; t=11.197, P=0.001, respectively). The analysis of clinicopathological features showed that the expression of SST was related to TNM stage, lymph node metastasis and tissue differentiation degree in HCC patients, all of which had statistically significant (χ²=5.562, P=0.001; χ²=24.688, P=0.001; χ²=18.685, P=0.001). The supernatant of culture medium of CAFs significantly promoted the proliferation and invasion of Huh7 cells, whereas the supernatant of culture medium of SST-overexpressed CAFs inhibited the proliferation and invasion of Huh7. ELISA results showed that the levels of chemokine CCL2, CCL5, CXCL21 and CXCL 25 in the supernatant of CAFs were significantly different when compared with those of NFs (98.50±3.98, 78.32±4.21 24.32±5.11, and 20.34±4.77pg/mL, vs. 3.2±5.36, 1.40±4.35, 1.02±4.67, and 1.11±5.01, respectively. F=78.324, P=0.001; F=53.611, P=0.001; F=32.847, P=0.001; F=25.635, P=0.001). After overexpression of SST, the expression levels of these chemokines and proteins related to Wnt/β-catenin signaling pathway were markedly suppressed (F=15.951, P=0.001; F=13.806, P=0.001; F=17.824, P=0.001; F=18.347, P=0.001). The progression-free survival (χ²=4.679, P=0.031) and overall survival (χ²=4.304, P=0.038) rates of HCC patients with high SST expression were higher than those of patients with low SST expression. Conclusion The expression of SST was down-regulated in CAFs and associated with the prognosis of HCC patients. The supernatant of CAFs transfected with pcDNA-SST inhibited the proliferation and invasion of hepatoma cells by inhibiting chemokines secretion and Wnt/β-catenin signaling pathway.

Key words: Liver cancer, tumor-associated fibroblasts, somatostatin, prognosis