Overexpression of interleukin-32 promotes invasion by modulating VEGF in hepatocellular carcinoma

Interleukin-32 alpha (IL-32 alpha) was reported to exhibit pluripotent pro-inflammatory properties. Recent studies indicate that it promotes the migration and invasion of cancers. We detected the expression of IL-32 alpha in hepatocellular carcinoma (HCC) tissues and investigated its role in tumor angiogenesis and invasion. IL-32 alpha expression in HCC was evaluated by real-time PCR, western blot analysis and immunohistochemical (IHC) staining. Secreted serum IL-32 alpha and VEGF concentrations were detected using a custom-made sandwich ELISA. Furthermore, IL-32 alpha was knocked down in HCC cell lines using siRNA and the cell migration and invasion abilities were assessed. IHC staining showed that IL32 alpha-positive particles were mainly located in the cytoplasm of cancer cells, and it was significantly upregulated in the tumor tissues compared with that in peritumoral tissues. Notably, IL-32 alpha was strongly expressed in perivascular areas. The mean serum concentration of IL-32 alpha in HCC patients was significantly higher than that in the control group (571.45 +/- 102.28 vs. 144.60 +/- 51.172 pg/ml; P<0.01). Real-time RT-PCR showed that IL-32 alpha mRNA was significantly overexpressed in HCC tumor tissues (IL-32/beta-actin, 15.59 +/- 7.8 vs. 3.37 +/- 0.47; P<0.01). The in vitro results indicated that IL-32 alpha knockdown inhibited the activation of VEGF-STAT3 signaling in HCC tumor cell lines. IL-32 alpha expression was correlated with clinical relevance in HCC tumor tissues. It is strongly suggested that IL-32 alpha may be a potential predictor of anti-angiogenesis therapy and prognosis of HCC.