Abstract: Background and purpose: Multiple proinflammatory cytokines in tumorigenic microenvironment are involved in the acquired capability for invasive growth and metastasis. It is not clear whether protein kinase CβⅡ(PKCβⅡ) can modulate the secretion of proinflammatory cytokines to promote the progression of hepatocellular carcinoma (HCC). This study aimed to explore the function and mechanism of PKCβⅡ in the invasion of HCC to investigate the relationship between PKCβⅡ and tumor inflammatory microenvironment. Methods: The effect of conditioned medium from PKCβⅡ-overexpressing cells on the invasion of HCC cells was detected by the transwell assay. Serum-free culture supernatants were analyzed by cytokine arrays. The effect of PKCβⅡ overexpression on the expression of interleukin-6 (IL-6) in supernatants and at mRNA level was examined by enzyme- linked immunosorbent assay (ELISA) and real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) respectively. The effects of IL-6 neutralizing antibody and IL-6 receptor (IL-6R) neutralizing antibody on PKCβⅡ overexpression-induced invasion of HCC cells were detected by the transwell assay. The expressions of signal transducer and activator of transcription 3 (STAT3) and P-STAT3 were detected by Western blot. Correlation of PKCβⅡ with the expression of IL-6 in clinical HCC cases was analyzed using the nonparametric Spearman test. Results: Conditioned medium obtained from PKCβⅡ-overexpressing cells significantly induced the invasiveness of Huh7 (P<0.01) and Hep3B (P<0.05), and the upregulated secretion of IL-6 (P<0.01) and mRNA level (P<0.01) upon PKCβⅡ overexpression were observed respectively. Administrations of IL-6 neutralizing antibody and IL-6R neutralizing antibody blocked PKCβⅡ overexpression-induced invasion of HCC cells (P<0.01). The protein level of P-STAT3 increased significantly upon PKCβⅡ overexpression (P<0.05). Immunohistochemical analysis also presented a strong positive correlation between PKCβⅡ and IL-6 expression in clinical HCC samples (r=0.697, P<0.01). Conclusion: PKCβⅡ promotes the invasion of HCC by modulating autocrine of IL-6.

Key words: Protein kinase CβⅡ, Interleukin-6, Autocrine, Hepatocellular carcinoma, Invasion