Effect of IL-8 on hepatocellular carcinoma-associated metastasis by targeting MMP9 in mice

BACKGROUND: Interleukin-8 (IL-8) and matrix metallopeptidase 9 (MMP9) are overexpressed in hepatocellular carcinoma (HCC), and both are related to tumor metastasis, but whether they regulate HCC metastasis is still unclear. METHODS: HCC orthotopic implantation and colonization mice models were established in vivo. Model mice were treated with IL-8 and or MMP9 inhibitors, protein kinase C (PKC) inhibitors, or extracellular regulated protein kinases 1/2 (ERK1/2) inhibitors. Liver metastasis and lung metastasis of model mice were confirmed by hematoxylin and eosin staining. The population of circulating tumor cells (CTCs) was detected by flow cytometry. The expression of MMP9 in tumor tissues was determined by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry. In vitro, HCC LM6 (HCCLM6) cells were treated with IL-8 combined PKC inhibitor or ERK1/2 inhibitor. The expression of MMP9 was confirmed by qRT-PCR and Western blot, and the activation of the PKC/ERK1/2 signaling pathway was confirmed by Western blot. RESULTS: IL-8 promoted liver metastasis and lung metastasis in orthotopic transplantation model mice, increased the proportion of CTCs and promoted the expression of MMP9 in tumor tissues, but these effects were reversed by PKC inhibitor or ERK1/2 inhibitor. In vivo colonization experiments, IL-8 promoted tumor cell metastasis to the liver and lung, but the MMP9 inhibitor reversed the metastasis-promoting effect of IL-8. In cell experiments, IL-8 promoted the expression of p-PKC and p-ERK1/2 and inhibited the expression of PKC and ERK1/2; the promotion of MMP9 expression by IL-8 was reversed by PKC inhibitor or ERK1/2 inhibitor. CONCLUSIONS: IL-8 up-regulated the expression of MMP9 by activating the PKC/ERK1/2 signaling pathway, thereby promoting the metastasis and colonization of HCC.