CCL2, IL-8, and CXCL16, the identified differential cytokines from CM, modulated the expression of HCC invasion/metastasis genes, especially MMP2 and MMP9. CCL2 or CXCL16 alone stimulated significantly the upregulation

of phosphorylated AKT in MHCC97H cells, but had no change in ERK phosphorylation. CCL2 or CXCL16 alone also increased the contents of NF-κB compared with the control. These findings hinted that the released CCL2 or CXCL16 from HUVECs may be responsible for HCC cell migration and invasion by increasing MMP2 and MMP9 production through the PI3K/Akt selleck compound pathway. Other studies on Huh7 cells and chondrosarcoma cells have also revealed a similar molecular mechanism in which CCL2 regulates MMP2 and MMP9 expression through the PI3K/Akt and NF-κB signaling selleckchem pathways [25, 46]. In prostate cancer cells [47], a CXCR6/CXCL16 pair may activate the PI3K/Akt signal pathway. Surprisingly, although IL-8 upregulated the expression of HCC invasion/metastasis genes and increased the contents of NF-κB, it did not affect the activation of the Akt and ERK pathways in MHCC97H. NF-κB is an inducible transcription factor

for MMP2 and MMP9 expression in some literatures [46, 48, 49]. We speculate RAAS inhibitor that IL-8 may activate NF-κB through other signal pathways to regulate the expression of MMP2 and MMP9. Here, we also mention that the used human cytokine array in the study belongs to a functional protein chip with limited number of cytokine antibodies on it, which is not able to cover all released cytokines from HUVECs. Accordingly, except for 25 identified differential cytokines, the other unidentified cytokines derived from ECs still deserve to be further investigated in the following study. In summary, several secreted factors from ECs directly influenced HCC cell proliferation, migration, and invasiveness. ASK1 The differential

cytokines CCL2 and CXCL16 identified in CM may be involved in HCC invasion and metastasis by activating the PI3K/Akt and NF-κB signaling pathways. IL-8 may activate NF-κB through other signal pathways to regulate the expression of MMP2 and MMP9 (Figure 6C). Further studies are needed to identify and characterize the signaling events initiated by ECs for future implication in cancer therapy. Acknowledgments This study was sponsored by grants from the National Natural Science Foundation of China (Nos. 81,071,902, 81,272,583 and 81,272,723) and the Shanghai Science and Technology Programme (11JC1402100). References 1. Parkin DM, Bray F, Ferlay J, Pisani P: Global cancer statistics, 2002. Ca-a Cancer Journal for Clinicians 2005, 55:74–108.PubMedCrossRef 2. Yang JD, Nakamura I, Roberts LR: The tumor microenvironment in hepatocellular carcinoma: current status and therapeutic targets. Semin Cancer Biol 2011, 21:35–43.PubMedCrossRef 3.