Rosmarinic acid (RA) has been used as an anti-inflammatory, anti-diabetic, and anti-cancer agent. Although RA has also been shown to exert an anti-metastatic effect, the mechanism of this effect has not been reported to be associated with AMP-activated protein kinase (AMPK). The aim of this study was to elucidate whether RA could inhibit the metastatic properties of colorectal cancer (CRC) cells via the phosphorylation of AMPK. RA inhibited the proliferation of CRC cells through the induction of cell cycle arrest and apoptosis. In several metastatic phenotypes of CRC cells, RA regulated epithelial–mesenchymal transition (EMT) through the upregulation of an epithelial marker, E-cadherin, and the downregulation of the mesenchymal markers, N-cadherin, snail, twist, vimentin, and slug. Invasion and migration of CRC cells were inhibited and expressions of matrix metalloproteinase (MMP)-2 and MMP-9 were decreased by RA treatment. Adhesion and adhesion molecules such as ICAM-1 and integrin β1 expressions were also reduced by RA treatment. In particular, the effects of RA on EMT and MMPs expressions were due to the activation of AMPK. Moreover, RA inhibited lung metastasis of CRC cells by activating AMPK in mouse model. Collectively, these results proved that RA could be potential therapeutic agent against metastasis of CRC.

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BackgroundInhibition of metastasis through upregulation of immune surveillance is a major purpose of chemokine gene therapy. In this study, we focused on a membrane-bound chemokine CXCL16, which has shown a correlation with a good prognosis for colorectal cancer (CRC) patients.MethodsWe generated a CXCL16-expressing metastatic CRC cell line and identified changes in TNF and apoptosis-related factors. To investigate the effect of CXCL16 on colorectal liver metastasis, we injected SL4-Cont and SL4-CXCL16 cells into intraportal vein in C57BL/6 mice and evaluated the metastasis. Moreover, we analyzed metastatic liver tissues using flow cytometry whether CXCL16 expression regulates the infiltration of M1 macrophages.ResultsCXCL16 expression enhanced TNF-α-induced apoptosis through activation of PARP and the caspase-3-mediated apoptotic pathway and through inactivation of the NF-κB-mediated survival pathway. Several genes were changed by CXCL16 expression, but we focused on IRF8, which is a regulator of apoptosis and the metastatic phenotype. We confirmed CXCL16 expression in SL4-CXCL16 cells and the correlation between CXCL16 and IRF8. Silencing of IRF8 significantly decreased TNF-α-induced apoptosis. Liver metastasis of SL4-CXCL16 cells was also inhibited by TNF-α-induced apoptosis through the induction of M1 macrophages, which released TNF-α. Our findings suggest that the accumulation of M1 macrophages and the enhancement of apoptosis by CXCL16 might be an effective dual approach against CRC liver metastasis.ConclusionsCollectively, this study revealed that CXCL16 regulates immune surveillance and cell signaling. Therefore, we provide the first evidence of CXCL16 serving as an intracellular signaling molecule.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-949) contains supplementary material, which is available to authorized users.

Background: Colorectal cancer (CRC) is one of the diseases with high prevalence and mortality worldwide. In particular, metastatic CRC shows low probability of surgery and lacks proper treatment. In this study, we conducted experiments to investigate the inhibitory effect of betulin against metastatic CRC and related mechanisms. Methods: Water-soluble tetrazolium assay was used to determine the effect of betulin on metastatic CRC cell viability. Flow cytometry and TUNEL assay were performed to confirm whether betulin can induce apoptosis, autophagy, and cell cycle arrest. A lung metastasis mouse model was employed to estimate the anti-metastatic effect of betulin. Results: betulin decreased viability of metastatic CRC cells, including CT26, HCT116, and SW620 cell lines. Through PI3K/Akt/mTOR inactivation, betulin induced AMPK-mediated G0/G1 phase arrest and autophagy of CT26 and HCT116 cells. In addition, betulin occurred caspase-dependent apoptosis via the mitogen-activated protein kinase signaling pathway in metastatic CRC cells. Moreover, orally administered betulin significantly inhibited metastasis of CT26 cells to the lung. Conclusion: Our results demonstrate the anti-metastatic effect and therapeutic potential of betulin in metastatic CRC treatment.

Colorectal cancer (CRC) is a typical lifestyle-related disease, and it metastasizes mostly to the liver. It is important to understand the molecular mechanisms of CRC metastasis in order to design new and effective treatments for CRC patients. Chemokines are known to have antitumor effects as their chemoattractant properties stimulate the accumulation of infiltrating immune cells (TILs) in tumors. Chemokine (C-X-C motif) ligand 16 (CXCL16), also known as SR-PSOX, is a unique membrane-bound chemokine that induces the expression of its specific receptor CXCR6. We previously reported that the expression of CXCL16 by cancer cells enhances the recruitment of TILs, thereby improving the prognosis of CRC. It has since been reported that CXCL16/CXCR6 expression is involved in the metastasis of various types of cancer. However, there is no report of the association between CXCL16 expression and liver metastasis in CRC. In this study, we investigated the role of cancer-derived CXCL16 and the possibility of gene therapy using CXCL16. Therefore, we examined the metastasis of colon 38 SL4 cells to the liver in an experimental model. Following injection of cancer cells into the intraportal vein, CXCL16-expressing CRC cells drastically inhibited liver metastasis. We also found that CD8 T cells and natural killer T (NKT) cells, known as CXCR6-expressing cells, increased in CXCL16-expressing metastatic tissue. Collectively, the inhibitory effect on metastasis to the liver by CXCL16 was observed in NKT cell-depleted mice but not in CD8 T cell-depleted mice. These results demonstrate the inhibitory effect of CXCL16 on liver metastasis via NKT cells in CRC.