u-0126 and diallyl-disulfide

TNFα receptors are constitutively overexpressed in tumor cells, correlating to sustain elevated NFκB and monocyte chemotactic protein-1 (MCP-1/CCL2) expression. The elevation of CCL2 evokes aggressive forms of malignant tumors marked by tumor associated macrophage (TAM) recruitment, cell proliferation, invasion and angiogenesis. Previously, we have shown that the organo-sulfur compound diallyl disulfide (DADS) found in garlic (Allium sativum) attenuates TNFα induced CCL2 production in MDA-MB-231 cells. In the current study, we explored the signaling pathways responsible for DADS suppressive effect on TNFα mediated CCL2 release using PCR Arrays, RT-PCR and western blots. The data in this study show that TNFα initiates a rise in NFκB mRNA, which is not reversed by DADS. However, TNFα induced heightened expression of IKKε and phosphorylated ERK. The expression of these proteins corresponds to increased CCL2 release that can be attenuated by DADS. CCL2 induction by TNFα was also lessened by inhibitors of p38 (SB202190) and MEK (U0126) but not JNK (SP 600125), all of which were suppressed by DADS. In conclusion, the obtained results indicate that DADS down regulates TNFα invoked CCL2 production primarily through reduction of IKKε and phosphorylated-ERK, thereby impairing MAPK/ERK, and NFκB pathway signaling. Future research will be required to evaluate the effects of DADS on the function and expression of TNFα surface receptors.

Topics: Allyl Compounds; Anthracenes; Anticarcinogenic Agents; Butadienes; Cell Line, Tumor; Chemokine CCL2; Disulfides; Garlic; Gene Expression Regulation, Neoplastic; Humans; Imidazoles; Macrophages; MAP Kinase Kinase 4; MAP Kinase Kinase Kinases; MAP Kinase Signaling System; NF-kappa B p50 Subunit; Nitriles; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Pyridines; Tumor Necrosis Factor-alpha

Diallyl disulfide (DADS) is a major constituent of garlic. Previously, we found that DADS both inhibited proliferation in human gastric cancer cells in vitro and in vivo, and induced G2/M arrest. In this study, we investigated whether this differentiation effect was induced by DADS in human gastric cancer MGC803 cells, and whether it was related to an alteration in ERK activity. The results showed that the growth of MGC803 cells was inhibited by DADS. Cells treated with DADS displayed a lower nucleocytoplasmic ratio and tended to form gland and intercellular conjunction structures. The ConA-mediated cell agglutination ratio and cells' ALP specific activity decreased. In MGC803 cells, dye transfer was limited to a few cells neighbouring the dye-injected cell and to a depth of 1-2 layers beneath the scrape site. However, after treatment with DADS, the LY (Lucifer Yellow) was transferred to several cells immediately neighbouring the microinjected cell and to a depth of 2-4 cell layers from the scrape site. This indicated that DADS induced differentiation in MGC803 cells. Western blot analysis revealed that although DADS did not influence the quantity of ERK1/2 protein expressed, it did decrease its phosphorylation in a concentration-dependent manner, compared with the controls. At 30 mg x L(-1), DADS inhibited the activation of ERK1/2 in 15-30 min. These results suggested that the DADS-induced differentiation of MGC803 cells involved an alteration of the ERK1/2 signaling pathway.

Topics: Agglutination; Alkaline Phosphatase; Allyl Compounds; Butadienes; Cell Differentiation; Cell Line, Tumor; Cell Survival; Concanavalin A; Disulfides; Humans; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Nitriles; Phosphoproteins; Phosphorylation; Stomach Neoplasms