Dietary grape seed proanthocyanidins inhibit 12-O-tetradecanoyl phorbol-13-acetate-caused skin tumor promotion in 7,12-dimethylbenz[a]anthracene-initiated mouse skin, which is associated with the inhibition of inflammatory responses.

Grape seed proanthocyanidins (GSPs) possess anticarcinogenic activities. Here, we assessed the effects of dietary GSPs on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin tumor promotion in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mouse skin. Administration of dietary GSPs (0.2 and 0.5%, wt/wt) supplemented with control AIN76A diet resulted in significant inhibition of TPA-induced skin tumor promotion in C3H/HeN mice. The mice treated with GSPs developed a significantly lower tumor burden in terms of the percentage of mice with tumors (P < 0.05), total number of tumors per group (P < 0.01, n = 20) and total tumor volume per tumor-bearing mouse (P < 0.01-0.001) as compared with the mice that received the control diet. GSPs also delayed the malignant progression of papillomas into carcinomas. As TPA-induced inflammatory responses are used routinely as markers of skin tumor promotion, we assessed the effect of GSPs on biomarkers of TPA-induced inflammation. Immunohistochemical analysis and western blotting revealed that GSPs significantly inhibited expression of cyclooxygenase-2 (COX-2), prostaglandin E(2) (PGE(2)) and markers of proliferation (proliferating cell nuclear antigen and cyclin D1) in both the DMBA-initiated/TPA-promoted mouse skin and skin tumors. In short-term experiments in which the mouse skin was treated with acute or multiple TPA applications, we found that dietary GSPs inhibited TPA-induced edema, hyperplasia, leukocytes infiltration, myeloperoxidase, COX-2 expression and PGE(2) production in the mouse skin. The inhibitory effect of GSPs was also observed against other structurally different skin tumor promoter-induced inflammation in the skin. Together, our results show that dietary GSPs inhibit chemical carcinogenesis in mouse skin and that the inhibition of skin tumorigenesis by GSPs is associated with the inhibition of inflammatory responses caused by tumor promoters.

Inhibition of non-small cell lung cancer cell migration by grape seed proanthocyanidins is mediated through the inhibition of nitric oxide, guanylate cyclase, and ERK1/2.

Tumor cell migration is considered as a major event in the metastatic cascade. Here we examined the effect of grape seed proanthocyanidins (GSPs) on migration capacity and signaling mechanisms using nonsmall cell human lung cancer cells. Using in vitro migration assay, we found that treatment of A549 and H1299 cells with GSPs resulted in concentration-dependent inhibition of migration of these cells. The migration capacity of cells was reduced in presence of N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase. GSPs suppressed the elevated levels of endogenous NO/NOS in A549 and H1299 cells and blocked the migration promoting capacity of L-arginine. Treatment with guanylate cyclase (GC) inhibitor 1-H-[1,2,4]oxadiaxolo[4,3-a]quinolalin-1-one (ODQ) reduced the migration of A549 cells whereas additional presence of 8-bromoguanosine 3'5'-cyclic monophosphate (8-Br-cGMP, cGMP analogue) restored the migration of these cells, suggesting a role for GC in migration of A549 cells. GSPs reduced the elevated levels of cGMP in cancer cells and also blocked the migration restoring activity of 8-Br-cGMP. The mitogen-activated protein kinase kinase (MAPKK) inhibitor, UO126, inhibited the migration of A549 cells, indicating a role for MAPKK in the migration. Additionally, UO126 and ODQ inhibited the migration restoring effects of L-arginine in L-NAME-treated cells, suggesting the involvement of cGMP and MAPK pathways in NO-mediated migration. GSPs inhibited L-arginine and 8-Br-cGMP-induced activation of ERK1/2 in A549 cells. Together, these results indicate sequential inhibition of NO/NOS, GC, and MAPK pathways by GSPs in mediating the inhibitory signals for cell migration, an essential step in invasion and metastasis.