Plant galactolipid dLGG suppresses lung metastasis of melanoma through deregulating TNF-α-mediated pulmonary vascular permeability and circulating oxylipin dynamics in mice

This study demonstrates the bioefficacy and gives mechanistic insights into a plant galactolipid 1,2-di-O-linolenoyl-3-O-β-galactopyranosyl-sn-glycerol (dLGG) against metastatic melanoma using a syngeneic mouse model implanted with B16 ^COX-2/Luc melanoma. dLGG-20 (p.o. dLGG 20 mg/kg) and anti-cancer drug CP-2 (i.p. cisplatin 2 mg/kg) treatment significantly inhibited lung metastasis of melanoma in mice 91 and 57%, respectively, as determined by bioluminescence intensity. Moreover, dLGG-20 and CP-2 treatment prolonged mouse mean survival time. dLGG-20 treatment significantly inhibited the expression levels of several molecular markers, that is, PCNA, MMP2, COX-2, VEGF, vimentin, snail, TGF-β, β-catenin, TNF-α, PD-1 and PD-L1 in mouse lung tissues compared to tumor control mice. Significant inhibition of macrophage and neutrophil infiltration and promotion of CD8 + Tc cell recruitment in the lung microenvironment was observed in dLGG-20-treated mice. A LC/MS-based comparative oxylipin metabolomics study showed that dLGG-20 treatment significantly induced (5.0- to 12.8-fold) the 12/15-LOX catalyzed oxylipin products in mouse serum including 17-HDHA from DHA, 15-HEPE from EPA, 8- and 12-HETEs from AA, and CYP450-derived 20-HETE from AA. CP-2 treatment increased 12/15-LOX derived 8-, 11- and 12-HETEs from AA, and CYP450 derived 11,12-EET from AA ad 9,10-DHOME from LA by 5.3- to 8.1-fold. Of note, dLGG and 17-HDHA were more effective than CP in preventing B16 melanoma cell-induced pulmonary vascular permeability in mice through inhibition of TNF-α production, up-regulation of tight junction proteins claudin1 and ZO-2 and deregulation of Src activation. In conclusion, this study shows the novel therapeutic effect of phytoagent dLGG and suggests its potential as a therapeutic agent for metastatic melanoma.