The Regulation Mechanism Of The Increased Circulating Galectin-3 In The Metastasis Of Breast Cancer

Galectins are a family of carbohydrate-binding proteins with a high affinity for?-galactoside.So far,15 mammalian members of the galectin family have been isolated and identified;members of the family have specific sequence homologies for specific carbohydrate-binding motifs(carbohydrate recognition domain,CRD).Galectin-3,the only member of vertebrate chimera type of galectin family,contains one CRD that is connected to an extended non-lectin N-terminal domain.Galectin-3 could be expressed in intracellular and extracellular.Studies from various laboratories have suggested the possible involvement of galectin-3 in tumor cell apoptosis,adhesion,proliferation and angiogenesis.Galectin-3 is widely expressed in normal tissues and tumor tissues,and the level of galectin-3 is related to the progression of cancer.Compared with that in localized tumors,galectin-3 serum levels in patients with metastatic tumor were significantly elevated.These evidences indicated that circulating galectin-3 may play a crucial role in tumor progression and metastasis.Low serum level of galectin-3 was detected in healthy individuals.The concentrations of galectin-3 in serum from cancer patients were at least 1.5 times higher than that of healthy individuals.This study aims to explore the source of high levels of galectin-3 in the serum of breast cancer patients with metastases and their relationship with Breast cancer metastasis1.Experiments in vitroMethods:(1)HUVECs were incubated with medium supernatant of breast cancer MCF-7 cells or MDA-MB-231 cells for 24 hours,and then the conditioned cultural supernatants were collected.The levels of galectin-3 in the supernatants of monocytes(THP-1)treated by the conditioned cultural supernatants are detected by western blotting method(2)Using western blotting method,ELISA,cytokine array analysis to determine the cytokines mediating the interaction between human breast cancer cells,vascular endothelial cells and monocytesResults:(1)Culture medium supernatant of breast cancer cells could stimulate HUVECs to secrete some cytokines which can induce the secretion of galectin-3 from monocytes.Three kinds of cell are indispensable.(2)Culture medium supernatant of breast cancer cells could induce HUVECs to secrete GM-CSF,and then induced the secretion of galectiin-3 from Monocyte(3)MDA-MB-231 cells expressed high level of VEGFA to induce the secretion of GM-CSF through binding to VEGF receptors on the surface of HUVECs.Sorafenib,an inhibitor of VEGFR,could inhibit the secretion of GM-CSF from HUVECs2.Experiments in vivoMethod:Pulmonary metastasis model of breast cancer in nude mice was established by intravenous injection of MDA-MB-23 1-Luc-D3-H2LN cells by tail vein to observe the regulation mechanism of the increased circulating galectin-3 in the metastasis of breast cancer in vivo.30 female BALB/c mice of 6-8 weeks were randomly divided into 5 groups:(1)Normal control group;(2)Pulmonary metastasis model groups;(3)Sorafenib groups;(4)Clodronate liposomes group;(5)Sorafenib combined with clodronate liposomes groups.The galectin-3 level in serum was detected by ELISA,pulmonary metastases in mice were imaged and quantified using IVIS Imaging SystemResults:(1)Clodronate liposome combined with sorafenib enhanced anti-metastatic effect of clodronate liposome or sorafenib with less toxicity(2)Clodronate liposomes significantly reduced serum level of galectin-3 in vivoConclusions:(1)HUVEC could secrete large amount of GM-CSF induced by VEGFA expressed by breast cancer cells.GM-CSF stimulates THP-1 cells to secrete galectin-3.(2)Monocyte-macrophages are the main secreting source of circulating galectin-3 in the metastasis of breast cancer(3)Clodronate liposomes decreased the levels of circulating galectin-3 by depletion of monocyte-macrophages and inhibited pulmonary metastasis of breast cancer in nude mice.