Antiangiogenic Action of Chemically Modified Tetracyclines in Breast Cancer

摘要

The nonantimicrobial Chemically Modified Tetracyclines (CMTs) inhibit invasiveness and metastasis in tumors. This study examined CMTs as inhibitors of the angiogenic response in human breast cancer cell lines, a tumor-infiltrating macrophage model and endothelial cells. CMT 308, a 9-amino derivative of CMT 300 (6-demethyl-6- deoxy-4-dedimethyl- aminotetracycline) reduced basal VEGF secretion from MCF-7 and MDA-MB-453 cells (early breast cancer models) and from MDA-MB-435s and MDA-MB-231 cells (late stage disease models). Sub-cytotoxic doses of CMT 308 also specifically reduced basal VEGF secretion from MonoMac 6 cells (a model of tumor-infiltrating macrophages). In time course studies with MCF-7 cells, VEGF secretion was detected within 4 hours of plating but addition of CMT 308 inhibited further VEGF secretion for up 8 hours. In MonoMac 6 cells, CMT 308 suppressed VEGF secretion for at least 24 hours. CMT 308 inhibited new secretion of VEGF but did not affect pre- existing VEGF levels. Treatment of breast tumor cells with TGF increased intracellular and secreted VEGF protein levels, but not VEGF mRNA levels. CMT 308 decreased levels of TGF -induced VEGF protein in MDA-MB-435s cell lysates. CMT 300, like CMT 308, did not affect VEGF mRNA levels in the breast cancer cells, but unlike CMT 308, CMT 300 did not diminish levels of secreted VEGF protein. In contrast to its effects on breast tumor lines, CMT 308 decreased VEGF mRNA levels as well as secreted VEGF protein levels in MonoMac 6 cells. Both CMT 300 and CMT 308 reduced tube formation, migration and invasion of endothelial cells through layers of Matrigel in the absence of toxicity. These results indicate that CMT 308 acts at a post-transcriptional level to inhibit basal secretion, as well as some fraction of TGF -stimulated secretion of VEGF in breast cancer and monocytic cells.