12347 Cholesterol Biosynthesis Inhibitor Ro 48-8071 Suppresses Growth Of Triple-negative Breast Cancer Cells By Inducing Apoptosis And Suppressing Angiogenesis

Abstract Disclosure: Y. Liang: None. S.M. Hyder: None. Triple-negative breast cancers (TNBC) lack ER, PR and Her2neu, proteins that are commonly targeted in breast cancer therapies. Women who suffer from TNBC have limited treatment options and are administered toxic chemotherapeutic agents. They have poor prognosis due to the emergence of drug-resistant cells that lead to tumor metastasis. New non-toxic therapeutic strategies to control TNBC progression, and prevent metastasis are urgently needed. Cholesterol is an essential structural and functional component of cell membranes necessary for tumor growth and progression. Therefore, inhibiting cholesterol production is an attractive therapeutic strategy since tumor cells grow rapidly, and need a greater supply of cholesterol. We targeted oxidosqualene cyclase (OSC), an enzyme that occurs downstream of HMGCoA-reductase in the cholesterol biosynthetic pathway, to disrupt tumor growth. RO 48-8071 (4′-[6-(allylmethylamino)hexyloxy]-4-bromo-2′-fluorobenzophenone fumarate) (RO), has emerged as a useful chemotherapeutic agent for treating several forms of primary tumors but its effect on TNBC is not known. Pharmacological doses of RO potently reduced the viability of both MDA-MB-231 and BT20 TNBC cells in a dose dependent manner (1-50 μM). IC50 values for loss of cell viability was approximately 10 μM for both cell lines following 48 h exposure to RO. Doses close to the IC50 for OSC (1-10 nM) also reduced cell viability following exposure of TNBC cells to RO for a week. Importantly, RO had no effect on the viability of normal human mammary cells. FACS analysis revealed that RO dose-dependently induced apoptosis of TNBC cell lines in vitro. In vivo, administration of 5-10 mg/kg RO to mice with BT-20 TNBC cell-derived xenografts (100 mm[3]) inhibited tumor growth with no apparent toxicity. Immunohistochemical analysis of tumor tissues at the end of treatment showed that RO increased TUNEL expression, suggesting that the in vivo effects of RO were also exerted through mechanisms affecting apoptosis. Furthermore, IHC of tumor sections showed that RO also reduced levels of the angiogenic markers VEGF and CD-31 (blood vessels) in vivo, indicating that suppression of angiogenesis is also part of the mechanism through which RO exerts its anti-tumor effects. We conclude that RO is a potent inhibitor of TNBC and that its anti-tumor effects involve mechanisms that induce apoptosis and suppress angiogenesis. Presentation: 6/2/2024