Treating Breast Cancer with Tunicamycin – A New Paradigm

Introduction: Breast cancer is a multi-factorial progressive disorder with unknown etiology and exists in multiple molecular subtypes. In the last 50 years, it has become a public health problem diagnosing nearly 2 million cases per year with a mortality rate of approximately half a million, worldwide. Current treatment strategies have not succeeded in eliminating the disease. Objectives: A symbiotic relationship between microvascular endothelial cells and cancer cells is the driving force for breast cancer progression. N-glycan gives corporate identity to asparagine-linked (N-linked) glycoproteins which are cell-type specific. We have taken a holistic approach and evaluated the effect of Tunicamycin (Mr844Da), a natural product (source: Streptomyces lysosuperificus), and a protein N-glycosylation inhibitor on angiogenesis and breast tumor progression. Methods: Capillary endothelial cells and breast cancer cells in culture have been used as in vitro models, and Balb/c (nu/nu) mice as in vivo models to test Tunicamycin's anti-angiogenic and anti-tumorigenic effects. Cellular and molecular biological/biotechnological techniques, as well as structural studies, have been used to measure the outcome. Results: Tunicamycin, a competitive inhibitor of N-acetylglucosaminyl 1-phosphate transferase (GPT) in the endoplasmic reticulum (ER) blocks the synthesis of Glc3Man9GlcNAc2-PP-Dol [i.e., a lipid-linked oligosaccharide (LLO)], a "key step" in protein N-glycosylation in a dose- and time-dependent manner. In the absence of N-glycosylation, the proteins are not folded causing "ER stress" that follows the cell cycle arrest in G1 with an end result of programmed cell death (i.e., apoptosis) by unfolded protein response (upr) signaling. In vivo, testing on breast tumors in athymic nude mice supports a significant reduction in tumor size (~55-65% in 1-3 weeks at 0.25μg-1.0μg/Kg body weight) whether Tunicamycin has been administered intravenously (iv) or orally. Immunohistochemistry, immunocytochemistry, and other molecular/structural techniques reveal a quantitative reduction of N-glycan expression both in blood vessels and in tumor cells. Mechanistic details indicate there are transcriptional and translational attenuations. Conclusions: Our study supports that Tunicamycin is 15-60 fold more effective than the FDA breast cancer drug Taxol and the effect is irreversible or cannot be washed out or neutralized. VEGF/FGF or any other cell/tumor growth promoters cannot override the apoptotic effect of Tunicamycin either. Importantly, Tunicamycin is active against the proliferative cells only, so no collateral cells or tissue damage are expected. Additionally, Tunicamycin gold nanoparticles are three times more potent than the natural formulation. Because of its ability to block angiogenesis and tumor cell proliferation, Tunicamycin targets the tumors holistically and eliminates breast cancer progression indiscriminately. We, therefore, conclude that Tunicamycin would be the next-generation "Glycotherapy" treating breast cancer in the clinic and saving lives.