Research Grants Awarded
Endoplasmic Reticulum Stress Induced Apoptosis of Capillary Endothelia: A New Target for Treating Breast Cancer
Tumor Cell Biology I
Background: The incidence of breast cancer is diverse among ethnic backgrounds. The exact causes of breast cancer are unknown, but it involves a combination of genetic (e.g., mutation of BRCA1 and BRCA2 genes), hormonal, dietary, and environmental factors. There are no proven prevention strategies against breast cancer, and the current methods of treatment (surgery, radiation, chemotherapy, hormone therapy, and biological therapy) do not support long-term survival. Continued growth of a malignant tumor requires neo-vascularization (i.e., angiogenesis), and the relative balance of inducers and inhibitors plays a critical role. Using a cytokine mimic tunicamycin (a glucosamine-containing pyrimidine nucleoside, and an antibiotic) we have identified a new therapeutic target to inhibit angiogenesis. Our preliminary results on tunicamycin inhibition of capillary endothelial cell (CE) proliferation, and the reduction of human breast tumor xenograft in nude mice suggest selective induction of "endoplasmic reticulum stress" (ER stress)-mediated apoptosis. Objective/Hypothesis: The long-term objective of the proposal is to establish the signaling mechanism of tunicamycin-induced apoptosis in CE. The hypothesis is that tunicamycin induces “endoplasmic reticulum stress” in CE leading to cell cycle arrest mediated by unfolded protein response . Specific Aims: These are: (1) Demonstration of tunicamycin inhibition of breast tumor growth and increased survival rate of athymic nude mice; (2) Demonstration of decreased angiogenesis by tunicamycin in breast carcinoma in athymic nude mice; (3) Elucidation of unfolded protein response inducible proteins in tunicamycin-treated capillary endothelia of breast tumors in nude mice; and (4) Demonstration of "ER stress” mediated cell growth arrest in G1 and activation of apoptosis in CE are due to differential expression of pro- and anti-apoptotic family of genes/gene products. Study Design: The study will employ mouse model of breast tumor (Aims 1-3) and in vitro model of a non-transformed capillary endothelial cell line (Aim 4). Various cell and molecular biological techniques will be used. Potential Outcomes and Benefits of the Research: Our innovative approach to a more efficacious intervention strategy will allow developing new anti-angiogenic glyco-therapeutics with a significant reduction in morbidity and mortality due to breast cancer.
Breast cancer is the second leading cause of cancer deaths among women of all ages. The exact causes of breast cancer are unknown. It involves a combination of genetic, hormonal, dietary, and environmental factors. There are no proven prevention strategies against breast cancer, and the current methods of treatment (surgery, radiation, chemotherapy, hormone therapy, and biological therapy) neither yielding long-term survival nor providing the quality of life. A growing breast tumor needs much blood flow to support its growth, and is provided by the formation of new blood capillaries through a process known as angiogenesis. The blood capillaries are made up of a specialized cell type called endothelial cells, and tumors cause them to break away from the parent capillaries to form a new capillary network. The more the angiogenesis, the more the breast tumor growth. In malignant breast tissue the endothelial cells proliferate 45 times faster than that of the surrounding benign breast. Therefore, a genetic reprogramming "switches" endothelial cells close to the tumor from a resting state to a rapidly growing state. The branching network of new capillaries requires gene expression and signal processing. Endoplasmic reticulum (ER), the largest intracellular organelle is intimately involved with angiogenesis. The essential functions the vast structure performs include protein synthesis, protein folding, attachment of glycan chains to specific amino acid residue (e.g., asparagine) among other. Our research supports that increased protein N-glycosylation is a driving force for increased proliferation of capillary endothelial cells. Therefore, when treated with tunicamycin, an antibiotic and a selective inhibitor of N-linked protein glycosylation, the capillary endothelial cells develop “ER stress” which arrests cell cycle progression and signals to activate “programmed cell death” i.e., "apoptosis". In addition, when given orally tunicamycin reduces the tumor progression in nude mice xenografts. We, therefore, want to test the hypothesis that by inhibiting protein N-glycosylation, tunicamycin alters protein folding and creates an unfolded protein response, which ultimately signals “ER stress” leading to cell cycle arrest and apoptosis. The expected goal of this application is to make fundamental contributions in developing new generation anti-angiogenic glyco-therapeutics against breast cancer.