Inhibitors of nm23 Suppress MDA‐MB‐435 Human Breast Carcinoma Mediated Angiogenesis In Vitro

We have previously discovered that human breast cancer cells secrete a factor that may support tumor angiogeneis. Inhibitors of nucleoside diphosphate kinase (NDPK) are represented by epigallocatechin gallate (EGCG) and ellagic acid (EA). We hypothesize that NDPK‐B secreted by human breast cancer cells contributes to tumor angiogenesis and subsequent metastasis by modulating ATP levels, thereby activating endothelial P2Y purinergic receptors. Supporting this notion, extracellular purine nucleotides (e.g. ATP) have recently emerged as a novel class of proliferative agents with putative roles in cancer and angiogenesis. In proliferation assays, 10μM EGCG but only 3μM EA is required to significantly inhibit MDA‐MB‐435S human breast cancer cell growth while 3μM of either EGCG or EA significantly inhibited CD31 + human endothelial cell growth. CD31 + cell tubule formation on Matrigel™ demonstrated that 30μM EGCG compared to only 1μM EA is sufficient to significantly inhibit angiogenesis. Using Matrigel™, we also determined that MDA‐MB‐435S cell conditioned media significantly induced angiogenesis in a cell number and time dependent manner. Furthermore, 1μM EA but not equamolar EGCG significantly attenuated this cell number induced angiogenesis. In a collagen based in vitro angiogenesis assay, we observed that P2Y 1 R activation by 100μM ATP or 10μM 2‐methyl‐thio‐ATP significantly promoted angiogenesis. Generally, EA was a more potent inhibitor than EGCG for all experiments. We believe this is related to EA > EGCG potency on inhibiting NDPK activity. Further investigation and delineation of NDPK’s hypothesized role in human breast cancer induced angiogenesis may reveal unique therapeutic targets in its treatment and lethal metastatic spread.