Teleocidin A2 inhibits human proteinase‐activated receptor 2 signaling in tumor cells

Enhanced expression of the proteinase‐activated receptor 2 ( PAR 2) is linked to cell proliferation and migration in many cancer cell types. The role of PAR 2 in cancer progression strongly illustrates the need for PAR 2‐inhibiting compounds. However, to date, potent and selective PAR 2 antagonists have not been reported. The natural product teleocidin A2 was characterized against PAR 2‐activating peptide SLIGKV ‐ NH 2 , and trypsin‐induced PAR 2‐dependent intracellular Ca 2+ mobilization in tumor and in primary endothelial or epithelial cells. Further biochemical and cell‐based studies were conducted to evaluate teleocidin specificity. The antagonizing effect of teleocidin A2 was confirmed in PAR 2‐dependent cell migration and rearrangement of actin cytoskeleton of human breast adenocarcinoma cell line ( MDA ‐ MB 231) breast cancer cells. Teleocidin A2 antagonizes PAR 2‐dependent intracellular Ca 2+ mobilization induced by either SLIGKV ‐ NH 2 or trypsin with IC 50 values from 15 to 25 nmol/L in MDA ‐ MB 231, lung carcinoma cell line, and human umbilical vein endothelial cell. Half maximal inhibition of either PAR 1 or P2Y receptor‐dependent Ca 2+ release is only achieved with 10‐ to 20‐fold higher concentrations of teleocidin A2. In low nanomolar concentrations, teleocidin A2 reverses both SLIGKV ‐ NH 2 and trypsin‐mediated PAR 2‐dependent migration of MDA ‐ MB 231 cells, and has no effect itself on cell migration and no effect on cell viability. Teleocidin A2 further controls PAR 2‐induced actin cytoskeleton rearrangement of MDA ‐ MB 231 cells. Thus, for the first time, the small molecule natural product teleocidin A2 exhibiting PAR 2 antagonism in the low nanomolar range with potent antimigratory activity is described.