Salvianolic acid A inhibits tumor-associated angiogenesis by blocking GRP78 secretion

Glucose-regulated protein 78 (GRP78) often highly expresses in a wide range of tumors, which plays promotive functions due to its diversity of location in the development of tumor. Particularly, GRP78 can be secreted into microenvironment by tumor cells through the pathway of exosome, which promotes proliferation, angiogenesis, and drug resistance in cancer cells. Hence, we discovered a potential inhibitor to block GRP78 secretion. We screened five small molecules that may interact with the GRP78 from 51 traditional Chinese medicine molecules by molecular docking. By using western blot, we found that one of the molecules can inhibit the secretion of GRP78, which is salvianolic acid A (SAA). Further, SAA could interact with the lysine residue 633 (K633) of GRP78, which inhibited GRP78 secretion. Moreover, SAA-GRP78 interaction can facilitate GRP78 of cytosol sorted into lysosome for degradation rather than exosome. In conclusion, our research revealed that SAA has the novel function of anti-angiogenesis via the tumor environment.