Microenvironment and Immunology Chromogranin A Regulates Tumor Self-Seeding and Dissemination

Cancer progression involves the seeding ofmalignant cells in circulation and the colonization of distant organs. However, circulating neoplastic cells can also reinfiltrate the tumor of origin. This process, called "tumor-self seeding," can selectmore aggressive cells thatmay contribute to cancer progression. Here, usingmousemammary adenocarcinoma models, we observed that both tumor self-seeding and organ colonization were inhibited by chromogranin A (CgA), a protein present in variable amounts in the blood of cancer patients. Mechanism studies showed that CgA inhibited the shedding of cancer cells in circulation from primary tumors, as well as the reinfiltration of tumors and the colonization of lungs by circulating tumor cells. CgA reduced gap formation induced by tumor cell–derived factors in endothelial cells, decreased vascular leakage in tumors, and inhibited the transendothelial migration of cancer cells. Together, our findings point to a role for circulating CgA in the regulation of tumor cell trafficking from tumor-to-blood and from blood-to-tumor/normal tissues. Inhibition of the multidirectional trafficking of cancer cells in normal and neoplastic tissues may represent a novel strategy to reduce cancer progression. Cancer Res; 72(2); 449–59. 2011 AACR.