Background:A soluble form of IL-6 receptor mediates pathogenic IL-6 trans-signaling. Results: ADAM10 and ADAM17 release IL-6 receptor from both human and murine monocytes/macrophages, whereas in the blood IL-6 receptor is also present on microvesicles. Conclusion: Shedding of endogenous IL-6 receptor is similar in humans and mice. Significance: Microvesicle release represents a novel mode of soluble IL-6 receptor generation with potential clinical implications.

A disintegrin and metalloproteinase 17 (ADAM17) is significantly upregulated not only in malignant cells but also in the pro-inflammatory microenvironment of breast cancer. There, ADAM17 is critically involved in the processing of tumor-promoting proteins. Therefore, ADAM17 appears to be an attractive therapeutic target to address not only tumor cells but also the tumor-promoting environment. In a previous study, we generated a monoclonal anti-ADAM17 antibody (A300E). Although showing no complement-dependent cytotoxicity or antibody-dependent cellular cytotoxicity, the antibody was rapidly internalized by ADAM17-expressing cells and was able to transport a conjugated toxin into target cells. As a result, doxorubicin-coupled A300E or Pseudomonas exotoxin A-loaded A300E was able to kill ADAM17-expressing cells. This effect was strictly dependent on the presence of ADAM17 on the surface of target cells. As a proof of principle, both immunotoxins killed MDA-MB-231 breast cancer cells in an ADAM17-dependent manner. These data suggest that the use of anti-ADAM17 monoclonal antibodies as a carrier might be a promising new strategy for selective anti-cancer drug delivery.