Anticancer research

Doxorubicin overcomes resistance to drozitumab by antagonizing Inhibitor of Apoptosis Proteins (IAPs).

PMID 25503127


Drozitumab is a fully human agonistic monoclonal antibody that binds to death receptor DR5 and induces apoptosis. However, drozitumab resistance is a major obstacle limiting anticancer efficacy. We examined the potential for the chemotherapeutic agent doxorubicin to overcome resistance against drozitumab-resistant breast cancer cells both in vitro and in vivo. Treatment with doxorubicin increased cell surface expression of DR5, reduced levels of Inhibitors of Apoptosis Proteins (cIAPs) and re-sensitised cells to drozitumab-induced apoptosis. Animals implanted with resistant breast cancer cells into the mammary fat pad and treated with a combination of drozitumab and doxorubicin showed inhibition of tumor growth and a substantial delay in tumor progression compared to untreated controls and mice treated with each agent alone. These results suggest that combination of drozitumab with chemotherapy and agents that modulate IAP levels could potentially be a useful strategy in the treatment of breast cancer.