Necroptotic virotherapy of oncolytic alphavirus M1 cooperated with Doxorubicin displays promising therapeutic efficacy in TNBC.

Triple-negative breast cancer (TNBC) is the most aggressive molecular subtype among breast tumors and remains a challenge even for the most current therapeutic regimes. Here, we demonstrate that oncolytic alphavirus M1 effectively kills both TNBC and non-TNBC. ER-stress and apoptosis pathways are responsible for the cell death in non-TNBC as reported in other cancer types, yet the cell death in TNBC does not depend on these pathways. Transcriptomic analysis reveals that the M1 virus activates necroptosis in TNBC, which can be pharmacologically blocked by necroptosis inhibitors. By screening a library of clinically available compounds commonly used for breast cancer treatment, we find that Doxorubicin enhances the oncolytic effect of the M1 virus by up to 100-fold specifically in TNBC in vitro, and significantly stalls the tumor growth of TNBC in vivo, through promoting intratumoral virus replication and further triggering apoptosis in addition to necroptosis. These findings reveal a novel antitumor mechanism and a new combination regimen of the M1 oncolytic virus in TNBC, and highlight a need to bridge molecular diagnosis with virotherapy.