Sortilin-related receptor is a druggable therapeutic target in breast cancer

In breast cancer, the currently approved anti-receptor tyrosine-protein kinase erbB-2 (HER2) therapies do not fully meet the expected clinical goals due to therapy resistance. Identifying alternative HER2-related therapeutic targets could offer means to overcome these resistance mechanisms. We have previously demonstrated that an endosomal sorting protein, sortilin-related receptor (SorLA), regulates the traffic and signaling of HER2 and HER3, thus promoting resistance to HER2-targeted therapy in breast cancer. This study aims to assess the feasibility of targeting SorLA using a monoclonal antibody. Our results demonstrate that anti-SorLA antibody (SorLA ab) alters the resistance of breast cancer cells to HER2 monoclonal antibody trastuzumab in vitro and in ovo . We found that SorLA ab and trastuzumab combination therapy also inhibits tumor cell proliferation and tumor cellularity in a mouse xenograft model of HER2-positive breast cancer. In addition, SorLA ab inhibits the proliferation of breast cancer patient-derived explant three-dimensional cultures. These results provide for the first time proof-of-principle that SorLA is a druggable target in breast cancer.