In Vivo Antibody-Based Targeting of SUSD3 in Primary and Metastatic Breast Cancers.

Breast cancer is the second leading cause of cancer death in women. AIs are the standard endocrine therapy for postmenupausal cancer. However as AI resistance is the most common reason for the failureof this endocrine treatment. We identified SUSD3 as a key mediator of estrogen in breast cancer cells. The lack of SUSD3 expression in breast cancer tissue was the most significant predictor for non-reponsiveness to an AI. Our proposed study will be the first to target SUSD3 using an antibody strategy to combat breast cancer in vivo, and may serve as a basis for future clinical trials.