Our recent study identified the E3 ubiquitin ligase NEDD4 as a novel interaction partner of HER3 and a negative correlation between NEDD4 and HER3 levels in prostate cancer, which suggests that the level of NEDD4 may serve as a biomarker in the development of HER3 targeting cancer antibody therapies [13]. The gene discussed is NEDD4; the disease is prostate cancer.