ERBB3 and neoplasm: It was reported that the observed potent decrease in TNBC tumor growth upon treatment with a combination of a HER3 inhibitor and an EGFR inhibitor,[54] which suggests that simultaneous activation of EGFR and HER3 may contribute to tumor growth, implicating a potential role for PCSK9 in modulating the activity or localization of these receptors on the cell surface.