ERBB2 and breast cancer: Furthermore, EPHA2 overexpression synergizes with HER2 to promote breast cancer progression and correlates with worse OS and DFS in HER2 positive cancers; in addition, EPHA2 contributes to the development of resistance against the anti-HER2 monoclonal antibody trastuzumab, while its inhibition could restore sensitivity against this regimen [27,44].