To test if luminal A cancer cell lines might be intrinsically addicted to HER3 oncogenic signaling [43], cells were challenged with increasing doses of the therapeutic monoclonal antibody lumretuzumab, which blocks binding of NRG1 to HER3 [44], or pertuzumab, which blocks HER2/HER3 heterodimer formation [45]. This evidence concerns the gene NRG1 and cancer.