ERBB2 and breast cancer: Therapeutic targeting of the IL-6-IL6ST/GP130-JAK-STAT cascade in breast cancer is currently being explored in a phase I clinical trial using the anti-IL-6R antibody Tocilizumab in combination with HER2-targeting agents in patients with HER2-positive tumors resistant to first-line therapy with Trastuzumab (ClinicalTrials.gov Identifier: NCT03135171).