ERBB2 and cancer: These changes can drive cancer progression through overexpression of immune inhibitory motifs (e.g. sialic acids and PD-L1),22,23 metastasis drivers (e.g. integrins),24 and receptors that initiate proliferation and anti-apoptosis signals (e.g. HER2).25 Therapeutically, these markers are used as targeting epitopes for antibody–drug conjugates (ADCs), checkpoint inhibitors, and targeted enzyme therapeutics.