ERBB2 and breast cancer: Baseline tumor-infiltrating NK cells in primary HER2+ breast cancers are a predictive biomarker for pCR to anti-HER2 antibody therapy.80 In breast cancer patients, increased NK infiltration in the TME has been observed upon treatment with HER2-targeting agents, supporting the notion that NK cells are important contributors to the antitumor activity observed with currently approved HER2-targeted therapies.81 Multiple ongoing clinical trials are evaluating the impact of NK-directed treatment on the efficacy of HER2-targeting agents (NCT02627274; NCT03319459).