The cell division control protein 42 homolog (CDC42) is frequently upregulated by several cell surface receptors and breast cancer oncogenes, as noted by Cruz-Collazo et al. (2021); the CDC42 inhibitor inhibits infiltration and metastasis of triple-negative breast cancer cells while also inducing cell cycle arrest and apoptosis of HER2-overexpression-type breast cancer cells. The gene discussed is ERBB2; the disease is breast carcinoma.