Dysregulation of the protein phosphatase 3 catalytic subunit beta (PPP3CB)-FOXO3a-miRNA axis in heceptin-resistant human epithelial growth factor receptor-2 (HER2)-positive breast cancer disrupts this feedback mechanism, leading to the overproduction of insulin like growth factor 2 (IGF2) in heceptin-resistant breast cancer cells. The gene discussed is ERBB2; the disease is breast cancer.