The panel included ER-positive breast cancer cells with activating PIK3CA mutations (helical domain mutation: MCF7 and BT-483; kinase domain mutation: T47D), PTEN mutation (MDA-MB-415, ZR75-1 and CAMA-1), HER2 gene amplification (HCC1419) or wild-type PIK3CA and PTEN (HCC712, HCC1428, HCC1500 and MDA-MB-175), and ER-negative breast cancer cell lines with HER2 amplification (SK-BR-3), and wild-type PIK3CA and PTEN (HCC1806). The gene discussed is ESR1; the disease is breast cancer.