In this study, our in vitro results indicate that GTE treatment induces G1 phase arrest via modulation of cell cycle regulators (e.g., cyclins D1 and E, p21, and p27) in HER2-overexpressing SKOV-3 ovarian cancer and BT-474 breast cancer cells (Figure 2 and Supplementary Figure S4). The gene discussed is CCND1; the disease is breast carcinoma.