Neoadjuvant endocrine therapy: A potential strategy for ER-positive breast cancer

Figure 1 The crosstalk between estrogen receptor and growth factor receptor intracellular signaling pathways. Growth factor receptors (GFRs) activate the downstream PI3K/AKT/mTOR signaling pathway and the Cyclin D1/CDK4/6 complex, while the ER-E2 complex has the same effect[79]. The Cyclin D1/CDK4/6 complex drives cell proliferation by inducing Rb phosphorylation and promotes cell cycle from G1 phase to S phase in the nucleus[80]. Targeted agents against the CDK4/6 pathway and the PI3K/AKT/mTOR pathway can trigger cell cycle arrest and control tumor progression. ER: Estrogen receptor; GFR: Growth factor receptor; CDK4/6: Cyclin-dependent kinase; PI3K: Phosphatidylinositol 3-kinase; PIP2: Phosphatidylinositol 4,5-biphosphate; PIP3: Phosphatidylinositol triphosphate; mTOR: Mammalian target of rapamycin; Rb: Retinoblastoma protein.