HER2

Human epidermal growth factor receptor 2 (HER2) is a transmembrane protein with tyrosine kinase activity in the epidermal growth factor receptor (EGFR) family. HER2 has no known natural ligand, but it can form heterodimer structure with other family members, activating various pathways to promote cell proliferation and inhibit apoptosis. Abnormal HER2 expression is found in about 20% of breast cancer, so HER2, together with ER, PR and Ki-67, becomes the most crucial diagnostic indicator of breast cancer. Moreover, HER2 positivity is considered as an independent risk factor for poor prognosis. It can down-regulate the tumor suppressor gene P53 by continuously activating the P13K/AKT pathway, thereby inhibiting apoptosis and increasing invasiveness. Meanwhile, HER2 expression heterogeneity is an important reference factor for treatment decision. Some research suggested that patients with its low expression have lower therapeutic reactivity to trastuzumab compared to its high expression. In addition, the research on the mechanism of HER2 in lung cancer, colorectal cancer, cervical cancer and other tumors has been gradually carried out.