The 24D2 recognizes human CD340 also known as HER2/erbB2, tyrosine kinase cell surface receptor HER2, oncogene ERBB2, and oncogene NGL, neuroblastoma- or glioblastoma-derived. CD340 is a member of the epidermal growth factor receptor family of cell membrane tyrosine kinases containing a single transmembrane domain with an approximate molecular weight of 185 kD. CD340 Contains three furin repeats and two cheY homologous receiver domains in the extracellular region. The HER2/erbB2 protein is expressed on many tumor cells including some breast cancers, lung adenocarcinoma, gastric cancer, ovarian cancer, gliblastoma, some c-ALL blasts and bone marrow MSC. Although the erbB2/HER2 protein contains no ligand binding domain, this protein interacts with other EGF receptor family members to form a heterodimer, stabilize ligand binding, and enhance kinase-mediated downstream signaling. CD340 has been shown to be involved in embryonic development and cancer progression; this protein is amplified in adenocarcinoma of the lung, some breast cancers, glioblastoma, gastric cancer, and ovarian carcinoma, where it functions as an oncogene. Over-expression of erbB2 in breast cancers has been shown to confer Taxol resistance and is a therapeutic target in a number of human cancers. The erbB2/HER-2 protein has been shown to interact with a large number of proteins including SHC1, EGF receptorm, neuroregulin 1, c-Src, integrin β4, Grb2, Grb7, SOS1, caveolin 1, JAK2, PAK1, FAK, and β-catenin, among others. CD340 is extensively modified by tyrosine phosphoryation on multiple residues (Y 1023, Y1139, Y1196, Y1221, Y1222, Y1248). The 24D2 antibody has been shown to be useful for flow cytometry.

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