BRK (Breast Tumor Kinase) is a non-receptor tyrosine kinase from the Src family. It is predominantly expressed in epithelial cells, especially in breast tissue. BRK participates in regulating signaling pathways involved in cell proliferation, differentiation, and survival through the phosphorylation of various substrates. In cells, BRK is mainly localized to the cytoplasm and cell membrane. Its gene expression is abnormally elevated in some cancers, associated with cancer development and prognosis. Mutations or overexpression of the BRK gene may lead to aberrant cellular signaling, promoting tumor progression.