DOK3 and histiocytic sarcoma: The adaptor protein family downstream of kinase 1 (DOK1) to DOK3 is mainly found in immune cells, and they are closely related, with some functional redundancy.16 Mice deficient in DOK1 to DOK3 develop lung cancer and histiocytic sarcomas,17 revealing the functional importance of DOK proteins in regulating cellular responses in vivo.