[Widely expressed (highest in myeloid leukocytes) by human SECTM1 Gene, 248-aa 27-kDa (precursor) Secreted and Transmembrane 1 Protein is an integral type 1a transmembrane protein (extracellular N terminus and cleaved signal peptide) found in the Golgi apparatus and thought to be involved in hematopoietic and/or immune system processes. K12 interacts with CD7 and an approximately 20-kD soluble form is secreted by cells. (NCI) ( NCI )]