The blue cell shows the release of the cytosolic tyrosine kinase c-SRC (blue triangles) in exosomes. The orange cell shows the release of the serine-threonine kinase p85 S6K1 from cells through the endoplasmic reticulum-Golgi pathway. p85 S6K1 may enter this trafficking route, because the protein has a cell membrane-penetrating 6-Arg motif at the N-terminal end. Release of c-SRC phosphorylates and activates the protein TIMP2, which increases its ability to activate the protease MMP2. MMP2 cleaves the extracellular matrix, enabling increased cell migration. The released p85 S6K1 penetrates neighboring cells and stimulates cell growth, cell transformation, and cell motility. Both secreted enzymes may have pro-tumorigenic roles. c-SRC release is not inhibited by brefeldin A; p85 S6K1 release is inhibited by brefeldin A. Credit: Nancy R. Gough, BioSerendipity, LLC. Cell images and some protein images created with BioRender.