ADAM21 and astrocytic tumor: When the expression patterns were compared with those in human astrocytic tumor and normal brain tissues [9], they were different in that more ADAM species, including ADAM9, ADAM10, ADAM15, ADAM17, ADAM20, ADAM21 and ADAM28, are constitutively expressed in brain tumor and normal brain tissues, but similar in that the expression of ADAM8 and ADAM30 is negligible.