MTAP is an enzyme that is essential for the salvage pathway for both adenine and methionine synthesis. MTAP catalyzes the cleavage of 5’-methylthioadenosine into adenine and 5-methylthio-D-ribose-1-phosphate. Adenine is then used to generate AMP whereas 5-methylthio-D-ribose-1-phosphate is converted into methionine (1,2). MTAP is expressed in all normal cells and tissues, although frequently lost in different human tumors including pancreatic adenocarcinoma, neuroendocrine tumors, non-small cell lung carcinoma and breast carcinoma. MTAP is usually codeleted with p16 (cdkN2a/ARF) (3-5). MTAP overexpression in breast cancer cells inhibits their ability to form colonies in soft agar, thereby implicating its function as a tumor suppressor (6).
