It can also be activated by upstream kinases, such as liver kinase B1 (LKB1), a tumor-suppressor gene product linked to Peutz-Jeghers syndrome, and Ca2+/calmodulin-dependent protein kinase kinase-β (CaMKKβ), which phosphorylate threonine 172 on the catalytic α subunit (Hawley et al., 2003). This evidence concerns the gene STK11 and Peutz-Jeghers syndrome.