We found that the tumor-suppressor TAp63 regulates the Hippo pathway effector TAZ through transcriptional regulation of LKB1, which has previously been shown to have important roles in stem cell regulation and metastasis.22, 38, 47 Our laboratory had already made two key discoveries: (1) TAp63 transcriptionally activates Lkb1 in liver, muscle and fat tissues to regulate glucose metabolism,40 and (2) loss of TAp63 results in the development of metastatic mammary adenocarcinoma.14 What was unknown were the mechanisms employed by TAp63 that lead to the development of mammary adenocarcinomas. This evidence concerns the gene STK11 and neoplasm.