PTEN and triple-negative breast carcinoma: By studying genetically engineered mouse models, Liu and colleagues found that combined PTEN and p53 inactivation in the mammary gland resulted in claudin-low triple-negative breast cancers [TNBC, a subset of ER-negative breast cancers that are predominantly classified as IC10 and IC4 in Curtis et al (2012)], with hyperactive AKT signaling (Liu et al, 2014).