Here we have shown, by using a panel of normal endometrial tissue, endometrial cancer samples and EC cell lines that PIR2 (i) is exclusively expressed in EC and not in normal endometrium (Fig. 1), (ii) is important for EC cell proliferation (Fig. 1), and (iii) can be targeted by using GSK3β inhibitors (Figs. 3 and 4); substantiating PIR2 is a potential targetable biomarker for EC. Here, GSK3B is linked to endometrial cancer.