MAP2K3 and endometrial cancer: MAPK3 (mitogen-activated protein kinase 3, also called ERK1) was present at higher levels in endometrial cancer specimens from Black compared to White patients in our study (mean ± SD 113.23 ± 45.03 vs. 27 ± 17.88 RU, p = 0.001); however, CPTAC data of all races demonstrated lower MAPK3 expression in endometrial cancer compared to control tissue.