PLAC1 and breast cancer: Indirect support for the idea that PLAC1 function is crucial for normal placental development and maintenance comes from the discovery that PLAC1 is expressed in a variety of human solid tumors including gastric cancers [23], non-small cell lung cancers [24], breast cancers [5], hepatocellular and colorectal cancers [25, 26], and endometrial and ovarian cancers [27, 28].