GREB1 and ovarian serous tumor: We noted that among spheroid culture-induced genes were several changes typically associated with ovarian cancer, including activation of the transcription factor Pax8, which is present in approximately 80% of ovarian tumors but not typically expressed in murine OSE26; activation of Greb1, which promotes ovarian cancer growth27; and loss of Brca1, which, along with Brca2, is mutated in approximately 22% of high-grade serous ovarian tumors.