International Journal of Academic Health and Medical Research (IJAHMR)   Year: 2020 | Volume: 4 | Issue: 7 | Page No.: 9-19 The Role of the Retinoic Acid Pathway in Decidualization of Endometrial Stromal Cells Farah Bashir, Ayesha Batool, Muhammad Asif Abstract: This study found RBP1 levels to be reduced in endometriosis lesions and in ME-SFCs derived from endometriosis subjects. In addition to endometriosis lesions, RBP1 levels have been found to be reduced in breast cancer, ovarian cancer, cervical, and endometrial cancer. The reduction of RBP1 in cancer suggests that RBP1 may act as a tumor suppressor (Mendoza-Rodriguez, et al. 2013). In fact, in a study of breast cancer cell lines over- expressing RBP1 led to reduced survival of breast cancer cells in suspension by inhibiting anchorage independent growth mediated by the PI3K/AKT. The PI3K/AKT has been shown to be elevated in endometriosis lesions compared to normal eutopic endometrium of control subjects, however, this is thought to contribute to the decidualization defects observed in endometriosis-associated infertility. It is, however, interesting to make a comparison between breast cancer and endometriosis. In breast cancer higher levels of RBP1 reduced p-AKT/AKT levels, thereby inhibiting the PI3K/AKT pathway leading to reduced survival of cells in suspension cultures; this is thought to be due to altered levels of retinoic acid. Endometriosis lesions have reduced expression of RBP1 and higher levels of pAKT/AKT that is not reduced upon decidualization. RBP1 expression and the PI3K/AKT pathway in endometriosis have not yet been connected in the same way that they are connected in breast cancer. In our future studies we should focus on the other potential roles that RBP1 could play in the development of endometriosis rather than solely investigating its effect on decidualization.