Abstract
Glioblastomas (GBM) are the most frequent and aggressive primary tumor of the central nervous system. In recent years, it has been proposed that sex hormones such as progesterone play an essential role in GBM biology. Membrane progesterone receptors (mPRs) are a group of G protein-coupled receptors with a wide distribution and multiple functions in the organism. There are five mPRs subtypes described in humans: mPRα, mPRβ, mPRγ, mPRδ, and mPRε. It has been reported that human-derived GBM cells express the mPRα, mPRβ, and mPRγ subtypes, and that progesterone promotes GBM progression in part by mPRα specific activation; however, it is still unknown if mPRδ and mPRε are also expressed in this type of tumor cells. In this study, we characterized the expression and hormonal regulation of mPRδ and mPRε in human GBM cells. We also analyzed a set of biopsies from TCGA. We found that the expression of these receptors is dependent on the tumor's grade and that mPRδ expression is directly correlated to patients' survival while the opposite is observed for mPRε. By RT-qPCR, Western blot, and immunofluorescence, the expression of mPRδ and mPRε was detected for the first time in human GBM cells. An in silico analysis showed possible progesterone response elements in the promoter regions of mPRδ and mPRε, and progesterone treatments downregulated the expression of these receptors. Our results suggest that mPRδ and mPRε are expressed in human GBM cells and that they are relevant to GBM biology.