Progesterone Receptor Expression in Different Regions of Glioblastoma Multiforme and in an In Vitro Model

The progesterone receptor (PGR) is involved in processes associated with tumor progression, also in glioblastoma multiforme (GBM). GBM is characterized by regional heterogeneity, with distinct tumor areas differing in their cellular profiles and access to nutrients and oxygen. The aim of this study was to assess the effect of the tumor microenvironment on PGR mRNA and protein expression and to characterize PGR expression in different regions of GBM. To this end, GBM tumor tissues were collected from patients, and an in vitro model was established using the U87 cell line to reproduce hypoxic (H) and nutrient-deficient (ND) conditions. PGR mRNA expression was assessed by real-time PCR, while PGR protein expression was analyzed using ELISA, Western blot, confocal microscopy, and immunohistochemistry. The microenvironmental conditions examined, including H and ND, did not affect PGR protein expression in U87 cells, while H conditions significantly increased PGR mRNA expression. Different GBM regions showed variable levels of PGR protein expression, with the highest expression observed at the peritumoral area. No effect of sex on PGR expression was observed in any of the GBM regions analyzed. Overall, the results indicate regional heterogeneity of PGR expression in GBM.