EVALUATING THE INHIBITORY EFFECT OF ELAGOLIX & RELUGOLIX ON LEIOMYOMA GROWTH IN 2D CELL CULTURE.

Elagolix and relugolix, both oral GnRH antagonists, are structurally similar; however their pharmakinetic properties differ. At the GnRH receptor elagolix’s IC50 is 1.5 nM with a half-life of 4-6 hours, while relugolix’s IC50 is 0.33 nM with a half-life of 49 hours. The goal of this study is to compare the effect elagolix and relugolix have on the expression of extracellular matrix (ECM) proteins in human leiomyoma cells in 2D cell culture. We hypothesized that both GnRH antagonists directly impact ECM protein expression relative to untreated leiomyoma cells. Leiomyoma cells were grown 2-dimentionally and exposed to elagolix and relugolix for 24 and 48 hours. Expression of various ECM proteins and GnRHR were analyzed using western blot and immunohistochemistry. At 100 nM relugolix (n=10) resulted in maximal, decreased expression of col1A1 at 24 hours (1.78 ± 0.06-fold; p<0.01) and 48 hours (1.92 ± 0.14-fold; p<0.04) and the difference between the two time points was not significant (p=0.87). Elagolix (n=11) resulted in maximal, decreased expression of col1A1 at 24 hours (1.56 ± 0.14-fold; p<0.03) but suppression was lost by 48 hours; the difference between the time points was significant (p<0.01). At 100 nM relugolix resulted in maximal, decreased expression of fibronectin at 24 hours (1.7 ± 0.07-fold; p<0.01) and 48 hours (1.8 ± 0.07-fold; p<0.01) with the difference between the two time points not being significant (p=0.52); elagolix resulted in maximal, decreased expression of fibronectin at 24 hours (1.7 ± 0.14-fold; p=0.01) and 48 hours (2.0 ± 0.09-fold; p<0.01) with no significant difference between the time points (p=0.19). An upregulation was seen in versican expression when cells were treated with relugolix for 24 hours though no concentration achieved growth to statistical significance when compared to untreated cells. A significant, concentration dependent downregulation was achieved at 48 hours (p<0.01) and at 100 nM relugolix resulted in maximal, decreased expression of versican (1.5 ± 0.07-fold; p<0.01). At 24 hours maximal, decreased expression of versican was seen at 100 nM (1.6 ± 0.10-fold; p<0.01) for cells treated with elagolix; a statistically significant upregulation was seen at 48 hours (p=0.02). In terms of the GnRH receptor, no significant difference between GnRH receptor protein expression in relugolix and elagolix was seen at 24 hours (p=0.57). At 48 hours, GnRH receptor protein expression increased in cells treated with elagolix when compared to cells treated with relugolix (p=0.037) suggesting the suppressive effect of elagolix at the receptor is lost by 48 hours. Our findings suggest that treatment with relugolix and elagolix directly regulated collagen, fibronectin, versican, and GnRH receptor protein expression in our 2D human leiomyoma cell culture model.