TWIST1 and granular cell tumor: Treatment of GCT mesenchymal stromal cells from two representative primary GCT cell lines with the ERK-inhibitor PD98059 under FGF-2 stimulation resulted in a significant reduction of ALP, OPN and OC mRNA levels, with optimized 1 nM concentration of inhibitor (Fig. 7c).We also observed a slight increase in TWIST1 expression in both cell lines.