PTGS2 and glioblastoma: It was also observed that GBM cells, Pt#3 and U87MG, gradually showed increased tolerance to TMZ in the long-term treatment, and this increased tolerance was compromised by the PTGS2 inhibitor, celecoxib, resulting in a decrease in the number of adhered cells, an increase in the number of round-up cells, and the destruction of cell morphology (Additional file 1: Fig. S4c, d).