PARP1 and glioblastoma: Similar to the effect in M059K cells, knocking down RECQ1 expression sensitized U251 glioblastoma cells to TMZ treatment, while PARP1 supplementation restored GBM cell survival rates and viability (Figures 6C,D), confirming that RECQ1-PARP1 regulation causes significant resistance of glioblastoma cells to the influence of the methylating drug TMZ.