SP1 and central nervous system cancer: Figure 2C clearly showed that the nuclear expression of DNA PKcs, Ku70, Ku80 and EGFR was downregulated after pMU and pMC treatments. Moreover, the expression of SP1, a known transcription factor of DNA PKcs, Ku70 and Ku80, was reduced in pMU- and pMC-treated glioma cells compared to untreated cells (Figure 2A).