SP1 and cancer: The maximal (>50%) decrease was only observed in cells transfected with iSp1/3/4 (combined); however, the overall decrease in p65 in this experiment (Fig. 5B) was less than observed in other cancer cell lines [22], [25] and aspirin-induced inhibition of NFκB was only due, in part, to downregulation of Sp1, Sp3 and Sp4 transcription factors.