SP1 and cancer: Western blot analysis of expression of Sp TFs after transfection of the cancer cell lines with siControl (siCtl, non-specific oligonucleotide) or oligonucleotides targeting Sp1 (siSp1), Sp3 (siSp3), Sp4 (siSp4), or their combination (siSp1,3,4) showed that Sp1, Sp3 and Sp4 proteins were highly expressed in the eight cancer cell lines and this includes both the high and low molecular weight bands for Sp3 [15, 29] (Figure 2).