PTTG1 and malignant colon neoplasm: Moreover combined knockdown of Sp1, Sp3 and Sp4 using an oligonucleotide cocktail (iSp) [20,21,32-34] also decreased expression of p65, PTTG-1, EGFR and cyclin D1 in RKO cells (Figure 2C) confirming their regulation by Sp transcription factors in colon cancer cells.