SP1 and breast carcinoma: Additionally, Sp1/Sp3 binding sites located in the core promoter are known to play a role in transcriptional regulation of VEGF in a variety of cell lines including NIH3T3 cells [12], ZR-75 breast cancer cells [13], Y79 retinoblastoma cells [14], NCI-H322 bronchioloalveolar cells [15], and PANC-1 pancreatic cells [16].