SP1 and cancer: Several other studies reported that RXR interactions with Sp1 were involved in the activation of the ATP-binding cassette transporter 1 (ABCA1; LXR partner) [85], urokinase (RAR partner) [86,87], tissue-type plasminogen activator (t-PA; RAR partner) [88] and acyl-coenzyme A oxidase (ACO; PPAR partner) [89] in non-cancer cell lines.