Several compounds including betulinic acid, tolfenamic acid and curcumin induce proteasome-dependent degradation of Sp proteins in prostate, pancreatic and bladder cancer cells respectively [22, 23, 38, 39]; however, proteasome inhibitors did not block downregulation of Sp1, Sp3 or Sp4 by sulindac sulfide in SW480 and RKO cells (data not shown). The gene discussed is SP4; the disease is urinary bladder cancer.