Raloxifene inhibits growth of RT4 urothelial carcinoma cells via estrogen receptor-dependent induction of apoptosis and inhibition of proliferation

Horm Cancer. 2013 Feb;4(1):24-35. doi: 10.1007/s12672-012-0123-9. Epub 2012 Sep 11.


Bladder cancer is the fifth most common type of cancer in the USA, with over 70,000 new cases diagnosed each year. Treatment often involves invasive surgical therapies, as chemotherapy alone is often ineffective and associated with high recurrence rates. Identification of estrogen receptor-β (ERβ) in up to 75 % of urinary tumors raises the question of whether this receptor could be targeted to effectively treat bladder cancer. In this study, a panel of five bladder cancer cell lines representing a variety of disease stage and grades were treated with the antiestrogens 4-hydroxytamoxifen, raloxifene, or the pure antagonist ICI 182,780. All cell lines were ERβ positive while only a few expressed estrogen receptor-α (ERα). Notably, all but the TCCSUP cell line were growth inhibited 20-100 % by at least two antiestrogens. Using RT4 cells, we demonstrate that growth inhibition by raloxifene is ER dependent and either ERα or ERβ can mediate this response. Activation of caspase-3 and its effector poly-ADP ribose polymerase (PARP) demonstrate that raloxifene-induced growth inhibition is in part the result of increased apoptosis; this PARP cleavage was ER dependent. Moreover, changes in the expression of cell cycle genes indicate that cell proliferation is also affected. Specifically, raloxifene treatment results in the stabilization of p27 protein, likely via the downregulation of S-phase kinase-associated protein (SKP2). Expression of the negative cell cycle regulator B-cell translocation gene (BTG2) is also increased, while cyclin D1 transcription is reduced. These results indicate that antiestrogens may be useful therapeutics in the treatment of bladder cancer by targeting ER and inhibiting growth via multiple mechanisms.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Apoptosis / drug effects*
  • Apoptosis / genetics
  • Carcinoma, Transitional Cell / drug therapy*
  • Carcinoma, Transitional Cell / genetics
  • Carcinoma, Transitional Cell / metabolism
  • Carcinoma, Transitional Cell / pathology
  • Caspase 3 / genetics
  • Caspase 3 / metabolism
  • Cell Line, Tumor
  • Cell Proliferation / drug effects*
  • Cyclin D1 / genetics
  • Cyclin D1 / metabolism
  • Down-Regulation / drug effects
  • Down-Regulation / genetics
  • Estradiol / analogs & derivatives
  • Estradiol / pharmacology
  • Estrogen Antagonists / pharmacology
  • Estrogen Receptor alpha / genetics
  • Estrogen Receptor alpha / metabolism*
  • Estrogen Receptor beta / genetics
  • Estrogen Receptor beta / metabolism*
  • Fulvestrant
  • Humans
  • Immediate-Early Proteins / genetics
  • Immediate-Early Proteins / metabolism
  • MCF-7 Cells
  • Poly(ADP-ribose) Polymerases / genetics
  • Poly(ADP-ribose) Polymerases / metabolism
  • Raloxifene Hydrochloride / pharmacology*
  • S-Phase Kinase-Associated Proteins / genetics
  • S-Phase Kinase-Associated Proteins / metabolism
  • Tamoxifen / analogs & derivatives
  • Tamoxifen / pharmacology
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism
  • Urinary Bladder Neoplasms / drug therapy*
  • Urinary Bladder Neoplasms / genetics
  • Urinary Bladder Neoplasms / metabolism
  • Urinary Bladder Neoplasms / pathology


  • ESR1 protein, human
  • Estrogen Antagonists
  • Estrogen Receptor alpha
  • Estrogen Receptor beta
  • Immediate-Early Proteins
  • S-Phase Kinase-Associated Proteins
  • Tumor Suppressor Proteins
  • Tamoxifen
  • Cyclin D1
  • BTG2 protein, human
  • afimoxifene
  • Fulvestrant
  • Raloxifene Hydrochloride
  • Estradiol
  • Poly(ADP-ribose) Polymerases
  • Caspase 3