title: Silodosin inhibits the growth of bladder cancer cells and enhances the cytotoxic activity of cisplatin via ELK1 inactivation.
abstract: Silodosin, a selective α1A-adrenergic blocker prescribed for the symptomatic treatment of benign prostatic hyperplasia, was previously shown to decrease the expression of ELK1, a c-fos proto-oncogene regulator and a well-described downstream target of the PKC/Raf-1/ERK pathway, in human prostate smooth muscle cells. PKC/Raf-1/ERK activation has also been implicated in drug resistance. In the current study, we assessed the effects of silodosin on ELK1 expression/activity in bladder cancer cells as well as on their proliferation in the presence or absence of chemotherapeutic drugs, including cisplatin and gemcitabine. In bladder cancer cell lines, silodosin reduced the expression of ELK1 (mRNA/protein) and its downstream target, c-fos gene, as well as the transcriptional activity of ELK1. While silodosin alone (up to 10 μM) insignificantly affected the growth of bladder cancer cells cultured in androgen depleted conditions or those expressing ELK1-short hairpin RNA, it considerably inhibited the viability of androgen receptor (AR)-positive/ELK1-positive cells in the presence of androgens. Silodosin also inhibited the migration of ELK1-positive cells with or without a functional AR, but not that of ELK1 knockdown cells. Interestingly, silodosin treatment or ELK1 silencing resulted in increases in drug sensitivity to cisplatin, but not to gemcitabine, even in AR-negative cells or AR-positive cells cultured in an androgen-depleted condition. In addition, silodosin decreased the expression of NF-κB, a key regulator of chemoresistance, and its transcriptional activity. Moreover, immunohistochemistry in bladder cancer specimens from patients who received neoadjuvant chemotherapy revealed that phospho-ELK1 positivity strongly correlated with chemoresistance. Silodosin was thus found to not only inhibit cell viability and migration but also enhance the cytotoxic activity of cisplatin in bladder cancer lines via inactivating ELK1. Our results suggest that combined treatment with silodosin is useful for overcoming chemoresistance in patients with ELK1-positive urothelial carcinoma receiving cisplatin.
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA ; Department of Urology, Yokohama City University Graduate School of Medicine Yokohama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kawahara
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ide
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA.
authors.forename: Eiji
authors.initials: E
authors.lastname: Kashiwagi
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Patterson
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Inoue
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA ; Department of Biology, University of Babylon College of Science for Women Babylon, Iraq.
authors.forename: Hasanain Khaleel
authors.initials: HK
authors.lastname: Shareef
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA ; Department of Biology, University of Baghdad College of Science Baghdad, Iraq.
authors.forename: Ali Kadhim
authors.initials: AK
authors.lastname: Aljarah
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA.
authors.forename: Yichun
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Baras
authors.affiliation: Departments of Pathology and Urology, Johns Hopkins University School of Medicine Baltimore, MD, USA.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyamoto
keywords: ELK1; bladder cancer; cisplatin; drug sensitivity; silodosin; α1A-adrenergic blocker