A 90 kDa fragment of filamin A promotes Casodex-induced growth inhibition in Casodex-resistant androgen receptor positive C4-2 prostate cancer cells

Y. Wang, J. I. Kreisberg, R. G. Bedolla, M. Mikhailova, Ralph W deVere White, Paramita M Ghosh

Research output: Contribution to journalArticle

59 Scopus citations

Abstract

Prostate tumors are initially dependent on androgens for growth, but the majority of patients treated with anti-androgen therapy progress to androgen-independence characterized by resistance to such treatment. This study investigates a novel role for filamin A (FlnA), a 280 kDa cytoskeletal protein (consisting of an actin-binding domain (ABD) followed by 24 sequential repeats), in androgen-independent (AI) growth. Full-length FlnA is cleaved to 170 kDa (ABD+FlnA1-15) and 110 kDa fragments (FlnA16-24); the latter is further cleaved to a 90 kDa fragment (repeats 16-23) capable of nuclear translocation and androgen receptor (AR) binding. Here, we demonstrate that in androgen-dependent LNCaP prostate cancer cells, the cleaved 90 kDa fragment is localized to the nucleus, whereas in its AI subline C4-2, FlnA failed to cleave and remained cytoplasmic. Transfection of FlnA16-24 cDNA in C4-2 cells restored expression and nuclear localization of 90 kDa FlnA. Unlike LNCaP, C4-2 cells proliferate in androgen-reduced medium and in the presence of the AR-antagonist Casodex. They also exhibit increased Akt phosphorylation compared to LNCaP, which may contribute to their AI phenotype. Nuclear expression of 90 kDa FlnA in C4-2 cells decreased Akt phosphorylation, prevented proliferation in androgen-reduced medium and restored Casodex sensitivity. This effect was inhibited by constitutive activation of Akt indicating that FlnA restored Casodex sensitivity in C4-2 cells by decreasing Akt phosphorylation. In addition, FlnA-specific siRNA which depleted FlnA levels, but not control siRNA, induced resistance to Casodex in LNCaP cells. Our results demonstrate that expression of nuclear FlnA is necessary for androgen dependence in these cells.

Original languageEnglish (US)
Pages (from-to)6061-6070
Number of pages10
JournalOncogene
Volume26
Issue number41
DOIs
StatePublished - Sep 6 2007

Keywords

  • Akt
  • Androgen receptor
  • Bicalutamide
  • Proliferation
  • Prostate cancer

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research
  • Genetics

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