Inhibition of androgen receptor functions by gelsolin FxxFF peptide delivered by transfection, cell-penetrating peptides, and lentiviral infection.
BACKGROUND
Prostate cancer (PC) growth is dependent on the androgen-androgen receptor (AR) axis. Because current androgen ablation therapies of PC lead to resistance, novel approaches to block AR activity are urgently needed.


METHODS
We inhibited AR function beyond the level of hormone binding by blockade of the coactivator groove in the ligand-binding domain (LBD) using a high-affinity gelsolin FxxFF peptide. Following peptide selection, the effect of the gelsolin FxxFF peptide on AR functions was determined in Hep3B cells that were transiently transfected with pM-peptide expression vectors or were incubated with synthetic gelsolin FxxFF peptide coupled to the TAT cell-penetrating peptide. Lentiviruses expressing the gelsolin FxxFF peptide were used to study endogenous AR target gene expression in LNCaP cells.


RESULTS
pM-Gelsolin FxxFF efficiently interfered with AR N/C interaction and specifically inhibited AR-regulated reporter gene activity. The peptide did not inhibit progesterone receptor (PR) and glucocorticoid receptor (GR) activity, nor constitutively active gene promoters. The peptide also specifically blocked in vitro interactions of AR LBD with peptides. Like the gelsolin FxxFF peptide expressed by an expression vector, synthetic TAT-gelsolin FxxFF peptide efficiently blocked AR N/C interaction and inhibited full-length AR-regulated reporter gene activity. It hardly affected PR and GR activity, but the effect on constitutively active promoters was variable. Lentiviral gelsolin FxxFF peptide inhibited expression of KLK2 and NDRG1, but hardly affected PSA and TMPRSS2.


CONCLUSIONS
Our results show that the AR coactivator groove may function as a target to overcome therapeutic failure that arises during current androgen ablation therapies.
van de Wijngaart
Dennis J
DJ
Department of Pathology, Josephine Nefkens Institute, Erasmus MC, Rotterdam, the Netherlands.
Dubbink
Hendrikus J
HJ
Molier
Michel
M
de Vos
Carola
C
Jenster
Guido
G
Trapman
Jan
J
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D059002:Androgen Receptor Antagonists / Q000008:administration & dosage*; D057846:Cell-Penetrating Peptides / Q000008:administration & dosage*; D018260:Gelsolin / Q000008:administration & dosage* / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D016086:Lentivirus / Q000235:genetics*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011944:Receptors, Androgen / Q000737:chemistry / Q000502:physiology*; D014162:Transfection
C410798:AR protein, human; D059002:Androgen Receptor Antagonists; D057846:Cell-Penetrating Peptides; D018260:Gelsolin; D011944:Receptors, Androgen