A naturally derived small molecule disrupts ligand-dependent and ligand-independent androgen receptor signaling in human prostate cancer cells.

Abstract

Continued reliance on androgen receptor (AR) signaling is a hallmark of prostate cancer, including the development of castration-resistant prostate cancer (CRPC), making it an attractive therapeutic target for prostate cancer treatment. Mahanine is a novel carbazole alkaloid derived from the leaves of Murraya koenigii, commonly known as the curry leaf plant, which grows widely across East-Asia. We show here that mahanine possesses the ability to inhibit ligand-dependent and -independent AR transactivation, leading to a prominent decline in AR target gene expression. Mahanine treatment causes a time- and dose-dependent decline in AR protein levels, including truncated AR splice variants, in a panel of androgen-responsive and -independent prostate cancer cells. The decrease in AR levels induced by mahanine occurs posttranslationally by proteasomal degradation, without any change in the AR gene expression. Mahanine treatment induces an outward movement of the AR from the nucleus to the cytoplasm, leading to an initial increase in cytoplasmic AR levels, followed by a gradual decline in the AR levels in both cellular compartments. Ligand-induced AR phosphorylation at Ser-81, a phospho-site associated with prostate cancer cell growth and AR transactivity, is greatly diminished in the presence of mahanine. The decline in AR phosphorylation at Ser-81 by mahanine occurs via the inactivation of mitotic kinase CDK1. Collectively, our data demonstrate that mahanine strongly disrupts AR signaling and inhibits the growth of androgen-dependent and -independent prostate cancer cells, thereby implicating a therapeutic role of mahanine in prostate cancer treatment.

• Authors: Karishma S Amin, Shankar Jagadeesh, Gakul Baishya, Paruchuri G Rao, Nabin C Barua, Samir Bhattacharya, Partha P Banerjee
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 13 Issue 2 Pg. 341-52 (Feb 2014) ISSN: 1538-8514 [Electronic] United States
• PMID: 24258347 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• AR protein, human
• Androgens
• Carbazoles
• Ligands
• Receptors, Androgen
• mahanine
• Dihydrotestosterone
• Serine
• CDC2 Protein Kinase
• Proteasome Endopeptidase Complex

Topics

• Androgens (pharmacology)
• Blotting, Western
• CDC2 Protein Kinase (metabolism)
• Carbazoles (chemistry, pharmacology)
• Cytoplasm (metabolism)
• Dihydrotestosterone (pharmacology)
• Dose-Response Relationship, Drug
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Ligands
• Male
• Microscopy, Fluorescence
• Molecular Structure
• Murraya (chemistry)
• Phosphorylation (drug effects)
• Plant Leaves (chemistry)
• Prostatic Neoplasms (genetics, metabolism, pathology)
• Proteasome Endopeptidase Complex (metabolism)
• Protein Transport (drug effects)
• Receptors, Androgen (genetics, metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Serine (metabolism)
• Signal Transduction (drug effects, genetics)
• Transcriptional Activation (drug effects)