Increased Expression of Androgen Receptor Sensitizes Prostate Cancer Cells to Low Levels of Androgens

• Published in: Cancer research (Chicago, Ill.) Vol. 69; no. 20; pp. 8141 - 8149
• Main Authors: WALTERING, Kati K, HELENIUS, Merja A, SAHU, Biswajyoti, MANNI, Visa, LINJA, Marika J, JÄNNE, Olli A, VISAKORPI, Tapio
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 15.10.2009
• Subjects: Androgens - pharmacology; Antineoplastic agents; Antineoplastic Agents - pharmacology; Biological and medical sciences; Biomarkers, Tumor - genetics; Biomarkers, Tumor - metabolism; Blotting, Western; Cell Line, Tumor; Cell Proliferation - drug effects; Chromatin Immunoprecipitation; Dose-Response Relationship, Drug; Fluorescent Antibody Technique; Gene Expression Profiling; Gynecology. Andrology. Obstetrics; Humans; Male; Male genital diseases; Medical sciences; Neoplasms, Hormone-Dependent - drug therapy; Neoplasms, Hormone-Dependent - genetics; Neoplasms, Hormone-Dependent - metabolism; Nephrology. Urinary tract diseases; Oligonucleotide Array Sequence Analysis; Pharmacology. Drug treatments; Prostatic Neoplasms - drug therapy; Prostatic Neoplasms - genetics; Prostatic Neoplasms - metabolism; Purines - pharmacology; Receptors, Androgen - genetics; Receptors, Androgen - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; Tumors; Tumors of the urinary system; Urinary tract. Prostate gland; Urinary system disease; Prostate disease; Androgen; Androgen receptor; Malignant tumor; Sex steroid hormone; Gene expression; Male genital diseases; Prostate cancer; Tumor cell; Cancer; Hormonal receptor
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.CAN-09-0919

Androgen receptor (AR) is known to be overexpressed in castration-resistant prostate cancer. To interrogate the functional significance of the AR level, we established two LNCaP cell sublines expressing in a stable fashion two to four times (LNCaP-ARmo) and four to six times (LNCaP-ARhi) higher level of AR than the parental cell line expressing the empty vector (LNCaP-pcDNA3.1). LNCaP-ARhi cell line grew faster than the control line in low concentrations, especially in 1 nmol/L 5alpha-dihydrotestosterone (DHT). Microarray-based transcript profiling and subsequent unsupervised hierarchical clustering showed that LNCaP-ARhi cells clustered together with VCaP cells, containing endogenous AR gene amplification and overexpression, indicating the central role of AR in the overall regulation of gene expression in prostate cancer cells. Two hundred forty genes showed >2-fold changes on DHT treatment in LNCaP-ARhi at 4 h time point, whereas only 164 and 52 showed changes in LNCaP-ARmo and LNCaP-pcDNA3.1, respectively. Many androgen-regulated genes were upregulated in LNCaP-ARhi at 10-fold lower concentration of DHT than in control cells. DHT (1 nmol/L) increased expression of several cell cycle-associated genes in LNCaP-ARhi cells. ChIP-on-chip assay revealed the presence of chromatin binding sites for AR within +/-200 kb of most of these genes. The growth of LNCaP-ARhi cells was also highly sensitive to cyclin-dependent kinase inhibitor, roscovitine, at 1nmol/L DHT. In conclusion, our results show that overexpression of AR sensitizes castration-resistant prostate cancer cells to the low levels of androgens. The activity of AR signaling pathway is regulated by the levels of both ligand and the receptor.