The Role Of Acetylation Of Androgen Receptor Mediated By Androgen-Induced ARD1in Prostate Cancer

Prostate cancer (PCa) is one of the common male malignancies in the developed countries, Europe and America, especially in the United States, ranking second among cancer mortality of male patients caused deaths. Presently, the morbidity of PCa has increased gradually in men worldwide. Many previous results indicated that the biological action of androgens through the androgen receptor, AR, plays a critical role in normal prostate development and differentiation, and furthermore, the cell growth and proliferation of PCa are also dependent on these regulatory mechanisms. Moreover, AR belongs to one of transcription factors of nuclear receptor superfamily, and its transcriptional activity is regulated by multiple coregulators, of which aberrant expression contributes to prostate tumorigenesis.Protein acetylation is an important regulatory mechanism for protein co-tranlational and post-translational modification, participated in multiple biological processes including DNA repair, protein stability and nuclear translocation, protein-protein interaction, etc. Also, in yeast S. cerevisiae and mammalian cells, the arrest defective protein1(ARD1) functions as a N-terminal transferase to regulate the Na-and NE-acetylation modification of many proteins, of which related to various cell functions, involving cell cycle, cell growth and proliferation, apoptosis, autophagy and tumor metastasis. Although many results showed that aberrant expression of ARD1contributed to breast cancer, lung caner, colorectal cancer, thyroid neoplasm, hepatocellular carcinoma, the more detailed function and mechanism of ARD1in tumorigenesis are still controversial. In addtion, there has no any reports about the role of ARD1in PCas, and here, we revealed that ARD1functions as a unique AR coregulator in PCa development.Through Western blotting and immunohistochemal assay, compared to the normal prostate epithelial cell lines and normal tissues, the levels of ARD1protein in prostate cancer cell lines and primary cancer tissues were up-regulated, and were distinctly related to PCas, of which62/64(97%) of PCa sections were ARD1positive, more higher than1/17(6%) in normal tissues (P<0.001). In addition, increasing of ARD1was induced with an AR-dependent manner by androgen, R1881at protein level, but no effect on its transcriptional level. Furthermore, under the stimulation of R1881, the level of ARD1protein was not induced in AR-null cells, PC-3and DU-145, or after silencing of AR with siRNA, or blocking the AR function using the AR antagonist, bicalutamide (CDX) in LNCaP cells. Also, depletion of ARD1by ARD1shRNA lentiviral particles in LNCaP cells obviously suppressed PCa cell proliferation, the anchorage-independent growth in soft agar and in vivo exonograft tumor growth in nonobese diabetic NOD/SCID mice.In vivo and in vitro results have shown that through AR transactivation, ARD1was critical for transcriptionally regulating a number of AR target genes that are involved in prostate tumorigenesis, including PSA, TMPRSS2, ACPP, SLC45A3, FASN. Concerning this, we further confirmed that ARDl interacted physically with and acetylated the AR protein, which facilitating the recruitment of AR to bind with androgen response elements (ARE) of genes and initiating the transcription. We further confirmed that the ARD1-mediated acetylation of AR is independent of histone acetyltransferase p300, and the p300acetylation motif mutant, ARK630,632,633Q, has no effect on the ARD1-mediated acetylation of AR. Furthermore, ARD1-mediated acetylation of AR is also dependent on the N-terminal acetyltransferase activity, and the actyltransferase-null ARD1mutant, ARD1-dead has no changes on acetylation level of AR.In summary, these findings suggest that the biological function of ARD1as an oncogenen is partial dependent on AR in PCa development, and ARD1also regulates AR through a positive feedback loop as a unique coregulator of AR for prostate tumorigenesis, of which are mediated through ARD1binding with AR, enhancing the acetylation and activating the transcriptional activity of AR. Thus, disruption of AR-ARD1interactions or inhibition of N-terminal acetylatransferase activity of ARDl may be a potent alternative intervention for androgen-dependent PCa therapy.