Studies Of Castrate Resistant 22rv1 Cells Identifies Ar Regulated Interrelated Networks Of Transcription Factors, Co-Regulators, Chromatin, And Nuclear Scaffolding Proteins.

Prostate cancer development, progression and acquisition of castrate resistance are reliant on the activity of the androgen receptor (AR), a transcription factor that governs the proliferation of prostate cancer cells. Multiple studies have focused on the principle components that are critical for cell cycle transversal and these studies have identified members of the E2F/RB family, c-Myc, cyclins and cyclin dependent kinase inhibitors as key proteins that are instrumental in prostate cell proliferation and development of castrate resistance. But the mechanism by which the AR dominates this process is unclear. To identify the link between the AR and cell cycle control we used 22Rv1 cells which are castrate resistant due to the expression of low molecular weight AR forms that are missing the ligand binding domain. However, a siRNA mediated decrease in AR expression induces a growth arrest confirming that proliferation is AR dependent. RNA-seq analysis of gene expression at castrate levels of androgen and following AR ablation identified transcripts that were AR dependent. This methodology reduced the number of AR regulated transcripts, by excluding transcripts regulated by super-physiological levels of androgens. The AR regulated transcripts included previously identified genes (PMEPA1, C1orf116, PCDH7, APP) including NFAT a gene shown to be regulated by a low molecular weight AR isoform. The analysis also revealed that interrelated networks of transcription factors and co-factors were AR transactivated or repressed. These included proteins such as the LBR, LMNB, TMPO and SATB1 that do not directly promote transcription, but rather link chromatin to the nuclear membrane or scaffolding, suggesting that the AR may modulate gene expression through epigenetics mechanisms. Network analysis showed connections between these proteins and cell cycle components including E2Fs and Myc where a number of the regulated transcripts are known E2F or Myc targets. In addition, this analysis identified a number of non-coding RNAs; some that have been previously described and some that have yet to be annotated. qPCR studies found that a number of the transcripts regulated in 22Rv1 cells are also AR regulated in LNCaP cells. Coupled with ChIP-seq data, the study characterizes the link between the AR and the cell cycle machinery and chromatin modulating proteins. Citation Format: Maria Mudryj, Stephen J. Libertini, Alan P. Lombard. Studies of castrate resistant 22Rv1 cells identifies AR regulated interrelated networks of transcription factors, co-regulators, chromatin, and nuclear scaffolding proteins. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3574. doi:10.1158/1538-7445.AM2013-3574