Drug-induced epigenomic plasticity reprograms circadian rhythm regulation to drive prostate cancer towards androgen-independence

In prostate cancer, androgen receptor (AR)-targeting agents are very effective in various stages of the disease. However, therapy resistance inevitably occurs and little is known about how tumor cells adapt to bypass AR suppression. Here, we performed integrative multi-omics analyses on tissues isolated before and after 3 months of AR-targeting enzalutamide monotherapy from high-risk prostate cancer patients enrolled in a neoadjuvant clinical trial. Transcriptomic analyses demonstrated that AR inhibition drove tumors towards a neuroendocrine-like disease state. In addition, epigenomic profiling revealed massive enzalutamide-induced reprogramming of pioneer factor FOXA1 - from inactive chromatin binding sites towards active cis-regulatory elements that dictate pro-survival signals. Notably, treatment-induced FOXA1 sites were enriched for the circadian rhythm core component ARNTL. Post-treatment ARNTL levels associated with poor outcome, and ARNTL suppression decreased cell growth in vitro. Our data highlight a remarkable cistromic plasticity of FOXA1 following AR-targeted therapy, and revealed an acquired dependency on circadian regulator ARNTL, a novel candidate therapeutic target.

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13-cis-retinoic acid (CRA) and interferon-alpha (IFN) combination with or without radiation has a greater in vitro biological effect in reducing bcl-2 expression and inducing apoptosis in prostate cancer cells (LNCaP) than in normal human colorectal (Co-18) and normal human lung fibrolast (IMR-91) cells: Rationale for a clinical trial

Journal of Clinical Oncology ◽

10.1200/jco.2007.25.18_suppl.21157 ◽

2007 ◽

Vol 25 (18_suppl) ◽

pp. 21157-21157

Author(s):

P. Kumar ◽

C. Hill

Keyword(s):

Prostate Cancer ◽

Radiation Effects ◽

Lncap Cells ◽

Maximum Increase ◽

Over Expression ◽

High Risk Prostate Cancer ◽

Risk Prostate Cancer ◽

Normal Human ◽

Differential Selectivity

21157 Background: Over expression of bcl-2 is a major cause of radioresistance and recurrence in prostate cancer patients treated with RT. In order to determine whether CRA/IFN could down-regulate bcl-2 expression, induce apoptosis and reduce radioresistance, we conducted several experiments in LNCaP (which naturally express bcl-2), Co-18 (to mimic radiation effects on rectum) and IMR-91 (to confirm findings in Co-18 cells) cell lines to determine any differential selectivity by CRA/IFN with or without radiation. Methods: LNCaP, Co-18 and IMR-91 cells were treated with CRA (200 nmolar) and IFN (1000 U/ml) for 48 hours to determine bcl-2 expression and apoptosis at various time points (0, 6, 12, 24 & 48 hours) post-drug removal. For determining bcl-2 expression, cells were suspended in trypsin, centrifuged, washed with PBS, pelleted, and sonicated with RIPA buffer and re-centrifuged followed by Western blot analysis. For determining apoptosis, cells were washed and fixed in paraformaldehyde, and stained with Roche Chemical fluorescent apoptosis kit. The number of fluorescing cells vs. total number of cells were then counted in 3 wells using 3 microscope fields per well to determine percent of apoptosis. LNCaP, Co-18 and IMR-91 cells were also treated with radiation (400 cGy) after 48 hours of CRA/IFN exposure to measure bcl-2 expression and apoptosis. Results: In LNCaP cells, CRA/IFN significantly reduced bcl-2 expression with a maximum increase in apoptosis (70%) at 48 hours. In Co-18 and IMR-91 cells, CRA/IFN marginally decreased bcl-2 expression with no induction of apoptosis. Following CRA/IFN exposure and radiation, apoptosis was measured to be at least 90%, 22% and 0% at 48 hours in LNCaP, Co-18 and IMR-91 cells, respectively. Conclusions: CRA/IFN with or without radiation selectively reduces bcl-2 expression and induces apoptosis in LNCaP cells as compared to Co-18 and IMR-91 cells. Our findings provide a therapeutic rationale for clinically evaluating CRA/IFN with RT in patients with high risk prostate cancer. No significant financial relationships to disclose.

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