Background Androgen receptor (AR) is critical to the initiation, growth, and progression of prostate cancer. Once activated, the AR binds to cis-regulatory enhancer elements on DNA that drive gene expression. Yet, there are 10–100× more binding sites than differentially expressed genes. It is unclear how or if these excess binding sites impact gene transcription. Results To characterize the regulatory logic of AR-mediated transcription, we generated a locus-specific map of enhancer activity by functionally testing all common clinical AR binding sites with Self-Transcribing Active Regulatory Regions sequencing (STARRseq). Only 7% of AR binding sites displayed androgen-dependent enhancer activity. Instead, the vast majority of AR binding sites were either inactive or constitutively active enhancers. These annotations strongly correlated with enhancer-associated features of both in vitro cell lines and clinical prostate cancer samples. Evaluating the effect of each enhancer class on transcription, we found that AR-regulated enhancers frequently interact with promoters and form central chromosomal loops that are required for transcription. Somatic mutations of these critical AR-regulated enhancers often impact enhancer activity. Conclusions Using a functional map of AR enhancer activity, we demonstrated that AR-regulated enhancers act as a regulatory hub that increases interactions with other AR binding sites and gene promoters.

Soluble ACE2 (sACE2) decoys are promising agents to inhibit SARS‐CoV‐2, as their efficiency is unlikely to be affected by escape mutations. However, their success is limited by their relatively poor potency. To address this challenge, multimeric sACE2 consisting of SunTag or MoonTag systems is developed. These systems are extremely effective in neutralizing SARS‐CoV‐2 in pseudoviral systems and in clinical isolates, perform better than the dimeric or trimeric sACE2, and exhibit greater than 100‐fold neutralization efficiency, compared to monomeric sACE2. SunTag or MoonTag fused to a more potent sACE2 (v1) achieves a sub‐nanomolar IC50, comparable with clinical monoclonal antibodies. Pseudoviruses bearing mutations for variants of concern, including delta and omicron, are also neutralized efficiently with multimeric sACE2. Finally, therapeutic treatment of sACE2(v1)‐MoonTag provides protection against SARS‐CoV‐2 infection in an in vivo mouse model. Therefore, highly potent multimeric sACE2 may offer a promising treatment approach against SARS‐CoV‐2 infections.

Androgen receptor (AR)-mediated transcription is critical in almost all stages of prostate cancer (PCa) growth and differentiation. This process involves a complex interplay of coregulatory proteins, chromatin remodeling complexes, and other transcription factors that work with AR at cis-regulatory enhancer regions to induce the spatiotemporal transcription of target genes. This enhancer-driven mechanism is remarkably dynamic and undergoes significant alterations during PCa progression. In this review, we discuss the AR mechanism of action in PCa with a focus on how cis-regulatory elements modulate gene expression. We explore emerging evidence of genetic variants that can impact AR regulatory regions and alter gene transcription in PCa. Finally, we highlight several outstanding questions and discuss potential mechanisms of this critical transcription factor.

Androgen receptor (AR) is critical to the initiation, growth and progression of almost all prostate cancers. Once activated, the AR binds to cis-regulatory enhancer elements on DNA that drive gene expression. Yet, there are 10-100x more binding sites than differentially expressed genes. It still remains unclear how individual sites contribute to AR-mediated transcription. While descriptive functional genomic approaches broadly correlate with enhancer activity, they do not provide the locus-specific resolution needed to delineate the underlying regulatory logic of AR- mediated transcription. Therefore, we functionally tested all commonly occuring clinical AR binding sites with Self-Transcribing Active Regulatory Regions sequencing (STARRseq) to generate the first map of intrinsic AR enhancer activity. This approach is not significantly affected by endogenous chromatin modifications and measures the potential enhancer activity at each cis- regulatory element. Interestingly we found that only 7% of AR binding sites displayed increased enhancer activity upon hormonal stimulation. Instead, the vast majority of AR binding sites were either inactive (81%) or constitutively active enhancers (11%). These annotations strongly correlated with enhancer-associated features in both cell line and clinical prostate cancer. With these validated annotations we next investigated the effect of each enhancer class on transcription and found that AR-driven inducible enhancers frequently interacted with promoters, forming central chromosomal loops critical for gene transcription. We demonstrated that these inducible enhancers act as regulatory hubs that increase contacts with both other AR binding sites and gene promoters. This functional map was used to identify a somatic mutation that significantly reduces the expression of a commonly mutated AR-regulated tumour suppressor. Together, our data reveal a complex interplay between different AR binding sites that work in a highly coordinated manner to drive gene transcription.

Soluble ACE2 (sACE2) decoy receptors are promising agents to inhibit SARS-CoV-2 as they are not affected by common escape mutations in viral proteins. However, their success may be limited by their relatively poor potency. To address these challenges, we developed a highly active multimeric sACE2 decoy receptor via a SunTag system that could neutralize both pseudoviruses bearing SARS-CoV-2 spike protein and SARS-CoV-2 clinical isolates. This fusion protein demonstrated a neutralization efficiency nearly 250-fold greater than monomeric sACE2. SunTag in combination with a more potent version of sACE2 achieved near complete neutralization at a sub-nanomolar range, which is comparable with clinical monoclonal antibodies. We demonstrate that this activity is due to greater occupancy of the multimeric decoy receptors on Spike protein as compared to monomeric sACE2. Overall, these highly potent multimeric sACE2 decoy receptors offer a promising treatment approach against SARS-CoV-2 infections including its novel variants.

Prostate cancer (PCa) is one of the most commonly diagnosed forms of cancer with one out of every nine North American men developing the disease in their lifetime. Despite robust early detection methods, new therapeutics, and advancements in surgical operations, PCa is still second leading cause of cancer death in men. An increasing number of studies have shown that non-coding mutations plays a critical role in the development and progression of PCa. These somatic mutations can disrupt regulatory elements such as enhancers and alter the transcriptional landscape of the cancer. Discovering and interpreting the non-coding elements is crucial to understand the nature of this disease. At all stages of PCa, androgen receptor (AR) signaling is essential to the cancer. Recent work from our laboratory demonstrated that there is a significant increase in somatic mutations at AR binding sites (ARBS). Given the importance of AR-mediated transcription, as well as the recurrent nature of these mutations, we proposed that these somatic mutations could play an important role in PCa development. To stratify the mutations, we conducted a massively multi-parallel enhancer assay to identify those ARBS sites with enhancer activity. With STARR-seq we found that 8% of the ARBS had strong inducible AR enhancer activity (341/4139). Interestingly, the majority of these sites did not contain a canonical androgen response element. With these results we incorporated high-throughput chromosome conformation capture (HiC) to formally define the genes regulated by each of these AR enhancers. Based on these results we have selected and characterized several non-coding ARBS mutations. We believe that the importance of the regulatory role of these regions will play a tremendous role in understanding of the prostate cancer and its progression. Citation Format: Dogancan Ozturan, Flora Huang, Tunc Morova, Mohammadali Saffarzadeh, Nathan A. Lack. Genome-wide AR enhancer activity in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5208.

Prostate cancer is an extremely common disease that affects one in every seven men in their lifetime. The standard care for late-stage cancer is designed to inhibit the activation of androgen receptor (AR). While this therapeutic approach is initially efficient, the cancer almost always develops resistance and gives rise to castration-resistant prostate cancer (CRPC). When therapy fails, the median survival of patients who suffer from CRPC is 12-16 months. It is critical to understand the mechanism of CRPC better to ameliorate the outcome of late-stage prostate cancer patients. AR is a transcription factor that consists of an N-terminal domain (NTD), a DNA binding domain (DBD) and a ligand binding domain (LBD). Upon activation by androgen, an intramolecular interaction between NTD and LBD occurs. The AR translocates into the nucleus where it forms a homodimer. It binds to the promoter and enhancer elements of the AR target genes and triggers gene transcription. It has been demonstrated in many clinical studies that AR is important for the progression of prostate cancer including CRPC. In CRPC, although androgen production and binding is inhibited, how the AR can still be activated is a fundamental question to be answered. One of the several different mechanisms proposed is the alternative splicing of the AR generating truncated AR variants that lack LBD. These variants do not require androgens to be activated and they are intrinsically resistant to clinically approved therapeutics. Despite the fact that the AR variants have been shown to be critical in late-stage prostate cancer, the mechanism of gene transcription initiation by the AR variants is not well-known. We propose to characterize the mechanism of the AR variant activation. Since ARV7 is the most commonly observed variant, we utilize ARV7. We develop a FRET based methodology to identify how ARV7 dimers form and to test if full-length AR is necessary for transcriptional activation mediated by ARV7. We are able to demonstrate possible intermolecular interaction between the full length AR and ARV7 measuring the FRET intensity between the fluorophores attached to the N and C terminus of two proteins. FRET measurements are analyzed by tracking single cells and recording the FRET intensities during the process. Our preliminary data suggest that the full-length AR and ARV7 may interact in the presence of androgen. ARV7 is always localized in the nucleus whereas the AR requires androgen to be activated and translocates into the nucleus. Being in close proximity, putative interaction between the AR and ARV7 occurs in the nucleus. Additionally, we use NTD and DBD point mutants to determine critical positions of intermolecular interaction between them. Supporting the significance of ARV7 in prostate cancer, our results clarify the dimerization process. It gives an opportunity to test clinical drugs currently in development to effectively inhibit ARV7 activation. Citation Format: Fatma Özgün, Zeynep Kaya, Halil Bayraktar, Selen Manioğlu, Doğancan Özturan, Nathan Lack. Structural characterization of androgen receptor variant 7 in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3522. doi:10.1158/1538-7445.AM2017-3522

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