Lanbo Xiao

The lncRNA landscape of breast cancer reveals a role for DSCAM-AS1 in breast cancer progression

Molecular classification of cancers into subtypes has resulted in an advance in our understanding of tumour biology and treatment response across multiple tumour types. However, to date, cancer profiling has largely focused on protein-coding genes, which comprise <1% of the genome. Here we leverage a compendium of 58,648 long noncoding RNAs (lncRNAs) to subtype 947 breast cancer samples. We show that lncRNA-based profiling categorizes breast tumours by their known molecular subtypes in breast cancer. We identify a cohort of breast cancer-associated and oestrogen-regulated lncRNAs, and investigate the role of the top prioritized oestrogen receptor (ER)-regulated lncRNA, DSCAM-AS1. We demonstrate that DSCAM-AS1 mediates tumour progression and tamoxifen resistance and identify hnRNPL as an interacting protein involved in the mechanism of DSCAM-AS1 action. By highlighting the role of DSCAM-AS1 in breast cancer biology and treatment resistance, this study provides insight into the potential clinical implications of lncRNAs in breast cancer.

Identification and Validation of PCAT14 as Prognostic Biomarker in Prostate Cancer

Rapid advances in the discovery of long noncoding RNAs (lncRNAs) have identified lineage- and cancer-specific biomarkers that may be relevant in the clinical management of prostate cancer (PCa). Here we assembled and analyzed a large RNA-seq dataset, from 585 patient samples, including benign prostate tissue and both localized and metastatic PCa to discover and validate differentially expressed genes associated with disease aggressiveness. We performed Sample Set Enrichment Analysis (SSEA) and identified genes associated with low versus high Gleason score in the RNA-seq database. Comparing Gleason 6 versus 9+ PCa samples, we identified 99 differentially expressed genes with variable association to Gleason grade as well as robust expression in prostate cancer. The top-ranked novel lncRNA PCAT14, exhibits both cancer and lineage specificity. On multivariate analysis, low PCAT14 expression independently predicts for BPFS (P = .00126), PSS (P = .0385), and MFS (P = .000609), with trends for OS as well (P = .056). An RNA in-situ hybridization (ISH) assay for PCAT14 distinguished benign vs malignant cases, as well as high vs low Gleason disease. PCAT14 is transcriptionally regulated by AR, and endogenous PCAT14 overexpression suppresses cell invasion. Thus, Using RNA-sequencing data we identify PCAT14, a novel prostate cancer and lineage-specific lncRNA. PCAT14 is highly expressed in low grade disease and loss of PCAT14 predicts for disease aggressiveness and recurrence.

Analysis of the androgen receptor–regulated lncRNA landscape identifies a role for ARLNC1 in prostate cancer progression

The androgen receptor (AR) plays a critical role in the development of the normal prostate as well as prostate cancer. Using an integrative transcriptomic analysis of prostate cancer cell lines and tissues, we identified ARLNC1 (AR-regulated long noncoding RNA 1) as an important long noncoding RNA that is strongly associated with AR signaling in prostate cancer progression. Not only was ARLNC1 induced by the AR protein, but ARLNC1 stabilized the AR transcript via RNA–RNA interaction. ARLNC1 knockdown suppressed AR expression, global AR signaling and prostate cancer growth in vitro and in vivo. Taken together, these data support a role for ARLNC1 in maintaining a positive feedback loop that potentiates AR signaling during prostate cancer progression and identify ARLNC1 as a novel therapeutic target.ARLNC1 is a newly discovered lncRNA that is induced by androgen receptor (AR) and maintains AR signaling by stabilizing the AR transcript. Knockdown of ARLNC1 suppresses AR expression, AR signaling and prostate cancer growth in vitro and in vivo.

Dynamic recruitment of single RNAs to processing bodies depends on RNA functionality

Cellular RNAs often colocalize with cytoplasmic, membrane-less ribonucleoprotein (RNP) granules enriched for RNA processing enzymes, termed processing bodies (PBs). Here, we track the dynamic localization of individual miRNAs, mRNAs and long non-coding RNAs (lncRNAs) to PBs using intracellular single-molecule fluorescence microscopy. We find that unused miRNAs stably bind to PBs, whereas functional miRNAs, repressed mRNAs and lncRNAs both transiently and stably localize within either the core or periphery of PBs, albeit to different extents. Consequently, translation potential and positioning of cis-regulatory elements significantly impact PB-localization dynamics of mRNAs. Using computational modeling and supporting experimental approaches we show that phase separation into large PBs attenuates mRNA silencing, suggesting that physiological mRNA turnover predominantly occurs outside of PBs. Instead, our data support a role for PBs in sequestering unused miRNAs to regulate their surveillance and provides a framework for investigating the dynamic assembly of RNP granules by phase separation at single-molecule resolution.

Epigenetic Reprogramming with Antisense Oligonucleotides Enhances the Effectiveness of Androgen Receptor Inhibition in Castration-Resistant Prostate Cancer

Advanced prostate cancer initially responds to androgen deprivation therapy (ADT), but the disease inevitably recurs as castration-resistant prostate cancer (CRPC). Although CRPC initially responds to abiraterone and enzalutamide, the disease invariably becomes nonresponsive to these agents. Novel approaches are required to circumvent resistance pathways and to extend survival, but the mechanisms underlying resistance remain poorly defined. Our group previously showed the histone lysine-N-methyltransferase EZH2 to be overexpressed in prostate cancer and quantitatively associated with progression and poor prognosis. In this study, we screened a library of epigenetic inhibitors for their ability to render CRPC cells sensitive to enzalutamide and found that EZH2 inhibitors specifically potentiated enzalutamide-mediated inhibition of proliferation. Moreover, we identified antisense oligonucleotides (ASO) as a novel drug strategy to ablate EZH2 and androgen receptor (AR) expression, which may have advantageous properties in certain settings. RNA-seq, chromatin immunoprecipitation sequencing, and assay for transposase-accessible chromatin using sequencing demonstrated that EZH2 inhibition altered the AR cistrome to significantly upregulate AR signaling, suggesting an enhanced dependence of CRPC cells on this pathway following inhibition of EZH2. Combination treatment with ASO targeting EZH2 and AR transcripts inhibited prostate cancer cell growth in vitro and in vivo better than single agents. In sum, this study identifies EZH2 as a critical epigenetic regulator of ADT resistance and defines ASO-based cotargeting of EZH2 and AR as a promising strategy for the treatment of CRPC.Significance: Simultaneous targeting of lysine methyltransferase EZH2 and the AR with ASO proves a novel and effective therapeutic strategy in patients with CRPC. Cancer Res; 78(20); 5731-40. ©2018 AACR.