Redefining Androgen Receptor Function: Clinical Implications in Understanding Prostate Cancer Progression and Therapeutic Resistance

The current description of the function of the human androgen receptor (AR), as a transcription factor directing androgen responsive gene expression, is limited in scope and thus is unable to account for the varied cellular and physiological transformation observed in the development and progression of prostate cancer (CaP). The chapter will focus on four important aspects of AR and CaP investigations: (1) a description of AR somatic mutations and the perils of AR-directed therapeutics; (2) our characterization of AR protein interactors that have imbued new functional properties for AR linked to prostatic disease; (3) review of the advances made and shortcomings of AR mouse models in describing CaP onset and progression; and (4) speculate as to the mechanisms by which new mutations can originate and initiate disease onset

Signaling Network Assessment of Mutations and Copy Number Variations Predicts Breast Cancer Subtype-specific Drug Targets

Individual cancer cells carry a bewildering number of distinct genomic alterations i.e., copy number variations and mutations, making it a challenge to uncover genomic-driven mechanisms governing tumorigenesis. Here we performed exome-sequencing on several breast cancer cell lines which represent two subtypes, luminal and basal. We integrated this sequencing data, and functional RNAi screening data (i.e., for identifying genes which are essential for cell proliferation and survival), onto a human signaling network. Two subtype-specific networks were identified, which potentially represent core-signaling mechanisms underlying tumorigenesis. Within both networks, we found that genes were differentially affected in different cell lines; i.e., in some cell lines a gene was identified through RNAi screening whereas in others it was genomically altered. Interestingly, we found that highly connected network genes could be used to correctly classify breast tumors into subtypes based on genomic alterations. Further, the networks effectively predicted subtype-specific drug targets, which were experimentally validated.Comment: 4 figs, more related papers at http://www.cancer-systemsbiology.org, appears in Cell Reports, 201

Functionalized Carbon Nanoparticles as Theranostic Agents and Their Future Clinical Utility in Oncology

Over the years, research of nanoparticle applications in pre-clinical and clinical applications has greatly advanced our therapeutic and imaging approaches to many diseases, most notably neoplastic disorders. In particular, the innate properties of inorganic nanomaterials, such as gold and iron oxide, as well as carbon-based nanoparticles, have provided the greatest opportunities in cancer theranostics. Carbon nanoparticles can be used as carriers of biological agents to enhance the therapeutic index at a tumor site. Alternatively, they can also be combined with external stimuli, such as light, to induce irreversible physical damaging effects on cells. In this review, the recent advances in carbon nanoparticles and their use in cancer theranostics will be discussed. In addition, the set of evaluations that will be required during their transition from laboratory investigations toward clinical trials will be addressed

Nonmuscle Myosin Promotes Cytoplasmic Localization of PBX

In the absence of MEIS family proteins, two mechanisms are known to restrict the PBX family of homeodomain (HD) transcription factors to the cytoplasm. First, PBX is actively exported from the nucleus via a CRM1-dependent pathway. Second, nuclear localization signals (NLSs) within the PBX HD are masked by intramolecular contacts. In a screen to identify additional proteins directing PBX subcellular localization, we identified a fragment of murine nonmuscle myosin II heavy chain B (NMHCB). The interaction of NMHCB with PBX was verified by coimmunoprecipitation, and immunofluorescence staining revealed colocalization of NMHCB with cytoplasmic PBX in the mouse embryo distal limb bud. The interaction domain in PBX mapped to a conserved PBC-B region harboring a potential coiled-coil structure. In support of the cytoplasmic retention function, the NMHCB fragment competes with MEIS1A to redirect PBX, and the fly PBX homologue EXD, to the cytoplasm of mammalian and insect cells. Interestingly, MEIS1A also localizes to the cytoplasm in the presence of the NMHCB fragment. These activities are largely independent of nuclear export. We show further that the subcellular localization of EXD is deregulated in Drosophila zipper mutants that are depleted of nonmuscle myosin heavy chain. This study reveals a novel and evolutionarily conserved mechanism controlling the subcellular distribution of PBX and EXD proteins

Investigation of androgen receptor-dependent alternative splicing has identified a unique subtype of lethal prostate cancer

A complete proteomics study characterizing active androgen receptor (AR) complexes in prostate cancer (PCa) cells identified a diversity of protein interactors with tumorigenic annotations, including known RNA splicing factors. Thus, we chose to further investigate the functional role of AR-mediated alternative RNA splicing in PCa disease progression. We selected two AR-interacting RNA splicing factors, Src associated in mitosis of 68 kDa (SAM68) and DEAD (Asp-Glu-Ala-Asp) box helicase 5 (DDX5) to examine their associative roles in AR-dependent alternative RNA splicing. To assess the true physiological role of AR in alternative RNA splicing, we assessed splicing profiles of LNCaP PCa cells using exon microarrays and correlated the results to PCa clinical datasets. As a result, we were able to highlight alternative splicing events of clinical significance. Initial use of exon-mini gene cassettes illustrated hormone-dependent AR-mediated exon-inclusion splicing events with SAM68 or exon-exclusion splicing events with DDX5 overexpression. The physiological significance in PCa was investigated through the application of clinical exon array analysis, where we identified exon-gene sets that were able to delineate aggressive disease progression profiles and predict patient disease-free outcomes independently of pathological clinical criteria. Using a clinical dataset with patients categorized as prostate cancer-specific death (PCSD), these exon gene sets further identified a select group of patients with extremely poor disease-free outcomes. Overall, these results strongly suggest a nonclassical role of AR in mediating robust alternative RNA splicing in PCa. Moreover, AR-mediated alternative spicing contributes to aggressive PCa progression, where we identified a new subtype of lethal PCa defined by AR-dependent alternative splicing

Visualization of double-stranded RNAs from the myotonic dystrophy protein kinase gene and interactions with CUG-binding protein

Myotonic dystrophy (DM) is associated with a (CTG) (n) triplet repeat expansion in the 3'-untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. Using electron microscopy, we visualized large RNAs containing up to 130 CUG repeats and studied the binding of purified CUG-binding protein (CUG-BP) to these RNAs. Electron microscopic examination revealed perfect double-stranded (ds)RNA segments whose lengths were that expected for duplex RNA. The RNA dominant mutation model for DM pathogenesis predicts that the expansion mutation acts at the RNA level by forming long dsRNAs that sequester certain RNA-binding proteins. To test this model, we examined the subcellular distribution and RNA-binding properties of CUG-BP. While previous studies have demonstrated that mutant DMPK transcripts accumu-late in nuclear foci, the localization pattern of CUG-BP in both normal and DM cells was similar. Although CUG-BP in nuclear extracts preferentially photocrosslinked to DMPK transcripts, this binding was not proportional to (CUG) (n) repeat size. Moreover, CUG-BP localized to the base of the RNA hairpin and not along the stem, as visualized by electron micro-scopy. These results provide the first visual evidence that the DM expansion forms an RNA hairpin structure and suggest that CUG-BP is unlikely to be a sequestered factor

Correction: Engineering Multi-Walled Carbon Nanotube Therapeutic Bionanofluids to Selectively Target Papillary Thyroid Cancer Cells.

[This corrects the article DOI: 10.1371/journal.pone.0149723.]