Primary mucinous adenocarcinoma of the urethra: A clinicopathological analysis of 35 cases.

AIM: Primary mucinous adenocarcinoma of the urethra represents an extremely rare entity. We sought to characterise further these tumours' clinicopathological, immunohistochemical and molecular features. METHODS AND RESULTS: Thirty-five cases were identified, occurring in 18 males and 17 females. The mean age at diagnosis was 65 years (28-89 years). The main presentation symptoms were haematuria and urinary outlet obstruction. Microscopic analysis revealed that all 35 tumours have stromal dissection by mucin. Ten tumours showed villoglandular dysplasia, nine showed mucinous metaplasia, two showed adenocarcinoma in situ and four showed signet ring cell features. All tumours were immunopositive for CEA, while immunonegative for nuclear ß-catenin; 19 of 23 (83%) expressed high molecular weight cytokeratin; 19 of 33 (58%) CK7; 28 of 34 (82%) CK20; 32 of 35 (91%) CDX2; 22 of 27 (81%) cadherin-17 (CDH-17); 26 of 29 (90%) SATB2; and one of 31 (3%) GATA3. Mismatch repair gene products, including MLH1, PMS2, MSH2 and MSH6, were immunopositive, suggesting the MSI-low genotype of mucinous adenocarcinoma of the urethra. BRAF V600E and ALK rearrangements were not detected. During the mean follow-up of 20 months, nine patients either developed distant metastasis or succumbed to the illness. CONCLUSION: Our study, encompassing the most extensive series of 35 cases of primary mucinous adenocarcinoma of the urethra, provides crucial insights into its precise diagnosis, management and potential targeted treatments. We found a greater CDX2, SATB2 and CDH17 sensitivity in these urethral tumours for the first time, to our knowledge. We identified characteristics such as an MSI-low profile, non-V600E BRAF mutations and an absence of ALK rearrangements.

Correction: Metformin inhibits the proliferation of benign prostatic epithelial cells.

[This corrects the article DOI: 10.1371/journal.pone.0173335.].

Frequent Telomerase Reverse Transcriptase Promoter and Fibroblast Growth Factor Receptor 3 Mutations Support the Precursor Nature of Papillary Urothelial Hyperplasia of the Urinary Bladder.

The precursor nature of papillary urothelial hyperplasia of the urinary bladder is uncertain. In this study, we investigated the telomerase reverse transcriptase (TERT) promoter and fibroblast growth factor receptor 3 (FGFR3) mutations in 82 patients with papillary urothelial hyperplasia lesions. Thirty-eight patients presented with papillary urothelial hyperplasia and concurrent noninvasive papillary urothelial carcinoma, and 44 patients presented with de novo papillary urothelial hyperplasia. The prevalence of the TERT promoter and FGFR3 mutations is compared between de novo papillary urothelial hyperplasia and those with concurrent papillary urothelial carcinoma. Mutational concordance between papillary urothelial hyperplasia and concurrent carcinoma was also compared. The TERT promoter mutations were detected in 44% (36/82) of papillary urothelial hyperplasia, including 23 (23/38, 61%) papillary urothelial hyperplasia with urothelial carcinoma and 13 (13/44, 29%) de novo papillary urothelial hyperplasia. The overall concordance of TERT promoter mutation status between papillary urothelial hyperplasia and concurrent urothelial carcinoma was 76%. The overall FGFR3 mutation rate of papillary urothelial hyperplasia was 23% (19/82). FGFR3 mutations were detected in 11 patients with papillary urothelial hyperplasia and concurrent urothelial carcinoma (11/38, 29%) and 8 patients with de novo papillary urothelial hyperplasia (8/44, 18%). Identical FGFR3 mutation status was detected in both papillary urothelial hyperplasia and urothelial carcinoma components in all 11 patients with FGFR3 mutations. Our findings provide strong evidence of a genetic association between papillary urothelial hyperplasia and urothelial carcinoma. High frequency of TERT promoter and FGFR3 mutations suggests the precursor role of papillary urothelial hyperplasia in urothelial carcinogenesis.

Tumor microenvironment heterogeneity an important mediator of prostate cancer progression and therapeutic resistance.

Prostate cancer is characterized by a high degree of heterogeneity, which poses a major challenge to precision therapy and drug development. In this review, we discuss how nongenetic factors contribute to heterogeneity of prostate cancer. We also discuss tumor heterogeneity and phenotypic switching related to anticancer therapies. Lastly, we summarize the challenges targeting the tumor environments, and emphasize that continued exploration of tumor heterogeneity is needed in order to offer a personalized therapy for advanced prostate cancer patients.

Methylation of SRD5A2 promoter predicts a better outcome for castration-resistant prostate cancer patients undergoing androgen deprivation therapy.

PURPOSE: To determine whether SRD5A2 promoter methylation is associated with cancer progression during androgen deprivation therapy (ADT) in CRPC. PATIENTS AND METHODS: In a Local CRPC cohort, 42 prostatic specimens were collected from patients who were diagnosed as CRPC and underwent transurethral resection of the prostate (TURP) at Massachusetts General Hospital (MGH). In a metastatic CRPC (Met CRPC) cohort, 12 metastatic biopsies were collected from CRPC patients who would be treated with abiraterone plus dutasteride (Clinical Trial NCT01393730). As controls, 36 benign prostatic specimens were collected from patients undergoing prostate reduction surgery for symptoms of bladder outlet obstruction secondary to benign prostatic hyperplasia (BPH). The methylation status of cytosine-phosphate-guanine (CpG) site(s) at SRD5A2 promoter regions was tested. RESULTS: Compared with benign prostatic tissue, CRPC samples demonstrated higher SRD5A2 methylation in the whole promoter region (Local CRPC cohort: P < 0.001; Met CRPC cohort: P <0.05). In Local CRPC cohort, a higher ratio of methylation was correlated with better OS (R2 = 0.33, P = 0.013). Hypermethylation of specific regions (nucleotides -434 to -4 [CpG# -39 to CpG# -2]) was associated with a better OS (11.3±5.8 vs 6.4±4.4 years, P = 0.001) and PFS (8.4±5.4 vs 4.5±3.9 years, P = 0.003) with cutoff value of 37.9%. Multivariate analysis showed that SRD5A2 methylation was associated with OS independently (whole promoter region: P = 0.035; specific region: P = 0.02). CONCLUSION: Our study demonstrate that SRD5A2 methylation in promoter regions, specifically at CpG# -39 to -2, is significantly associated with better survival for CRPC patients treated with ADT. Recognition of epigenetic modifications of SRD5A2 may affect the choices and sequence of available therapies for management of CRPC.

Androgenic to oestrogenic switch in the human adult prostate gland is regulated by epigenetic silencing of steroid 5α-reductase 2.

Benign prostatic hyperplasia is the most common proliferative abnormality of the prostate. All men experience some prostatic growth as they age, but the rate of growth varies among individuals. Steroid 5α-reductase 2 (SRD5A2) is a critical enzyme for prostatic development and growth. Previous work indicates that one-third of adult prostatic samples do not express SRD5A2, secondary to epigenetic modifications. Here we show that the level of oestradiol is dramatically elevated, concomitant with significant upregulation of oestrogen response genes, in prostatic samples with methylation at the SRD5A2 promoter. The phosphorylation of oestrogen receptor-α in prostatic stroma is upregulated when SRD5A2 expression is absent. We show that tumour necrosis factor (TNF)-α suppresses SRD5A2 mRNA and protein expression, and simultaneously promotes expression of aromatase, the enzyme responsible for conversion of testosterone to oestradiol. Concomitant suppression of SRD5A2 and treatment with TNF-α synergistically upregulate the aromatase levels. The data suggest that, in the absence of prostatic SRD5A2, there is an androgenic to oestrogenic switch. These findings have broad implications for choosing appropriate classes of medications for the management of benign and malignant prostatic diseases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Metformin inhibits the proliferation of benign prostatic epithelial cells.

OBJECTIVE: Benign prostatic hyperplasia (BPH) is the most common proliferative abnormality of the prostate affecting elderly men throughout the world. Epidemiologic studies have shown that diabetes significantly increases the risk of developing BPH, although whether anti-diabetic medications preventing the development of BPH remains to be defined. We have previously found that stromally expressed insulin-like growth factor 1 (IGF-1) promotes benign prostatic epithelial cell proliferation through paracrine mechanisms. Here, we seek to understand if metformin, a first line medication for the treatment of type 2 diabetes, inhibits the proliferation of benign prostatic epithelial cells through reducing the expression of IGF-1 receptor (IGF-1R) and regulating cell cycle. METHODS: BPE cell lines BPH-1 and P69, murine fibroblasts3T3 and primary human prostatic fibroblasts were cultured and tested in this study. Cell proliferation and the cell cycle were analyzed by MTS assay and flow cytometry, respectively. The expression of IGF-1R was determined by western-blot and immunocytochemistry. The level of IGF-1 secretion in culture medium was measured by ELISA. RESULTS: Metformin (0.5-10mM, 6-48h) significantly inhibited the proliferation of BPH-1 and P69 cells in a dose-dependent and time-dependent manner. Treatment with metformin for 24 hours lowered the G2/M cell population by 43.24% in P69 cells and 24.22% in BPH-1 cells. On the other hand, IGF-1 (100ng/mL, 24h) stimulated the cell proliferation (increased by 28.81% in P69 cells and 20.95% in BPH-1 cells) and significantly enhanced the expression of IGF-1R in benign prostatic epithelial cells. Metformin (5mM) abrogated the proliferation of benign prostatic epithelial cells induced by IGF-1. In 3T3 cells, the secretion of IGF-1 was significantly inhibited by metformin from 574.31pg/ml to 197.61pg/ml. The conditioned media of 3T3 cells and human prostatic fibroblasts promoted the proliferation of epithelial cells and the expression of IGF-1R in epithelial cells. Metformin abrogated the proliferation of benign prostatic epithelial cells promoted by 3T3 conditioned medium. CONCLUSIONS: Our study demonstrates that metformin inhibits the proliferation of benign prostatic epithelial cells by suppressing the expression of IGF-1R and IGF-1 secretion in stromal cells. Metformin lowers the G2/M cell population and simultaneously increases the G0/G1 population. Findings here might have significant clinical implications in management of BPH patients treated with metformin.

Metformin represses cancer cells via alternate pathways in N-cadherin expressing vs. N-cadherin deficient cells.

Metformin has emerged as a potential anticancer agent. Here, we demonstrate that metformin plays an anti-tumor role via repressing N-cadherin, independent of AMPK, in wild-type N-cadherin cancer cells. Ectopic-expression of N-cadherin develops metformin-resistant cancer cells, while suppression of N-cadherin sensitizes cancer to metformin. Manipulation of AMPK expression does not alter sensitivity of cancer to metformin. We show that NF-kappaB is a downstream molecule of N-cadherin and metformin regulates NF-kappaB signaling via suppressing N-cadherin. Moreover, we also suggest that TWIST1 is an upstream molecule of N-cadherin/NF-kappaB signaling and manipulation of TWIST1 expression changes the sensitivity of cancer cells to metformin. In contrast to the cells that express N-cadherin, in N-cadherin deficient cells, metformin plays an anti-tumor role via activation of AMPK. Ectopic expression of N-cadherin makes cancer more resistant to metformin. Therefore, we suggest that metformin's anti-cancer therapeutic effect is mediated through different molecular mechanism in wild-type vs. deficient N-cadherin cancer cells. At last, we selected 49 out of 984 patients' samples with prostatic cancer after radical prostatectomy (selection criteria: Gleason score ≥ 7 and all patients taking metformin) and showed levels of N-cadherin, p65 and AMPK could predict post-surgical recurrence in prostate cancer after treatment of metformin.

Age and Obesity Promote Methylation and Suppression of 5α-Reductase 2: Implications for Personalized Therapy of Benign Prostatic Hyperplasia.

PURPOSE: In men with symptomatic benign prostatic hyperplasia 5α-reductase inhibitors are a main modality of treatment. More than 30% of men do not respond to the therapeutic effects of 5α-reductase inhibitors. We have found that a third of adult prostate samples do not express 5α-reductase type 2 secondary to epigenetic modifications. We evaluated whether 5α-reductase type 2 expression in benign prostatic hyperplasia specimens from symptomatic men was linked to methylation of the 5α-reductase type 2 gene promoter. We also identified associations with age, obesity, cardiac risk factors and prostate specific antigen. MATERIALS AND METHODS: Prostate samples from men undergoing transurethral prostate resection were used. We determined 5α-reductase type 2 protein expression and gene promoter methylation status by common assays. Clinical variables included age, body mass index, hypertension, hyperlipidemia, diabetes, prostate specific antigen and prostate volume. Univariate and multivariate statistical analyses were performed followed by stepwise logistic regression modeling. RESULTS: Body mass index and age significantly correlated with methylation of the 5α-reductase type 2 gene promoter (p <0.05) whereas prostate volume, prostate specific antigen or benign prostatic hyperplasia medication did not correlate. Methylation highly correlated with 5α-reductase protein expression (p <0.0001). In a predictive model increasing age and body mass index significantly predicted methylation status and protein expression (p <0.01). CONCLUSIONS: Increasing age and body mass index correlate with increased 5α-reductase type 2 gene promoter methylation and decreased protein expression in men with symptomatic benign prostatic hyperplasia. These results highlight the interplay among age, obesity and gene regulation. Our findings suggest an individualized epigenetic signature for symptomatic benign prostatic hyperplasia, which may be important to choose appropriate personalized treatment options.

DNA methyl transferase 1 reduces expression of SRD5A2 in the aging adult prostate.

5-α Reductase type 2 (SRD5A2) is a critical enzyme for prostatic development and growth. Inhibition of SRD5A2 by finasteride is used commonly for the management of urinary obstruction caused by benign prostatic hyperplasia. Contrary to common belief, we have found that expression of SRD5A2 is variable and absent in one third of benign adult prostates. In human samples, absent SRD5A2 expression is associated with hypermethylation of the SRD5A2 promoter, and in vitro SRD5A2 promoter activity is suppressed by methylation. We show that methylation of SRD5A2 is regulated by DNA methyltransferase 1, and inflammatory mediators such as tumor necrosis factor α, NF-κB, and IL-6 regulate DNA methyltransferase 1 expression and thereby affect SRD5A2 promoter methylation and gene expression. Furthermore, we show that increasing age in mice and humans is associated with increased methylation of the SRD5A2 promoter and concomitantly decreased protein expression. Artificial induction of inflammation in prostate primary epithelial cells leads to hypermethylation of the SRD5A2 promoter and silencing of SRD5A2, whereas inhibition with tumor necrosis factor α inhibitor reactivates SRD5A2 expression. Therefore, expression of SRD5A2 is not static and ubiquitous in benign adult prostate tissues. Methylation and expression of SRD5A2 may be used as a gene signature to tailor therapies for more effective treatment of prostatic diseases.

5α-Reductase inhibitors and risk of high-grade or lethal prostate cancer.

IMPORTANCE: 5α-Reductase inhibitors (5ARIs) are widely used for benign prostatic hyperplasia despite controversy regarding potential risk of high-grade prostate cancer with use. Furthermore, the effect of 5ARIs on progression and prostate cancer death remains unclear. OBJECTIVE: To determine the association between 5ARI use and development of high-grade or lethal prostate cancer. DESIGN, SETTING, AND PARTICIPANTS: Prospective observational study of 38,058 men followed up for prostate cancer diagnosis and outcomes between 1996 and 2010 in the Health Professionals Follow-up Study. EXPOSURES: Use of 5ARIs between 1996 and 2010. MAIN OUTCOMES AND MEASURES: Cox proportional hazards models were used to estimate risk of prostate cancer diagnosis or development of lethal disease with 5ARI use, adjusting for possible confounders including prostate specific antigen testing. RESULTS: During 448,803 person-years of follow-up, we ascertained 3681 incident prostate cancer cases. Of these, 289 were lethal (metastatic or fatal), 456 were high grade (Gleason sum [GS] 8-10), 1238 were GS 7, and 1600 were low grade (GS 2-6). A total of 2878 (7.6%) men reported use of 5ARIs between 1996 and 2010. After adjusting for confounders, men who reported ever using 5ARIs over the study period had a reduced risk of overall prostate cancer (hazard ratio [HR], 0.77; 95% CI, 0.65-0.91). 5ARI users had a reduced risk of GS 7 (HR, 0.67; 95% CI, 0.49-0.91) and low-grade (GS 2-6) prostate cancer (HR, 0.74; 95% CI, 0.57-0.95). 5ARI use was not associated with risk of high-grade (GS 8-10) prostate cancer (HR, 0.97; 95% CI, 0.64-1.46) or lethal disease (HR, 0.99; 95% CI, 0.58-1.69). Increased duration of use was associated with significantly lower risk of overall prostate cancer (HR for 1 year of additional use, 0.95; 95% CI, 0.92-0.99), localized (HR, 0.95; 95% CI, 0.90-1.00), and low-grade disease (HR, 0.92; 95% CI, 0.85-0.99). There was no association for lethal, high-grade, or grade 7 disease. CONCLUSIONS AND RELEVANCE: While 5ARI use was not associated with developing high-grade or lethal prostate cancer, it was associated with a reduction in low-grade, GS 7, and overall prostate cancer. Because the number of patients with high-grade or lethal prostate cancer in our cohort was limited, we cannot rule out potential risk of harm with 5ARI use.

Personalized medicine for the management of benign prostatic hyperplasia.

PURPOSE: Benign prostatic hyperplasia affects more than 50% of men by age 60 years, and is the cause of millions of dollars in health care expenditure for the treatment of lower urinary tract symptoms and urinary obstruction. Despite the widespread use of medical therapy, there is no universal therapy that treats all men with symptomatic benign prostatic hyperplasia. At least 30% of patients do not respond to medical management and a subset require surgery. Significant advances have been made in understanding the natural history and development of the prostate, such as elucidating the role of the enzyme 5α-reductase type 2, and advances in genomics and biomarker discovery offer the potential for a more targeted approach to therapy. We review the current understanding of benign prostatic hyperplasia progression as well as the key genes and signaling pathways implicated in the process such as 5α-reductase. We also explore the potential of biomarker screening and gene specific therapies as tools to risk stratify patients with benign prostatic hyperplasia and identify those with symptomatic or medically resistant forms. MATERIALS AND METHODS: A PubMed® literature search of current and past peer reviewed literature on prostate development, lower urinary tract symptoms, benign prostatic hyperplasia pathogenesis, targeted therapy, biomarkers, epigenetics, 5α-reductase type 2 and personalized medicine was performed. An additional Google Scholar™ search was conducted to broaden the scope of the review. Relevant reviews and original research articles were examined, as were their cited references, and a synopsis of original data was generated with the goal of informing the practicing urologist of these advances and their implications. RESULTS: Benign prostatic hyperplasia is associated with a state of hyperplasia of the stromal and epithelial compartments, with 5α-reductase type 2 and androgen signaling having key roles in the development and maintenance of the prostate. Chronic inflammation, multiple growth factor and hormonal signaling pathways, and medical comorbidities have complex roles in prostate tissue homeostasis as well as its evolution into the clinical state of benign prostatic hyperplasia. Resistance to medical therapy with finasteride may occur through silencing of the 5α-reductase type 2 gene by DNA methylation, leading to a state in which 30% of adult prostates do not express 5α-reductase type 2. Novel biomarkers such as single nucleotide polymorphisms may be used to risk stratify patients with symptomatic benign prostatic hyperplasia and identify those at risk for progression or failure of medical therapy. Several inhibitors of the androgen receptor and other signaling pathways have recently been identified which appear to attenuate benign prostatic hyperplasia progression and may offer alternative targets for medical therapy. CONCLUSIONS: Progressive worsening of lower urinary tract symptoms and bladder outlet obstruction secondary to benign prostatic hyperplasia is the result of multiple pathways including androgen receptor signaling, proinflammatory cytokines and growth factor signals. New techniques in genomics, proteomics and epigenetics have led to the discovery of aberrant signaling pathways, novel biomarkers, DNA methylation signatures and potential gene specific targets. As personalized medicine continues to develop, the ability to risk stratify patients with symptomatic benign prostatic hyperplasia, identify those at higher risk for progression, and seek alternative therapies for those in whom conventional options are likely to fail will become the standard of targeted therapy.

Inhibition of TNF-α improves the bladder dysfunction that is associated with type 2 diabetes.

Diabetic bladder dysfunction (DBD) is common and affects 80% of diabetic patients. However, the molecular mechanisms underlying DBD remain elusive because of a lack of appropriate animal models. We demonstrate DBD in a mouse model that harbors hepatic-specific insulin receptor substrate 1 and 2 deletions (double knockout [DKO]), which develops type 2 diabetes. Bladders of DKO animals exhibited detrusor overactivity at an early stage: increased frequency of nonvoiding contractions during bladder filling, decreased voided volume, and dispersed urine spot patterns. In contrast, older animals with diabetes exhibited detrusor hypoactivity, findings consistent with clinical features of diabetes in humans. The tumor necrosis factor (TNF) superfamily genes were upregulated in DKO bladders. In particular, TNF-α was upregulated in serum and in bladder smooth muscle tissue. TNF-α augmented the contraction of primary cultured bladder smooth muscle cells through upregulating Rho kinase activity and phosphorylating myosin light chain. Systemic treatment of DKO animals with soluble TNF receptor 1 (TNFRI) prevented upregulation of Rho A signaling and reversed the bladder dysfunction, without affecting hyperglycemia. TNFRI combined with the antidiabetic agent, metformin, improved DBD beyond that achieved with metformin alone, suggesting that therapies targeting TNF-α may have utility in reversing the secondary urologic complications of type 2 diabetes.

Reduced levels of 5-α reductase 2 in adult prostate tissue and implications for BPH therapy.

BACKGROUND: 5-α reductase 2 (5-AR 2) is a key enzyme that is responsible of proper development of prostate tissue. Inhibition of 5-AR 2 has proven to be efficacious for management of urinary symptoms secondary benign prostatic hyperplasia (BPH). However, some patients are resistant to the therapeutic effects of 5-AR 2 inhibitor. We wished to determine why some benign non-cancerous adult human prostates do not express 5-AR 2, and hypothesized that methylation of 5-AR 2 promoter region correlated with low expression of 5-AR 2 protein. METHODS: The transition zone of 42 human prostate tissues after radical prostatectomy was used for evaluation. Initially, 21 paraffin embedded samples were used to assess immunoreactivity to 5-AR 2 antibody in non-cancerous BPH samples. In the next 21 samples, fresh frozen prostate transition zone samples without cancer were assessed for immunoreactivity and methylation of the 5-AR 2 promoter using methyl-specific PCR. RESULTS: We show that 6/21 (29%) of benign human prostate samples did not express the 5-AR 2 protein. Moreover, the promoter region of 5-AR 2 contains a CpG island that is methylated in benign prostate epithelial cells in culture and also in 39% (7/18) human prostate tissues. We show a strong correlation between methylation of the 5-AR 2 promoter region and absence of 5-AR 2 protein expression (P = 0.0025, Fisher's exact test). CONCLUSIONS: Methylation of 5-AR 2 promoter may account for low or absent expression of 5-AR 2 in some human adult prostate tissues.

Sequence-specific inhibition of RNA polymerase III-dependent transcription using Zorro locked nucleic acid (LNA).

BACKGROUND: RNA polymerase III (pol III)-dependent transcripts are involved in many fundamental activities in a cell, such as splicing and protein synthesis. They also regulate cell growth and influence tumor formation. During recent years vector-based systems for expression of short hairpin (sh) RNA under the control of a pol III promoter have been developed as gene-based medicines. Therefore, there is an increasing interest in means to regulate pol III-dependent transcription. Recently, we have developed a novel anti-gene molecule 'Zorro LNA (Locked Nucleic Acid)', which simultaneously hybridizes to both strands of super-coiled DNA and potently inhibits RNA polymerase II-derived transcription. We have now applied Zorro LNA in an attempt to also control U6 promoter-driven expression of shRNA. METHODS: In this study, we constructed pshluc and pshluc2BS plasmids, in which U6 promoter-driven small hairpin RNA specific for luciferase gene (shluc) was without or with Zorro LNA binding sites, respectively. After hybridization of Zorro LNA to pshluc2BS, the LNA-bound plasmid was cotransfected with pEGFPluc into mammalian cells and into a mouse model. In cellular experiments, cotransfection of unhybridized pshluc2BS, Zorro LNA and pEGFPluc was also performed. RESULTS: The results showed that the Zorro LNA construct efficiently inhibited pol III-dependent transcription as an anti-gene reagent in a cellular context, including in vivo in a mouse model. CONCLUSIONS: Thus, this new form of gene silencer 'Zorro LNA' could potentially serve as a versatile regulator of pol III-dependent transcription, including various forms of shRNAs.

Zorro locked nucleic acid induces sequence-specific gene silencing.

Locked nucleic acids (LNAs) are synthetic analogs of nucleic acids that contain a bridging methylene carbon between the 2' and 4' positions of the ribose ring. In this study, we generated a novel sequence-specific antigene molecule "Zorro LNA", which simultaneously binds to both strands, and that induced effective and specific strand invasion into DNA duplexes and potent inhibition of gene transcription, also in a cellular context. By comparing the Zorro LNA with linear LNA as well as an optimized bisPNA (peptide nucleic acid) oligonucleotide directed against the same target sites, respectively, we found that the Zorro LNA construct was unique in its ability to arrest gene transcription in mammalian cells. To our knowledge, this is the first time that in mammalian cells, gene transcription was blocked by a nucleic acid analog in a sequence-specific way using low but saturated binding of a blocking agent. This offers a novel type of antigene drug that is easy to synthesize.

Cooperative strand invasion of supercoiled plasmid DNA by mixed linear PNA and PNA-peptide chimeras.

Peptide nucleic acid (PNA) is a DNA analog with broad biotechnical applications, and possibly also treatment applications. Its suggested uses include that of a specific anchor sequence for biologically active peptides to plasmids in a sequence-specific manner. Such complexes, referred to as Bioplex, have already been used to enhance non-viral gene transfer in vitro. To investigate how hybridization of PNAs to supercoiled plasmids would be affected by the binding of multiple PNA-peptides to the same strand of DNA, we have developed a method of quantifying the specific binding of PNA using a PNA labeled with a derivative of the fluorophore thiazole orange (TO). Cooperative effects were found at a distance of up to three bases. With a peptide present at the end of one of the PNAs, steric hindrance occurred, reducing the increase in binding rate when the distance between the two sites was less than two bases. In addition, we found increased binding kinetics when two PNAs binding to overlapping sites on opposite DNA strands were used, without the use of chemically modified bases in the PNAs.