Human phosphodiesterase 4D7 (PDE4D7) expression is increased in TMPRSS2-ERG-positive primary prostate cancer and independently adds to a reduced risk of post-surgical disease progression.

BACKGROUND: There is an acute need to uncover biomarkers that reflect the molecular pathologies, underpinning prostate cancer progression and poor patient outcome. We have previously demonstrated that in prostate cancer cell lines PDE4D7 is downregulated in advanced cases of the disease. To investigate further the prognostic power of PDE4D7 expression during prostate cancer progression and assess how downregulation of this PDE isoform may affect disease outcome, we have examined PDE4D7 expression in physiologically relevant primary human samples. METHODS: About 1405 patient samples across 8 publically available qPCR, Affymetrix Exon 1.0 ST arrays and RNA sequencing data sets were screened for PDE4D7 expression. The TMPRSS2-ERG gene rearrangement status of patient samples was determined by transformation of the exon array and RNA seq expression data to robust z-scores followed by the application of a threshold>3 to define a positive TMPRSS2-ERG gene fusion event in a tumour sample. RESULTS: We demonstrate that PDE4D7 expression positively correlates with primary tumour development. We also show a positive association with the highly prostate cancer-specific gene rearrangement between TMPRSS2 and the ETS transcription factor family member ERG. In addition, we find that in primary TMPRSS2-ERG-positive tumours PDE4D7 expression is significantly positively correlated with low-grade disease and a reduced likelihood of progression after primary treatment. Conversely, PDE4D7 transcript levels become significantly decreased in castration resistant prostate cancer (CRPC). CONCLUSIONS: We further characterise and add physiological relevance to PDE4D7 as a novel marker that is associated with the development and progression of prostate tumours. We propose that the assessment of PDE4D7 levels may provide a novel, independent predictor of post-surgical disease progression.

Sensitive detection of mitochondrial DNA variants for analysis of mitochondrial DNA-enriched extracts from frozen tumor tissue.

Large variation exists in mitochondrial DNA (mtDNA) not only between but also within individuals. Also in human cancer, tumor-specific mtDNA variation exists. In this work, we describe the comparison of four methods to extract mtDNA as pure as possible from frozen tumor tissue. Also, three state-of-the-art methods for sensitive detection of mtDNA variants were evaluated. The main aim was to develop a procedure to detect low-frequent single-nucleotide mtDNA-specific variants in frozen tumor tissue. We show that of the methods evaluated, DNA extracted from cytosol fractions following exonuclease treatment results in highest mtDNA yield and purity from frozen tumor tissue (270-fold mtDNA enrichment). Next, we demonstrate the sensitivity of detection of low-frequent single-nucleotide mtDNA variants (≤1% allele frequency) in breast cancer cell lines MDA-MB-231 and MCF-7 by single-molecule real-time (SMRT) sequencing, UltraSEEK chemistry based mass spectrometry, and digital PCR. We also show de novo detection and allelic phasing of variants by SMRT sequencing. We conclude that our sensitive procedure to detect low-frequent single-nucleotide mtDNA variants from frozen tumor tissue is based on extraction of DNA from cytosol fractions followed by exonuclease treatment to obtain high mtDNA purity, and subsequent SMRT sequencing for (de novo) detection and allelic phasing of variants.

Complete sequence-based pathway analysis by differential on-chip DNA and RNA extraction from a single cell.

We demonstrate on-chip, differential DNA and RNA extraction from a single cell using a microfluidic chip and a two-stage lysis protocol. This method enables direct use of the whole extract, without additional washing steps, reducing sample loss. Using this method, the tumor driving pathway in individual cells from a colorectal cancer cell line was determined by applying a Bayesian computational pathway model to sequences obtained from the RNA fraction of a single cell and, the mutations driving the pathway were determined by analyzing sequences obtained from the DNA fraction of the same single cell. This combined functional and mutational pathway assessment of a single cell could be of significant value for dissecting cellular heterogeneity in tumors and analyzing single circulating tumor cells.

A novel quantitative multiplex NASBA method: application to measuring tissue factor and CD14 mRNA levels in human monocytes.

A new method to quantify two individual mRNAs in a single NASBA reaction is described. In this study, tissue factor and CD14 mRNAs were used as a model system. RNA ratios of -4 to +4 log units were determined with good precision (within 0.3 log) and accuracy (within 0.2 log). By measuring both mRNAs in human monocytes that were stimulated with LPS, the multiplex Q-NASBA proved to be a successful tool to monitor the expression levels of two individual mRNAs in a single-tube amplification system. The method has potential in all fields in which quantitative information is needed on two individual RNAs.

Distinct changes in HIV type 1 RNA versus p24 antigen levels in serum during short-term zidovudine therapy in asymptomatic individuals with and without progression to AIDS.

Serum HIV-1 RNA and p24 antigen levels were examined in 28 seropositive asymptomatic individuals participating in a trial on the efficacy of zidovudine. Sixteen individuals remained asymptomatic until 4 years after the onset of the trial, whereas 12 individuals were diagnosed with an AIDS-defining event. The serum HIV-1 RNA load and p24 antigen levels were determined before the onset of therapy and during the first 8 weeks of therapy to establish whether the patterns of change were predictive of clinical outcome. Among the 28 participants 43% had measurable pretreatment concentrations of p24 antigen. Initiation of zidovudine therapy was followed by a similar decline of p24 antigen levels in nonprogressors as well as progressors and, therefore, these groups could not be distinguished on the basis of this parameter. HIV-1 RNA was detected in the pretreatment samples of 82% of the individuals and could be detected in p24 antigen-positive as well as p24 antigen-negative individuals. Similar changes in HIV-1 RNA load during zidovudine therapy were observed in p24 antigen-positive and -negative individuals. Analysis of the HIV-1 RNA response according to clinical outcome demonstrated that HIV-1 RNA copy numbers had declined significantly after 4 weeks of therapy in both nonprogressors and progressors, but the decline in RNA load was much stronger in the nonprogressors. Our data show that the HIV-1 RNA load in serum can be used to monitor the response to antiviral therapy in p24 antigen-positive as well as -negative individuals. Posttreatment changes in p24 antigen levels are not indicative for clinical outcome, whereas RNA copy numbers are.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of HIV-1 distribution in different blood fractions by two nucleic acid amplification assays.

A new amplification procedure, NASBA (nucleic acid sequence-based amplification), was used together with the polymerase chain reaction (PCR) to detect HIV-1 sequences in different blood fractions of both HIV-infected and uninfected samples. We tested whole blood, plasma, peripheral blood mononuclear cells (PBMCs), and platelets. No HIV-1 sequences were found in blood fractions of 37 uninfected persons either by PCR, reverse transcriptase-PCR (RT-PCR), or NASBA. We found that none of the infected plasma samples contained HIV-1 DNA sequences. However, a high percentage of these plasma samples was positive for HIV-1 RNA: 86% by NASBA and 80% by RT-PCR. The concordance on a sample-to-sample basis of NASBA and RT-PCR was 91%. Only 33% of the plasma samples was HIV-1 p24-antigen positive, demonstrating the superior sensitivity of amplification procedures. We found that almost all PBMC fractions were positive for HIV-1 (pro)viral sequences (99% HIV-1 DNA positive, 91% HIV-1 RNA positive). A large proportion of the platelet fractions contained HIV-1 RNA, as demonstrated by positive RT-PCR and NASBA results. We found an inverse relation between CD4+ T cell count and T cell reactivity on the one hand and detection of HIV-1 sequences by PCR, RT-PCR, and NASBA on the other hand in all blood fractions. Quantification of the HIV-1 PCR signal in PBMCs revealed an inverse relation of proviral titers with CD4+ levels. This finding supports earlier observations that clinical disease and low CD4+ cell counts are related to an increased viral burden.

NASBA isothermal enzymatic in vitro nucleic acid amplification optimized for the diagnosis of HIV-1 infection.

Isothermal nucleic acid amplification of target RNA or DNA sequences is accomplished by the simultaneous enzymatic activity of AMV reverse transcriptase, T7 RNA polymerase and RNase H. Amplification factors of the nucleic acid sequence based amplification (NASBA) method range from 2 x 10(6) to 5 x 10(7) after 2.5 h incubation at 41 degrees C. During NASBA there is a major accumulation of specific single stranded RNA. RNA:DNA hybrid and double stranded DNA are also synthesized, although to a minor extent. The system is optimized for the detection of HIV-1 sequences in in vitro infected cells, blood and plasma. Detection levels are 10 molecules of HIV-1 in a model system with in vitro generated HIV-1 RNA as input and 5 infected cells on a background of 5 x 10(4) non-infected cells. Blood and plasma can also be used as the source of nucleic acid for detection of HIV-1 sequences using a specifically developed sample preparation method. Using NASBA it is possible to amplify specifically RNA or DNA from a pool of total nucleic acid, which permits the investigation of the expression of specific genes involved in pathogenesis of infectious agents. The combination of NASBA with a rapid and user-friendly nucleic acid extraction method makes the whole procedure suitable for large scale diagnosis of infectious agents (e.g. HIV-1).

A one-tube quantitative HIV-1 RNA NASBA nucleic acid amplification assay using electrochemiluminescent (ECL) labelled probes.

Quantification of HIV-1 viral RNA based on co-amplification of an internal standard Q-RNA dilution series requires a number of NASBA nucleic acid amplification reactions. For each internal standard Q-RNA concentration a separate NASBA amplification has to be performed. The development of an electrochemiluminescent (ECL) detection system with a dynamic signal detection range over 5 orders of magnitude enabled simplification of the Q-NASBA protocol. Three distinguishable Q-RNAs (QA, QB and QC) are mixed with the wild-type sample at different amounts (i.e. 10(4) QA, 10(3) QB and 10(2) QC molecules) and co-amplified with the wild-type RNA in one tube. Using ECL-labelled oligonucleotides the wild-type, QA, QB and QC amplificates are separately detected with a semi-automated ECL detection instrument and the ratio of the signals determined. The amount of initial wild-type RNA can be calculated from the ratio of wild-type signal to QA, QB and QC signals. This one-tube Q-NASBA protocol was compared to the earlier described protocol with six amplifications per quantification using model systems and HIV-1 RNA isolated from plasma of HIV-1-infected individuals. In all cases the quantification results of HIV-1 RNA were comparable between the two methods tested. Due to the use of only one amplification per quantification in the one-tube Q-NASBA protocol the QA, QB and QC internal standard RNA molecules can be added to the sample before nucleic acid isolation. The ratio of QA:QB:QC:WT RNAs, from which the initial input of WT-RNA is calculated, will remain constant independent of any loss that might occur during the nucleic acid isolation.

Quantification of HIV-1 RNA in plasma using NASBA during HIV-1 primary infection.

Quantification of HIV-1 viral RNA in plasma was achieved by competitive co-amplification of a dilution series of in vitro generated RNA using the nucleic acid sequence based amplification (NASBA) technology. This 1.5 kilobase in vitro RNA, comprising the gag and part of the pol region, differs only by sequence-randomization of a 20 nt fragment from the wild-type RNA, ensuring equal efficiency of amplification. In model systems the accuracy of this method is within one log. Application of the Q-NASBA to plasma samples of a patient with a primary HIV-1 infection shows good concordance of the HIV-1 RNA profile with the p24 antigen profile. However, the HIV-1 RNA determination is more sensitive than the p24 antigen determination. Peak values of HIV-1 RNA are around 10(8) RNA molecules per ml plasma at the moment of seroconversion. Quantitative nucleic acid detection methods, like Q-NASBA, allow the monitoring of HIV-1 RNA during the course of infection which might have predictive value for disease development.

Use of the direct RNA amplification technique NASBA to detect factor V Leiden, a point mutation associated with APC resistance.

APC resistance is a common and strong hereditary risk factor for venous thrombosis. This plasma abnormality appears to be almost always caused by the same defect in the coagulation factor V gene (a G --> A transition at nucleotide 1691 leading to replacement of 506 Arg by Gln; factor V Leiden). Therefore, it is possible to consider a simple and specific genetic test as an alternative to a plasma APC resistance test that is compromised by treatment and other factors. We have investigated whether a new amplification procedure, NASBA, together with the detection procedure ELGA would provide a simple protocol for the nucleotide specific detection of the factor V mutation.

Typing of Mycoplasma pneumoniae by nucleic acid sequence-based amplification, NASBA.

Nucleic acid sequence-based amplification, NASBA, is an isothermal amplification technique for nucleic acids and was used for typing a collection of 24 Mycoplasma pneumoniae strains. A set of primers was chosen from the 16S rRNA sequence alignment of Mycoplasma species. The nucleotide sequences of the (-)RNA amplicons were determined for M. pneumoniae strains M15/83 (type 1) and FH (type 2), and revealed a one-point difference at the 16S rRNA level between the two types. Based on this result, two type-specific probes were constructed. The probes were hybridized in solution with the amplified nucleic acids of 24 M. pneumoniae strains in an enzyme-linked gel assay (ELGA). The results obtained by NASBA-based typing are in agreement with the classification of the 24 M. pneumoniae strains into two types by other typing methods, confirming the reliability of this technique.

Quantitative detection of hepatitis B virus DNA by real-time nucleic acid sequence-based amplification with molecular beacon detection.

We have developed a hepatitis B virus (HBV) DNA detection and quantification system based on amplification with nucleic acid sequence-based amplification (NASBA) technology and real-time detection with molecular beacon technology. NASBA is normally applied to amplify single-stranded target RNA, producing RNA amplicons. In this work we show that with modifications like primer design, sample extraction method, and template denaturation, the NASBA technique can be made suitable for DNA target amplification resulting in RNA amplicons. A major advantage of our assay is the one-tube, isothermal nature of the method, which allows high-throughput applications for nucleic acid detection. The homogeneous real-time detection allows a closed-tube format of the assay, avoiding any postamplification handling of amplified material and therefore minimizing the risk of contamination of subsequent reactions. The assay has a detection range of 10(3) to 10(9) HBV DNA copies/ml of plasma or serum (6 logs), with good reproducibility and precision. Compared with other HBV DNA assays, our assay provides good sensitivity, a wide dynamic range, and high-throughput applicability, making it a viable alternative to those based on other amplification or detection methods.

The natural history of HIV-1 infection: virus load and virus phenotype independent determinants of clinical course?

Virus load and virus phenotype have both been indicated as major determinants of disease progression in HIV-1 infection. In this study HIV-1 RNA copy numbers in serum, virus phenotype, and CD4+ cell counts were analyzed longitudinally in a group of 20 seroconverters progressing to AIDS within 5.5 years. In this group 12 individuals developed AIDS without syncytium-inducing (SI) viruses ever being isolated, while 8 individuals showed a non-SI (NSI) to SI phenotypic switch prior to AIDS development. HIV-1 RNA copy numbers in sera of all progressors were stable and high from seroconversion until development of AIDS. Twenty-one seroconverters remaining asymptomatic for more than 5.5 years were selected as nonprogressing controls, and both progressors and nonprogressors were evaluated at seroconversion and early in infection (3 years post seroconversion). Comparative analysis revealed that at the point of seroconversion HIV-1 RNA copy numbers in sera from NSI progressors, SI progressors, and nonprogressors were not significantly different, nor were their CD4+ cell counts. At seroconversion all individuals harbored viruses with an NSI phenotype. In contrast to the progressors, HIV-1 RNA copy numbers in sera of nonprogressors had declined significantly during the early period of infection. At the second time point RNA copy numbers in the sera of NSI progressors and nonprogressors differed significantly (P = 0.0005), while RNA copy numbers in the sera of SI progressors and nonprogressors did not. However, at this time point the CD4+ cell counts of SI progressors were significantly lower than those from nonprogressors (P = 0.002), while the CD4+ cell counts of NSI progressors and nonprogressors did not differ significantly. These results show that early in HIV-1 infection progressors and nonprogressors are distinguishable. NSI progressors can be distinguished from nonprogressors on the basis of serum HIV-1 RNA load and S1 progressors on the basis of CD4+ cell decline. In addition, a significant decrease in the number of HIV-1 RNA copies in the early phase of infection seems to postpone the development of AIDS.