Gary McMaster

A New Potent Secondary Amphipathic Cell–penetrating Peptide for siRNA Delivery Into Mammalian Cells

RNA interference constitutes a powerful tool for biological studies, but has also become one of the most challenging therapeutic strategies. However, small interfering RNA (siRNA)-based strategies suffer from their poor delivery and biodistribution. Cell-penetrating peptides (CPPs) have been shown to improve the intracellular delivery of various biologically active molecules into living cells and have more recently been applied to siRNA delivery. To improve cellular uptake of siRNA into challenging cell lines, we have designed a secondary amphipathic peptide (CADY) of 20 residues combining aromatic tryptophan and cationic arginine residues. CADY adopts a helical conformation within cell membranes, thereby exposing charged residues on one side, and Trp groups that favor cellular uptake on the other. We show that CADY forms stable complexes with siRNA, thereby increasing their stability and improving their delivery into a wide variety of cell lines, including suspension and primary cell lines. CADY-mediated delivery of subnanomolar concentrations of siRNA leads to significant knockdown of the target gene at both the mRNA and protein levels. Moreover, we demonstrate that CADY is not toxic and enters cells through a mechanism which is independent of the major endosomal pathway. Given its biological properties, we propose that CADY-based technology will have a significant effect on the development of fundamental and therapeutic siRNA-based applications.

Small Interfering RNA and Gene Expression Analysis Using a Multiplex Branched DNA Assay without RNA Purification

The authors have developed a novel multiplex detection system that quantitatively measures the expression level of 11 messenger RNAs (mRNAs) directly from cell lysates or tissue homogenates without RNA purification. The system incorporates branched DNA (bDNA) technology from Bayer and a multiplex bead array platform from Luminex. In this study, a 21-nt synthetic small interfering RNA (siRNA; specifically designed to knockdown interleukin-8 [IL-8] expression) was delivered into HeLa cells. Using the multiplex bDNA assay, gene expression levels were measured simultaneously from cell lysates for 11 genes. After treating the HeLa cells for 20 h with phorbol myristate acetate (PMA), IL-8 mRNA levels were induced by almost 50-fold; transfection with 30 nM IL-8-specific siRNA reduced the PMA-induced IL-8 mRNA by 80%. In addition, PMA induced mRNA expression in IL-1α (3-fold) and IL-6 (4-fold); however, the IL-8 siRNA did not affect the expression of either of these 2 cytokine genes, indicating that the siRNA was selective for IL-8 mRNA expression. Three housekeeping genes’ expression levels were measured under all conditions tested. The multiplex bDNA assay provides a powerful tool for quantitative multiplex gene expression analysis directly from cell lysates, which could be extremely valuable for conservation of rare or difficult-to-obtain samples.

Evaluation of the branched-chain DNA assay for measurement of RNA in formalin-fixed tissues.

We evaluated the branched-chain DNA (bDNA) assay QuantiGene Reagent System to measure RNA in formalin-fixed, paraffin-embedded (FFPE) tissues. The QuantiGene Reagent System does not require RNA isolation, avoids enzymatic preamplification, and has a simple workflow. Five selected genes were measured by bDNA assay; quantitative polymerase chain reaction (qPCR) was used as a reference method. Mixed-effect statistical models were used to partition the overall variance into components attributable to xenograft, sample, and assay. For FFPE tissues, the coefficients of reliability were significantly higher for the bDNA assay (93-100%) than for qPCR (82.4-95%). Correlations between qPCR(FROZEN), the gold standard, and bDNA(FFPE) ranged from 0.60 to 0.94, similar to those from qPCR(FROZEN) and qPCR(FFPE). Additionally, the sensitivity of the bDNA assay in tissue homogenates was 10-fold higher than in purified RNA. In 9- to 13-year-old blocks with poor RNA quality, the bDNA assay allowed the correct identification of the overexpression of known cancer genes. In conclusion, the QuantiGene Reagent System is considerably more reliable, reproducible, and sensitive than qPCR, providing an alternative method for the measurement of gene expression in FFPE tissues. It also appears to be well suited for the clinical analysis of FFPE tissues with diagnostic or prognostic gene expression biomarker panels for use in patient treatment and management.

Direct quantification of gene expression in homogenates of formalin-fixed, paraffin-embedded tissues

Formalin-fixed, paraffin-embedded (FFPE) tissues represent an important source of archival materials for gene expression profiling. We report here the development of a modified branch DNA assay that allows direct quantification of messenger RNA (mRNA) transcripts in homogenates from FFPE tissue sections without the need for RNA isolation and reverse transcription into cDNA. Formalin fixation essentially has no effect on the branch DNA assay, and RNA degradation only marginally reduces the signal by 2- to 3-fold. Under the same conditions, formalin fixation and RNA degradation greatly reduces real-time reverse transcription PCR (RT-PCR) efficiency, reducing signals by as much as 15- and 1400-fold, respectively. Although both technologies can generate biologically meaningful expression profiles from FFPE human lung tumor specimens, the branch DNA assay is more sensitive than real-time RT-PCR under the conditions tested. Our results therefore suggest that the branch DNA assay is an ideal tool for retrospective analysis of gene expression in archival tissues.

Detection of TMPRSS2-ERG Fusion Gene Expression in Prostate Cancer Specimens by a Novel Assay Using Branched DNA

OBJECTIVES To develop a novel assay that uses branched DNA technology to measure TMPRSS2-ERG fusion, as genetic rearrangement of TMPRSS2 regulatory sequences and coding sequences of the ERG gene has been detected in nearly half of prostate cancers, but quantitative assays to detect such TMPRSS2-ERG gene fusion have been limited to real-time polymerase chain reaction (PCR) techniques that rely on reverse transcriptase-based amplification. METHODS Branched DNA probes were designed to detect TMPRSS2-ERG gene fusion in prostate cancer cell lines. Nonquantitative nested reverse transcription (RT)-PCR and fluorescence in situ hybridization (FISH) were used to ascertain TMPRSS2-ERG gene fusion status in prostate tissues. RESULTS The branched DNA assay detected TMPRSS2-ERG gene fusion from less than 200 pg of prostate cancer RNA, whereas more than 600 pg of RNA was required for fusion gene detection by one step real-time RT-PCR. In evaluation of clinical prostatectomy specimens, the branched DNA assay showed a concordant detectable fusion signal in all 9 clinical samples that had fusion detected by nested RT-PCR or FISH. Moreover, branched DNA detected gene fusion in 2 of 16 prostate cancer tissue specimens that was not detected by FISH or nested RT-PCR. CONCLUSIONS Our findings demonstrate a branched DNA assay that is effective for detection of TMPRSS2-ERG gene fusion in prostate cancer clinical specimens, thus providing an alternative method to ascertain TMPRSS2-ERG gene fusion in human prostate cancer tissue.

Multiplex transcriptional analysis of paraffin-embedded liver needle biopsy from patients with liver fibrosis

BackgroundThe possibility of extracting RNA and measuring RNA expression from paraffin sections can allow extensive investigations on stored paraffin samples obtained from diseased livers and could help with studies of the natural history of liver fibrosis and inflammation, and in particular, correlate basic mechanisms to clinical outcomes.ResultsTo address this issue, a pilot study of multiplex gene expression using branched-chain DNA technology was conducted to directly measure mRNA expression in formalin-fixed paraffin-embedded needle biopsy samples of human liver. Twenty-five genes were selected for evaluation based on evidence obtained from human fibrotic liver, a rat BDL model and in vitro cultures of immortalized human hepatic stellate cells. The expression levels of these 25 genes were then correlated with liver fibrosis and inflammation activity scores. Statistical analysis revealed that three genes (COL3A1, KRT18, and TUBB) could separate fibrotic from non-fibrotic samples and that the expression of ten genes (ANXA2, TIMP1, CTGF, COL4A1, KRT18, COL1A1, COL3A1, ACTA2, TGFB1, LOXL2) were positively correlated with the level of liver inflammation activity.ConclusionThis is the first report describing this multiplex technique for liver fibrosis and has provided the proof of concept of the suitability of RNA extracted from paraffin sections for investigating the modulation of a panel of proinflammatory and profibrogenic genes. This pilot study suggests that this technique will allow extensive investigations on paraffin samples from diseased livers and possibly from any other tissue. Using identical or other genes, this multiplex expression technique could be applied to samples obtained from extensive patient cohorts with stored paraffin samples in order to correlate gene expression with valuable clinically relevant information. This method could be used to provide a better understanding of the mechanisms of liver fibrosis and inflammation, its progression, and help development of new therapeutic approaches for this indication.

Abstract 44: Tissue image analysis tool to quantify HER2 RNA and protein expression by colorimetric in situ hybridization and immunohistochemistry for breast cancer diagnosis.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Early cancer diagnosis and risk assessment are powerful drivers in discovery of oncology biomarkers for diagnostic tests and simultaneous improvement of already identified biomarkers. Molecular tools such as RNA Colorimetric in situ hybridization (CISH) and immunohistochemistry (IHC) combined with conventional histopathology promise to increase the sensitivity and specificity of cancer staging and overall survival prediction. Changes in oncogene and proto-oncogene expression are a hallmark of cancer. For this reason, simultaneous quantification of mRNA and protein expression using RNA CISH and IHC combined with image-analysis is of interest. One such proto-oncogene is HER2, which is encoded by ERBB2 gene located at the long arm of human chromosome 17 (17q12). Here, we combine RNA CISH and IHC with image-analysis to develop a reliable quantitative HER2 assay that enables quantification of HER2 mRNA and protein expression in the context of human breast cancer. Since HER2 is only over-expressed in a subset of human breast cancers, we initially focused our analysis by screening tissue microarrays (TMAs) using RNA CISH and IHC. TMAs containing 20 normal and 20 breast tumor tissues were tested and whole-slide imaging was used to obtain CISH and IHC signals. HER2 mRNA and protein expression were analyzed, quantified, and compared both at tissue- and individual cell-levels using proprietary image-analysis based tools. Moreover, we compared heterogeneity of RNA and protein expression and further extended our studies to several other cancer-related genes. Finally, since oncogene expression plays a role in cancer pathologies, successful quantification of oncogene in situ expression in human cancer tissues may prove to be beneficial to further understanding of cancer pathology, for drug screening and development of biomarkers and ultimately diagnostic tests. Citation Format: Mirza Peljto, Joseph Krueger, Erik Hagendorn, David Young, Steve Potts, Quan Nguyen, Botoul Maqsodi, Takuro Yaoi, Gary McMaster. Tissue image analysis tool to quantify HER2 RNA and protein expression by colorimetric in situ hybridization and immunohistochemistry for breast cancer diagnosis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 44. doi:10.1158/1538-7445.AM2013-44

Abstract 30: ERG oncoprotein expression in prostate cancer: Potential for ERG-based stratification

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Introduction: Prevalent gene fusions involving regulatory sequences of the androgen receptor (AR) regulated prostate associated genes (predominantly TMPRSS2) and protein coding sequences of nuclear transcription factors in the ETS gene family (primarily ERG), result in frequent overexpression of ERG in prostate tumors. Emerging studies suggest oncogenic functions of ERG in prostate cancer (CaP). Despite numerous reports of gene fusions and mRNA expression, ERG oncoprotein in CaP still remains to be defined. Using an anti-ERG monoclonal antibody (ERG-MAb) developed by our group, a global view of ERG oncoprotein expression has been established in the context of multi-focal CaP. Experimental procedures: Specificity of the ERG MAb was established using wt ERG and TMPRRSS2-ERG encoded proteins expressed in HEK 293 cells and ERG si RNA treated VCaP cells harboring TMPRRSS2-ERG fusion. ERG expression in formalin fixed paraffin embedded (FFPE), whole mount-prostate specimens was optimized by immuno-histochemistry assay. TMPRSS2-ERG fusion status in representative specimens was analyzed by b-DNA assay or fluorescent in situ hybridization (FISH). Results: Through exhaustive evaluations of 132 whole-mount prostates (227 tumor foci and over 200,000 benign glands), we demonstrate 99.9 % specificity of an anti-ERG monoclonal antibody. Specimens from over 60% patients had one or more ERG positive tumor focus. Over 80% concordance was noted between the presence of ERG protein and the common TMPRSS2-ERG fusion (A type) transcript in representative specimens from 35 pateints. Conclusions: Unequivocal association of focally ERG positive PIN lesions with ERG positive carcinoma (80 out of 80 specimens) and vice versa (52 out of 52 specimens) strongly affirms biological role of ERG in clonal progression of prostate tumors. Taken together, the homogeneous and strong ERG expression in individual tumors establishes the potential for ERG based stratification of prostate cancers. Funding sources: NIH Grants RO1 DK065977 and Center for Prostate Disease Research Program HU001-04-C-1502 Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 30.