A novel xenonucleic acid-mediated molecular clamping technology for early colorectal cancer screening.

BACKGROUND: Colorectal cancer (CRC) is one of the leading causes of cancer-related death. Early detection is critical to reduce CRC morbidity and mortality. In order to meet this need, we developed a molecular clamping assay called the ColoScape TM assay for early colorectal cancer diagnostics. METHODS: Nineteen mutations in four genes (APC, KRAS, BRAF and CTNNB1) associated with early events in CRC pathogenesis are targeted in the ColoScapeTM assay. Xenonucleic Acid (XNA)-mediated qPCR clamping technology was applied to minimize the wild-type background amplification in order to improve assay sensitivity of CRC mutation detection. The assay analytical performance was verified and validated, cfDNA and FFPE CRC patient samples were evaluated, and an ROC curve was applied to evaluate its performance. RESULTS: The data showed that the assay analytical sensitivity was 0.5% Variant Allele Frequency, corresponding to ~7-8 copies of mutant DNA with 5 ng total DNA input per test. This assay is highly reproducible with intra-assay CV of <3% and inter-assay CV of <5%. We have investigated 380 clinical samples including plasma cfDNA and FFPE samples from patients with precancerous and different stages of CRC. The preliminary assay clinical specificity and sensitivity for CRC cfDNA were: 100% (95% CI, 80.3-97.5%) and 92.2% (95% CI, 94.7-100%), respectively, with AUC of 0.96; 96% specificity (95% CI, 77.6-99.7%) and 92% sensitivity (95% CI, 86.1-95.6%) with AUC of 0.94 for CRC FFPE; 95% specificity (95% CI, 82.5%-99.1%) and 62.5% sensitivity (95% CI, 35.8%-83.7%) with AUC of 0.79 for precancerous lesions cfDNA. CONCLUSIONS: The XNA-mediated molecular clamping assay is a rapid, precise, and sensitive assay for the detection of precancerous lesions cfDNA and CRC cfDNA or FFPE samples.

Saliva as a testing specimen with or without pooling for SARS-CoV-2 detection by multiplex RT-PCR test.

BACKGROUND: Sensitive and high throughput molecular detection assays are essential during the coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The vast majority of the SARS-CoV-2 molecular assays use nasopharyngeal swab (NPS) or oropharyngeal swab (OPS) specimens collected from suspected individuals. However, using NPS or OPS as specimens has apparent drawbacks, e.g. the collection procedures for NPS or OPS specimens can be uncomfortable to some people and may cause sneezing and coughing which in turn generate droplets and/or aerosol particles that are of risk to healthcare workers, requiring heavy use of personal protective equipment. There have been recent studies indicating that self-collected saliva specimens can be used for molecular detection of SARS-CoV-2 and provides more comfort and ease of use for the patients. Here we report the performance of QuantiVirus™ SARS-CoV-2 test using saliva as the testing specimens with or without pooling. METHODS: Development and validation studies were conducted following FDA-EUA and molecular assay validation guidelines. Using SeraCare Accuplex SARS-CoV-2 reference panel, the limit of detection (LOD) and clinical performance studies were performed with the QuantiVirus™ SARS-CoV-2 test. For clinical evaluation, 85 known positive and 90 known negative clinical NPS samples were tested. Additionally, twenty paired NPS and saliva samples collected from recovering COVID-19 patients were tested and the results were further compared to that of the Abbott m2000 SARS-CoV-2 PCR assay. Results of community collected 389 saliva samples for COVID-19 screening by QuantiVirus™ SARS-CoV-2 test were also obtained and analyzed. Additionally, testing of pooled saliva samples was evaluated. RESULTS: The LOD for the QuantiVirus™ SARS-CoV-2 test was confirmed to be 100-200 copies/mL. The clinical performance studies using contrived saliva samples indicated that the positive percentage agreement (PPA) of the QuantiVirus™ SARS-CoV-2 test is 100% at 1xLOD, 1.5xLOD and 2.5xLOD. No cross-reactivity was observed for the QuantiVirus™ SARS-CoV-2 test with common respiratory pathogens. Testing of clinical samples showed a positive percentage agreement (PPA) of 100% (95% CI: 94.6% to 100%) and a negative percentage agreement (NPA) of 98.9% (95% CI: 93.1% to 99.9%). QuantiVirus™ SARS CoV-2 test had 80% concordance rate and no significant difference (p = 0.13) between paired saliva and NPS specimens by Wilcoxon matched pairs signed rank test. Positive test rate was 1.79% for 389 saliva specimens collected from local communities for COVID-19 screening. Preliminary data showed that saliva sample pooling up to 6 samples (1:6 pooling) for SARS-CoV-2 detection is feasible (sensitivity 94.8% and specificity 100%). CONCLUSION: The studies demonstrated that the QuantiVirus™ SARS-CoV-2 test has a LOD of 200 copies/mL in contrived saliva samples. The clinical performance of saliva-based testing is comparable to that of NPS-based testing. Pooling of saliva specimens for SARS-CoV-2 detection is feasible. Saliva based and high-throughput QuantiVirus™ SARS-CoV-2 test offers a highly desirable testing platform during the ongoing COVID-19 pandemic.

A multiplex branched DNA assay for parallel quantitative gene expression profiling.

We describe a novel method to quantitatively measure messenger RNA (mRNA) expression of multiple genes directly from crude cell lysates and tissue homogenates without the need for RNA purification or target amplification. The multiplex branched DNA (bDNA) assay adapts the bDNA technology to the Luminex fluorescent bead-based platform through the use of cooperative hybridization, which ensures an exceptionally high degree of assay specificity. Using in vitro transcribed RNA as reference standards, we demonstrated that the assay is highly specific, with cross-reactivity less than 0.2%. We also determined that the assay detection sensitivity is 25,000 RNA transcripts with intra- and interplate coefficients of variance of less than 10% and less than 15%, respectively. Using three 10-gene panels designed to measure proinflammatory and apoptosis responses, we demonstrated sensitive and specific multiplex gene expression profiling directly from cell lysates. The gene expression change data demonstrate a high correlation coefficient (R(2)=0.94) compared with measurements obtained using the single-plex bDNA assay. Thus, the multiplex bDNA assay provides a powerful means to quantify the gene expression profile of a defined set of target genes in large sample populations.

Light controllable siRNAs regulate gene suppression and phenotypes in cells.

Small interfering RNA (siRNA) is widely recognized as a powerful tool for targeted gene silencing. However, siRNA gene silencing occurs during transfection, limiting its use is in kinetic studies, deciphering toxic and off-target effects and phenotypic assays requiring temporal, and/or spatial regulation. We developed a novel controllable siRNA (csiRNA) that is activated by light. A single photo removable group is coupled during oligonucleotide synthesis to the 5' end of the antisense strand of the siRNA, which blocks the siRNA's activity. A low dose of light activates the siRNA, independent of transfection resulting in knock down of specific target mRNAs and proteins (GAPDH, p53, survivin, hNuf2) without stimulating non-specific effects such as regulated protein kinase PKR and induction of the interferon response. We demonstrate survivin and hNuf2 csiRNAs temporally knockdown their mRNAs causing multinucleation and cell death by mitotic arrest, respectively. Furthermore, we demonstrate a dose-dependent light regulation of hNuf2 csiRNA activity and resulting phenotype. The light controllable siRNAs are introduced into cells using commercially available reagents including the MPG peptide based delivery system. The csiRNAs are comparable to standard siRNAs in their transfection efficiency and potency of gene silencing. This technology should be of interest for phenotypic assays such as cell survival, cell cycle regulation, and cell development.

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-1alpha (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.