Joel A. Lefferts

Evaluation of the Nanosphere Verigene System and the Verigene F5/F2/MTHFR Nucleic Acid Tests.

BACKGROUND Our ability to detect single nucleotide polymorphisms (SNPs) and gene mutations has become commonplace in the clinical laboratory setting. Molecular genetic testing for gene variants associated with hypercoagulability has become a standard of practice for Factor V and Factor II polymorphisms. METHODS In this study, we evaluated a novel technology that allows for the routine assessment of these SNPs, the Verigene System (Nanosphere Inc, Northbrook, IL), as a low-density array that does not require PCR amplification prior to detection. Precision was assessed by using multiple operators for within and between run performance evaluations. Accuracy was assessed by evaluating 176 DNA samples from patients who had been previously tested for the SNPs of interest in this multicenter study. RESULTS No mis-calls were made during the precision studies. Testing of the 176 DNA samples resulted in individual call rates for the F5, F2 and MTHFR genotypes of 98.3%, 94.9%, and 92.6%, respectively. CONCLUSIONS The Verigene F5/F2/MTHFR Nucleic Acid Tests for the Factor V (1691G>A), Factor II (20210G>A) and MTHFR (677C>T) genes were robust methods for SNP detection without the need for DNA amplification. The ease of use and performance of this system makes it suitable for the clinical laboratory setting.

Automation of genomic DNA isolation from formalin-fixed, paraffin-embedded tissues

Isolation of DNA from formalin-fixed, paraffin-embedded (FFPE) tissue remains a laborious task for clinical laboratories and researchers who need to screen several samples for genetic variants. The objective of this study was to evaluate DNA isolation methods from FFPE tissues and to choose an efficient method with less hands-on time to obtain DNA of optimum concentration and purity for use in routine molecular diagnostic assays. Three methods were compared in this study: Gentra Puregene Tissue Kit, EZ1 DNA Tissue Kit and QIAamp FFPE Tissue Kit. Samples consisted of FFPE tissues of head/neck and lung tumor resections. Quality control for the extraction process end product included determination of the concentration and purity of isolated DNA and the ability to amplify a housekeeping gene, GAPDH, using real-time PCR assay. The hands-on-time required was less for the EZ1 protocol compared to the other methods. The average DNA concentration obtained was 112, 61 and 40 ng/μl, respectively, for the Gentra Puregene Tissue Kit, Qiagen EZ1 DNA Tissue Kit and QIAamp FFPE Tissue Kit. The purity and quality of samples obtained using the different DNA isolation methods were comparable. Comparative evaluation of three DNA isolation methods indicated that the Qiagen EZ1 method surpassed the other methods with reduced hands-on-time to produce optimum concentration of quality DNA for use in routine molecular analyses.

Regulatory T cells are not a strong predictor of survival for patients with glioblastoma

BACKGROUND Regulatory T cells (Tregs) are potentially prognostic indicators in patients with glioblastoma. If differences in frequency of Tregs in tumor or blood account for substantial variation in patient survival, then reliably measuring Tregs may enhance treatment selection and improve outcomes. METHODS We measured Tregs and CD3+ T cells in tumors and blood from 25 patients with newly diagnosed glioblastoma. Tumor-infiltrating Tregs and CD3+ T cells, measured by quantitative DNA demethylation analysis (epigenetic qPCR) and by immunohistochemistry, and peripheral blood Treg proportions measured by flow cytometry were correlated with patient survival. Additionally, we analyzed data from The Cancer Genome Atlas (TCGA) to correlate the expression of Treg markers with patient survival and glioblastoma subtypes. RESULTS Tregs, as measured in tumor tissue and peripheral blood, did not correlate with patient survival. Although there was a correlation between tumor-infiltrating Tregs expression by epigenetic qPCR and immunohistochemistry, epigenetic qPCR was more sensitive and specific. Using data from TCGA, mRNA expression of Forkhead box protein 3 (FoxP3) and Helios and FoxP3 methylation level did not predict survival. While the classical glioblastoma subtype corresponded to lower expression of Treg markers, these markers did not predict survival in any of the glioblastoma subtypes. CONCLUSIONS Although immunosuppression is a hallmark of glioblastoma, Tregs as measured in tissue by gene expression, immunohistochemistry, or demethylation and Tregs in peripheral blood measured by flow cytometry do not predict survival of patients. Quantitative DNA demethylation analysis provides an objective, sensitive, and specific way of identifying Tregs and CD3+ T cells in glioblastoma.

A validation study of a new molecular diagnostic assay: the Dartmouth-Hitchcock Medical Center experience with the GeneSearch BLN assay in breast sentinel lymph nodes.

BACKGROUND Sentinel lymph node (SLN) processing remains variable in terms of performing multiple tissue levels and immunohistochemical (IHC) or PCR-based assays. A rapid and reliable molecular pathology assay, as an adjunct to routine SLN processing, could minimize and standardize the histologic evaluation needed for an accurate and clinically significant diagnosis. We compared the recently FDA-approved Veridex GeneSearch Breast Lymph Node (BLN) Assay (Veridex, LLC; Warren, NJ), a real time reverse transcriptase-polymerase chain reaction assay that is designed to detect metastases >0.2 mm, with our standard lymph node processing. MATERIALS AND METHODS The GeneSearch BLN assay evaluates RNA expression data for three target genes (mammaglobin, cytokeratin 19, and internal control porphobilinogen deaminase), and provides a qualitative (positive/negative) result. In 59 patients, the assay was performed on SLN tissue that would normally be deep within the tissue block and not routinely evaluated histologically. Two 1 -mm slices from the outer node portions were submitted fresh for RNA extraction; the remaining tissue was submitted for routine histology. RESULTS Of the 59 patients, the assay determined 43 as true negative, eight as true positive, one as false-negative, three as false-positive, and four as invalid. Assay sensitivity was 88.9%, specificity 93.5%. DISCUSSION The sensitivity of the assay sampling from the outer node tissue was high (88.9%) and identical to that validated in the large registration study in which half of the node was assessed as alternate slices (87.6%). Our protocol uses this assay as an adjunct to traditional histologic evaluation, to reduce and standardize the number of tissue sections needed for thorough SLN evaluation, and to enhance our ability to bank RNA.

Merkel cell polyomavirus and extrapulmonary small cell carcinoma.

The Merkel cell polyomavirus (MCV) is involved in the development of up to 100% of Merkel cell cancer (MCC) cases. Early studies have reported that the virus was infrequently detected in other small cell or neuroendocrine lung carcinomas, which share histological features with MCC. The present study investigated the presence of MCV in cases of extrapulmonary small cell carcinoma (ESCC), which also shares histological features with MCC. A total of 25 cases of ESCC that were diagnosed between 2004 and 2009 were identified at The Dartmouth Hitchcock Medical Center. Archived tissue was available for testing in 16 of these cases. A total of 11 tissue specimens of MCC were used as positive controls. DNA that was extracted from the archived tissue was subjected to five separate quantitative (q)PCR assays for the detection of four MCV genomic targets. MCV DNA was detected in 3/16 (19%) of the ESCCs and in all 11 MCCs. In the three MCV-positive ESCCs, the viral target was only detected by either one or two of the PCR assays. In 8/11 MCV-positive MCCs, the DNA tested positive by either three or all four assays and the remaining three MCCs tested positive by either one or two assays. The β-globin endogenous control was detected in all the samples that were tested. Although MCC and ESCC share numerous histological features, MCV is detected at a lower frequency in ESCC. The possible role for MCV in the etiology of ESCC remains uncertain and may account for the rare cases of ESCC with no other identifiable etiology. The failure of other assays to detect MCV may be due to sequence variability in the MCV genome.

Establishment of a CYP2C19 Genotyping Assay for Clinical Use

Conversion of clopidogrel (Plavix) to its active metabolite is catalyzed largely by the P450 enzyme 2C19 (CYP2C19). Numerous allelic variants of CYP2C19 exist. The *1 allele is considered wild type, whereas the *2 and *3 alleles have no in vivo enzymatic activity. Conversely, the *17 allele has increased expression, resulting in increased clopidogrel activation. Poor metabolizers (*2/*2 and *2/*3 genotypes) experience higher rates of therapeutic failure. For this reason, we have validated a CYP2C19 genotyping assay for the *1, *2, *3, and *17 alleles. Genomic DNA extracted from 30 deidentified EDTA whole-blood samples from patients was analyzed at 2 independent facilities using specific TaqMan realtime polymerase chain reaction primers and probes. Concordant genotypes were generated on all samples tested. Of the 30 samples, 15 were CYP2C19*1/*1, 8 were CYP2C19*1/*17, 5 were CYP2C19*1/*2, and 2 were CYP2C19*2/*17. There were no CYP2C19*3 alleles or *2/*2 homozygous genotypes detected. This CYP2C19 genotyping assay is appropriate for clinical testing, demonstrating excellent interlaboratory concordance, enabling the selection of the most effective clopidogrel treatment regimen for patients undergoing percutaneous coronary intervention.

KRAS detection in colonic tumors by DNA extraction from FTA paper: the molecular touch-prep.

DNA isolated from formalin-fixed paraffin-embedded (FFPE) tissue is usually more degraded and contains more polymerase chain reaction (PCR) inhibitors than DNA isolated from nonfixed tissue. In addition, the tumor size and cellular heterogeneity found in tissue sections can often impact testing for molecular biomarkers. As a potential remedy to this situation, we evaluated the use of Whatman FTA paper cards for collection of colorectal tumor samples before tissue fixation and for isolation of DNA for use in a real-time PCR-based KRAS mutation assay. Eleven colon tumor samples were collected by making a cut into the fresh tumor and applying the Whatman FTA paper to the cut surface. Matched FFPE tissue blocks from these tumors were also collected for comparison. KRAS mutation analysis was carried out using the Applied Biosystems 7500 Fast Real-time PCR System using 7 independent custom TaqMan PCR assays. Of the 11 colon tumors sampled, 6 were positive for KRAS mutations in both the Whatman FTA paper preparations and corresponding FFPE samples. Whatman FTA paper cards for collection of colorectal tumor samples before tissue fixation and for isolation of DNA have many advantages including ease of use, intrinsic antimicrobial properties, long storage potential (stability of DNA over time), and a faster turnaround time for results. Extracted DNA should be suitable for most molecular diagnostic assays that use PCR techniques. This novel means of DNA preservation from surgical specimens would benefit from additional study and validation as a dependable and practical technique to preserve specimens for molecular testing.

Development of a rapid clinical TPMT genotyping assay.

OBJECTIVES Thiopurine compounds are commonly used in the treatment of childhood acute lymphoblastic leukemia, and as immunosuppressants following organ transplantation or for treatment of various autoimmune disorders. Thiopurine S-methyltransferase (TPMT) is required for detoxification, through S-methylation, of 6-thioguanine nucleotides (TGNs), a byproduct of thiopurine metabolism. Single nucleotide polymorphisms (SNPs) in the TPMT gene have been shown to affect its function, with some variants associated with serious clinical manifestations including severe to fatal myelosuppression and organ transplant rejection following treatment with standard thiopurine doses. In this study, we describe a TaqMan real time PCR allelic discrimination assay requiring minimal DNA input for TPMT genotyping. DESIGN AND METHODS We designed controls for the homozygous wild type and allelic variants of TPMT*2, *3B, and *3C. Genomic DNA was extracted from an additional 412 human blood samples. The samples were tested for the TPMT*2, *3B, *3C, and *3A polymorphisms by TaqMan genotyping assays using the AB 7500 FAST Real-Time PCR instrument. Allelic discrimination plots were used to identify each mutation. RESULTS The TaqMan assay correctly genotyped all custom control DNA samples. Of the 412 tested samples, our assay identified 375 samples as wild-type *1/*1 (91.02%), 3 as *1/*2 (0.73%), 1 as *1/*3B (0.24%), 3 as *1/*3C (0.73%), 27 presumed to be *1/*3A (6.55%), and 3 as *3B/*3A (0.73%). CONCLUSIONS The clinical implications of TPMT genotyping, along with the simplicity and specificity of the TaqMan genotyping assays make this test highly suitable for use in a clinical laboratory.

Correlation of polypoid colorectal adenocarcinoma with pre-existing adenomatous polyps and KRAS mutation.

Cetuximab is an anti-epidermal growth factor receptor that helps effectively treat patients with advanced colorectal adenocarcinoma without KRAS activating mutations. KRAS mutations are associated with 16% to 50% of isolated villous adenomas and approximately 30% of colorectal cancer. Correlation between the gross and histological subset of colorectal adenocarcinoma with KRAS mutation is unknown. Archived surgical resection specimens of colorectal adenocarcinoma (n = 42) and villous adenoma (n = 9) were collected. The gross appearance and histopathological features of these lesions were thoroughly reviewed, including the presence of a pre-existing adenomatous polyp. DNA was extracted from formalin-fixed, paraffin-embedded tissue sections and then subjected to TaqMan real-time polymerase chain reaction to detect the seven most common KRAS mutations. KRAS mutations were found in 13 of 42 cases (31%) of colorectal adenocarcinoma and 7 of 9 cases (78%) of villous adenoma. All 13 cases of colorectal carcinoma with a KRAS mutation showed a gross polypoid configuration, compared to no KRAS mutation in the colorectal carcinomas with ulcerative configuration. In addition, 13 of 17 of these cases (76%) had histological features of adenocarcinoma with a persistent preexisting adenomatous polyp with villous architecture. In summary, grossly polypoid colorectal adenocarcinomas with a persistent pre-existing adenomatous polyp with villous architecture are strongly associated with KRAS mutations.

Utility of the Roche Cobas 4800 for detection of high-risk human papillomavirus in formalin-fixed paraffin-embedded oropharyngeal squamous cell carcinoma.

Clinical laboratories are expected to reliably identify human papilloma virus (HPV) associated oropharyngeal squamous cell carcinoma (OPSCC) for prognostic and potential therapeutic applications. In addition to surrogate p16 immunohistochemistry (IHC) testing, DNA-based HPV-specific testing strategies are widely utilized. Recognizing the efficiency of the Roche Cobas 4800 platform for testing gynecological cytology specimens for high-risk HPV, we elected to evaluate the potential utility of this platform for testing formalin-fixed paraffin-embedded (FFPE) OPSCC tissue. Using the Roche Linear Array assay for comparison, we tested twenty-eight samples (16 primary OPSCC, 2 lymph node metastases from primary OPSCC, 1 oral tongue carcinoma, 3 benign squamous papillomas, and 3 non-oropharyngeal carcinoma tissues). Excluding two invalid results, the Roche Cobas 4800 testing resulted in excellent inter-assay concordance (25/26, 96.2%) and 100% concordance for HPV-16/HPV-18 positive samples. This data suggests that the Roche Cobas 4800 platform may be a cost-effective method for testing OPSCC FFPE tissues in a clinical molecular pathology laboratory setting.