应用基因芯片检测喉鳞状细胞癌甲醛固定石蜡包埋组织microRNA表达谱

目的 建立以甲醛固定石蜡包埋组织为材料、基于基因芯片技术的microRNA(miRNA)表达谱的分析方法 ;筛选与喉鳞状细胞癌(简称喉癌)生物学特征密切相关的差异表达miRNA.方法 从喉癌甲醛固定石蜡包埋组织中制备总RNA,经质量鉴定后进行荧光标记.采用Agilent公司的容纳723条人类miRNA探针的基因芯片完成杂交实验,以获得喉癌的miRNA表达谱.以GeneSpring GX和R-Project软件处理分析基因芯片实验数据,筛选与喉癌转移相关的差异表达miRNA.结果 从24例甲醛固定石蜡包埋组织标本中获得了符合基因芯片实验质量标准的RNA样品,并完成了基因芯片杂交及数据分析.从中共鉴定到319个miRNA,有96个miRNA在24例喉癌中均有表达,其中与淋巴结转移密切相关的(检错率<0.05)差异表达miRNA有5个,分别为miR-23a* 、miR-28-5p、miR-15a、miR-16和miR-425.结论 甲醛固定石蜡包埋组织可以提供符合基因芯片分析质量要求的miRNA,是研究miRNA的重要样品资源.从喉癌的miRNA表达谱中筛选出的转移相关差异表达miRNA(miR-23a*、miR-28-5p、miR-15a、miR-16和miR-425)有可能成为评估喉癌转移风险的新型分子标志.     

应用基因芯片检测喉鳞状细胞癌甲醛固定石蜡包埋组织microRNA表达谱

目的 建立以甲醛固定石蜡包埋组织为材料、基于基因芯片技术的microRNA(miRNA)表达谱的分析方法 ;筛选与喉鳞状细胞癌(简称喉癌)生物学特征密切相关的差异表达miRNA.方法 从喉癌甲醛固定石蜡包埋组织中制备总RNA,经质量鉴定后进行荧光标记.采用Agilent公司的容纳723条人类miRNA探针的基因芯片完成杂交实验,以获得喉癌的miRNA表达谱.以GeneSpring GX和R-Project软件处理分析基因芯片实验数据,筛选与喉癌转移相关的差异表达miRNA.结果 从24例甲醛固定石蜡包埋组织标本中获得了符合基因芯片实验质量标准的RNA样品,并完成了基因芯片杂交及数据分析.从中共鉴定到319个miRNA,有96个miRNA在24例喉癌中均有表达,其中与淋巴结转移密切相关的(检错率<0.05)差异表达miRNA有5个,分别为miR-23a* 、miR-28-5p、miR-15a、miR-16和miR-425.结论 甲醛固定石蜡包埋组织可以提供符合基因芯片分析质量要求的miRNA,是研究miRNA的重要样品资源.从喉癌的miRNA表达谱中筛选出的转移相关差异表达miRNA(miR-23a*、miR-28-5p、miR-15a、miR-16和miR-425)有可能成为评估喉癌转移风险的新型分子标志.     

应用基因芯片检测喉鳞状细胞癌甲醛固定石蜡包埋组织microRNA表达谱

目的 建立以甲醛固定石蜡包埋组织为材料、基于基因芯片技术的microRNA(miRNA)表达谱的分析方法 ;筛选与喉鳞状细胞癌(简称喉癌)生物学特征密切相关的差异表达miRNA.方法 从喉癌甲醛固定石蜡包埋组织中制备总RNA,经质量鉴定后进行荧光标记.采用Agilent公司的容纳723条人类miRNA探针的基因芯片完成杂交实验,以获得喉癌的miRNA表达谱.以GeneSpring GX和R-Project软件处理分析基因芯片实验数据,筛选与喉癌转移相关的差异表达miRNA.结果 从24例甲醛固定石蜡包埋组织标本中获得了符合基因芯片实验质量标准的RNA样品,并完成了基因芯片杂交及数据分析.从中共鉴定到319个miRNA,有96个miRNA在24例喉癌中均有表达,其中与淋巴结转移密切相关的(检错率<0.05)差异表达miRNA有5个,分别为miR-23a* 、miR-28-5p、miR-15a、miR-16和miR-425.结论 甲醛固定石蜡包埋组织可以提供符合基因芯片分析质量要求的miRNA,是研究miRNA的重要样品资源.从喉癌的miRNA表达谱中筛选出的转移相关差异表达miRNA(miR-23a*、miR-28-5p、miR-15a、miR-16和miR-425)有可能成为评估喉癌转移风险的新型分子标志.     

RNA expression analysis of formalin-fixed paraffin-embedded tumors

RNA expression analysis is an important tool in cancer research, but a limitation has been the requirement for high-quality RNA, generally derived from frozen samples. Such tumor sets are often small and lack clinical annotation, whereas formalin-fixed paraffin-embedded (FFPE) materials are abundant. Although RT-PCR-based methods from FFPE samples are finding clinical application, genome-wide microarray analysis has proven difficult. Here, we report expression profiling on RNA from 157 FFPE tumors. RNA was extracted from 2- to 8-year-old FFPE or frozen tumors of known and unknown histologies. Total RNA was analyzed, reverse-transcribed and used for the synthesis of labeled aRNA after two rounds of amplification. Labeled aRNA was hybridized to a 3'-based 22K spot oligonucleotide arrays, and compared to a labeled reference by two-color microarray analysis. After normalization, gene expression profiles were compared by unsupervised hierarchical clustering. Using this approach, at least 24% of unselected FFPE samples produced RNA of sufficient quality for microarray analysis. From our initial studies, we determined criteria based on spectrophotometric analyses and a novel TaqMan-based assay to predict which samples were of sufficient quality for microarray analysis before hybridization. These criteria were validated on an independent set of tumors with a 100% success rate (20 of 20). Unsupervised analysis of informative gene expression profiles distinguished tumor type and subtype, and identified tumor tissue of origin in three unclassified carcinomas. Although only a minority of FFPE blocks could be analyzed, we show that informative RNA expression analysis can be derived from selected FFPE samples.     

Antigen unmasking on formalin-fixed,paraffin-embedded tissue sections

Enzymatic and non-enzymatic treatments for antigen unmasking on formalin-fixed, paraffin-embedded, dewaxed sections were optimized and compared by the use of a panel of antibodies of diagnostic relevance (anti-cytokeratins, vimentin. S-100. T- and B-cell receptors, Ki-67/MIB 1, muscle actin). Non-enzymatic unmasking was obtained by boiling the slides in a microwave oven in 0.01 M salt solution (pH 6) or in 6 M urea. Trypsin or pronase digestion was used for comparison and found to be necessary for some of the reagents. The investigation was then extended to 256 antibodies; the epitopic amino acid sequence was known for 48 of them. We found that enzymatic and non-enzymatic antigen unmasking are not dependent on the epitope sequence, but some antigens benefit selectively from one treatment but not from the other. Denaturation of proteins is the likely mechanism which leads to immunodetection on microwave oven-boiled slides; this suggestion is supported by the use of denaturating solutions and by the observation that endogenous enzymes were inactivated and a few antigens were no longer immunodetectable after boiling. Non-enzymatic methods for antigen unmasking are a powerful new tool for broadening the use of antibodies for immunostaining formalin-fixed, paraffin-embedded sections and should be used in parallel with the traditional enzymatic methods.     

PolyA PCR amplification of cDNA from RNA extracted from formalin-fixed paraffin-embedded tissue.

RNA extraction still relies almost exclusively on the use of fresh or frozen tissue, limiting the number of samples that can be analyzed, and there is a growing need for means of global mRNA analysis of archived formalin-fixed paraffin-embedded tissue (FFPET). Previous reports of RNA extraction and amplification from FFPET are limited and do not enable global cDNA amplification. This study used polyA PCR to generate globally amplified cDNA from RNA extracted from formalin-fixed paraffin-embedded samples. RNA was extracted from nine routinely processed archival FFPET samples (lymph node, nasopharynx, prostate, lung and bone marrow) using an Ambion Paraffin Block RNA Isolation Kit. Global cDNA was generated by polyA RT-PCR and used in GAPDH specific PCR and PCR for CD33, c-myb, and SNF2. PolyA cDNA was reamplified by polyA PCR and the reamplified cDNA also used in GAPDH PCR. RNA was extracted from all nine samples, but was degraded. PolyA RT-PCR generated cDNA from all samples and was positive for GAPDH PCR in seven. PCR for CD33, c-myb, and SNF2 was positive in all samples tested. Following reamplification, the polyA cDNA remained positive for GAPDH by PCR. The results demonstrate the feasibility of globally amplifying RNA isolated from archival FFPET samples using polyA RT-PCR, which generates a renewable cDNA pool that can be probed for any cDNA species and reamplified as necessary.     

Comparison of different tissue sampling methods for protein extraction from formalin-fixed and paraffin-embedded tissue specimens

Aims

Protein extracts from formalin-fixed and paraffin-embedded (FFPE) tissue for proteomic analysis has recently gained attention. In this study, we explored the possibility to standardize tissue sampling from paraffin blocks and compared the protein extracts with those obtained from fresh frozen material.

Materials and methods

Fresh frozen and FFPE material was obtained from five patients with pancreatic ductal adenocarcinoma either by cutting sections with a microtome or by stamping a cylinder with tissue micro-array technology. All samples were weighed, forwarded to protein extraction and analyzed by polyacrylamide gel electrophoresis and Western blotting. Immunohistochemistry allocated proteins in tissue sections.

Results

Sampling of tissue was highly reproducible, as assessed by sample weight. While protein concentrations were significantly higher in fresh frozen material compared to FFPE material, equal amounts of protein were extracted from FFPE using either paraffin sections or core cylinders in SDS-PAGE, all three procedures showed comparable protein patterns. In Western blotting, annexin I had the same molecular weight independent of the sample source and sampling procedure.

Conclusions

The sampling of FFPE specimens for protein extraction and analysis can be standardized, uncovering equal amounts of tissue and protein. In addition, the proteins extracted from FFPE tissue seem to be the same compared with those extracted from fresh frozen tissue.     

Elevated hydrostatic pressure promotes protein recovery from formalin-fixed, paraffin-embedded tissue surrogates

High-throughput proteomic studies on formalin-fixed, paraffin-embedded (FFPE) tissues have been hampered by inefficient methods to extract proteins from archival tissue and by an incomplete knowledge of formaldehyde-induced modifications to proteins. We previously reported a method for the formation of 'tissue surrogates' as a model to study formalin fixation, histochemical processing, and protein retrieval from FFPE tissues. In this study, we demonstrate the use of high hydrostatic pressure as a method for efficient protein recovery from FFPE tissue surrogates. Reversal of formaldehyde-induced protein adducts and crosslinks was observed when lysozyme tissue surrogates were extracted at 45 000 psi and 80-100 degrees C in Tris buffers containing 2% sodium dodecyl sulfate and 0.2 M glycine at pH 4. These conditions also produced peptides resulting from acid-catalyzed aspartic acid cleavage. Additives such as trimethylamine N-oxide or copper (II) chloride decreased the total percentage of these aspartic acid cleavage products, while maintaining efficient reversal of intermolecular crosslinks in the FFPE tissue surrogates. Mass spectrometry analysis of the recovered lysozyme yielded 70% sequence coverage, correctly identified all formaldehyde-reactive amino acids, and demonstrated hydrolysis at all of the expected trypsin cleavage sites. This study demonstrates that elevated hydrostatic pressure treatment is a promising approach for improving the recovery of proteins from FFPE tissues for proteomic analysis.     

Immunohistochemical detection of Yersinia pestis in formalin-fixed, paraffin-embedded tissue

Yersinia pestis infection usually is limited to lymph nodes (bubo); rarely, if bacteria are aerosolized, pneumonic plague occurs. We developed an immunohistochemical assay using a monoclonal anti-fraction 1 Y pestis antibody for formalin-fixed tissues. We studied 6 cases using this technique. Respiratory symptoms were prominent in 2 cases; histologically, one showed intra-alveolar inflammation, and the other had alveolar hemorrhage and edema. By using the immunohistochemical assay, we found intact Yersinia and granular bacterial antigen staining in alveoli, bronchi, and blood vessels. Of the remaining cases, 2 had septicemia and 2 had a bubo. Pathologic changes included lymphocyte depletion, necrosis, edema, and foamy macrophages in lymph nodes; multiple abscesses in the spleen; fibrin thrombi in glomeruli; and unremarkable lungs. By using the immunohistochemical assay, we identified intact bacteria inside monocytes and granular antigen staining in blood vessels. The immunohistochemical assay provided a fast, nonhazardous method for diagnosing plague. The immunohistochemical assay localizes bacteria, retaining tissue morphologic features, and can help define transmission mechanisms.     

Detection of early myocardial infarction in formalin-fixed, paraffin-embedded tissue

Whether the early infarct area in formalin-fixed, paraffin-embedded tissue could be delineated by the immunohistochemical method using myoglobin-antibody was studied in 23 pig hearts without collateral circulation. Five hearts were examined at 20 minutes, 2 hours, 4 hours, and 6 hours after occlusion of the distal one third of the left anterior descending coronary artery, respectively. Three pigs were killed 24 hours after occlusion. Heart rate and aortic pressure before and after occlusion did not change in any groups. The subepicardial and subendocardial regional blood flows were reduced to almost zero in all hearts after occlusion (0.88 +/- 0.10 to 0.02 +/- 0.02 mL/g/min). Slight myoglobin defects in the ischemic tissue were noted in the five pigs examined 2 hours after occlusion and definite myoglobin defects were detected in all pigs examined at 4, 6, and 24 hours after occlusion. Nitrotetrazorium blue stain of myocardial tissue before formalin fixation showed slight demarcation of the ischemic area at 4 hours after occlusion and definite demarcation at 6 and 24 hours after occlusion. Slight demarcation was noted at 2 hours after occlusion in Masson trichrome stain and 4 hours after occlusion in the hematoxylin-eosin stain. However, definite demarcation of the ischemic area was seen in Masson trichrome stain only at 24 hours after occlusion and was not noted in hematoxylin-eosin stain even at 24 hours after occlusion. Our previous electron microscopic study revealed that, in the pig heart, irreversible cellular damage was transmurally seen at two hours after occlusion of the coronary artery. Therefore, a definite myoglobin defect reflects irreversible cellular damage such as infarction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of clinical formalin-fixed paraffin-embedded tissue quality for targeted-bisulfite sequencing

Formalin-fixed paraffin-embedded (FFPE) tissues are promising biological resources for genetic research. Recent improvements in DNA extraction from FFPE samples allowed the use of these tissues for multiple sequencing methods. However, fundamental research addressing the application of FFPE-derived DNA for targeted-bisulfite sequencing (TB-seq) is lacking. Here, we evaluated the suitability of FFPE-derived DNA for TB-seq. We conducted TB-seq using FFPE-derived DNA and corresponding fresh frozen (FF) tissues of patients with kidney cancer and compared the quality of DNA, libraries, and TB-seq statistics between the two preservation methods. The approximately 600-bp average fragment size of the FFPE-derived DNA was significantly shorter than that of the FF-derived DNA. The sequencing libraries constructed using FFPE-derived DNA and the mapping ratio were approximately 10 times and 10% lower, respectively, than those constructed using FF-derived DNA. In the mapped data of FFPE-derived DNA, duplicated reads accounted for > 60% of the obtained sequence reads, with lower mean on-target coverage. Therefore, the standard TB-seq protocol is inadequate for obtaining high-quality data for epigenetic analysis from FFPE-derived DNA, and technical improvements are necessary for enabling the use of archived FFPE resources.     

Enhanced fungal DNA-extraction from formalin-fixed, paraffin-embedded tissue specimens by application of thermal energy

Determining the etiology of invasive fungal infections (IFI) is critical for patient management as fungi vary in their susceptibility to antifungals. However, the etiology remains obscure in many cases due to negative culture results. The identification of fungal DNA by PCR in pathology blocks and sequencing it is an alternative approach to determine the cause of IFI. Previous studies identified fungal DNA in only 50% of samples with positive histopathology results, probably due to DNA damage by tissue fixation. We used realtime PCR to quantify human and fungal DNA from formalin-fixed, paraffin-embedded tissue specimens in order to study the effect of thermal energy during extraction on the yield of amplifiable DNA and subsequent identification of fungal DNA. Tissue sections from eight patients with proven IFI were subjected to DNA extraction with varying exposure to thermal energy. Amplifiable DNA increased up to 76-fold by increasing the incubation temperature from 65°C to 90°C and an additional increase was documented by incubating samples for up to 6 hours at this temperature. The augmented amplification of fungal DNA was associated with improved species identification by the sequencing of the PCR amplicons. This may help illuminate the etiology of IFI and thereby improve patient management by guiding antifungal therapy.     

Validation of a standardized extraction method for formalin-fixed paraffin-embedded tissue samples

BackgroundFormalin-fixed paraffin-embedded (FFPE) samples can be DNA-extracted and used for human papillomavirus (HPV) genotyping. The xylene-based gold standard for extracting FFPE samples is laborious, suboptimal and involves health hazards for the personnel involved.ObjectivesTo compare extraction with the standard xylene method to a xylene-free method used in an HPV LabNet Global Reference Laboratory at the Centers for Disease Control (CDC); based on a commercial method with an extra heating step.Study designFifty FFPE samples were randomly selected from a national audit of all cervical cancer cases diagnosed in Sweden during 10 years. For each case-block, a blank-block was sectioned, as a control for contamination. For xylene extraction, the standard WHO Laboratory Manual protocol was used. For the CDC method, the manufacturers’ protocol was followed except for an extra heating step, 120 °C for 20 min. Samples were extracted and tested in parallel with β-globin real-time PCR, HPV16 real-time PCR and HPV typing using modified general primers (MGP)-PCR and Luminex assays.ResultsFor a valid result the blank-block had to be betaglobin-negative in all tests and the case-block positive for beta-globin. Overall, detection was improved with the heating method and the amount of HPV-positive samples increased from 70% to 86% (p = 0.039). For all samples where HPV type concordance could be evaluated, there was 100% type concordance.ConclusionsA xylene-free and robust extraction method for HPV-DNA typing in FFPE material is currently in great demand. Our proposed standardized protocol appears to be generally useful.     

Whole genome SNP arrays using DNA derived from formalin-fixed, paraffin-embedded ovarian tumor tissue

Array-based genotyping platforms, such as the Affymetrix mapping array, have been validated as reliable methods for obtaining high-resolution copy number and allele status information when using DNA derived from fresh tissue sources. However, the suitability of such systems for the examination of DNA derived from formalin-fixed, paraffin-embedded (FFPE) tissues has not been tested. Therefore, we analyzed DNA derived from five matching fresh frozen and FFPE ovarian tumors for gene copy number changes and loss of heterozygosity using the Affymetrix GeneChip Human Mapping 10 K Array Xba 131. The data was analyzed using Affymetrix proprietary software, GeneChip DNA Analysis Software, and Chromosome Copy Number Tool. The average SNP call rate (rate of successful genotype identification) of the fresh samples was 89.44% (range 78.72-96.22%, median 92.72%) and was only slightly lower for the matching FFPE samples at 83.48% (range 76.93-93.17%, median 82.60%). The average concordance (rate of agreement between successful genotype calls) between the fresh and matching FFPE samples was 97.06% (range 92.70-99.41%, median 97.52%). Loss of heterozygosity (LOH) profiles of the fresh and FFPE samples were essentially identical across all chromosomes. Copy number data was also comparable, although the quantification of copy number changes appears overstated in the FFPE samples. In conclusion, we have shown that it is possible to achieve high-performance outcomes using FFPE-derived DNA in the Affymetrix 10 K mapping array. This advance will open up vast archival tissue resources to high-resolution genetic analysis and unlock a wealth of biological information.     

Immunohistochemical detection of cell growth fraction in formalin-fixed and paraffin-embedded murine tissue

Monoclonal antibody MIB-1 is a reliable tool for determining proliferating cells in human tissues, but does not react with the homologous mouse antigen and is therefore useless in experimental pathology using mice as model systems. Standard method for assessment of cellular proliferation in formalin-fixed, paraffin-embedded murine tissues is immunohistochemical detection of DNA synthesis using antibodies against exogenously injected 5-bromodeoxyuridine (BrdU), which is a tedious procedure and not useful for routine investigations. We tested monoclonal antibody MIB-5 and monoclonal and polyclonal anti-MCM3 antibodies as immunohistochemical proliferation markers for paraffin-embedded nonneoplastic and neoplastic tissues of wild-type and transgenic mice, compared to anti-BrdU immunostaining. Percentage of proliferating cells was determined with continuously decreasing antibody dilutions. Percentages of MIB-5 and anti-BrdU immunostained cells correlated strongly, as well as percentage of MIB-5-decorated cells and frequency of mitotic figures. Anti-MCM3 antibodies labeled significantly higher percentages of cells than anti-BrdU or MIB-5, and showed a linear decrease with increasing antibody dilutions. We conclude that MIB-5 detects reliably the cell growth fraction in formalin fixed, paraffin-embedded murine tissues, bypassing methodological drawbacks of BrdU. Anti-MCM3 antibodies are less useful for determination of proliferating cells although they might detect the fraction of cells remaining competent for proliferation.