A Highly Sensitive Method to Efficiently Profile the Histone Modifications of FFPE Samples.

The majority of biopsies in both basic research and translational cancer studies are preserved in the format of archived formalin-fixed paraffin-embedded (FFPE) samples. Profiling histone modifications in archived FFPE tissues is critically important to understand gene regulation in human disease. The required input for current genome-wide histone modification profiling studies from FFPE samples is either 10–20 tissue sections or whole tissue blocks, which prevents better resolved analyses. But it is desirable to consume a minimal amount of FFPE tissue sections in the analysis as clinical tissues of interest are limited. Here, we present FFPE tissue with antibody-guided chromatin tagmentation with sequencing (FACT-seq), the first highly sensitive method to efficiently profile histone modifications in FFPE tissues by combining a novel fusion protein of hyperactive Tn5 transposase and protein A (T7−pA−Tn5) transposition and T7 in vitro transcription. FACT-seq generates high-quality chromatin profiles from different histone modifications with low number of FFPE nuclei. We proved a very small piece of FFPE tissue section containing ∼4000 nuclei is sufficient to decode H3K27ac modifications with FACT-seq. H3K27ac FACT-seq revealed disease-specific super enhancers in the archived FFPE human colorectal and human glioblastoma cancer tissue. In summary, FACT-seq allows decoding the histone modifications in archival FFPE tissues with high sensitivity and help researchers to better understand epigenetic regulation in cancer and human disease.

Background/Objectives: Obtaining reliable DNA profiles from archival tissue preserved as formalin-fixed, paraffin-embedded (FFPE) samples remains a major challenge in both forensic and medical evaluations. The quality of DNA isolated from FFPE material is frequently compromised due to formalin-induced fragmentation and chemical modifications. These limitations are particularly relevant in cases of suspected medical malpractice related to cancer diagnosis or treatment, where retrospective molecular analyses may provide critical evidence. The aim of this study was to evaluate the performance of the Maxwell® RSC Xcelerate DNA FFPE Kit (Promega) in generating DNA profiles from archival FFPE tissue blocks of endometrial cancer and to identify the limitations associated with this approach. Methods: Archival FFPE blocks of endometrial cancer were analyzed using the Maxwell® RSC Xcelerate DNA FFPE Kit. DNA yield, purity, and degradation indices were assessed using standard real-time PCR-based quantification methods. Short tandem repeat (STR) profiling was performed with forensic genotyping kits, and the completeness, allele balance, and reliability of obtained profiles were evaluated. The obtained results were compared with reference quality thresholds commonly used in forensic practice. Results: The Maxwell® RSC Xcelerate Kit allowed for recovery of relatively high DNA yields with consistently low degradation indices, confirming good extraction efficiency from FFPE samples. Nevertheless, despite favorable quantitative values, the generation of complete STR profiles was often unsuccessful. Partial or incomplete profiles were frequent, characterized by allele dropout and imbalance, which substantially reduced their evidentiary value. These findings suggest that DNA fragmentation and fixation-related artifacts impair amplification efficiency and limit the usefulness of STR analysis. Conclusions: This study emphasizes the persistent challenges of DNA profiling from FFPE tissue in forensic-medical contexts. Although the Maxwell® RSC Xcelerate Kit demonstrated effective DNA recovery, the ability to generate complete and interpretable STR profiles remained limited. Further refinement of extraction protocols, as well as improved interpretative strategies, are required to enhance the reliability and evidentiary significance of molecular analyses based on archival FFPE material.

ObjectiveThe power of genome-wide association studies (GWAS) to identify common disease variants depends primarily on the number of included samples. The availability of formalin-fixed paraffin-embedded (FFPE) samples in pathology institutes provides a valuable resource for GWAS, but the use of this material poses significant challenges. To explore the suitability of utilizing FFPE tissue for GWAS, we analysed the genotyping concordance between corresponding FFPE and blood samples. We evaluated both microarray technology and low-coverage whole-genome sequencing (lcWGS) to determine whether there were differences between genotyping methods.ResultsIn our concordance study, FFPE tissue showed high recall and precision values across both genotyping methods when compared to matched blood samples for single nucleotide polymorphisms. This demonstrates that FFPE samples are suitable for GWAS and that both methods are viable options for genotyping. However, microarray technology outperformed lcWGS, as evidenced by significantly higher recall (p = 0.005) and precision (p = 0.003) values. This, together with the lower cost of genotyping and computational efficiency, makes microarray technology currently the superior method for GWAS using FFPE tissue. Nevertheless, lcWGS has shown reliable results and holds the potential to provide more comprehensive and unbiased genetic variant analysis across diverse populations in the future. Our results show that the large number of FFPE samples stored in pathology institutes can significantly increase the power of future GWAS.

Formalin-fixed paraffin-embedded (FFPE) tissue represents a valuable source for translational cancer research. However, the widespread application of various downstream methods remains challenging. Here, we aimed to assess the feasibility of a genomic and gene expression analysis workflow using FFPE breast cancer (BC) tissue. We conducted a systematic literature review for the assessment of concordance between FFPE and fresh-frozen matched tissue samples derived from patients with BC for DNA and RNA downstream applications. The analytical performance of three different nucleic acid extraction kits on FFPE BC clinical samples was compared. We also applied a newly developed targeted DNA Next-Generation Sequencing (NGS) 370-gene panel and the nCounter BC360® platform on simultaneously extracted DNA and RNA, respectively, using FFPE tissue from a phase II clinical trial. Of the 3701 initial search results, 40 articles were included in the systematic review. High degree of concordance was observed in various downstream application platforms. Moreover, the performance of simultaneous DNA/RNA extraction kit was demonstrated with targeted DNA NGS and gene expression profiling. Exclusion of variants below 5% variant allele frequency was essential to overcome FFPE-induced artefacts. Targeted genomic analyses were feasible in simultaneously extracted DNA/RNA from FFPE material, providing insights for their implementation in clinical trials/cohorts.

PurposeThe purpose of the present study was to investigate the biological and clinical significance of GATA binding protein 3 (GATA3) in bladder cancer patients.Patients and MethodsFor the detection of the correlation between GATA3 expression and bladder cancer, we downloaded the mRNA expression data from the Cancer Genome Atlas (TCGA) database and conducted immunohistochemistry staining on formalin-fixed paraffin-embedded (FFPE) sample tissues. Then, bladder cancer cell lines were utilized to investigate the potential functions of GATA3 by cell apoptosis, proliferation and cycle assays.ResultsThe mRNA data from TCGA database and bladder cancer cell lines suggested that GATA3 mRNA expression was significantly higher compared with normal tissues and cells. Conversely, the Western blot assay revealed that the expression of GATA3 was significantly lower in bladder cancer than normal urothelial cell line. Additionally, we found that over-expression of GATA3 was significantly associated with tumor subtype (P = 0.001 in TCGA; P = 0.004 in FFPE tissues), earlier clinical stage (P < 0.001 in TCGA; P < 0.001 in FFPE) and lower grade tumor (P = 0.057 in TCGA; P = 0.002 in FFPE). Kaplan-Meier analysis and multivariate Cox regression analysis indicated that age (P < 0.001 in both cohort), clinical stage (P = 0.028 in TCGA; P = 0.011 in FFPE), recurrence (P < 0.001) and low GATA3 in TCGA cohort (P = 0.035) but high GATA3 in FFPE cohort (P = 0.033) were independent risk factors for overall survival in patients. The assay to detect potential functions of GATA3 indicated that this biomarker could arrest the cell cycle of G2/M and S phase in T24 cells, and inhibit bladder cancer cells proliferation.ConclusionCollectively, our findings identified that GATA3 served as an important prognosis biomarker for bladder cancer patients. However, the mechanism of GATA3 in bladder cancer deserves further studies.

Purpose: Benign breast disease (BBD) is viewed as a non-obligate precursor stage in the development of breast cancer (BC). Transcriptome profiling using RNA sequencing (RNA-seq) of bulk formalin-fixed paraffin-embedded (FFPE) tissue blocks has been routinely used in BC research. However, RNA-seq of heterogeneous bulk samples represents an averaged expression profile across all cell mixtures. Downstream analyses, such as biomarker discovery, are likely confounded by differences in cell proportions. There is a lack of research in optimizing strategies for cell type deconvolution especially for FFPE samples. We evaluated and optimized strategies for cell type deconvolution using existing single cell RNA-seq (scRNA-seq) and single nucleus RNA-seq (snRNA-seq) breast tissue references, and applied these to a cohort of BBD FFPE samples to assess risk of subsequent BC. Methods: 7 scRNA-seq and 3 snRNA-seq public samples from women’s breast tissue were normalized using SCTransform, then integrated using Harmony to form a complete reference set. Bioinformatics evaluations examined the performance of existing statistical and deep learning-based deconvolution methods. Computational simulations were conducted to evaluate those methods on three scenarios: 1) baseline; 2) incomplete reference set; 3) FFPE artifacts. FFPE artifacts were simulated based on a generalized additive model using 7 in-house paired FFPE-fresh frozen samples. Finally, we applied the best performing method to our BBD cohort of 62 samples. Differential expression analysis adjusting for cell proportions was performed to identify transcriptomic aberrations in BBD cases. Results: snRNA-seq was more sensitive in capturing adipocytes, while scRNA-seq was more sensitive in detecting lymphocytes in breast tissue. The median number of detectable genes per cell was higher for scRNA-seq than snRNA-seq before integration (1264 vs 558). Marker gene-based regression methods (e.g. CIBERSORT) displayed higher variance and lower bias compared to methods directly using scRNA-seq data (e.g. SCDC). Incomplete reference data led to increased bias and little effect on variance. FFPE artifacts had a higher impact on performance compared to incomplete reference data. Overall, Scaden, a deep learning-based method, was the top performing method across all simulation scenarios and was especially robust to FFPE artifacts. 59 differential expressed genes (DEGs) were identified with fold change &amp;gt; 1.5 and p value &amp;lt; 0.01. DEGs involved in BC, e.g. S100A8, WNT4 and HIST1H3H, would be left out if cell proportions were not properly adjusted. Conclusions: We constructed the first complete single cell reference data for women’s breast tissue and benchmarked existing cell type deconvolution methods. Compared to analyses not adjusting for cell proportions, we observed substantial differences in perturbed genes and pathways associated with BC risk for BBD patients. Citation Format: Yuanhang Liu, Chen Wang, Stacey J. Winham, Aditya Bhagwate, Robert A. Vierkant, Julie M. Cunningham, Bryan M. McCauley, William A. Jons, Derek C. Radisky, Amy C. Degnim. Deconvolution of cell type composition in FFPE tissue: Application to benign breast disease. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4291.

Fluorescence in situ hybridization (FISH) has revolutionized molecular cytogenetic analysis since the 1980s, enabling precise localization of DNA sequences in cells and tissues. Despite its relevance, applying FISH to formalin-fixed paraffin-embedded (FFPE) tissue samples encounters significant technical challenges. This review addresses the main issues encountered in this context, such as inadequate fixation, contamination, block and slide age, inadequate pretreatment, and FISH technique. Proposed solutions include optimized pretreatment protocols, monitoring of blockage, careful selection of probes, and thorough analysis of results. Implementing good laboratory practices and quality control strategies are essential to ensure reliable results. Additionally, the use of emerging technologies such as artificial intelligence and digital pathology offers new perspectives for improving the efficiency and accuracy of FISH in FFPE samples. This review highlights the importance of a careful and personalized approach to overcome the technical challenges associated with FISH in FFPE samples, strengthening its role in research and clinical diagnosis. RESEARCH HIGHLIGHTS: Few FISH studies on FFPE: The scarcity of studies specifically addressing FISH applications in FFPE tissues highlights a critical gap in the literature. Troubleshooting FISH in FFPE tissues: Identifying and addressing common challenges in FISH techniques when applied to FFPE samples, such as signal quality and hybridization efficiency. Critical aspects of FISH technique: Discuss the main technical considerations crucial for successful FISH in FFPE tissues, including sample preparation, probe selection, and protocol optimization.

We here characterize the usability of archival formalin-fixed paraffin-embedded (FFPE) brain tissue as a resource for genetic and DNA methylation analyses with potential relevance for brain-manifested diseases. We analyzed FFPE samples from The Brain Collection, Aarhus University Hospital Risskov, Denmark (AUBC), constituting 9479 formalin-fixated brains making it one of the largest collections worldwide. DNA extracted from brain FFPE tissue blocks was interrogated for quality and usability in genetic and DNA methylation analyses by different molecular techniques. Overall, we found that DNA quality was inversely correlated with storage time and DNA quality was insufficient for Illumina methylation arrays; data from methylated DNA immunoprecipitation, clonal bisulfite sequencing, and pyrosequencing of BDNF and ST6GALNAC1 suggested that the original methylation pattern is indeed preserved. Proof-of-principle experiments predicting sex based on the methylation status of the X-inactivated SLC9A7 gene, or genotype differences of the Y and X chromosomes, showed consistency between predicted and actual sex for a subset of FFPE samples. In conclusion, even though DNA from FFPE samples is of low quality and technically challenging, it is likely that a subset of samples can provide reliable data given that the methodology used is designed for small DNA fragments. We propose that simple PCR-based quality control experiments at the genetic and DNA methylation level, carried out at the beginning of any given project, can be used to enrich for the best-performing FFPE samples. The apparent preservation of genetic and DNA methylation patterns in archival FFPE samples may bring along new perspectives for the identification of genetic and epigenetic changes associated with brain-manifested diseases.

Archived formalin-fixed paraffin-embedded (FFPE) specimens represent excellent resources for biomarker discovery, but it has been a major challenge to study gene expression in these samples due to mRNA degradation and modification during fixation and processing. We have developed methods for small RNA and whole transcriptome analysis of FFPE samples on the Ion Torrent PGM™ System using Ion total RNA-Seq Kit v2 and RiboMinus Eukaryote System v2. Paired FFPE and fresh-frozen RNA samples from lung adenocarcinoma tissue were used in this study. Small RNA libraries were prepared using the Ion Total RNA-Seq kit v2 with modified protocol, followed by sequencing on PGM™ system. Results show that small RNA extracted from FFPE sample was successfully converted to small RNA library. Although percentage of reads mapped to miRBase was slightly lower when compared to fresh-frozen sample, the overall miRBase coverage and detection sensitivity were comparable. For whole transcriptome analysis, RiboMinus Eukaryote System v2 kit was used to deplete rRNA from FFPE samples, followed by library construction using the Ion Total RNA-Seq kit v2 with a modified protocol. Significant reduction in rRNA reads was observed after sequencing. High RefSeq correlations were observed between fresh-frozen and FFPE samples. In conclusion, a full spectrum of gene expression data, from both small RNA and whole transcriptome, were generated from FFPE samples using Ion Total RNA-Seq kit v2 with modified protocols. High correlations were observed between paired fresh-frozen and FFPE samples, demonstrating the reliability of the modified workflow for gene expression profiling on FFPE samples. This study provides feasibility for systematic gene expression analysis on FFPE samples from cancer and other diseases. Citation Format: Jian Gu. Expression profiling of paired formalin-fixed, paraffin-embedded (FFPE) and fresh-frozen tissue samples on Ion Torrent PGMTM. [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 4127. doi:10.1158/1538-7445.AM2013-4127

Detection of MERS-CoV antigen on formalin-fixed paraffin-embedded nasal tissue of alpacas by immunohistochemistry using human monoclonal antibodies directed against different epitopes of the spike protein

Targeted Next-generation Sequencing of Advanced Prostate Cancer Identifies Potential Therapeutic Targets and Disease Heterogeneity

11018 Background: While several recently discovered gene fusions already play an important role in personalized cancer treatment, many cancer gene fusions remain to be discovered. Next generation sequencing has enabled identification of many rare gene fusion events in fresh or frozen solid tumors. There is a need to detect gene fusions in transcriptomes of formalin-fixed paraffin-embedded (FFPE) tumor tissue, for which there is long-term clinical outcome data. We therefore sought to develop bioinformatics methods to detect fusion transcripts in FFPE tissue and to characterize their association with clinical outcomes. Methods: RNA sequencing libraries were created and sequenced from tumor biopsy tissues (Plos One 2012 7(7): e40092) of two ER+ breast cancer cohorts consisting of 136 and 77 patients, for which clinical outcomes were available. The fusion junctions were nominated by the RNA-seq aligner GSNAP and further filtered to consider discontinuous expression patterns at exon/intron levels. Results: A total of 108 candidate fusion transcripts were detected and RT-PCR assays confirmed 89% of the top ranking fusion transcript candidates. The majority (82%) of identified fusion gene partners are listed in the COSMIC database of known cancer sequence variations. Of note, several patients expressed multiple fusion transcripts that are significantly associated with tumor progression (P&lt;0.001), including genes associated with cell proliferation and cellular metabolism. Furthermore, these patients also harbored inter-chromosomal gene fusions. It is noteworthy that several gene fusions were present in multiple patients. In one of these recurrent fusions the estrogen receptor gene acts as the fusion pair donor. Conclusions: Novel bioinformatics approaches developed here demonstrate the ability to detect fusion transcripts as biomarkers from archival FFPE tissues that associate with breast cancer progression. Some gene fusions were common in multiple patients and deserved further study.

Discussion: Breast cancer is the most common malignancy diagnosed amongst women, with more the two million new cases identified globally each year. Thus, considerable resources have been devoted to a better understanding of the disease and how to optimize outcomes for patients. Genetics and genomics have become part of routine care with the latter used to inform treatment planning for patients with ER+ breast cancer (ER+ BC). A multitude of assays may be used to determine the need for adjuvant chemotherapy but none of the current tests on the market are guideline-recommended for making decisions related to neoadjuvant chemotherapy, surgery, or radiation. The 24-gene StemPrintER assay was developed to measure the “stemness” of tumors, or how much a tumor behaves like stem cells, which could have important and novel implications for breast cancer treatment planning. The assay has been validated for predicting prognosis using formalin-fixed paraffin-embedded (FFPE) tissue blocks from several clinical cohorts, including TransATAC. The goal of current and future research will be to determine whether the assay can determine the ideal surgical intervention for ER+BC patients. Early in silico work demonstrated a trend toward this predictive capacity for the assay and suggests the assay may be able to identify the benefit of mastectomy versus quadrantectomy. Here, we report on the ability to set up and run the assay in our lab using synthetic oligonucleotides and archival tissue blocks. Methods: Synthetic oligonucleotides and archival FFPE breast cancer tissue were used to set up and analytically validate the assay’s performance in two phases. The initial phase was intended to confirm the individual assay design performance by assessing linearity and precision and the ability to amplify RNA from FFPE, which confirmed compatibility with standard extraction methods. The second phase was intended to determine whether these methods could be implemented to reliably extract and amplify RNA from FFPE &amp;gt;10 years old (range: 10-14 years) in order to generate a StemPrintER score. The assay was run according to standard operating procedures for StemPrintER. Analyses were conducted Python 3.9.12. Results: Two assay runs with duplicate samples for each run using a 7-point dilution series demonstrated linearity (coefficient of correlation, r2) results ranging from 0.978 to 0.999 for each of the 24 genes in the assay. Amplification efficiency was between 100-101% for each gene. Using 14 FFPE samples from patients with triple-negative breast cancer, we demonstrated a consistent extraction yield of RNA from tumor blocks which produced amplification of each of the targets. Analysis of intra- and inter-run precision resulted in coefficients of variation (CV) ranging from 0.2-1.07% and inter-run CV’s ranging from 0.66%-5.56%. Utilizing FFPE &amp;gt;10 years old from ER+BC patients demonstrated that the lab could extract RNA from 100% of samples and amplify the material to obtain binary StemPrintER results. Conclusion: These data demonstrate that StemPrintER can be run reliably on FFPE tissue up to 14 years old. In addition, our laboratory has demonstrated that assay results are highly linear and reproducible. Additional studies are planned to build on preliminary surgical prediction data and determine whether the assay can meet the unmet need of identifying the ideal surgical intervention in patients with early-stage ER+/HER2- breast cancer. Citation Format: Catie Cronister, Brock Schweitzer, Hannah Gilmore, Tyler Nielsen. Analytical Validation of the StemPrintER Assay in Patients with Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-14-03.

Microsatellite instability (MSI), detected via immunohistochemistry and/or polymerase chain reaction (PCR), is a hallmark for Lynch syndrome and a prognostic marker in colorectal cancer. While MSI status is assessed using immunohistochemistry on archival formalin-fixed paraffin-embedded (FFPE) tissue, interpretation can be challenging due to preanalytical variability, antigen decay, and observer subjectivity. PCR-based methods, like the Idylla system, offer a rapid automated alternative with minimal hands-on time and no requirement for specialized molecular facilities. We evaluated Idylla's performance on archival (≥ 10years old) FFPE colorectal cancer resections by comparing BRAF and MSI analysis results with immunohistochemistry for DNA mismatch repair (MMR) proteins and previously performed PCR MSI (Pentaplex) and BRAF genotyping assays. MSI concordance was 94.3% (50/53) between Idylla and immunohistochemistry, and 98.1% (52/53) between Idylla and PCR. Two discordant samples were classified as MSI-high by Idylla and PCR, whereas immunohistochemistry showed normal MMR expression. Conversely, the third discordant sample was classified as microsatellite stable by Idylla and PCR, while immunohistochemistry indicated deficient MMR expression. For BRAF genotyping, concordance between Idylla and PCR was 92.7% (38/41). In two discordant samples, BRAF variants identified by PCR were not included in the Idylla panel, while the third discordant sample showed a pathogenic BRAF variant by Idylla not confirmed by PCR. This is the largest study evaluating Idylla on archival FFPE material. High concordance with traditional methods suggests that Idylla can be used as an alternative approach for Lynch syndrome screening, improving accessibility and reliability of MSI and BRAF testing in challenging archival specimens.

Formalin fixed, paraffin embedded (FFPE) tissue is the most common specimen available for application of diagnostic assays on tissue after microscopic examination. However this approach is not molecular biology friendly, with significant damage to both nucleic acids and proteins by degradation and cross-linking. Extraction of sufficient, quality RNA from FFPE tissue is a barrier to the development of new diagnostic assays. We have optimized a reliable RNA extraction method based on deparaffinization at high temperature coupled with 3-day lysis at 65°C. The average total RNA yield is 4.5 to 5.5 pg per 1 μm3 of archival FFPE tissue, and 260/280 ratios are between 1.80 and 1.95. With a new optimized RNA isolation protocol, we are investigated the fundamental factors which influence on RNA integrity within FFPE tissue. Using mouse kidneys as a standardized tissue, we profiled the pattern of RNA degradation based on fixation time, tissue processing time and fixative buffer. Quality was measured by bioanalyzer tracings, RT-PCR and branched DNA assays of specific genes. Fixation time and tissue processing time have significant impact on RNA quality. Our data suggested that the middle region of gene could be a promising target for RNA analysis. Overall, these date of this study provide fundamental knowledge in studies of gene expression analysis using archival FFPE tissues.