Formalin-fixed Paraffin-embedded Research Articles

Towards routine proteome profiling of FFPE tissue: insights from a 1,220-case pan-cancer study

AbstractProteome profiling of formalin-fixed paraffin-embedded (FFPE) specimens has gained traction for the analysis of cancer tissue for the discovery of molecular biomarkers. However, reports so far focused on single cancer entities, comprised relatively few cases and did not assess the long-term performance of experimental workflows. In this study, we analyze 1220 tumors from six cancer entities processed over the course of three years. Key findings include the need for a new normalization method ensuring equal and reproducible sample loading for LC-MS/MS analysis across cohorts, showing that tumors can, on average, be profiled to a depth of >4000 proteins and discovering that current software fails to process such large ion mobility-based online fractionated datasets. We report the first comprehensive pan-cancer proteome expression resource for FFPE material comprising 11,000 proteins which is of immediate utility to the scientific community, and can be explored via a web resource. It enables a range of analyses including quantitative comparisons of proteins between patients and cohorts, the discovery of protein fingerprints representing the tissue of origin or proteins enriched in certain cancer entities.

Abstract B004: Identification of distinct subpopulations of cancer associated fibroblasts in oral squamous cell carcinoma by imaging mass cytometry

Abstract Background: Although cancer associated fibroblast (CAF) heterogeneity is recognized in oral squamous cell carcinoma (OSCC), the phenotype and role of CAF subpopulations in OSCC is still unknown. Objectives: This study aimed to dissect CAF heterogeneity and spatial location by using imaging mass cytometry on formalin fixed paraffin embedded (FFPE) tissues from primary OSCC. Methods: Imaging mass cytometry (Hyperion technology) was used to identify 24 markers (E-cadherin, EGFR, Ki-67, α-SMA, CD140β, FAP, FSP-1/S100A4, CD90/Thy-1, integrin α-11, collagen-1, tenascin-C, caveolin-1, CD4, CD8a, CD16, CD20, CD68, CD163, FoxP3, granzyme B, CD31, podoplanin, CD146, and YAP-1) in HPV-negative OSCC lesions (n=10). Tissue images were segmented employing the Steinbock framework. Unsupervised clustering of single-cell data was carried out using a bioinformatics pipeline developed in R language. Results: Unsupervised clustering identified several major cell types, with E-cadherin+ cells being the most abundant (30%) and CD146+ being the least abundant cell type (0.62%). Within the immune compartment CD4+ cells were most abundant (11.72%) followed by CD8+ cells (10.6%) and CD68+ cells (10.25%). Cells negative for other major lineage markers and positive for stromal markers were considered as CAFs and they clustered in 6 clusters defined as CAF1 to CAF6. CAF1-3 were high in FAP and CD140β while CAF 4-6 were low expressing FAP and CD140β. CAF1 and 6 expressed high αSMA, while CAF 3 and 5 expressed high collagen-1. CAF6 had high expression of integrin α-11. CAF1 and 3 subtypes were found closer to immune cells whereas CAF2 and 6 were closely located to cancer cells. Conclusions: We identified six distinct subpopulations of CAFs in OSCC by using imaging mass cytometry. Their clinical implications can be further revealed by using this method on larger patient cohorts with FFPE tissues available in diagnostic biobanks. Citation Format: Stian Tornaas, Siren Fromreide, Dimitrios Kleftogiannis, Hans Jørgen Aarstad, Olav K. Vintermyr, Lars Akslen, Harsh Dongre, Daniela Elena Costea. Identification of distinct subpopulations of cancer associated fibroblasts in oral squamous cell carcinoma by imaging mass cytometry [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B004.

Abstract C040: Spatial transcriptomics unveils disparities in tumor microenvironment dynamics between breast cancer responders and non-responders

Abstract Spatial transcriptomics is revolutionizing our understanding of cellular dynamics and interactions in the tumor microenvironment (TME). By mapping distinct cellular populations and their interactions, we can gain valuable insights into tumor behavior. To investigate these dynamics in breast cancer, we conducted Xenium In-situ spatial transcriptomics on twenty formalin-fixed paraffin-embedded (FFPE) samples taken from eight patients undergoing neoadjuvant chemotherapy. These samples have been taken pre-treatment, mid-treatment and post-treatment from four cases with pathological complete response (pCR), and four cases with residual disease (RD) at time of surgery. Our analyses have found distinct cellular composition changes between pCR and RD cases. Patients with RD demonstrated an increase in endothelial, perivascular-like (PVL) and epithelial cells from pre- to post-treatment. This was accompanied by a decrease in myeloid and malignant epithelial cells at mid-treatment. In contrast, patients with pCR demonstrated increases in cancer-associated fibroblasts (CAFs) and myeloid cells, with reductions in plasmablasts and cancer epithelial cells at mid-treatment. This suggests that an increase in CAF and myeloid cells observed between pre-treatment and mid-treatment samples may be predictive of response. We performed ligand-receptor (LR) analyses, which demonstrated diverse myeloid interactions in RD cases and diverse CAF interactions in pCR cases in pre-treatment samples. Mid-treatment samples exhibited a decrease in interactions for CAFs, myeloid and T cells in pCR and RD cases. The most frequently identified CAF LR interactions, as senders, were between TGFB1/TGFB3 and TGFBR1/TGFBR2, while the most frequently identified myeloid LR interactions were between PDCD1LG2 - PDCD1 (encoding PDL2 & PD1), CCL8 - ACKR1 (encoding Atypical Chemokine Receptor 1) and CCL2 - ACKR1. Our findings indicate that the dynamic changes in cellular composition and interactions within the TME differs between responders and non-responders. To further explore these differences, we plan to perform spatially constrained analyses to identify unique cellular niches that may serve as potential biomarkers for informing novel therapeutic strategies. Citation Format: Jeremy Mo, Hanyun Zhang, Kate Harvey, Alexander Swarbrick. Spatial transcriptomics unveils disparities in tumor microenvironment dynamics between breast cancer responders and non-responders [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C040.

Abstract A022: Patho-DBiT: Spatially exploring RNA biology in archival formalin-fixed paraffin- embedded tissues

Abstract Despite recent breakthroughs in spatial biology, either imaging-based or sequencing-based spatial transcriptomics is largely equivalent to spatial messenger RNA (mRNA) expression quantification. An RNA molecule experiences a complex life cycle involving transcription, splicing, maturation, translation, and degradation . It is highly desirable to profile all these RNA species spanning their life cycle to explore the biology of RNA at genome scale and cellular level. Furthermore, formalin-fixed paraffin-embedded (FFPE) tissues are essential in clinical practice, being the backbone of human disease histopathological diagnoses . Pathology departments have accrued vast collections of FFPE blocks over time, creating a rich, yet underutilized compendium of materials that, accompanied by clinical data, stands as a treasure trove for human biology and translational research . In this evolving landscape, we present “Pathology-compatible Deterministic Barcoding in Tissue” (Patho-DBiT) not only enabling spatial full-coverage base-by-base whole transcriptome sequencing but also crafted to address the challenges of clinically archived FFPE tissues. Patho-DBiT integrates in situ polyadenylation, microfluidic in tissue barcoding, and computational innovations to decode rich RNA biology inherent in FFPE samples. The platform capitalizes on RNA fragmentation naturally occurring in FFPE specimens and appends poly(A) tails to a broad spectrum of RNA species, thereby overcoming traditional barriers associated with FFPE samples and even outperforming the assays conducted with frozen tissues. Patho-DBiT permits spatial co-profiling of gene expression and alternative splicing, unveiling region-specific isoforms in the mouse brain. High-sensitivity transcriptomics is constructed from 5-year archived T-cell lymphoma tissues, with cross-validation conducted using super-resolution spatial phenotyping technology (CODEX). Furthermore, genome-scale single nucleotide RNA variants (SNVs) are captured to distinguish malignant subclones from non-malignant cells in human B-cell lymphomas, dissecting spatial clonal architectures based on both SNVs and copy number variation (CNV) profiles. Patho-DBiT also enables spatially resolved co-profiling of large and small RNAs, facilitating the analysis of a microRNA-mRNA regulatory network and tRNA utilization within clinical biopsies and elucidating their roles in tumorigenesis. With superior intronic read capture efficiency, Patho-DBiT spatially mapped RNA splicing dynamics associated with the developmental trajectory of tumor B cells. High resolution Patho-DBiT with a 10-μm spot size reveals the heterogeneities of human lymphomas within a spatial neighborhood and traces the spatiotemporal molecular kinetics driving tumorprogression at the cellular level. Patho-DBiT represents a first-of-its-kind technology, enabling the spatial exploration of rich RNA biology in FFPE tissues to aid in clinical pathology research. Citation Format: Zhiliang Bai, Dingyao Zhang, Yan Gao, Bo Tao, Mingyao Li, Yi Xing, Jun Lu, Mina Xu, Rong Fan. Patho-DBiT: Spatially exploring RNA biology in archival formalin-fixed paraffin- embedded tissues [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr A022.

Abstract A013: Quality control of the biobanked matched tissue: Blood samples for the development of diverse liquid based molecular assays

Abstract The availability of high-quality matched biological samples (tumor-blood) is the major limiting factor for research and development of novel, liquid biopsy-based assays in oncology. Frequently, ongoing specifically timed collections of blood samples are required. De-identified tissue blocks (formalin-fixed, paraffin embedded (FFPE) or flash frozen) matched with patient's blood samples collected in fixative-containing (Streck) of EDTA containing tubes, were collected at worldwide geographic locations and transferred to biobanking facility (Reference Medicine, Phoenix, AZ). Additional blood samples were collected at various times regarding the cancer surgery. Plasma and buffy coat samples were locally prepared and shipped to the biobank. A subset of blood samples without matched tissues from healthy donors were also collected. All samples were shipped under strict transport conditions. Quality control performed at the biobanking facility included pathology review and nucleic acids quality assessment. A total of over 3,000 cases were collected and provided to end-users working on various assays based on cfDNA (e.g. monitoring for minimal residual disease or multi-cancer early detection). Immuno-reactivity to various antigens in samples collected in Streck and EDTA tubes (from 50 patients) was assessed by peptide microarray binding assay. Feedback information on the quality of samples was shared in 900 cases. Approximately 4% of cases had failed internal pathology review, due to poor preservation, lack of adequate tissue composition, or low tumor volume and 11% failed internal nucleic acid quality assessment (DNA concetration and integrity). The blood collection tubes had no significant impact on serologic testing using peptide microarary assay. Customer feedback data showed that overall success rate exceeded 85%. Type of blood collection tubes (Streck vs EDTA) had no impact on serologic testing and studies looking at predicted neoantigens based on NGS data can be confirmed using peptide epitope arrays. Blood collected for NGS works without compromise on peptide arrays. Future validation of other collection tubes for blood or other types of fluids is needed to confirm their adequacy for specific assays. Citation Format: Zoran Gatalica, Phillip Stafford, Chris Diehnelt, Inga Rose. Quality control of the biobanked matched tissue: Blood samples for the development of diverse liquid based molecular assays [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr A013.

MicroRNAome profiling of breast cancer unveils hsa-miR-5683 as a tumor suppressor microRNA predicting favorable clinical outcome.

Breast cancer is a heterogeneous disease with diverse molecular subtypes, underscoring a better understanding of its molecular features and underlying regulatory mechanisms. Therefore, identifying novel prognostic biomarkers and therapeutic targets is crucial for advancing the current standard of care for breast cancer patients. Ninety-six formalin-fixed paraffin-embedded (FFPE) breast cancer samples underwent miRNAome profiling using QIAseq microRNA library kit and sequencing on Illumina platform. Mature miRNA quantification was conducted using CLC Genomics Workbench v21.0.5, while Relapse-free survival (RFS) analysis was conducted using RStudio 2023.09.1. Gain-of-function studies were conducted using miRNA mimics, while the effects of miRNA exogenous expression on cancer hallmark were assessed using 2-dimentional (2D) proliferation assay, three-dimensional (3D) organotypic culture, and live-dead staining. TargetScan database and Ingenuity Pathway Analysis (IPA) were used for miRNA target identification. Hierarchical clustering based on miRNA expression revealed distinct patterns in relation to PAM50 classification and identified miRNAs panels associated with luminal, HER2, and basal subtypes. hsa-miR-5683 emerged as a potential prognostic biomarker, showing a favorable correlation with RFS and suppressing tumorigenicity under 2D and 3D conditions in triple-negative breast cancer (TNBC) models. Findings were further extended to the MCF7 hormone receptor positive (HR+) model. Transcriptomic profiling of hsa-miR-5683 overexpressing TNBC cells revealed its potential role in key oncogenic pathways. Integration of downregulated genes and CRISPR-Cas9 perturbational effects identified ACLY, RACGAP1, AK4, MRPL51, CYB5B, MKRN1, TMEM230, NUP54, ANAPC13, PGAM1, and SOD1 as bona fide gene targets for hsa-miR-5683. Our data provides comprehensive miRNA expression atlas in breast cancer subtypes and underscores the prognostic and therapeutic significance of numerous miRNAs, including hsa-miR-5683 in TNBC. The identified gene targets unravel the intricate regulatory network in TNBC progression, suggesting promising avenues for further research and targeted therapeutic interventions.

Imaging Mass Cytometry to Decipher the Maturation of Tertiary Lymphoid Structures.

In the realm of inflammation, including conditions like cancers, infections, and autoimmune diseases, the emergence of tertiary lymphoid structures (TLS) holds significant implications for prognosis and treatment response. Yet, traditional methodologies such as immunohistochemistry and immunofluorescence falter in capturing the nuanced complexities of TLS, necessitating innovative approaches, like imaging mass cytometry (IMC), to unravel their significance. With the capacity to concurrently assess nearly 40 markers within the same tissue section, IMC transcends the constraints of traditional approaches.This chapter delineates the IMC methodology tailored for TLS visualization and subsequent quantification. By leveraging IMC on formalin-fixed, paraffin-embedded (FFPE) sections of human colorectal cancer (CRC) tissues, we aim to establish a standardized protocol that elucidates the intricacies of TLS dynamics and composition.

Advancement of Techniques for Precise Visualization and Quantification of Tertiary Lymphoid Structure-Associated Immune Cells in Tissue Samples.

Tertiary Lymphoid Structures (TLS) are considered as genuine markers of inflammation. Their presence within inflamed tissues or the tumor microenvironment has been associated with the local development of an active immune response. While high densities of TLS are correlated with disease severity in autoimmune diseases or during graft rejection, it has been associated with longer patient survival in many cancer types and more recently with positive responses to anti-PD-1 immunotherapy. Their efficient visualization and quantification within human tissues may represent new tools for helping clinicians in adjusting their therapeutic strategy. In clinical settings, the use of single-marker immunohistochemistry (IHC) protocols prevails in immune cell infiltration in formalin-fixed, paraffin-embedded (FFPE) tissues. In contrast, the development of automated multiplex immunofluorescence markings, i.e., 40-plex, requires very costly investments in equipment and analysis stations. Yet, employing two or more markers can enhance the characterization of immune infiltrates, particularly in the context of TLS. Besides the growing development of multiplex labeling approaches, imaging can also be used to overcome some technical difficulties encountered during the immunolabeling of tissues with several markers.This chapter describes IHC methods to visualize in human tissue (tumoral or not) the presence of TLS. These methods are based on the immunostaining of four TLS-associated immune cell populations, namely, follicular B cells, follicular dendritic Cells (FDCs), mature Dendritic Cells (mDCs), and Follicular Helper T cells (TFH), together with non-TFH T cells. Methodologies for subsequent quantification of TLS density are also proposed, as well as a virtual multiplexing method based on image registration using the open-source software ImageJ (IJ), aiming at co-localizing several immune cell populations from different IHC stainings performed on serial tissue sections.

The prognostic impact of CDKN2A/B hemizygous deletions in IDH-mutant glioma.

Homozygous deletions of CDKN2A/B are known to predict poor prognosis in gliomas, but the impact of hemizygous deletions is less clear. This study aimed to evaluate the prognostic significance of hemizygous CDKN2A/B deletions in IDH-mutant low-grade astrocytomas and oligodendrogliomas. Tissue samples diagnosed as astrocytoma, IDH-mutant and oligodendroglioma, IDH-mutant, 1p/19q co-deleted CNS WHO grade 2 and 3 were collected from the archives of the Institute of Neuropathology in Heidelberg. DNA methylation analysis was performed on formalin-fixed paraffin-embedded (FFPE) samples. Evaluation of the CDKN2A/B locus was performed by visual inspection of copy-number plots derived from methylation-array data for each case. Hemizygous and homozygous losses were assessed in relation to whole chromosomal or larger segmental losses and gains in the chromosomal profile. Survival probabilities were assessed using the Kaplan-Meier method. A total of 334 low-grade glioma cases were identified, including 173 astrocytomas and 161 oligodendrogliomas. Hemizygous deletions in CDKN2A/B (37/173 in astrocytomas, 15/161 in oligodendrogliomas) did not confer significantly worse survival outcomes compared to CDKN2A/B wildtype cases in neither low grade astrocytoma (log-rank p= 0.2556; HR 2.29, 95% CI [0.76; 6.40], p= 0.135) nor oligodendroglioma (log-rank p= 0.2760; HR 0.17; 95% CI [0.01; 5.05]; p= 0.305), regardless of CNS WHO grade, which was further demonstrated on a subgroup of astrocytoma, IDH mutant CNS WHO 4 cases (log-rank p= 0.1680; HR 4.55, 95% CI [0.88; 24.51], p= 0.0689). Hemizygous CDKN2A/B deletions do not significantly worsen OS or PFS in IDH-mutant astrocytomas and oligodendrogliomas, CNS WHO grade 2 and 3.

Automated Quantification of Tertiary Lymphoid Structures in Human Tumor Samples Using Immunofluorescence and AI-Powered Analysis Pipeline.

The tumor microenvironment (TME) is a complex entity comprising not only tumor cells but also immune, stromal, and endothelial cells. Preclinical and clinical studies indicate that the density, localization, function, and organization of immune infiltration can influence survival probability and treatment response in many cancers. Among these cell organizations, the clustering of T and B cells into tertiary lymphoid structures (TLS) has been associated with favorable clinical outcomes. In this protocol, we propose a protocol for 7-plex immunofluorescence staining for identifying six cell types enriched in TLS in formalin-fixed paraffin-embedded (FFPE) human tumor sections. Additionally, we provide a detailed methodology for quantifying these cell subtypes using the Halo-AI analysis software. This approach will enable a more precise and detailed characterization of TLS in the TME, opening new avenues for understanding their role in anticancer treatment response.

PATH-55. RAMAN-BASED MACHINE LEARNING PLATFORM REVEALS UNIQUE METABOLIC DIFFERENCES BETWEEN IDHMUT AND IDHWT GLIOMA

Abstract BACKGROUND Formalin-fixed, paraffin-embedded (FFPE) tissue slides are routinely used in cancer diagnosis, clinical decision-making, and stored in biobanks, but their utilization in Raman spectroscopy-based studies has been limited due to the background coming from embedding media. METHODS Spontaneous Raman spectroscopy was used for molecular fingerprinting of FFPE tissue from 46 patient samples with known methylation subtypes. Spectra were used to construct tumor/non-tumor, IDH1WT/IDH1mut, and methylation-subtype classifiers. Support vector machine and random forest were used to identify the most discriminatory Raman frequencies. Stimulated Raman spectroscopy was used to validate the frequencies identified. Mass spectrometry of glioma cell lines and TCGA were used to validate the biological findings. RESULTS Here we develop APOLLO (rAman-based PathOLogy of maLignant glioma) – a computational workflow that predicts different subtypes of glioma from spontaneous Raman spectra of FFPE tissue slides. Our novel APOLLO platform distinguishes tumors from nontumor tissue and identifies novel Raman peaks corresponding to DNA and proteins that are more intense in the tumor. APOLLO differentiates isocitrate dehydrogenase 1 mutant (IDH1mut) from wildtype (IDH1WT) tumors and identifies cholesterol ester levels to be highly abundant in IDHmut glioma. Moreover, APOLLO achieves high discriminative power between finer, clinically relevant glioma methylation subtypes, distinguishing between the CpG island hypermethylated phenotype (G-CIMP)-high and G-CIMP-low molecular phenotypes within the IDH1mut types. CONCLUSIONS Our results demonstrate the potential of label-free Raman spectroscopy to classify glioma subtypes from FFPE slides and to extract meaningful biological information thus opening the door for future applications on these archived tissues in other cancers.

PATH-22. SINGLE-CELL RNA (SCRNA) SEQUENCING OF PAIRED PRIMARY AND RECURRENT ATYPICAL TERATOID/RHABDOID TUMORS (AT/RT) REVEALED MOLECULAR DIFFERENCES AND THERAPY-RESISTANT PRIMARY TUMOR CELLS

Abstract Atypical teratoid/rhabdoid tumors (AT/RT) are the most common malignant brain tumors during infancy. They split into four molecular types. The major three (AT/RT-SHH, AT/RT-TYR, and AT/RT-MYC) all carry mutations in SMARCB1, the fourth smaller type is characterized by SMARCA4 mutations (AT/RT-SMARCA4). AT/RT are associated with a dismal outcome, and 50% of the patients suffer a progress or recurrence of the tumor. Molecular mechanisms of disease recurrence are currently unclear. Here, we identified molecular characteristics of AT/RT primaries and recurrences, which could help to improve the therapy for relapsed patients. Previously, we investigated tumor tissue from 26 patients revealing signatures of recurrences in comparison to matched primary tumor samples using histology, DNA methylation analysis, and bulk RNA sequencing. To further identify mechanisms regarding tumor progression and recurrence, we performed single-cell RNA (scRNA) sequencing for five of these primary-recurrence pairs so far using formalin-fixed paraffin-embedded (FFPE) tissue. Using Uniform Manifold Approximation and Projection (UMAP) for dimensionality reduction, we observed a distinct separation in the gene expression profiles of primary and recurrent tumor cells. In addition, we aimed to identify primary tumor cells which potentially persisted after therapy and developed to recurrences. Therefore, we identified primary tumor cells showing highest similarity to recurrent tumor cells using CIBERSORT and trajectory analysis. Differentially expressed genes of these specific primary tumor cells were investigated. They are involved in cell migration, -adhesion, -proliferation, and -stability, among others. Overall, molecular characteristics that occur in the course of the disease were identified, which may help to define new therapeutic targets for AT/RT recurrences.

PATH-32. THE PROGNOSTIC IMPACT OF CDKN2A/B HETEROZYGOUS DELETIONS IN IDH-MUTANT GLIOMA

Abstract BACKGROUND Homozygous deletions of CDKN2A/B have been shown to be a prognosticator for an unfavorable prognosis in gliomas, but the role of heterozygous CDKN2A/B deletions remains less well understood. The aim of this study was to assess the prognostic impact of CDKN2A/B heterozygous deletions in IDH-mutant low-grade astrocytoma and oligodendroglioma. METHODS Tissue samples diagnosed as astrocytoma, IDH-mutant and oligodendroglioma, IDH-mutant, 1p/19q co-deleted CNS WHO grade 2 and 3 were collected from the archive of the Institute of Neuropathology in Heidelberg. DNA methylation analysis was performed on formalin-fixed paraffin-embedded (FFPE) samples. Evaluation of the CDKN2A/B locus was performed by visual inspection of copy-number plots derived from methylation-array data for each case. Heterozygous and homozygous losses were assessed in relation to whole chromosomal or larger segmental losses and gains in the chromosomal profile. Survival probabilities were assessed using the Kaplan–Meier method. RESULTS A total of 334 low-grade glioma cases were identified. Those cases included 173 astrocytomas and 161 oligodendrogliomas. Heterozygous deletions in CDKN2A/B (37/173 in astrocytomas, 15/161 in oligodendrogliomas) did not confer worse survival outcomes compared to CDKN2A/B wildtype cases in neither low grade astrocytoma (p= 0.2556) nor oligodendroglioma (p= 0.2760), regardless of CNS WHO grade, which was further validated on a subgroup of astrocytoma, IDH mutant CNS WHO 4 cases (p= 0.1680). CONCLUSION In summary, our study suggests that heterozygous CDKN2A/B deletions do not confer worse survival rates with respect to OS and PFS in astrocytoma, IDH-mutant and oligodendroglioma, IDH-mutant, 1p/19q co-deleted CNS WHO grade 2 and 3.

CNSC-65. ELECTROPHYSIOLOGICAL AND SPATIAL TRANSCRIPTOMIC PROFILING OF GLIOMA-INFILTRATED CORTEX REVEAL LAYER SPECIFIC ALTERATIONS

Abstract Specialized neocortical circuits selectively organize neuronal signals and encode features of cognitive processing via local and long-range connections. Since glioma-infiltrated cortex is excitable and can participate in cognitive processing, the underlying laminar structure and functionality may still be preserved despite infiltration. Moreover, since glioma cells remodel existing neural circuits and microenvironmental factors drive invasion and proliferation, neuron-glioma interactions may demonstrate layer specificity. As glioma-infiltrated cortex remains poorly understood, we sought to characterize these regions using electrophysiological, structural, and genomic approaches. We assessed the power spectra of normal-appearing and glioma-infiltrated cortex using magnetoencephalography and subdural high-density electrode arrays. Immunohistochemistry of formalin-fixed paraffin-embedded (FFPE) samples of infiltrated cortex enabled protein-level neuronal and glioma identification to determine laminar preservation and spatial invasion patterns. Spatial transcriptomics of FFPE tissues and single-nucleus RNA-sequencing were used to identify cell populations, genomic alterations, and cell-cell communication within and across samples at testing and validation sites across the US and Europe. Increased delta range (1-4 Hz) power and decreased power in the beta range (12-20 Hz), activity thought to originate from deep layers, were identified as robust features of infiltrated cortex which were maintained across glioma subtypes (n = 139 patients) and preserved in a validation cohort (n = 8 patients). Immunohistochemistry revealed greater tumor burden within deep laminae regardless of glioma subtype (n = 20 samples). Tissue proteomics and spatial genomics analyses performed using glioma-infiltrated cortical samples (n = 10 samples; 29,011 spots) confirmed routine preservation of laminar organization, greater tumor burden in deep layers, as well as layer specific differences in glioma-related expression programs. Cell-cell communication analyses demonstrated increased interactions in glioma-infiltrated cortex across layers. These findings suggest that laminar structure may be preserved in glioma-infiltrated cortex while remodeling of neural circuits alters spatiotemporal activity in a predictable manner and support a deep to superficial invasion pattern. Thus, investigating glioma infiltration using layer-centric approaches may facilitate novel insights into neuron-glioma interactions.

Demonstration of T-Cell Monotypia Using Anti-TCRbeta1/2 (TRBC1/2) Immunostaining as a Rapid and Cost-Effective Alternative to PCR-Based Clonality Studies for the Diagnosis of T-Cell Lymphoma

Background/Objectives: T-cell lymphomas are often histologically indistinguishable from benign T-cell infiltrates, and diagnosis typically relies on slow, complex, and expensive multiplexed PCR reactions, requiring significant training and experience to interpret them. We aimed to raise highly specific antibodies against the two alternatively used and very similar T-cell receptor beta constant regions, TCRbeta1 and TCRbeta2, encoded by the TRBC1 and TRBC2 gene segments, respectively. We sought to demonstrate the feasibility of detecting TCRbeta1 and TCRbeta2 immunohistochemically in routine clinical (formalin-fixed, paraffin-embedded (FFPE)) tissue sections as a novel diagnostic strategy for T-cell lymphomas. Methods: Recombinant rabbit antibodies were validated using Western blotting and FFPE immunostaining of T-cell leukemia lines. The immunostaining of FFPE tissue containing benign and lymphomatous T-cell populations was undertaken, with corroboration by BaseScopeTM high-sensitivity in situ hybridization and quantitative real-time PCR (Q-PCR). An additional Q-PCR literature review and analysis of publicly available RNAseq data was used to determine the TCRbeta2/TCRbeta1 ratio cut-off to separate benign and malignant T-cell populations. Results: Our TCRbeta1/TCRbeta2 antibody pair gave highly specific FFPE tissue staining. All benign samples analyzed (immunohistochemically, by BaseScopeTM, by Q-PCR, and by RNAseq data analysis) had TCRbeta1/TCRbeta2 or TRBC1/TRBC2 ranges well within the previously published flow cytometric benign range (TCRbeta2/TCRbeta1 = 0.18:1–5.7:1), while samples of T-cell lymphoma did not. One out of thirteen (7.7%) lymphoma samples showed some detectable TCRbeta1/TCRbeta2 protein co-expression, and 4 out of 13 (30.8%) T-cell lymphomas showed a TRBC1/TRBC2 transcript co-expression using BaseScopeTM. Conclusions: Analyzing T-cell monotypia immunohistochemically, analogous to B-cell monotypia (kappa: lambda ratio for B-cell and plasma cell neoplasms), could make the diagnosis of T-cell lymphomas cheaper, quicker, and more accurate. Larger studies are needed to validate our antibodies for clinical use.

Modification of the hi-c technology for molecular genetic analysis of formalin-fixed paraffin-embedded sections of tumor tissues

Molecular genetic analysis of tumor tissues is the most important step towards understanding the mechanisms of cancer development, and it is also necessary for the choice of targeted therapy. Hi-C (high-throughput chromatin conformation capture) technology can be used to detect various types of genomic variants, including balanced chromosomal rearrangements: inversions and translocations. In this work, we propose a modification of the Hi-C method for the analysis of chromatin contacts in formalin-fixed paraffin-embedded (FFPE) sections of tumor tissues. Our results demonstrate that this protocol allow to generate high-quality Hi-C data and detect all types of chromosomal rearrangements. We have analyzed various databases to compile a comprehensive list of translocations that hold clinical importance for targeted therapy selection. The practical value of molecular genetic testing is its ability to influence patient treatment strategies and provide prognostic insights. Detecting specific chromosomal rearrangements can guide the choice of targeted therapies, which is a critical aspect of personalized medicine in oncology.

Infrared Laser Ablation and Capture of Formalin-Fixed Paraffin-Embedded Tissue.

Formalin-fixed paraffin-embedded (FFPE) tissue is a ubiquitous and invaluable resource for biomedical research and clinical applications. However, FFPE tissue proteomics is challenging due to protein cross-linking and chemical modification. Laser ablation sampling allows precise removal of material from tissue sections with high spatial control and reproducibility for offline proteomics by liquid chromatography coupled with tandem mass spectrometry. In this work, we used a pulsed mid-infrared laser for microsampling of rat liver tissue for subsequent identification and quantification of proteins. It was found that more proteins were identified by FFPE tissue laser ablation sampling compared to fresh frozen (FF) tissue laser ablation sampling and that more proteins were identified by laser ablation than by manual dissection of FFPE tissue. In contrast to previous studies, no loss of hydrophilic proteins due to residual cross-linking was observed. The efficient capture of proteins by laser ablation microsampling is attributed to efficient laser breakup of the tissue which facilitates downstream processing of the proteins.

Mycosis Fungoides: Histopathology and T Cell Receptor Gene Rearrangements in Indian Patients

Introduction: Mycosis fungoides (MF) is the commonest cutaneous T cell lymphoma. MF presents in three stages the patch, plaque, and tumor. The distinction of patch-stage MF from inflammatory dermatoses is a diagnostic challenge. Need for the Study: MF shows T cell receptor gamma and beta gene rearrangements (TCRG and TCRB), detectable by polymerase chain reaction (PCR). Data about the clonality of infiltrates in our population and their utility in diagnosis is lacking. Materials and Methods: Skin biopsies from 50 patients with mycosis fungoides from January 2007 to July 2015 were studied for microscopic features. TCR gamma and beta gene rearrangement assays were performed on 14 patients where formalin fixed paraffin embedded (FFPE) was available. DNA was extracted using the phenol-chloroform method. PCR was performed using primers from Invivoscribe Identiclone assay. Clonality was analyzed using Agarose gel electrophoresis. Results: Of the 50 cases, 37 were patch, nine were plaque, and four were tumor stage. All cases showed disproportionate lymphocyte epidermotropism, 38 showed lymphocyte atypia, and 33 showed adnexotropism (11 eccrotropism and 22 folliculotropism). Clonality was assessed in 14 cases. Of these, 3/9 patch stages were monoclonal (1/3 monoclonal for beta, and 2/3 monoclonal for gamma and beta). 3/3 plaque stage MF was monoclonal (1/3 for gamma, 2/3 for both), and 1/2 tumor stage MF was monoclonal for gamma and beta receptors. Conclusion: The patch stage was the most common presentation. TCR gene rearrangements were noted in 50% of MF, with TCR gamma rearrangements being more common. Plaque and tumor stages yielded higher positive rates.

Targeted Therapy in Salivary Gland Cancer: Prevalence of a Selected Panel of Actionable Molecular Alterations in a German Tertiary Referral Center Patient Cohort.

Salivary gland carcinomas (SGC) are a heterogeneous group of malignancies, with 24 subtypes defined by the World Health Organization (WHO). The standard of therapy is surgical resection, with adjuvant radiotherapy in most cases. However, disease recurrence (R) or metastasis (M) is common and no active systemic therapies are currently available for RM-SGC resulting in a 5-year survival rate of only 20%. Overall, 55 SGC patients with seven different histological tumor subtypes were included in this study. formalin-fixed paraffin-embedded (FFPE) tissue samples were used for immunohistochemical (IHC) staining targeting HER2/neu, androgen receptor (AR), PD-L1, EGFR, panTRK, and TROP2. Fluorescence in situ hybridization (FISH) was performed for detecting HER2/neu amplifications and NTRK1/2/3 translocations in selected cases with relevant HER2/neu and panTRK protein expression, respectively. IHC and FISH results were correlated with patients' clinical and histopathological data. The overall prevalence of druggable molecular alterations, defined as an immunoreactive score ≥ 9 in at least one of the analyzed targets, was 54.4% with the highest percentage in oncocytic carcinomas (100%) and lowest percentage in acinic cell carcinomas (10%). EGFR overexpression proved to be the most common alteration (32.7% of cases) followed by overexpression of TROP2 (27.3%), AR (10.9%), HER2/neu (7.3%), PD-L1 (1.8%), and panTRK (1.8%). HER2/neu amplifications were found in 50% and NTRK translocations were found in 100% of all cases with elevated Her2/neu and panTRK protein expression, respectively. Our data indicate that targeted therapy using e.g., trastuzumab deruxtecan, bicalutamide, pembrolizumab, cetuximab, entrectinib or sacituzumab govitecan might be a promising option especially for a relevant subset of patients with RM-SGC not suitable for salvage surgery. However, evidence from clinical studies regarding response rates to these therapies remains sparse, which underlines the need of multicenter clinical trials.

Nanopore Sequencing for T-Cell Receptor Rearrangement Analysis in Cutaneous T-Cell Lymphoma.

Background: Analysis of T-cell receptor (TCR) clonality is a major diagnostic tool for lymphomas, particularly for cutaneous T-cell lymphomas (CTCL) like Mycosis fungoides and Sézary syndrome. However, a fast and cost-effective workflow is needed to enable widespread use of this method. Methods: We established a procedure for TCR rearrangement analysis via Oxford Nanopore Technology (ONT) sequencing. TCR receptor rearrangements (TCR-gamma and TCR-beta chains) were analyzed in samples from 45 patients with various diagnoses: Mycosis fungoides (37/45), Sézary Syndrome (2/45), folliculotropic CTCL (1/45), and non-CTCL diagnoses as polyclonal controls (5/45). Sample types included formalin-fixed paraffin-embedded (FFPE) samples (27/45), fresh frozen samples (9/45), and CD3-isolated cells (9/45). In addition, DNA of a Jurkat cell line was used as a monoclonal control. TCR amplicons were generated employing an optimized version of the protocol from the Euro Clonality consortium. Sequencing was conducted on the ONT GridION and Illumina MiSeq platforms, followed by similar bioinformatic analysis protocols. The tumor clone frequency (TCF), a crucial prognostic factor for CTCL patients, was used for method comparison. Results: The use of an optimized amplicon protocol and adapted bioinformatic tools demonstrated a strong correlation in TCF values between both sequencing methods across all sample types (range R: 0.992-0.996; range r2: 0.984-0.991). Conclusions: In summary, ONT sequencing was able to detect TCR clonality comparable to NGS, indicating its potential as a faster and more cost-effective option for routine diagnostic use.