FFPE Tissue Research Articles

Abstract 1532: Improved reproducibility in multiplex immunofluorescence analysis of the tumor microenvironment using a novel quenching solution

Abstract Formalin-fixed, paraffin-embedded (FFPE) tissues are commonly used in histopathology because the fixed tissues are stable and easy to store. In the context of immunofluorescence detection, however, endogenous autofluorescence of FFPE tissues can significantly reduce or mask immunofluorescent signals. The autofluorescence of FFPE tissues is caused by a variety of factors, including the presence of endogenous fluorophores, tissue fixation, and processing. While there are several methods that can be used to quench autofluorescence in FFPE tissues, chemical quenchers, which absorb or scatter light, are most frequently used for multiplex IF. Examples of chemical quenchers commonly used in manual multiplex staining include Sudan Black B and TrueBlack; however, these are not chemically compatible for use on automated platforms such as the Leica Biosystems BOND RX. Due to the need for increased throughput and decreased hands-on time, automation has risen in popularity versus manual staining, leading to a need for a versatile quenching solution compatible with automation. Here we demonstrate that NovaPlex Quenching Solution (NPQS), a novel proprietary quenching agent, reduces the background caused by autofluorescence and enhances the signal of the Cell IDx UltraPlex multiplex immunofluorescent (mxIF) assay across tissue types. Qualitative studies showed a decrease in autofluorescent signal in FFPE mouse spleen stained with antibodies against B220/Foxp3/CD3e, suggesting the utility of NPQS in mouse models of cancer and immunity. Similarly, nonspecific background was decreased across FFPE human tissue types, including lung adenocarcinoma stained for CD8/Foxp3/CD3e/CD4 and tonsil stained for CD8/Foxp3/PD-1/CD4. Further statistical studies in FFPE human tonsil tissue stained with CD8/Foxp3/PD-1/CD4 showed there was no significant decrease in dye intensity across all four markers and channels, resulting in a significant increase in signal-to-noise ratio for both CD8 at 490nm and PD-1 at 650nm (p<0.05). These experiments using Cell IDx/LBS UltraPlex mxIF technology demonstrate an effective method to improve the signal-to-noise ratios of fluorophores without reducing signal intensity from any of the target proteins in these parallel multiplex immunofluorescent assays. Citation Format: Matt Levin, Jack Heath, April Schrank-Hacker, Shelby Dunn, Minh-Chau Vu, Imane Hamza, David Schwartz. Improved reproducibility in multiplex immunofluorescence analysis of the tumor microenvironment using a novel quenching solution [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1532.

Abstract 1123: Genomic characterization of radiotherapy-associated bladder cancer

Abstract Background: Bladder cancer (BCa) is the 4th most common cancer diagnosed in men, with 82,290 new cases predicted in 2023. As BCa frequently occurs at an advanced patient age, its diagnosis may follow radiotherapy (RT) for the treatment of prostate cancer. Currently, data is limited regarding the influence of RT on the clinical course and genomic landscape of subsequent BCa, mainly due to a paucity of samples. From prior studies, pelvic radiation confers an increased risk of BCa, with resulting tumors that are largely genomically similar to non-RT tumors with the exception of an increase rate of genomic insertions. Our current study looks to expand on these findings by characterizing the genomes of the largest cohort of RT-associated bladder cancers to date. Methods: We identified BCa cases from patients with a prior history of pelvic radiation for prostate cancer, and tumor only targeted sequencing was performed using Foundation Medicine (FMI) on FFPE tissue (n=41). For control cases (CTRL), patients with no prior record of pelvic radiation and who had previously underwent standard of care FMI sequencing were included (n=41). Sequencing data were re-aligned to hg38 and mutation calling was performed on the newly aligned sequences. Results: CTRL and RT cohorts had similar distributions of patients based on race and smoking status. While cT stage was similar between the two cohorts, the CTRL cohort was biased toward higher cN and cM stages with no difference in overall survival (median OS: CTRL = 20m, RT = 23m), though the advanced stage of the CTRL cohort could mask a worse prognosis in the RT cohort. Latency specific analysis revealed short latency tumors (<10 years from RT) had a significantly shorter overall survival than long latency tumors (p<0.01, HR=5.59, CI=1.81-17.3), and a numerically, but not significantly, shorter survival than CTRL patients (p=0.17, HR=1.55, CI=0.82-2.94). Long latency tumor patients had a significantly longer overall survival than CTRL patients (p<0.01, HR = 0.22, CI=0.07-0.63). In line with prior studies, RT samples had increased numbers of insertions (p<0.01). In addition, we also detected an increase in SNVs in the RT samples (p<0.01). Of note, KDM6A alterations were enriched within the RT cohort (CTRL = 10/41, RT = 30/41, p<0.001), with series of splice site mutations exclusive to RT samples (p<0.001). Conclusion: Patients diagnosed with BCa within a short interval following pelvic radiation have a worse prognosis. Genomic analysis showed RT-associated tumors having an increased number of insertions, SNVs, and KDM6A splice site mutations compared to non-RT tumors. Overall, the spectrum of recurrent alterations within the cohorts were consistent with previous studies, with the exception of the KDM6A mutations. To our knowledge, this is the first report of a RT-associated alteration in a specific gene in bladder cancer and additional studies will be needed to validate and understand the consequences of this finding. Citation Format: N. Ari Wijetunga, Kathryn H. Gessner, Krishna Kanchi, Sara E. Wobker, David Corcoran, Matthew D. Galsky, Matthew I. Milowsky, William Y. Kim, Tracy L. Rose, Jeffrey S. Damrauer. Genomic characterization of radiotherapy-associated bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1123.

Abstract 2940: A comparative analysis of library preparation technologies for RNA sequencing from FFPE samples

Abstract Formalin-fixed, paraffin-embedded (FFPE) samples are an invaluable resource in the oncology space, providing access to a vast library of archived diseased tissue samples paired with relevant donor information. Despite the broad utility of these samples, RNA extracted from FFPE tissue is typically difficult to process due to the presence of residual crosslinks and its degraded nature. Further, these samples often vary widely in performance, as the fixation process, block age, block storage, and extraction method can impart large impacts on resulting template quality. As a result, robust and reproducible RNA sequencing from FFPE-derived RNA remains a challenge with unpredictable and high failure rates. We evaluated four commercially available WTA solutions to determine which performed best with this challenging sample type with respect to library complexity, inter-input and intra-sample concordance, and overall reproducibility. Matched fresh frozen and FFPE liver samples were used such that the fresh frozen data set serves as a comparative truth set for the FFPE data. RNA-Seq libraries were prepared from each sample at both 10 ng and 100 ng inputs. The higher input serves as a control while the lower input reflects achievable inputs from very challenging FFPE samples. For 10 ng FFPE-derived RNA, the Watchmaker RNA Library Prep Kit with Polaris Depletion detects more unique genes than other chemistries and has a much higher percentage of genes that overlap with the fresh frozen control libraries. Additionally, differential expression analysis between 10 ng and 100 ng FFPE libraries demonstrates that the Watchmaker solution better preserves the gene expression profile at low inputs, as fewer differentially expressed genes are identified. The Watchmaker chemistry includes a number of features aimed at improving library complexity, including a novel FFPE decrosslinking step, a reverse transcriptase specifically engineered to improve conversion of RNA to cDNA, and fewer bead purification steps to prevent sample loss. The concordance between FF and FFPE samples at variable input masses observed when using the Watchmaker solution promotes a higher degree of confidence when making decisions based on lower quantity and quality samples and enables researchers to access more meaningful biological information. Citation Format: Jennifer Pavlica, Travis Sanders, David Gelagay, Kailee Reed, Thomas Harrison, Giulia Corbet, Josh Haimes, Ariele Hanek, Kristina Giorda, Brian Kudlow. A comparative analysis of library preparation technologies for RNA sequencing from FFPE samples [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2940.

Abstract 6732: Immunomodulatory and anti-tumor effect of a CCR2-targeted STING agonist iADC in human lung cancer

Abstract Introduction: Antibody drug conjugates (ADCs) targeting cancer-cell antigens can improve therapeutic index and show prominent clinical impact. Limited studies have used ADCs to target antigens present in non-malignant cells in the tumor microenvironment or to deliver immunomodulatory agents. We developed an immune-cell directed antibody drug conjugate (iADC) TAK-500 that selectively activates STING in C-C chemokine receptor type 2 (CCR2) expressing cells to achieve enhanced efficacy over non-targeted STING agonists. Here, we spatially mapped CCR2 protein in human NSCLC and studied the immunomodulatory role and anti-tumor effect of the novel iADC TAK-500 on human lung cancer tumor explants ex vivo. Methods: Using multiplexed quantitative immunofluorescence (mQIF) panels we measured the levels of CCR2 protein, myeloid cell populations and tumor infiltrating lymphocyte (TIL) subsets in 411 primary NSCLC carcinomas from treatment-naïve patients in 2 independent cohorts and determined their clinical significance. In addition, we longitudinally studied CCR2 levels, myeloid cells (DAPI/CCR2/CD68/CD11b), TILs (DAPI/CK/CD4/CD8/CD20), T-cell functional markers (DAPI/CK/CD3/Ki-67/GZMB [Granzyme B]) and cancer-cell death/proliferation markers (DAPI/CK/TFR1/Ki-67/CC3 [Cleaved Caspase 3]) in 314 primary cultured tissue fragments from paired tumor and non-tumor specimens resected from 11 lung cancer patients at Yale New Haven Hospital between 2021-2023 (8 adenocarcinomas, 2 small cell carcinomas, and 1 squamous cell carcinoma). Each biopsy was divided into 4-mm2 fragments, cultured in extracellular matrix for 5 days with or without TAK-500 treatment. Samples were processed into FFPE tissue and stained with mQIF panels using a tissue microarray format. Results: CCR2 protein was detected in 386 of 411 (94%) NSCLCs from 2 independent cohorts predominantly localized in CD11b+ intratumor myeloid cells and CD68+ tumor-associated macrophages (TAMs). Elevated CCR2 was associated with adenocarcinoma histology, increased PD-L1, activating KRAS mutations and longer survival. Treatment with TAK-500 for 5 days reduced CCR2 levels in myeloid cells and CD68+ TAMs, without significant changes in TIL or T-cell GZMB/Ki-67 levels. TAK-500 also significantly reduced tumor proliferation (Ki-67 expression) and increased tumor cell apoptosis (CC3 levels) after 5 days of treatment. Notably, these TAK-500-induced changes were observed only in tumor specimens with high baseline CCR2 levels above the median in retrospective NSCLC cohorts. No significant effect was observed in the paired non-tumor fragments. Conclusion: Our results reveal prominent myeloid CCR2 expression in a subset of human NSCLCs with distinct clinicopathologic/molecular characteristics. Using a novel lung cancer explant ex vivo system, we demonstrate a CCR2-dependent immunomodulatory and anti-tumor effect of TAK-500 iADC. Citation Format: Angelo Porciuncula, Vicky A. Appleman, Alex Parent, Jeff Raizer, Richard C. Gregory, Neil Lineberry, Adnan O. Abu-Yousif, Kurt A. Schalper. Immunomodulatory and anti-tumor effect of a CCR2-targeted STING agonist iADC in human lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6732.

Abstract 7422: Enabling biomarkers of chromosomal instability for tumor only targeted gene panel sequencing

Abstract Capture-based targeted sequencing is routinely used for small variant detection in cancer clinical care. Alongside targeted DNA, off-target DNA is also sequenced. These off-target reads are distributed across the genome, allowing for a whole genome copy number profile to be derived without the need for a SNP backbone. Here we present CopyRight, a method that generates robust genome-wide copy number profiles, which can be used for downstream chromosomal instability (CIN) quantification, overcoming various sources of technical noise with a novel approach that only requires a single tumor sample. We analyzed a variety of capture-based NGS protocols using our novel computational method, including the TruSight Oncology 500 (TSO500) panel, and compared them to the current gold standard for genome-wide copy number profiling from FFPE tissues: shallow whole genome sequencing (sWGS). Comparable results were obtained from targeted sequencing depending on sample purity, preservation method, and read depth. Additionally, benchmarks of CopyRight against other computational algorithms show an improvement in performance without the need for a matched normal tissue, the usual drawback for other methods in the cancer field. CIN signatures are a new set of emerging biomarkers that reflect the diversity of defective pathways that have operated in a tumor, which require robust genome-wide copy number profiles. These CIN signatures can be used to predict response to cytotoxic agents and targeted therapies and could ultimately help guide therapy selection in patients. As most clinical sequencing workflows rely on targeted sequencing, CopyRight can be included in current clinical assays, enabling CIN biomarker quantification with no extra technical or experimental requirements. Citation Format: David Gómez-Sánchez, Joe Sneath Thompson, Barbara Hernando, Diego García-López, Hector de Galard, Abhipsa Roy, Amy Cullen, Laura Madrid, José Teles, Ania Piskorz, Jason Yip, Alice Cádiz, Maria Escobar-Rey, Roberto Moreno-Vellisca, Nuria Carrizo, Eva Álvarez, Miguel Quintela-Fandino, Mariano Barbacid, Javier Ramos-Paradas, Juan Manuel Coya, Irene Ferrer, Jon Zugazagoitia, Luis Paz-Ares, Geoff Macintyre. Enabling biomarkers of chromosomal instability for tumor only targeted gene panel sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7422.

Abstract 2309: 3D spatial quantification of lymphocyte infiltration and collagen features in the tumor microenvironment using a novel assay: 3D I/O Pro™

Abstract Background: The composition of the tumor microenvironment (TME) is a major determinant of response to therapy in many solid tumors. To-date, characterization of the TME has been based on limited analysis of thin tissue sections. Here we demonstrate the utility of an end-to-end 3D spatial biology workflow, the 3D I/O Pro™, based on whole tissue imaging, to identify and quantify tumor cells, lymphocytes, and collagen features in human FFPE tissue samples. Methods: Five human colorectal cancer FFPE blocks were deparaffinized, stained with nuclear (TO-PRO-3) and general protein (eosin) dyes, and cleared using a modified iDISCO protocol. Entire samples were imaged at 2 µm/pixel resolution with a hybrid open-top light-sheet microscope, the 3Di™. Regions of interest (ROIs) with a volume of 0.5 mm3 were re-imaged at 0.33 µm/pixel. Cell nuclei and collagen were segmented and 3D spatial relationships between tumor cells, lymphocytes, and collagen fibers were quantified. Analyses were performed within select ROIs using 3Dai™ tools including U-Net, CytoMAP, CT-FIRE, CurveAlign, and custom Python scripts. Results: The ratio of stromal to tumor parenchymal lymphocytes (lymphocyte infiltration ratio) varied from 1.4 up to 9.1 in 3D volumes and 1 to 25 in 2D virtual sections taken throughout all 5 CRC samples. The ratio of the collagen fibers within 100 µm of the tumor border-oriented perpendicular to the tumor-stromal boundary compared to those oriented parallel to the tumor-stromal boundary was 0.37 in a proof-of-concept evaluation of a 2D virtual section with a lymphocyte infiltration ratio of 12. Qualitatively, areas with perpendicular collagen had more lymphocyte infiltration into the tumor parenchyma than areas with parallel collagen orientation. Conclusions: We demonstrated that the 3D I/O Pro™ pipeline can quantify lymphocyte density in tumor parenchyma and stroma and analyze collagen features, including orientation, within 3D ROIs in the TME. This workflow allows us to characterize tumors based on many complex spatial relationships and could have broad applicability in research and development of novel cancer therapies that target tumor fibrosis or other features of the TME. In the future, we plan to correlate features from the 3D TME with response to immunotherapy and use these features to refine histologic definitions of immune spatial phenotypes. Citation Format: Caleb Stoltzfus, Jasmine Wilson, Nathan Grant, Alexandra Alvarsson, Anna DeWitt, David Simmons, Brandy Olin, Bonnie Phillips, Laura A. Dillon, G. Travis Clifton, Nicholas P. Reder. 3D spatial quantification of lymphocyte infiltration and collagen features in the tumor microenvironment using a novel assay: 3D I/O Pro™ [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2309.

Abstract 3767: A novel method to minimize HIER-induced alterations on H&E staining in an integrated mIF-H&E workflow

Abstract Background: Hematoxylin and eosin staining (H&E) is widely used as an anatomical assay for clinical diagnosis. Researchers and clinicians also rely on molecular in situ techniques, such as multiplexed immunofluorescence (mIF), to gain deeper insights on cellular phenotypes and tissue microenvironment. As a result, there has been significant interest in combining anatomical stains with molecular imaging techniques, most commonly by using a terminal H&E stain after mIF staining. This allows a combination of the two assays but has been observed to show alterations in the H&E staining pattern. In this work we identify heat-induced epitope retrieval (HIER) as the root cause of alterations of the terminal H&E stain after mIF. We further demonstrate a new workflow combining an initial H&E stain with subsequent InSituPlex assay, to avoid these alterations and thus enable co-registration of highly sensitive multiplexed immunofluorescence with an unaltered H&E stain. Methods: FFPE tissue slides were stained using a standard HIER protocol or a full mIF assay, followed by a standard H&E stain. Slides were imaged using a Zeiss Axioscan.Z1 scanner. Additional H&E-stained slides were prepared, and the H&E stain removed using a destaining protocol before carrying out InSituPlex® mIF staining for multiple markers. Fluorescence and brightfield images of the same slide were overlaid using UltiStacker® to assess qualitative differences between pre- and post-mIF H&E, and UltiAnalyzer.AI® was used to quantify cell densities and signal intensities between mIF image pre- and post-H&E. Results: Alterations in H&E staining were observed between slides directly stained with H&E and slides stained with a terminal H&E after HIER alone or a full mIF assay. Calculated cell counts and tissue area were consistent throughout, but some tissue microstructures could be difficult to resolve after either HIER or full mIF. Our destaining protocol was successful in removing hematoxylin and eosin from directly-stained H&E slides and allowing subsequent mIF staining. For most biomarkers, qualitative and quantitative differences in InSituPlex mIF staining were minimal. Brightfield and fluorescent images were co-registered with sub-micron accuracy using UltiStacker, enabling molecularly defined cellular phenotyping within a traditional H&E image. Conclusions: While the mIF to H&E workflow is widely used and is capable of allowing combined anatomical and cellular phenotyping, alterations in the H&E stain exist due to the use of HIER in most mIF protocols. An alternative method is possible in which H&E-stained slides are destained and then restained for mIF or other spatial assays, providing the same valuable combination of assay information but without the HIER-induced alterations in H&E staining pattern. Citation Format: Kevin Hwang, Grace Vezeau, Edyta Olejnik, Douglas Wood, Ruben Cardenes, Lauren Duro, Gourab Chatterjee, Je H. Lee. A novel method to minimize HIER-induced alterations on H&E staining in an integrated mIF-H&E workflow [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3767.

Abstract 3770: Comparative analysis of single cell expression and digital spatial profiling in FFPE tumor tissues

Abstract Formalin Fixed Paraffin Embedded (FFPE) tissues are a staple in clinical diagnostics associated with solid tumor. Next Generation Sequencing (NGS) approaches characterize genomes, epigenomes, transcriptomes, and proteomes from a single sample source. FFPE blocks from several different tumor tissue types were serially sliced into FFPE slides. Individual slides were then utilized to explore the genome, epigenome, single cell RNA-Seq (scRNA-Seq), and Digital Spatial Profiling (DSP). Here we present a comparative analysis of two transcriptomic modalities within one FFPE tissue sample: fixed-cell scRNA-Seq of the transcriptome and digital spatial profiling of the whole transcriptome. Independent analysis of scRNA-Seq and DSP identified common trends as well as distinct differences within the same sample. Comparative analysis within sample between modalities identified statistically significant differences, driven by local tumor microenvironment, but also highlighted commonalities between methods. Cross sample comparisons showed striking differences, as indicated by tumor type. These studies highlight the strengths of each assay individually, as well as the power of a dual-assay approach for comprehensive analysis of the tumor and its microenvironment. Conclusions from this standalone analysis were further aggregated into downstream multiomics analyses, including proteomics analysis, illustrating the expanding landscape of information that can be extracted from FFPE derived tissue and the potential for novel discovery and diagnostic power integrating these complex data types holds. Citation Format: Anthony Moore, Andrea O'Hara, Pranay Vishwanath, Laure Turner, Haythem Latif, Chris Mozdzierz, Ginger Zhou. Comparative analysis of single cell expression and digital spatial profiling in FFPE tumor tissues [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3770.

Abstract 314: Fixative eXchange (FX)-seq reveals single nucleus transcriptional landscapes of archived clinical cancer FFPE specimens

Abstract The wide availability of FFPE tissues stored in hospitals and biobanks could potentially be an invaluable resource to gain insights for improved medical treatment towards precision medicine by combining genomic and transcriptomic data with pathological annotations and medical records. Nevertheless, the majority of current single-cell sequencing methods depend on fresh or fresh-frozen samples to generate high-quality transcriptome data due to the limited reverse transcription (RT) yields in FFPE samples. Consequently, single-cell level transcriptomic studies of FFPE samples have been a longstanding challenge. Here, we present Fixative-eXchange (FX)-seq, a highly scalable snRNA-seq method for heavily paraformaldehyde (PFA)-fixed and/or FFPE samples. We successfully analyzed a total of nearly 320k nuclei from various samples, including PFA-fixed tissue, FFPE blocks, FFPE and hematoxylin and eosin (H&E)-stained sections from mouse brain and human clinical cancer specimens. In a human gastrointestinal stromal tumor (GIST) FFPE sample, we observed rare transcriptomic transitions toward increased epigenetic modifications affected by acquired resistance in response to prolonged imatinib treatment. Furthermore, in an archived human colorectal cancer (CRC) FFPE sample, spatially-contextualized FX-seq with pathologist annotation distinguishes tumor cells from epithelial progenitors along with identification of the tumor microenvironment (TME) such as cancer-associated fibroblasts (CAFs). We then proceeded to investigate transcriptional programs associated with drug resistance and lack of response in immunotherapy observed in CRC patients. With a hypothesis-driven curation, we compared transcription profiles at the single-nucleus level observed in MSS and MSI-H CRC patients from archived FFPE blocks and found distinctive transcriptional profiles from each group. Overall, FX-seq holds promise for clinical research, precision medicine, biomarker discovery, and molecular diagnosis using archived clinical FFPE specimens. Citation Format: Han-Eol Park, Yu Tak Lee, Jaewon Lee, Junsuk Lee, Hyelin Ji, Young-Lan Song, Yoon Dae Han, Hyunki Kim, Chang Ho Sohn. Fixative eXchange (FX)-seq reveals single nucleus transcriptional landscapes of archived clinical cancer FFPE specimens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 314.

Abstract 7622: ASPYRE-Lung: Validation of a simple, fast, robust and novel method for multi-variant genomic analysis of actionable NSCLC variants in tissue

Abstract Genomic variant testing of tumors is critical for patients to access the full potential of personalized oncology therapeutics. Current methods such as NGS are costly and challenging to interpret, while PCR assays are limited in the number of variants they can cover. We developed ASPYRE® (Allele-Specific PYrophosphorolysis REaction) technology to address the urgent need for rapid, accessible and affordable diagnostics informing actionable genomic target variants of a given cancer. The targeted ASPYRE-Lung® panel for NSCLC covers 114 variants in 11 genes (ALK, BRAF, EGFR, ERBB2, KRAS, RET, ROS1, MET & NTRK1/2/3) to robustly inform clinical management, based on practice guidelines. The assay detects single nucleotide variants, insertions, deletions, and gene fusions from tissue-derived DNA and RNA simultaneously. We tested the limit of detection, specificity, analytical accuracy and analytical precision of ASPYRE-Lung using FFPE lung tissue samples from patients with NSCLC, variant-negative FFPE tissue from tonsil tissue, and FFPE-based contrived samples with controllable variant allele fractions. The sensitivity of ASPYRE-Lung was determined to be ≤ 3% variant allele fraction for single nucleotide variants and insertions or deletions, ≤ 100 copies for fusions, and ≤ 200 copies for MET exon 14 skipping. The specificity was 100% with no false positive results. The analytical accuracy test yielded no discordant variants between ASPYRE-Lung and orthogonal testing (targeted enrichment NGS) or contrived samples, and results were replicable across operators, reagent lots, runs, and real-time PCR instruments with a high degree of precision. The technology is simple and fast, requiring only four reagent transfer steps using standard laboratory equipment (PCR and qPCR instruments) with analysis via a cloud-based analysis algorithm. ASPYRE-Lung has the potential to be transformative in facilitating access to rapid, actionable molecular profiling of tissue for patients with NSCLC. Citation Format: Ryan T. Evans, Elizabeth Gillon-Zhang, Julia Brown, Katherine Knudsen, Candace King, Amanda S. Green, Ana-Luisa Silva, Justyna M. Mordaka, Rebecca N. Palmer, Alessandro Tomassini, Alejandra Collazos, Christina Xyrafaki, Iyelola Turner, Chau Ha Ho, Dilyara Nugent, Jinsy Jose, Simonetta Andreazza, Kristine von Bargen, Eleanor R. Gray, Magdalena Stolarek-Januszkiewicz, AIshling Cooke, Wendy J. Levin, Honey V. Reddi, Barnaby W. Balmforth, Robert J. Osborne. ASPYRE-Lung: Validation of a simple, fast, robust and novel method for multi-variant genomic analysis of actionable NSCLC variants in tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7622.

Abstract 325: Validation of Aventa FusionPlus: An LDT NGS assay for comprehensive cancer genomic profiling

Abstract Next-generation sequencing (NGS) assays play a pivotal role in illuminating the genomic landscape of cancer by providing insights into gene regulation and biomarker detection for the purpose of guiding therapeutic decisions to advance personalized medicine. We validated the Aventa FusionPlus Test, a Laboratory-Developed Test (LDT) that integrates HiC technology to enhance detection of actionable gene fusions and rearrangements in solid tumors, including those that are missed by current standard of care tests. This is a DNA-based test that is robust to DNA degradation in FFPE specimens, in contrast with RNA-seq and long-read technologies. The test utilizes the Element Biosciences AVITI sequencing platform to achieve high quality sequencing data at low cost per sample. The Aventa FusionPlus test enables gene-level detection of structural variants near or within 361 medically actionable or diagnostically relevant cancer genes. The 3D structure and long-range linkages captured by the test amplify the signal counts for each rearrangement. The test integrates the Arima-HiC+ FFPE sample prep and the Arima Library Prep Kit workflow. After dewaxing and rehydrating the FFPE tissue, the chromatinized DNA is fragmented and the fragmented ends are filled in with a biotinylated nucleotide. Next, spatially proximal fragmented ends of DNA are ligated, capturing the 3D structure of the genome. The proximally-ligated DNA is then purified and further fragmented, and the biotinylated ligation fragments are enriched. DNA libraries are prepared from these enriched fragments and sequenced in “paired-end” mode. Genes involved in genomic rearrangements were detected using the Arima-SV pipeline along with manual curation. The test achieved robust detection of structural variants, with accuracy of 98.8% relative to reference methods. FFPE tumor specimens from 10 different tissue types and a wide range of tumor content (20%-100%) were included. No correlation between tumor cellularity and sensitivity was observed, suggesting that samples with as low as 20% tumor cellularity can be tested. When comparing to RNA-based and other targeted reference methods, we found additional fusions nearby oncogenes missed by these reference methods. As an example, in a breast cancer case, a fusion of genomic regions neighboring BRAF and MYC oncogenes on chromosomes 7 and 8 respectively, was missed by the reference method but was successfully detected by the Aventa FusionPlus test. The Aventa FusionPlus test is a highly sensitive, specific, and accurate method for comprehensive cancer genomic profiling. The enhanced understanding of gene fusions and rearrangements positions the test as a valuable tool for clinical decision-making in oncology. Citation Format: Shadi Melnyk, Jon Belton, Sofia Nomikou, Katelyn Powell, Daniel Heiney, Roy Khalife, Damien Jones, Anthony Schmitt, Catherine Wilson, Melissa Won, Anthony Magliocco, Chris Roberts. Validation of Aventa FusionPlus: An LDT NGS assay for comprehensive cancer genomic profiling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 325.

Abstract 1722: Subtype classification of small cell lung cancer (SCLC) tissues using the EpiCheck methylation sensitive restriction-based PCR platform

Abstract Small cell lung cancer (SCLC) is an aggressive neuroendocrine malignancy with poor survival rates. Despite molecular and clinical heterogeneity, SCLC is currently treated as a single entity without guidance of predictive biomarkers leading to expectedly poor outcomes. A recent study suggested classifying SCLC into four subtypes (“A”, “N”, “P” and “I”), each with unique molecular features and therapeutic vulnerabilities. While initially this classification was based on gene expression (RNA-seq) data, subsequent data suggest it can be recapitulated using reduced-representation bisulfite sequencing (RRBS) methylation profile. While the classification system accurately predicts responses to therapies, including immunotherapies, in retrospective analysis, both tissue-based RNAseq and RRBS are cumbersome, time-consuming and impractical for prospective treatment assignment in an aggressive malignancy. In this pilot study, we developed a methylation-based PCR assay for classification of SCLC subtypes based on the EpiCheck platform, which combines methylation-sensitive restriction endonuclease (MSRE) digestion with qPCR amplification to detect differential methylation at the DNA level. We developed a 13-marker assay and successfully classified, in a blinded study, 96.55% of FFPE tissue samples originating from SCLC patient of A, N and P subtypes. First, a bioinformatic analysis identified 41 candidate biomarkers that are differentially methylated between pairs of SCLC subtypes (A-N, A-P, and N-P) using RRBS data from 56 RNA-seq classified SCLC tumor samples (34 “A”, 19 “N”, 3 “P”). Development of primers and probes for these markers was followed by a biochemical selection process, identifying 13 markers that displayed optimal performance. A PCR EpiCheck assay, employing these 13 markers, was applied to a blinded set of 29 DNA samples from SCLC FFPE tumor tissues (21 “A”, 6 “N”, 2 “P”). Each sample received two ranks based on methylation levels of 5 A-N and 9 P-AN markers and was classified using determined thresholds for each rank. Finally, when comparing PCR-based and RNA-seq-based classifications, the 13-marker PCR assay classified 28/29 (96.55%) of the samples concordantly, misclassifying one "P" sample as "A". This pilot demonstrates the potential of a simple PCR EpiCheck-based assay to accurately differentiate between SCLC subtypes. For complete subtype classification, “I” markers need to be added to the panel, and the assay should be further validated using a larger cohort, particularly for the “P” subtype. Early detection and classification are critical for timely personalized therapy, and such an assay, performed on cfDNA samples, could potentially be used to shorten the time between a patient diagnosis and tailored treatment initiation or clinical study inclusion from a month in best case scenarios to a few days. Citation Format: Orna Savin, Dvir Netanely, Simon Heeke, Carl Michael Gay, Marcos Roberto Estecio, Shacade Danan, Sarah Zaouch, Aharona Shuali, Mathias Ehrich, Lauren Averett Byers, John Victor Heymach, Adam Wasserstrom, Danny Frumkin. Subtype classification of small cell lung cancer (SCLC) tissues using the EpiCheck methylation sensitive restriction-based PCR platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1722.

Abstract 3644: Uncover spatial signatures of tumor microenvironment and oncogenic pathways using 6,000-plex single-cell spatial molecular imaging on FFPE skin squamous cell carcinoma

Abstract Background: Tumor progression and therapeutic response are regulated by the tumor microenvironment. Understanding the spatial association and architecture of molecular characteristics and composition of tumor immune microenvironment at single-cell and subcellular resolution encourages improvements in clinical prognosis and immunotherapy benefits. Single-cell Spatial profiling technologies permit the study of transcriptional activity at the spatial, single-cell level and provide abundant, high-resolution information required for the identification of clinical-related features in immuno-oncology. Methods: We performed an ultra-high-plex RNA assay to detect 6,000 targets simultaneously in situ on FFPE human skin squamous cell carcinoma using the CosMx™ Spatial Molecular Imager (SMI). For the selection of regions of interest, four protein markers and DAPI were co-detected on the same tissue slide. Tertiary analysis algorithms were developed for cell typing, co-localization of genes and ligands, cell-cell interaction, and pathway analysis. Results: Thousands of transcripts were simultaneously detected with high sensitivity and specificity on the FFPE skin squamous cell carcinoma tissue section at single-cell subcellular resolution. We investigated the tumor microenvironment including cell types, their spatial distribution and proportion of diversified immune cells in the tumor compartment. The cell typing results revealed many cancerous subpopulations, which resolved spatially from cells that lacked any defining marker genes. We also assessed distances between immune cells and their nearest functional-related neighbors. Moreover, we revealed the ligands co-localization, as well as spatial patterns of direct cell-cell interactions and signaling pathways. We found that some genes have elevated expression in macrophages which are near cancer compared to those are far from cancer cells, empowering the molecular investigation of novel signaling between immune and cancer cells in tumor immune microenvironment. Conclusions: Single-cell spatial measurements of 6,000 RNA and four proteins on the same tissue section, along with a large viewing area on archival FFPE tissue, provide a novel tool to reveal the spatial signature of tumor microenvironment and oncogenic pathways, facilitating the next level of cancer and therapeutic research. FOR RESEARCH USE ONLY. Not for use in diagnostic procedures. FOR RESEARCH USE ONLY. Not for use in diagnostic procedures. Citation Format: Michael Patrick, Shanshan He, Saskia Ilcisin, David Kroeppler, Patrick Danaher, Jason Reeves, Mark Gregory, Haiyan Zhai, Michael Rhodes, Joseph Beechem. Uncover spatial signatures of tumor microenvironment and oncogenic pathways using 6,000-plex single-cell spatial molecular imaging on FFPE skin squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3644.

Abstract 5497: Towards a drag and drop spatial biology workflow: Introducing sample reinterrogation as a conduit for the progressive development and on-line analysis of high parameter spatial biology data

Abstract The potential for spatial biology in cancer research is understood and edified. With it we can understand the tumor microenvironment, unravel responsiveness to drug treatments and cell therapies, and ultimately stratify patients for targeted treatment and clinical trial enrollment. Yet, researchers exploring spatial biology may be discouraged by what can be a resource intensive exercise, and most importantly, a commitment of high value patient samples. Furthermore, the design of reagent panels used to study samples is not trivial, and a specimen’s unique biomarker expression profile may require adjustments. Here we present a novel solution that permits sample re-interrogation and in-flight adjustments of reagent panels in our spatial biology workflow. The CellScape™ platform for Precise Spatial Multiplexing paired with VistaPlex™ Assay Kits provide a ready-to-use cyclic multiplex immunofluorescence (IF) solution to interrogate fresh frozen and FFPE tissue samples. Tissues are mounted in enclosed fluidic chambers, while staining and imaging are conducted on the CellScape instrument. The experiment requires no additional autostainer equipment and is divided into separate staining and imaging rounds. The end user may therefore pause between rounds and conduct inter-round analyses, which can then guide decisions of whether and how to continue the experiment. To illustrate the benefit of this approach, we present a use case in which we applied VistaPlex antibody panels to reveal the spatial distribution of major immune cell populations. Inter-round analysis and conclusions were then drawn from this preliminary phenotype map before successive rounds of rationally planned staining were conducted to further deepen the depth and breadth of spatial phenotyping. The CellScape sample reinterrogation feature is a pragmatic spatial biology solution that optimizes the use of precious resources, whilst allowing researchers to generate informed decisions about antibody panel designs almost in real time. This enhanced utility may reduce the resistance to spatial biology among researchers working with samples that are limited or irreplaceable. Citation Format: Matthew H. Ingalls, Xenia Meshik, Charles E. Jackson, Kayla E. Cashion, Arne Christians, Anke Brix, Marcus Boettcher, J Spencer Schwarz, Oliver Braubach. Towards a drag and drop spatial biology workflow: Introducing sample reinterrogation as a conduit for the progressive development and on-line analysis of high parameter spatial biology data [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5497.

Abstract 6190: Patterns of EGFR and HER3 co-expression in solid tumors

Abstract EGFR and HER3 are members of the ERBB receptor family and transmit growth and survival signals to cancer cells upon ligand binding. While both receptors are well established targets for cancer therapy, greater understanding of the relationship of their expression patterns in human cancer is needed to establish the scope of therapeutic potential. To evaluate the co-expression pattern of EGFR and HER3, cancer FFPE tissue microarrays from several cancer types were evaluated by immunofluorescence imaging and digital pathology, including cell-by-cell marker intensity and spatial analyses within the tumor and stromal compartments. Tissue cores were assigned H-scores, and individual cells were binned into 0, 1+, 2+, 3+ scoring based on established digital pathology methods using QuPath software. Spatial cytometry was used to further evaluate single-cell expression intensity. Analysis was conducted widely on multiple normal human tissues as well as cases of NSCLC adenocarcinoma n=86, NSCLC squamous cell carcinoma n=84, SCLC n=43, TNBC n=45, Biliary tract cancers n=80, Nasopharyngeal carcinomas n=60. Overall, the results of this analysis show the intermediate to high prevalence of EGFR and HER3 co-expression within each indication, as well as the frequency of EGFR and HER3 expressing cells. Furthermore, EGFR and HER3 heterodimers were confirmed by proximity ligation assay in certain index cases. Notably, of several observations, we observe NSCLC cases show a profound absence of EGFR- HER3+ tumor cells. Additionally, we observe that co-expression of EGFR and HER3 in normal human tissues is rare and of low signal intensity. Citation Format: Matthew Wood, Cody Morrison, Jahan Salar Khalili, Yi Zhu. Patterns of EGFR and HER3 co-expression in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6190.

Abstract 2759: Transcriptional intra-tumoral heterogeneity of putative therapeutic targets in colorectal cancer peritoneal metastases

Abstract Background: The poor prognosis of peritoneal metastasis (PM) in colorectal cancer (CRC) is typically attributed to, and characterized by, resistance to systemic chemotherapy and immunotherapy. The evolutionarily conserved plasma-peritoneal barrier as well as reduced tumor tissue vascularity contributes to poorer responses to systemically administered antineoplastic therapy. Beyond these, we sought to understand transcriptomic variations of important therapeutic targets implicated in peritoneal organotropism and by extension, resistance to systemic regimens in CRC PM. Methodology: FFPE tissue samples from CRC patients were collected during oncological surgical resection of the synchronous PM (cytoreductive surgery [CRS] with or without hyperthermic intra-peritoneal chemotherapy [HIPEC]), or exploratory laparotomy for palliative surgery, with the majority of patients receiving systemic therapy prior to surgery. Samples were sequenced with whole transcriptomic sequencing. Paired and unpaired T-tests between PT and PM samples were undertaken with log2(fragments per kilobase of exon per million mapped [FPKM]) gene expression values. Results: Fifty-six (22 primary tumor [PT], 34 peritoneal metastases [PM]) samples from 35 patients, comprising 21 paired PT-PM samples, were included in this analysis. TEAD1 (unpaired T-test, p=0.087; paired T-test, p=0.041), FGFR1 (unpaired T-test, p=0.003; paired T-test, p<0.001), PIK3CA (unpaired T-test, p=0.034; paired T-test, p=0.003), SMAD4 (unpaired T-test, p=0.095; paired T-test, p=0.010), and HAVCR2 (unpaired T-test, p=0.009; paired T-test, p=0.007) were found to be upregulated in the PM. Conversely, MET was found to be downregulated in PM samples (unpaired T-test, p=0.004; paired T-test, p=0.002). There were no significant differences in gene expression profiles of BRAF, RHOA, CD274, CTLA4, PDCD1 and TIGIT between PT-PM (all p>0.05). Conclusion: Through CRC PT-PM comparisons, we identify potential therapeutic targets implicated in transcoelomic metastasis and provide rationale for development of immunotherapeutic biology and drug discovery for CRC PM. These findings underscore an exigent need to develop intra-peritoneal therapeutic strategies to overcome resistance to systemic regimens. Citation Format: Joseph J. Zhao, Johnny CA Ong, Daryl Kai Ann Chia, Melissa Ching Ching Teo, Qiu Xuan Tan, Gillian Ng, Joey Wee-Shan Tan, Haoran Ma, Xuewen Ong, Su Ting Tay, Patrick Tan, Raghav Sundar. Transcriptional intra-tumoral heterogeneity of putative therapeutic targets in colorectal cancer peritoneal metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2759.

Abstract 72: A spatial interactomics approach reveals interplay between the tumor microenvironment and T cell activation

Abstract Background: T cells play a fundamental role in immune response to tumors. However, the tumor microenvironment (TME) - a complex network of cells, signaling molecules, and extracellular matrix components - employs various strategies to evade immune surveillance and suppress T cell activity. Among the many molecular interactions taking place in the TME, the role of CD8/MHC I, LAG3/MHC II and PD1/PDL1 is pivotal in modulating anti-cancer response and the escape routes that cancer in turn uses to withstand immune defense. LAG3/MHC II and PD1/PDL1 interactions are inhibitory, causing T cell dysfunction and exhaustion, while the CD8/MHC I interaction is essential for initiating an effective anti-tumor response. Here, we used a cutting-edge in situ proximity ligation strategy combined with immunofluorescence (IF) to reveal these key interactions and TME biomarkers in hepatocellular carcinoma and Hodgkin lymphoma. Since the method does not compromise the structural integrity of tissues, communication between proteins can be studied in their native milieu. Method: Protein-protein interactions (PPIs) were detected with the NaveniFlex Tissue Atto647N kit in human FFPE tissues according to the manufacturer’s protocol. This technique can detect proteins located within interaction range (<40 nm) via oligonucleotide-antibody conjugates that create amplified fluorescent signal. Parallel IF co-staining for α-fetoprotein, Ki67, CD30 and CD3 was performed during the Naveni® detection step. Slides were mounted and imaged on the Olympus V200 automated scanner. Results: Tumor cells were identified by α-fetoprotein/Ki67 (hepatocellular carcinoma) or CD30 (Reed-Sternberg in Hodgkin lymphoma) IF staining, and tumor-infiltrating lymphocytes were visualized by CD3 staining. With the help of the Naveni® assay, we observed abundant interaction between CD8/MHC I in hepatocellular carcinoma and Hodgkin lymphoma. Suppressive immune checkpoint interactions such as LAG3/MHC II and PD1/PDL1 were also detected. In the case of Hodgkin lymphoma, the CD8/MHC I, LAG3/MHC II and PD1/PDL1 interactions were largely seen in the same areas, and specifically between T cells and Reed-Sternberg cells, indicating a crosstalk between the TME and the immune landscape in the cancer tissues. Conclusion: The interactomics approach, employing in situ proximity ligation for observing protein function as opposed to mere expression, allows the detection of key PPIs in the TME. Understanding the intricate crosstalk between them is crucial in developing effective immunotherapies. Targeting these pathways simultaneously or in combination, such as using immune checkpoint inhibitors against PD1/PDL1 while exploring strategies to modulate LAG3/MHC II and CD8/MHC I interactions, holds promise in reinvigorating T cell responses against cancer and improving the efficacy of immunotherapies within the complex landscape of the TME. Citation Format: Desirée Edén, Jonas Vennberg, Tanja Büsgen, Doroteya Raykova, Agata Zieba-Wicher. A spatial interactomics approach reveals interplay between the tumor microenvironment and T cell activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 72.

Abstract 1582: Cabozantinib changes the tumor microenvironment to increase the efficacy of immunotherapy in refractory metastatic pancreatic ductal adenocarcinoma

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies. Tumors evade immune surveillance by expressing PD-L1 that interacts with the T cell protein PD-1, subsequently inhibiting CD8+ cytotoxic T lymphocyte proliferation and effector function. A plausible reason for this observation may be that other, redundant, immune suppressive mechanisms are at play. Our research team has shown that elevated infiltration of polymorphonuclear (PMN)-MDSCs within the PDAC tumor microenvironment (TME) inhibit T cell effector function, regardless of PD-1/PD-L1 inhibition (Holokai et al., 2020). Objective: A Phase II clinical trial was developed to identify the potential therapeutic benefit of combinatorial anit-PD-L1/PD-1 and cabozantinib (cabo) treatment in therapy-resistant (refractory and metastatic) PDAC patients. Methods: NanoString CosMx™ spatial molecular transcriptomic imaging (CosMx™ SMI) was performed using FFPE sections collected from a liver or lung metastatic target lesions at visit 1 (pretreatment) and visit 2 (9 weeks on combinatorial treatment) from individual patients. FFPE sections were prepared from the same target lesion, and fields of view were chosen on the H&E in consultation with GI pathologist. Seurat V 4.0 was used for the analysis and visualization by spatial mapping of each FOV showing identified cell population indicated by color coding in visit 1 and visit 2 within the same patient. Multiplex immunofluorescence (MxIF) of patient FFPE tissues and single cell RNA sequencing (scRNAseq) of PDAC organoids (PDOs) generated from the core biopsies collected at visit 1 and matched visit 2 from each patient were used to validate the CosMx™ SMI data. Results: A uniform manifold approximation and projection showed loss of tumor cell populations within the PDAC TME in response to combinatorial treatment compared to pretreatment visit 1. Comparison between spatial maps of visit 1 to visit 2 demonstrated a shift in cell populations within defined NICHES (local cellular TME) whereby there was 1) a loss of tumor cell populations, 2) increase in CTL infiltration, 3) increase in endothelial cells, 4) decrease immunosuppressive MDSCs, 5) decrease in antigen presenting CAFs, and 6) change in myCAFs to an inflammatory CAF phenotype. Within the iCAF population IL-6, CXCL1, LIFR, ACTA2 and FAK were expressed; correlating with an increase in CD8 perforin and granzyme B positive cells in response to cabo and checkpoint inhibition. MxIF, spectral flow cytometry and scRNAseq analyses of the matched in vitro PDO model showed tumor cell death that correlated with decreased MDSC viability, increased CTL proliferation and a shift in CAF phenotypes. Conclusion: These findings suggest that cabo induces a TME conducive to increased response to immunotherapy in PDAC patients with refractory metastatic disease. Citation Format: Jayati Chakrabarti, Pritha Adhikary, Jiang Wang, Davendra Sohal, Syed A. Ahmad, Junaid Arshad, Aaron J. Scott, Rachna T. Shroff, Yana Zavros. Cabozantinib changes the tumor microenvironment to increase the efficacy of immunotherapy in refractory metastatic pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1582.

Abstract 3645: Unraveling spatial complexity of the tumor microenvironment: A whole transcriptomic perspective with Visium HD

Abstract In recent years, advances in spatial transcriptomics have revolutionized our understanding of the tumor microenvironment, providing crucial insights into the complex interplay of different cell types within cancer tissues. In this study, we employed the new, high definition Visium spatial transcriptomics assay (Visium HD) to investigate the intricate molecular landscape of prostate cancer at single-cell scale resolution and across the whole transcriptome. Our research focused on deciphering the spatial heterogeneity of gene expression patterns within the tumor microenvironment, shedding light on the interactions between cancer cells, stromal cells, and vasculature. The Visium HD assay enables an unbiased exploration of the transcriptome on FFPE tissue sections mounted on standard glass slides. Combining gene expression data with H&E images from the same section, it allows precise characterization of local molecular features and disease states at single-cell scale. We analyzed a set of human prostate adenocarcinoma samples with the Visium HD assay, and identified spatially regulated gene signatures associated with specific cell types and functional pathways. Our findings have recapitulated previously identified molecular markers, including VEGFA and MYC which have been implicated in tumor progression and angiogenesis. The spatial gene expression patterns had good correlation with histological annotations of cancerous and normal tissue within the H&E image. However, Visium HD allowed us to further observe molecular processes and pathways specific to this adenocarcinoma sample. This integrative approach offers valuable implications for personalized cancer therapy and the development of targeted interventions tailored to the spatial context of individual tumors. Our study underscores the significance of understanding the spatial organization of the whole transcriptome in cancer tissues, and highlights the potential of the Visium HD platform as a powerful tool for unraveling the complexities of the tumor microenvironment. These insights pave the way for the development of innovative therapeutic strategies and precision medicine approaches, ultimately contributing to improved outcomes for cancer patients. Citation Format: Yifeng Yin, Jerald Sapida, David Sukovich, David Patterson, Augusto Tentori. Unraveling spatial complexity of the tumor microenvironment: A whole transcriptomic perspective with Visium HD [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3645.

Abstract 3659: Development of customized circulating tumor DNA panel for minimal residual disease detection in biliary tract cancer

Abstract Biliary tract cancer (BTC) is a rare type of abdominal cancer and is more frequent in Asian countries than in Western. The 5-year survival rate for BTC is very low 7 to 20% and only 20% of BTC patients could undergo curative-intent surgery. BTC diagnosis based on biopsy and cytology are low in sensitivity that prompted the necessity to identify alternative biopsy. Liquid biopsy, specifically circulating tumor DNA (ctDNA) is known for the accessibility and low invasiveness received great interest for their potential uses in various clinical applications for patients with insufficient tumor tissue, including mutation profiling, treatment monitoring, and cancer detection. However, the panel available in the market up-to-date focused mainly targeted, actionable alterations and thus not suitable for minimal residual disease (MRD) monitoring. In this study, we aimed to develop a customized ctDNA panel for MRD monitoring in BTC. In this study, 124 BTC patients undergone curative resections were enrolled at Hokkaido University and Sapporo Medical University from May 2019 to April 22. All enrolled patients have BTC diagnosis confirmed by pathological diagnosis after surgery, and without other malignant tumors. Genomic profiles of FFPE tissue were conducted using Ampliseq CCP. 13 patients were excluded for high fragmentation. Referring to the genomic profiles of 111 patients in our study and 1924 patients in TCGA established a customized panel using Ion Ampliseq HD technology. The Ampliseq HD panel claims to detect variants at 0.1% LOD for ctDNA detection. It also integrates molecular barcodes to reduce NGS-related errors. The designed panel was 258 Amplicons and 20 genes including eleven therapeutically targetable genes. Clinical characteristics of ctDNA detection were also assessed. Results:The panel validation: concordance of the mutation allele frequency (MAF) between the NGS standard control and Ampliseq HD panel showed a coefficient of determination (R2) of 0.96. Also, concordance of MAF Ampliseq CCP and Ampliseq HD panel on FFPE tumor profiling showed R2 of 0.78. When assessing 70% of BTC patients were covered to have at least one tumor-derived Ampliseq HD panel. When assessing using plasma cell-free DNA, 55% of BTC patients were detected to have at least one tumor-derived ctDNA. Distribution of detected altered top4 genes using Ampliseq HD panels shows TP53 35%, KRAS 10%, SMAD4 5%, ARID1A 2.5%. Clinical characteristics may affected the concordance of plasma and FFPE tumor tissue; stage (P=0.035), size of tumors (P=0.0088), subtype (P=0.013), LN metastasis (P=0.11). Conclusions: A highly sensitive ctDNA customized panel for BTC was established. We also found that clinical characteristics of the BTC affects the detection of ctDNA from blood liquid biopsy. Future study: MRD evaluation using this customized panel. Citation Format: Yoshihito Shinohara, Siew-Kee Low, Toru Nakamura, Yasutoshi Kimura, Takeshi Murakami, Kazuma Kiyotani, Satoshi Hirano. Development of customized circulating tumor DNA panel for minimal residual disease detection in biliary tract cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3659.