Abstract 753: In situ RNA expression profiling of 1600+ immuno-oncology targets in FFPE tissue using NanoString GeoMx™Digital Spatial Profiler

Clinical specimens including formalin-fixed, paraffin embedded (FFPE) tumor sections preserve spatial and molecular information of tumor cells and their surrounding microenvironment. This valuable spatial information is loss with bulk RNA-seq, the most prevalent method for gene expression profiling of archival FFPE samples. In contrast, the NanoString GeoMx™ Digital Spatial Profiler (DSP) is a high multiplexing assay that can profile thousands of RNAs from user selectable regions of interest (ROIs) in FFPE sections. Here we introduce a 1600+ gene panel of tumor, stroma, and immune cell-specific content derived from NanoString nCounter® PanCancer series. We compare RNA profiling using our 1600+ immune-oncology panel to the RNA-seq methodology in FFPE samples. DSP RNA in situ probes are photocleavable oligonucleotides tags coupled to hybridization sequences that bind to mRNA transcripts in the FFPE tissue section. We gridded 96 ROIs upon the FFPE section, photocleaved oligonucleotide tags from each ROI were collected and prepared into sequencing libraries with our NGS readout workflow. After sequencing, reads were charted back to each ROI in the tissue section, generating a map of transcript activity within the tissue. We found high concordance between “bulk” DSP RNA (counts from all 96 gridded ROIs) and RNA-seq from the same FFPE block. Individually, however, each ROI showed different expression patterns than bulk and ROI expression patterns clustered based on similar tissue morphology. We further profiled the tumor and microenvironment compartments from multiple FFPE cancer tissues, comparing our 1600+ RNA expression profile to RNA-seq. DSP was able to detect a higher number of genes with low expression within each spatial compartment compared to bulk RNA-seq. These data demonstrate that DSP offers unparalleled sensitivity for large-scale gene expression while preserving critical information about tissue architecture. GeoMx™ DSP technology is for Research Use Only and not for use in diagnostic procedures. Citation Format: Margaret Hoang, Zoey Zhou, Michelle Kriner, Kristina Sorg, Zach Norgaard, Erin Piazza, Chris Merritt, Dae Kim, Joseph Beechem. In situ RNA expression profiling of 1600+ immuno-oncology targets in FFPE tissue using NanoString GeoMx™Digital Spatial Profiler [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 753.