Abstract PR012: A novel plasma-based epigenomic assay for comprehensive profiling of cancerous and inflammatory disease states

Abstract Background: We developed a method for comprehensive epigenomic profiling from 1 ml of patient (pt) plasma, targeting histone modifications and DNA methylation. This approach can be applied to plasma from pts with cancer and inflammatory conditions, allowing us to infer expression levels of diagnostic markers and drug targets, measure activity of therapeutically targetable transcription factors, and detect non-genomic mechanisms of resistance. By examining the transcriptional status of therapeutic gene targets and pathways, our method addresses the need for new approaches in liquid biopsy (LBx) assays, providing clinically actionable information that enhances the understanding of cancer and inflammatory biology and therapeutic response. Methods: We developed an innovative multimodal assay capable of revealing genome-wide transcriptional activity of promoters and enhancers from chromatin, as well as surveying the DNA methylome. Utilizing this assay on plasma samples from pts with 5 non- cancer conditions and 15 different tumor types, we generated comprehensive genome-wide transcriptional profiles across 21 conditions. Results: We identified transcriptional activation in cancer pt plasma of cancer-associated biomarkers (e.g., HER2, DLL3) in a tumor-specific manner and in autoimmune disorders such as rheumatoid arthritis and systemic lupus erythematosus/lupus nephritis. Epigenomic profiling simultaneously inferred the expression of multiple pertinent ADC and radio-immune targets (e.g., MET, HER2, HER3, TROP2, B7H4 in breast cancer and PSMA in prostate cancer), and SLFN11, a biomarker for sensitivity to these agents. The multimodal platform assesses transcriptional regulation genome-wide, enabling analysis of select genes as well as related pathways. For example, a multimodal classifier robustly predicted HER2 status across multiple HER2-expressing tumors. HER2 classification of breast cancer pts by epigenomic LBx was concordant with standard tissue-based IHC for 64/72 (89%) breast cancer samples (AUC 0.9). Accurate classification was achieved for 11/14 (79%) gastroesophageal adenocarcinoma and 4/4 (100%) ovarian cancer pts. A multi-modal predictive model trained on FOLH1 plasma epigenomic regulatory signals demonstrated significant accuracy in predicting quantitative readouts from PSMA PET scans (total SUVmean) in metastatic castration resistance prostate cancer pts and was associated with response to pluvicto. Epigenomic signatures also delineated activation of the endocrine signaling pathway in breast cancer and multiple mechanisms of resistance to androgen receptor signaling inhibition in prostate cancer, including reactivation of the androgen receptor, glucocorticoid signaling bypass, and histological transformation to a neuroendocrine subtype. Conclusions: This comprehensive epigenomic LBx assay offers a platform for simultaneous genome-wide transcriptional assessment of disease and therapy-relevant genes and pathways, marking a paradigm shift in our ability to assess the underlying transcriptional states of cancer and inflammatory diseases. Citation Format: Travis Clark, Anthony D'Ippolito, Aparna Gorthi, Jonathon Beagan, Jamey Guess, Amy Donahue, Mandy Greene, Alyssa Lau, Fernando Ramirez, Kristian Cibulskis, Jenna Wurster, Michael Coyne, Mary McGillicuddy, Baovy Tran, Tyrone Tamakloe, Hathairat Sawaengsri, Corrie Painter, Juliann Chmielecki, Geoff Otto, Matthew Eaton, Carl Barrett. A novel plasma-based epigenomic assay for comprehensive profiling of cancerous and inflammatory disease states [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 PR012.