Abstract 2541: Imaging mass cytometry detects the true dynamic range of low-abundance biomarker expression in human tumors

Abstract Detecting clinically relevant biomarkers in cancer tissues provides key insights into the unique tumor characteristics of patients, allowing for more personalized and effective therapies. Immunohistochemistry (IHC) is the gold-standard technique for biomarker detection and is widely used by pathologists to score low-abundance biomarkers (LABs) in tissues. Limitations related to plexity, quantitation and false signal detection are frequently observed using IHC and day-to-day variability due to multiple steps of signal amplification and pigment mistaken for true signal can misinform pathologists about LAB expression. Imaging Mass Cytometry™ (IMC™) technology is a multiplexed imaging technique that incorporates quantitative assessment of 40-plus biomarkers simultaneously on the same slide. The Hyperion™ XTi Imaging System, in association with an automated slide loader, permits 24/7 data acquisition and provides biological insights critical for assessment of the tumor microenvironment. We strove to determine whether IMC can be used for pathological evaluation of LABs and provides additional key biological insights for clinical evaluation offered through multiplexed analysis. We performed a comparison of IHC and IMC technology to detect clinically relevant LABs (PD-1, PD-L1, CTLA-4 and LAG-3) on human tumor tissue microarray and whole tissue samples. For IMC technology, we detected single cells using the Human Immuno-Oncology IMC Panel, which offers cell phenotyping of tumor and immune cell subtypes and their functional states. We stained serial sections of tissues using the same antibody clone and generated IHC and IMC data, which was assessed by a board-certified pathologist. We conducted quantitative image analysis to detect LAB expression on single cells. Our results demonstrate that while IMC and IHC are similar in detecting LABs, IMC technology can accomplish this without signal amplification, offering an opportunity to evaluate LABs in their true dynamic signal ranges. Quantitative analysis of IHC and IMC data further demonstrated the equivalent performance of both platforms. Multiplexed single-cell analysis using IMC data provided insights about LAB expression on specific immune and tumor cells. While IHC is semi-quantitative and cannot reliably determine the high abundance of a target, IMC technology offers the opportunity of signal quantitation as it displays the complete dynamic range of signal. Clinical assessment of tissues using IMC technology offers an advantage over traditional IHC methods by providing true biological context due to multiplexing capabilities. The ability of IMC to provide high-dimensional spatially resolved data makes it a powerful tool for clinical and translational applications and shows that it is poised to significantly contribute to biomarker discovery and drug development. For Research Use Only. Not for use in diagnostic procedures. Citation Format: Smriti Kala, Qanber Raza, Jyh Yun Chwee, Thomas D. Pfister, Liang Lim, David King, Christina Loh. Imaging mass cytometry detects the true dynamic range of low-abundance biomarker expression in human tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2541.