Abstract 3881: Distinguishing dendritic cell subtypes in the tumor microenvironment using MultiOmyx^TM

Dendritic cells (DCs) are key initiators and regulators of the innate and adaptive immune responses. An emerging interest in cancer therapies is the capability to activate endogenous DCs to induce antigen specific T cell responses and thereby generate DC-based immunotherapies. Understanding the function and diversity of DC subsets in the tumor environment will help improve therapies developed for cancer treatment. DC subpopulations have been recognized in humans and categorized based on their phenotype and functional criteria. These DC subsets are classified based on biomarker expressions and include CD123+ plasmacytoid dendritic cells (pDCs), two types of classical dendritic cells CD141+Clec9A+CD11c+ HLADR+ conventional type 1 dendritic cells (cDC1), CD1c+CD11c+HLADR+ conventional type 2 dendritic cells (cDC2) and CD14+CD11c+CD209+ monocyte derived dendritic cells (Mo-DCs). To help understand the complexity of distinct subsets of DCs, their spatial distribution within the tumor microenvironment (TME), and correlation with other immune cells, multiplex immunohistochemistry using a panel of antibodies broad enough to differentiate and characterize multiple DC subsets and T cell populations will be used. MultiOmyxTM, a novel hyperplexed multi ”omic” technology, enables visualization and characterization of multiple biomarkers across multiple assays on a single 4μm tissue section. MultiOmyx protein immunofluorescence (IF) assays utilize a pair of directly conjugated Cyanine dye-labeled (Cy3, Cy5) antibodies per round of staining. Each round of staining is imaged and followed by novel dye inactivation chemistry, enabling repeated rounds of staining and deactivation for up to 60 protein biomarkers. In this study, a MultiOmyx hyperplexed IF assay will be utilized to distinguish different DC subset within a tumor. Biomarkers including CD11c, CD123, CD141, CleC9A, CD1c, DC-Lamp, DC-sign, HLADR, CD14, CD68, CD163, CD3, CD4, CD8, FOXP3 and PanCK protein expression from a single 4 µm FFPE section in order to identify different subsets of DCs in tumor tissue from patients with Melanoma, a cancer type in which immunotherapeutic treatment has had a transformative effect and become the dominant therapeutic approach. Hopefully, a greater understanding of the phenotypes and functions of dendritic cells subsets will result in new cancer immunotherapy strategies. Citation Format: Maricel C. Gozo, Vivek Reddy, Mate Nagy, Nickolas Attanasio, Naiyun Zhou, Sara Pollan, Erinn Parnell, Eric Leones, Judy Kuo, Anna Juncker-Jensen, Josette William Ragheb, Qingyan Au. Distinguishing dendritic cell subtypes in the tumor microenvironment using MultiOmyxTM [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3881.