Abstract 6872: A spatio-temporal approach to mapping the dynamics of cutaneous squamous cell carcinoma progression and immunotherapy response: A journey through TiME

Abstract Background: Cutaneous squamous cell carcinoma (cSCC), arising from proliferation of malignant epidermal keratinocytes, is the second most common non-melanoma skin cancer. cSCC accounts for 75% of all skin cancer related deaths excluding melanoma, and metastatic and immunotherapy-resistant cases pose an emerging global threat. Tumor development is a gradual process characterized by high mutational burden and an immunosuppressive tumor immune microenvironment (TiME); therefore, identifying the underlying changes across the spatial and temporal landscape of these tumors will be crucial to understanding the key cellular and molecular drivers of disease progression and response. Methods: In this longitudinal study, we used a single-cell, whole-slide approach to mapping key proteins of immune lineage, tissue architecture, cellular metabolism, and stress to study the spatial landscape of cSCC at baseline (pre-treatment) and multiple time points over the course of immunotherapy with the aim to develop a temporal atlas of the tumor. An ultra-high plex antibody panel encompassing over 50 major determinants in the tumor microenvironment was employed on the PhenoCycler®-Fusion spatial biology platform. Deep bioinformatic analyses was performed to identify cellular phenotypes, spatial neighborhoods, heterogenous functional states and cellular interactions by spatial proximity determinations. Results: Previous studies in our laboratory have identified unique phenotypes correlating with response and resistance to immunotherapies in pre-treatment cSCC biopsies. Our results expand on these findings with temporal data tracking the dynamic changes in the TiME over the course of immune checkpoint inhibitor therapy. Apart from differences in immune cell composition and spatial localization patterns, we also saw differences in macrophage polarization and expression of metabolic markers in the responder and non-responder cohorts. Conclusions: Overall, ultrahigh-plex spatio-temporal monitoring of cSCC revealed distinct signatures of response and resistance and identified key features in the TiME that reveal deeper insights into the pathobiology of the tumor. Our discovery-based approach identifies novel biomarkers for patient stratification and therapeutic modulation. Citation Format: Niyati Jhaveri, Bassem Ben Cheikh, Dmytro Klymyshyn, Ning Ma, Aditya Pratapa, James Monkman, Nadine Nelson, Arutha Kulasinghe. A spatio-temporal approach to mapping the dynamics of cutaneous squamous cell carcinoma progression and immunotherapy response: A journey through TiME [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 6872.