LAUSR

The lack of suitable experimental approaches to investigate and model functional heterogeneity in vivo has had a profound negative impact on our understanding of how heterogeneity affects the response to immunotherapy. To bridge this technological gap, we leverage a new platform that visualizes the spatial architecture of subclones and microenvironments. To study heterogeneous populations of cells and their clonal dynamics in vivo, we performed barcode lineage tracing with next-generation sequencing analysis. It allows a quantitative evaluation of the spatial distribution and temporal clonal dynamic in vivo with multiple pharmacological perturbations, such as immune checkpoint blockade (ICB). We found that treatment with a PD1 inhibitor, despite a limited effect on tumor volume, induced dramatic changes in tumor clonal architecture. Furthermore, we revealed that subclones from well-defined geographical domains in vivo share differential behavior upon immune checkpoint blockade (ICB). By visualizing 40 different markers with multiplexed staining technology, we further identified that the microenvironment also exhibits a high level of spatial heterogeneity. Therefore, we coupled spatial barcode sequencing with high-content imaging and revealed the differential microenvironment feature of sensitive and resistant clones. We will further explore the mechanisms of immune evasion at the subclonal level. Through isolation and deep characterization of clonal lineages endowed with a distinct ability to engage the immune response, we hope to identify new vulnerabilities to overcome resistance to ICB. Citation Format: Er-Yen Yen, I-Lin Ho, Chieh-Yuan Li, Charles Dyke, Shan Jiang, Francesca Citron, Sergio Attanasio, Rutvi Shah, Ko-Chien Chen, Giulio Draetta, Andrea Viale. Uncovering key microenvironmental features for immunotherapy response at the subclonal level in pancreatic cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5868.