Abstract PR015: Clonal Heterogeneity in Human Pancreatic Ductal Adenocarcinoma and Its Impact on Tumor Progression

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer characterized by profound desmoplasia and cellular heterogeneity, which cannot be fully resolved using traditional bulk sequencing approaches. To understand how this heterogeneity contributes to PDAC biology, we analyzed a large cohort of primary tumors (n=62) profiled by scRNA-seq (443,451 single cells), including a subset of 11 tumors with matched spatial transcriptomics (53,236 spots), to map clonal, transcriptional, and spatial diversity. Moreover, our sample set includes a unique cohort of matched samples from six tumors collected before and after treatment with chemotherapy. To understand the contribution of this heterogeneity to PDAC biology, we analyzed a large primary PDAC cohort with matched single-cell and spatial transcriptomics methods (n=62), profiling 443,451 single cells and 53,236 spatial spots to map clonal, transcriptional, and spatial diversity. Our analysis revealed significant intratumoral heterogeneity, with multiple genetically distinct neoplastic clones co-existing within individual tumors. We also detected whole genome duplication (WGD) patterns in each sample by comparing the distribution of total UMI counts in malignant clones to those of non-malignant epithelial cells. Across all tumors, WGD was identified in 32.6% of samples, consistent with reported frequencies. We observed clone-specific ligand–receptor programs that are modulated by genomic dosage: amplifications of ligands or receptors enriched corresponding interactions, while deletions suppressed them, with; these genetically encoded differences were supported by spatial transcriptomics and multiplex immunofluorescence. Phylogenetic integration identified focal 8q24 (MYC) amplification as recurrently associated with classical-to-basal transitions occurring within tumor lineages at a frequency above chance; these transitions were accompanied by coordinated depletion of immune-response programs. Functional perturbation experiments in murine and primary human models showed that MYC knockdown reactivates classical transcriptional programs (GATA6, CDH1, FOXA2, MUC1, EPCAM) and restores immune-response pathways (MHC class I/II and B2M), supporting a role for MYC in maintaining a basal, immune-depleted state. Spatial analyses further revealed dispersed clones enriched for epithelial-to-mesenchymal transition (EMT) activity and immune suppression, correlating with metastatic potential and colonization of lymph node niches. These dispersed clones tended to shift toward a basal phenotype, contributing to disease progression. Our findings highlight the critical role of clonal diversity, transcriptional plasticity, and TME interactions in shaping human PDAC biology. This work provides new insights into a detailed view of the molecular and spatial heterogeneity of PDAC and offers potential avenues for therapeutic intervention targeting clonal evolution and the mechanisms driving metastasis. Citation Format: Despoina Kalfakakou, Sungsik Kim, Lidong Wang, Qi Su, Daniel C. Cameron, Emily A. Kawaler, Motoyuki Tsuda, Elektra Manolakos, Xiaohong Jing, Cristina Hajdu, Dylan L. Tamayo, Yoona Shim, Amanda Ackermann, Daniel Weissinger, Hayley Zimny, Rosmel Hernandez, Matthew Beier, Dacia Dimartino, Peter Meyn, Kalina Rice, Shanmugapriya Selvaraj, Cynthia Loomis, Adriana Heguy, Amanda W. Lund, Hannah Carter, Rosalie C. Sears, Theodore H. Welling, Igor Dolgalev, Aristotelis Tsirigos, Diane M. Simeone. Clonal Heterogeneity in Human Pancreatic Ductal Adenocarcinoma and Its Impact on Tumor Progression [abstract]. In: Proceedings of the AACR Conference on Pancreatic Cancer: New Frontiers in Biology and Therapeutic Development; 2026 Sep 25-28; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(18_Suppl_2): nr PR015.