Abstract LB199: High-plex spatial transcriptomics reveals triplatin-induced DNA damage signaling and tumor-fibroblast niche reprogramming in pancreatic cancer PDX models

Abstract Background: With an estimated 67, 440 cases anticipated in 2025, the fight against Pancreatic ductal adenocarcinoma (PDAC) is still challenging. PDAC is characterized by an extensive desmoplastic stroma rich in glycosaminoglycans (GAGs) that hinders chemotherapy and promotes resistance. Triplatin, a polynuclear platinum compound, exhibits a robust affinity for glycosaminoglycans (GAGs), synthesized by cancer-associated fibroblasts (CAFs). This feature indicates that Triplatin may selectively concentrate in fibroblast-dense areas, hence augmenting platinum-DNA adduct formation and activating DNA damage response pathways in specific tumor cell types. Methods: Study utilized Xenium 5k high-plex spatial transcriptomics on 20 tissue microarray cores obtained from two pancreatic patient-derived xenograft (PDX) models subjected to vehicle, Triplatin, or Oxaliplatin treatment. Approximately 257, 000 cells were analyzed at single-cell resolution across approximately 5, 000 genes. Tumor cells were categorized according to their spatial profile to fibroblasts, facilitating differential gene expression analysis under various treatment settings. Quantitative analysis of spatial cell-type proportions and tumor-stromal interaction networks was conducted to elucidate niche-specific treatment responses. Results: Triplatin showed unique spatially localized transcriptional program in tumor cells close to fibroblasts, which resulted in a significant improvement in overall survival compared to oxaliplatin. There was an increase in the activation of DNA damage and replication stress pathways in the tumor. These pathways include ATM/ATR signaling, CHK1/CHK2 checkpoint activation, p53-mediated stress responses, and homologous recombination and nucleotide excision repair. Triplatin was shown to selectively affect communication networks between tumors and fibroblasts, thereby changing the distribution of tumor cells in CAF-rich regions and disrupting stromal niches that are associated with drug tolerance. A Triplatin-specific mechanism linked with stromal contact rather than wide platinum cytotoxicity was proposed by the fact that the effects were greatly attenuated or nonexistent in tumors treated with Oxaliplatin. Conclusion: This study shows that Triplatin causes spatially limited DNA damage and transcriptional reprogramming in tumor cells by taking advantage of the GAG-rich, fibroblast-dense PDAC stroma. In ways not possible with traditional platinum treatments, triplatin reconfigures the functional architecture of the tumor microenvironment by modifying tumor-fibroblast closeness and remodeling intercellular communication networks. These results offer crucial mechanistic understanding of how to use stromal targeting and spatial drug retention to combat chemoresistance in pancreatic cancer. Citation Format: Praveen Bhoopathi, Khoa L. Huynh, Erica J. Peterson, Vashti Bandy, Anna Gibson, Vignesh Vudatha, Arunima Punjala, Dongyu Zhang, Jinze Liu, J Chuck Harrell, Nicholas P. Farrell, Jose G. Trevino. High-plex spatial transcriptomics reveals triplatin-induced DNA damage signaling and tumor-fibroblast niche reprogramming in pancreatic cancer PDX models abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86 (8Suppl): Abstract nr LB199.