Abstract 4827: Lymphatic vasculature as a non-genetic driver of tumorigenesis

Abstract Harboring genetic mutations with oncogenic potential is common, yet not everyone develops cancer. This suggests that non-genetic factors contribute to tumor initiation and progression. In epithelial cancers such as squamous cell carcinoma (SCC), stem cells exhibit plasticity, transforming from an epithelial to a mesenchymal identity through the epithelial-to-mesenchymal transition, a process linked to metastasis. The lymphatic vasculature, known for fluid balance and immune trafficking, also supports the stem cell niche. Given this dynamic, we hypothesized that lymphatic vessels may represent a non-genetic element that drives cancer progression by altering stem cell behavior. To characterize lymphatic arrangement in benign versus advanced tumors, we performed high resolution 3D whole-mount immunofluorescence imaging on optically cleared benign papillomas and progressed skin SCCs. Compared to papillomas, advanced SCCs exhibited greater lymphatic association and integration. Spatial transcriptomics showed that regions enriched for lymphatic signals aligned with domains expressing hybrid epithelial-mesenchymal states in SCCs, suggesting that lymphatic positioning helps define the spatial architecture of these transitional tumor states. To test whether lymphatic vessels are required for tumor progression, we used both chemical and genetic (SOX9-CreER; Krasmut; p53fl/fl; YFPfl/fl) mouse models of skin SCC. Tumors subjected to local lymphatic dysfunction stabilized or regressed in size, while matched controls continued to progress. Immunofluorescence revealed increased epithelial identity and reduced mesenchymal identity in regressing tumors, consistent with a shift toward a more epithelial and therapeutically responsive state. These findings suggest that lymphatic cues shape the regulatory programs governing tumor cell evolution. To define these programs, we profiled papillomas and SCCs using single cell RNA sequencing. The analyses resolved distinct epithelial, hybrid, and mesenchymal states. The hybrid state emerged as a key transition point, marked by selective induction of a secreted factor with a pro-lymphatic signature, suggesting a potential role in linking lymphatic cues to tumor cell evolution and malignant progression. Using a fluorescent lentiviral reporter, we confirmed that the secreted cue becomes highly expressed in advanced tumors in vivo. Functionally, silencing the pro-lymphatic cue in tumors derived from tumor-initiating cells slowed progression, demonstrating its active role in driving tumorigenesis. Together, these findings reveal that lymphatic interactions with tumor-initiating cells form a central regulatory axis in SCC, positioning the lymphatic vasculature as a promising therapeutic entry point to restrain malignant progression. Citation Format: Celeste K. Kanne, Jeremy Horrell, Hodaya Knafo, Savannah Martin, Aditya Verma, Ananya Goyal, Madison Conte, Shiri Gur-Cohen. Lymphatic vasculature as a non-genetic driver of tumorigenesis abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4827.