Project summary Radiation therapy is an important component of cancer treatments, yet its usage has been hampered due to side effects to normal tissue. The current K99/R00 project seeks to investigate the molecular landscape of radiation induced coronary heart disease (RICHD), a leading cause of morbidity and mortality among cancer survivors. The complex nature of RICHD necessitates a comprehensive understanding of patient-specific risk factors and underlying genetic variations. Focusing on the pivotal role of endothelial to mesenchymal transition (EndMT) and its correlation with variations in p53 signaling due to TP53 mutations, I will utilize human-induced pluripotent stem cells (iPSCs) from cancer patients with TP53 mutations and transgenic mouse models in the mentored K99 phase. In my first aim, I will utilize 3D vessel-on-a-chip model (VoC) lined with iPSC-derived endothelial cells and smooth muscle cells from cancer patients with or without TP53 mutations for longitudinal endothelial lineage tracing analysis with vascular functional assays after exposure to 2 Gy of X-rays radiation. In my second aim, I will generate a novel endothelial lineage tracing mouse model with TP53 mutations and elucidate the functional and molecular alterations after exposure to 20 Gy of X-rays radiation on the heart. Both projects employ in-depth single cell RNA-sequencing (scRNA-seq) analysis to map the gene regulatory networks perturbations across different cell-types at varied time points post-irradiation. This project will be guided by an advisory committee constituted of researchers bringing their distinct expertise: Joseph Wu (Precision Medicine), Laura Attardi (TP53 Biology), Sharon Gerecht (Vascular Engineering), Billy Loo (Radiation Oncology), Kristy Red-Horse (Lineage Tracing), Michael Snyder (Integrative Omics Analysis). The training received under this mentorship will equip me with invaluable expertise in tissue engineering, lineage tracing and scRNA-seq analysis. Ultimately, this will foster my transition to the independent phase (R00), where I aim to establish genotype-phenotype correlations for RICHD in iPSC-derivatives. Functional radiogenomics on vascular cells will provide novel insights and a roadmap for stratifying TP53 mutations in RICHD offering a significant advancement for cancer patients undergoing radiation therapy.