Project Summary Title: Tracing and targeting the epigenetic heterogeneity in breast cancer metastasis. Metastasis is major cause of cancer-related death and is the most challenging to treat. Besides the well-studied genomic mutations in cancer, our understanding of non-genomic alterations remains limited. The proposed approach is to dissect the mechanisms of non-genomic intra-metastasis heterogeneity in breast cancer. Recently, we demonstrated that osteoblasts (bone forming cells) promote a global alteration of chromatin organization which associates with increased stemness, epithelial to mesenchymal transition, and overexpression of multiple receptor tyrosine kinases included FGFR1 and PDGFRβ. Ultimately, estrogen signaling was inhibited while endocrine resistance was increased. Mechanistically, we identified FGF2/PDBFβ/ EZH2 axis as a novel regulator of epigenetic reprogramming in breast cancer bone metastasis. However, several outstanding questions remained unanswered: (i) what mechanisms drive phenotypic variations between neighboring cells in bone metastasis, (ii) are epigenetic traits inheritable during metastasis progression, and (ii) if yes, how do they influence therapeutic response? In this project, our goal is to understand the mechanisms of intra-tumor heterogeneity in bone metastases and determine how epigenetic heterogeneity affects therapeutic response beyond the genetic heterogeneity that has been extensively studied. We aim to trace and dissect the epigenetic intra-tumor heterogeneity (eITH) using a cutting-edge barcoding strategy (K99 phase), identify epigenetic modulators by integrating single cell multi-omics (K99-R00 phase), test new therapeutic approaches and eventually expand our findings to other breast cancer metastasis sites (R00 phase) including lung, liver, and brain. Baylor College of Medicine (BCM) is an internationally renowned institution for breast cancer research, which gives me the opportunity to closely interact, exchange ideas, and share my findings with leading scientists, clinicians and patient advocates. For my career transition, I assembled a team of senior scientists and experts including my mentor, Professor Xiang H-F Zhang, who is well-established in breast cancer bone metastasis. My co-mentor, Professor Jeffrey Rosen, is a distinguished scientist in mammary gland development and breast cancer modeling. Because of the clinical relevance of the project, I also included Professor C. Kent Osborne, founding director of the Dan L. Duncan Comprehensive Cancer Center (DLDCCC), Professor Matthew J. Ellis, a world-renowned oncologist and director of the Breast Center, Dr. Bora Lim, an expert in aggressive subtypes of breast cancer (e.g. inflammatory breast cancer), Professor Susan G. Hilsenbeck, a distinguished biostatistician, and Dr. Zhandong Liu a computational biologist and statistician with expertise in single cell analysis. Adding the expertise of my advisory team to the rich intellectual resource and cutt...