PROJECT SUMMARY/ABSTRACT Chronic musculoskeletal pain (MSKP) is a significant problem in many women with hormone receptor- positive early stage breast cancer receiving treatment designed to prevent cancer recurrence by blocking estrogen production via systemic inhibition of the aromatase enzyme. MSKP interferes with functional status, adherence to therapy, and increases utilization of health care resources. Unfortunately, very little is known about the molecular mechanisms underlying MSKP related to a decline in estrogen in women with breast cancer. Evidence supports that dysregulation of adrenergic function is present in women with MSKP. In fact, both ?-antagonists and ?2-agonists have been investigated as treatment for MSKP pain disorders, and evidence from our group as well as others support a role for pain inhibition via ?1-antagonists. The purpose of this K99R00 proposal is to provide the applicant with the necessary training and research experience to examine the dynamic RNA transcriptome and DNA methylome to identify genes and biological pathways that are involved in development of cancer pain. The purpose of the proposed K99 study is to generate knowledge about MSKP development within the context of declining estrogen in women with breast cancer. The K99 phase of this project capitalizes on data and blood samples generated through an ongoing project that recruits postmenopausal women newly diagnosed with early stage breast cancer who will receive aromatase inhibitor therapy (R01CA196762, the EPICC study). The K99 also benefits from an ongoing project generating DNA methylation data from blood samples of the women in the EPICC study (R01CA221882). The specific research aims for the K99 study are to (1) test the hypothesis that 6 months of decreased estrogen leads to changes in gene expression and this is related to changes in the pain phenotype in women with breast cancer; and (2) test the hypothesis that 6 months of decreased estrogen leads to changes in DNA methylation and this is related to changes in the pain phenotype in women with breast cancer. The K99 training plan leverages the superb research-intensive environment and resources at the University of Pittsburgh to ensure the applicant?s development of (a) proficiency in omics (particularly transcriptomics and epigenomics), (b) competency in analysis and bioinformatics of omics data, (c) proficiency in pain mechanisms, and (d) knowledge and skills for professional career development. The specific aims of the R00 study are to (1) identify changes in the regulation of genes that are associated with variability in cancer pain based on cancer type; (2) identify changes in the regulation of genes that are associated with variability in cancer pain based on cancer therapy; and (3) explore the potential mediating and moderating effects of sex on the relationship between gene regulation and pain. This research generates the knowledge needed to develop a research program focusing on developing a profile for predicting individuals at risk for chronic pain development that includes demographic, clinical, and omics data.