PROJECT SUMMARY/ABSTRACTCushings disease (CD) is a serious endocrine disorder characterized by an adrenocorticotropic hormone(ACTH)-secreting PitNET that subsequently stimulates the adrenal glands to overproduce cortisol. Chronicexposure to excess cortisol has wide ranging and detrimental effects on health including increased stroke ratesdiabetes obesity depression anxiety and death. Although CD is linked to a threefold increase in the risk ofdeath the advancement of current standard of care medical therapy is lacking. Current treatments exhibit lowefficacy and tolerability for patients. The absence of preclinical models that replicate the complexity of theadenoma tissue has prevented us from developing effective therapies that are targeted to the tumor directly. Thefirst-line treatment for CD is pituitary surgery. In the hands of an experienced surgeon tumor recurrence occursin as many as 30% to 50% of patients during the 10-year follow-up period. Despite multiple treatmentsbiochemical control is not achieved in approximately 50% of patients suggesting that in routine clinical practiceinitial and long-term disease remission is not achieved in a substantial number of CD patients . Hence medicaltherapy is often considered in the following situations: when surgery is contraindicated or fails to achieveremission or when recurrence occurs after apparent surgical remission. While stereotactic radiosurgery treatsincompletely resected or recurrent PitNETs the main drawbacks include the longer time to remission and therisk of hypopituitarism. There is an inverse relationship between disease duration and reversibility ofcomplications associated with CD thus emphasizing the importance of targeting the pituitary adenoma early.The primary barrier to developing new medical therapies is the lack of human relevant advanced in vitro tumormodels. Pituitary cell lines do not reproduce the multicellular complexity of PitNETs. In this instance the overallobjective is to develop PitNET organoids to advance our understanding of the pathogenesis and treatment ofpituitary tumors in CD patients. The overall goal will be successfully achieved by collaborative efforts betweenthe University of Arizona (UA) and Barrow Neurological Institute (BNI) that will leverage the expertise ofprofessionals trained in complimentary fields including surgical treatments pathology and cell biology of pituitarydisease organoid technology and high throughput data analysis including dug screening molecular profilingand transcriptomics. This led us to develop Specific Aims: 1) To use human PitNET derived organoids to definethe molecular signatures of corticotroph tumor subtypes in CD and 2) To use the pituitary tumor organoids as apreclinical model to accelerate targeted therapies for patients with CD. At the completion of the funding periodwe will be positioned to implement patient-relevant organoids to accelerate the development of therapies thatwill effectively target ACTH-secreting pituitary adenomas in patients with CD.