PROJECT SUMMARY The remarkable female bias in the prevalence of meningiomas, with a peak ratio exceeding 3:1 in patients 35-44 years of age and decreasing thereafter, is largely unexplained. Published clinical evidence strongly supports a relationship between meningioma and sex hormones; however, the mechanism is unknown. The majority of hormone receptor expression studies were conducted decades before the recent genetic characterization of meningiomas, which have now been classified into five “genomic subgroups” that cluster by gene expression and anatomical location. These genomic subgroups are characterized by mutually exclusive somatic coding driver mutations in 7 genes (AKT1, KLF4, POLR2A, TRAF7, PI3KCA, SMARCB1, and SMO), which, in addition to the previously established most prevalent driver, the loss of NF2, account for >80% of all meningiomas. Although, all meningiomas show a female predominance, correlated clinical data of over 2,500 meningiomas from our genetically characterized cohort identified that two subgroups in particular, KLF4 and POLR2A, independently show a disproportionately greater predominance in females. Understanding whether the subgroup mutation results in distinct physiological response to sex hormones may provide insight into the failed clinical trials of tamoxifen (phase II) and mifepristone (phase III), which showed either an agonistic or non-significant tumor responsiveness, respectively, in meningiomas. Unfortunately, neither trial rigorously assessed sex-hormone receptor or genomic mutation status. I hypothesize that meningioma driver mutations directly modulate the sex-hormone signaling network to alter gene expression in a manner that is favorable to meningioma growth, by a mechanism that differs predictably between tumors of different subgroups. Based on my preliminary evidence demonstrating: (1) expression of the estrogen receptor (ER) and G protein-coupled estrogen receptor (GPER1) proteins in meningiomas and variable expression of sex-hormone receptor proteins across subgroups; (2) biphasic growth response of human meninges to estrogen, regardless of sex; (3) changes in cell viability as well as estrogen-response element transactivation upon hormonal and anti-hormonal exposure, conferred by the recurrent mutations POLR2AQ403K (accounting for > 85% of all mutations in this gene), KLF4K409Q, and NF2KO, as assessed by luciferase reporter assay compared with normal meninges and with each other; and (4) enrichment of estrogen signaling by proliferating POLR2AQ403K primary cells. To my knowledge, an integrated genomic study classifying sex-hormone receptor transcriptional activation and influence on chromatin conformation has not previously been undertaken in meningiomas. I will address my hypothesis by two aims: Specific Aim 1: Investigate the relationship between meningioma genomic subgroups and sex-hormone receptor status by creating a Tumor Tissue Microarray (constructed by Yale Pathology) and assessing rec...