TXMicroRNAs (miRNAs) regulate mRNA stability and protein expression, and certain miRNAs have been demonstrated to act either as oncogenes or tumor suppressors. Differential miRNA expression signatures have been documented in many human cancers but the role of miRNAs in endometrioid endometrial cancer (EEC) remains poorly understood. This study identifies significantly dysregulated miRNAs of EEC cells, and characterizes their impact on the malignant phenotype. We studied the expression of 365 human miRNAs using Taqman low density arrays in EECs and normal endometriums. Candidate differentially expressed miRNAs were validated by quantitative real-time PCR. Expression of highly dysregulated miRNAs was examined in vitro through the effect of anti-/pre-miRNA transfection on the malignant phenotype. We identified 16 significantly dysregulated miRNAs in EEC and 7 of these are novel findings with respect to EEC. Antagonizing the function of miR-7, miR-194 and miR-449b, or overexpressing miR-204, repressed migration, invasion and extracellular matrix-adhesion in HEC1A endometrial cancer cells. FOXC1 was determined as a target gene of miR-204, and two binding sites in the 3 0 -untranslated region were validated by dual luciferase reporter assay. FOXC1 expression was inversely related to miR-204 expression in EEC. Functional analysis revealed the involvement of FOXC1 in migration and invasion of HEC1A cells. Our results present dysfunctional miRNAs in endometrial cancer and identify a crucial role for miR-204-FOXC1 interaction in endometrial cancer progression. This miRNA signature offers a potential biomarker for predicting EEC outcomes, and targeting of these cancer progression-and metastasis-related miRNAs offers a novel potential therapeutic strategy for the disease.Endometrial cancer is a common cause of gynecological cancer death. The most dominant subtype, endometrioid endometrial cancer (EEC), accounts for >80% of this cancer. Menopause and unopposed estrogenic stimulation are typical risk factors. Patients are generally treated with surgery, radiation, chemotherapy or hormone therapy. Patients with early stage disease have 5-year survival rates over 80%, however, about 15-20% develop metastasis. 1 These patients and those with advanced stage disease or recurrence have poor prognosis due to limitation of effective treatment. 2 Understanding the pathogenesis of this disease may provide insights for the development of novel therapeutic strategies.MicroRNAs (miRNAs) are small noncoding RNA molecules of 19-24 nucleotides that regulate gene expression posttranscriptionally through imperfect base pairing with the 3 0 -untranslated region (3 0 UTR) of target mRNAs, causing transcript degradation and translational inhibition. 3 Approximately 20-30% of all genes are targeted by miRNAs and a single miRNA may target as many as 200 genes. 4 In human cancers, >50% of the miRNA genes are located in chromosomal fragile sites, minimal regions containing loss of heterozygosity, minimal amplicons or common breakpoint regions. 5 DNA ...