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Abstract The orphan nuclear receptor DAX-1 (Dosage Sensitive Sex Reversal, Adrenal Hypoplasia Congenita, critical region on the X chromosome, gene 1) plays a key role in sex determination and the synthesis of steroid hormones. In addition to these canonical examples, DAX-1 has been shown to play a contradictory role in cancer development. While DAX-1 is overexpressed in some types of cancer, it is completely absent or downregulated in several other cancers such as prostate and breast. One of the explanations for the paradoxical role of DAX-1 in cancer development could be microRNAs (miRNAs). Recent research has demonstrated that the dysregulated expression of these short non-coding RNAs increases the proliferative and anti-apoptotic capabilities of cancer cells. After broadly surveying over 180 miRNAs historically upregulated in MCF7 cells, we compared the activity of DAX-1 in MCF7 breast cancer cells and MCF10a normal breast epithelial cells with the presence of specific miRNA inhibitors. Our primary hypothesis remains that multiple miRNAs negatively regulate the expression of DAX-1 in human breast cancer cells and are not overexpressed in normal breast cells, providing another mechanism of lifting the repression of DAX-1 expression. Quantitative PCR and western blot analysis was performed indicating that inhibiting miRNAs 29c, 199a, and 424 significantly upregulate DAX-1 expression in MCF10a cells. We examined the invasive and metastatic properties of MCF7 cells following inhibition of these specific miRNAs. This research will allow clinicians to screen for additional miRNAs that could be elevated in breast cancer patients substantially increasing the number of people diagnosed with breast cancer early on. In addition, elucidating the pathways of how more and more miRNAs influence downstream targets will offer drug designers novel targets to improve treatment for breast cancer and other cancer patients. Citation Format: Nicholas C. DeVito, Christina Tzagarakis-Foster. Downregulation of DAX-1 expression by miRNA overexpression as a mechanism to potentiate breast cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5687.
DeVito et al. (Fri,) studied this question.