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Desmosomes are cellular structures that are critical in cell-cell adhesion and in maintaining tissue architecture. Changes in the expression of desmocollin-2 (DSC2) have been noted during tumor progression into an invasive phenotype and as cells undergo epithelial-mesenchymal transition. We have previously reported that breast MDA-MB-453 cancer cells, a luminal androgen receptor (AR) model of triple-negative breast cancer, acquire mesenchymal features when treated with the AR agonist, dihydrotestosterone (DHT). We have therefore investigated androgen regulation of the expression and cellular localization of DSC2 in MDA-MB-453 cells. Treatment of the cells with DHT resulted in a dose-dependent reduction in DSC2 protein levels and dispersion of its membrane localization concomitant with AR-and β-cateninmediated mesenchymal transition of cells. A significant correlation was revealed between decreased expression of AR and increased expression of DSC2 in patient samples. In addition, whereas lower expression of AR was associated with a reduced overall and recurrence-free survival of breast cancer patients, higher expression of DSC2 was found in invasive breast tumors than in normal breast cells and was correlated with lower patient survival. Upon knocking down DSC2, the cells became elongated, mesenchymal-like, and slightly, but insignificantly, more migratory. The addition of DHT further stimulated cell elongation and migration. DSC2 siRNAtransfected cells reverted to a normal epithelial morphology upon inhibition of β-catenin. These results highlight the role of DSC2 in maintaining the epithelial morphology of MDA-MB-453 cells and the negative regulation of the desmosomal protein by DHT during stimulation of the androgen-induced, β-catenin-mediated mesenchymal transition of the cells.

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Epithelial-mesenchymal transition (EMT) of tumor cells is prerequisite to cancer cell invasion and metastasis. This process involves an intricate molecular network. Androgen receptor (AR) appears to play an important role in the biology of breast cancers, particularly those dependent on AR expression such as luminal AR (LAR) breast cancer subtype. We and others have previously shown that treatment of LAR breast MDA-MB-453 cancer cells with dihydrotestosterone (DHT) induces a mesenchymal phenotype via AR. In this study, the cellular and molecular dynamics of DHT-induced EMT in MDA-MB-453 cells were investigated. A plethora of techniques were used including PCR arrays, immunoblotting, immunoprecipitation, immunofluorescence, cell fractionation, and siRNA transfection. Change of cell morphology was concomitant with increased cell migration after treating cells with DHT. Exposure of cells to DHT for one hour was sufficient to induce changes in cell morphology and actin cytoskeleton after 72 hours indicating altered gene expression. Investigating changes in the expression of 84 EMT-related genes revealed induced expression of the transcription factor Slug and down-expression of the desmosomal DSC2, but, surprisingly DHT also reduced levels of pro-EMT β-catenin, N-cadherin, and TCF-4, and increased expression of anti-EMT RGS2, all of which were confirmed at the protein level. Not only early interaction of AR and β-catenin was observed following AR activation, inhibition of β-catenin blocked DHT-induced mesenchymal transition of cells and their migration. Interestingly, inhibition of AR prevented mesenchymal transition of cells by activation of β-catenin suggesting reciprocal requirement of both molecules. Activation of AR also resulted in its nuclear translocation and interaction with Slug. Knocking down Slug blocked DHT-induced cellular changes and also reduced basal, but not DHT-induced, cell migration indicating that mesenchymal transition of these cells and their migration are independent processes. Furthermore, not only activation of AR lowered expression and altered the pattern of and spatial intracellular localization of DSC2, the decrease in DSC2 levels was sufficient to induce EMT-like features in a β-catenin-dependent, but AR-independent manner. Expression of DSC2 was under the negative regulation of Slug. Shortly after AR activation, AR-RGS2 interaction increased concomitant with a significant increase of RGS2 protein without a change in its cellular localization. Transfection of cells with RGS2 siRNA was sufficient to induce mesenchymal characteristics of cells even in the absence of DHT. Interestingly, this morphological transition was blocked by inhibiting AR. These results indicate that AR modulates a molecular network in inducing partial EMT of MDA-MB-453 cells. Citation Format: Mamoun Ahram, Randa Bawadi, Mohammad Abdullah, Dana Alsafadi, Shahd Arqam. Activation of androgen receptor induces partial epithelial-mesenchymal transition of breast MDA-MB-453 cancer cells: Alterations of a molecular network [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB242.