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Endometrial cancer (EC) prognosis is dependent on many factors such as time of diagnosis, histological type, and degree of invasion. Type I EC has a more favorable prognosis as it is less prone to myometrial invasion, which is believed to be the first step in the metastatic cascade. Type II EC displays a more aggressive and motile phenotype, and therefore has a poorer prognosis. Recent work suggests that despite the epithelial nature of Type I and Type II endometrial tumors, both are capable of undergoing an epithelial-mesenchymal transition (EMT), which may facilitate myometrial invasion and metastasis. Activation of the PI3K/Akt pathway has been shown to contribute to EMT through the upregulation of EMT-associated factors. Recent research has also linked estrogen signaling and microRNAs to the regulatory mechanisms that drive EMT in EC. Understanding the intricate relationships between these pathways will provide a better understanding of metastatic progression in EC.

During development and the pathogenesis of certain diseases, including cancer, the epithelial-mesenchymal transition (EMT) program is activated. It is hypothesized that EMT plays a major role in tumor invasion and the establishment of distant metastases. Metastatic disease is responsible for the vast majority of cancer-related deaths, which provides a precedent for elucidating pathways that regulate EMT. EMT is defined as the transition of cells with an epithelial phenotype into cells with a mesenchymal phenotype through a series of genetic and environmental events. This leads to the repression of epithelial-associated markers, upregulation of mesenchymal-associated markers, a loss of cell polarity and adhesion, and increased cell motility and invasiveness. EMT is a reversible and dynamic process, and can be regulated by signals from the microenvironment such as inflammation, hypoxia, and growth factors or epigenetically via microRNAs. These signals modulate key EMT-associated transcription factors and effector proteins that control cellular phenotype and regulate tumor plasticity in response to changing conditions in the microenvironment and the progressive nature of cancer. Understanding the complex regulatory networks controlling EMT can provide insight into tumor progression and metastasis.

Breast cancer is the most commonly diagnosed malignancy in women, and has the second highest mortality rate. Over 90% of all cancer-related deaths are due to metastasis, which is the spread of malignant cells from the primary tumor to a secondary site in the body. It is hypothesized that one cause of metastasis involves epithelial-mesenchymal transition (EMT). When epithelial cells undergo EMT and transition into mesenchymal cells, they display increased levels of cell proliferation and invasion, resulting in a more aggressive phenotype. While many factors regulate EMT, microRNAs have been implicated in driving this process. MicroRNAs are short noncoding RNAs that suppress protein production, therefore loss of microRNAs may promote the overexpression of specific target proteins important for EMT. The goal of this study was to investigate the role of miR-96 and miR-183 in EMT in breast cancer. Both miR-96 and miR-183 were found to be downregulated in post-EMT breast cancer cells. When microRNA mimics were transfected into these cells, there was a significant decrease in cell viability and migration, and a shift from a mesenchymal to an epithelial morphology (mesenchymal-epithelial transition or MET). These MET-related changes may be facilitated in part by the regulation of ZEB1 and vimentin, as both of these proteins were downregulated when miR-96 and miR-183 were overexpressed in post-EMT cells. These findings indicate that the loss of miR-96 and miR-183 may help facilitate EMT and contribute to the maintenance of a mesenchymal phenotype. Understanding the role of microRNAs in regulating EMT is significant in order to not only further elucidate the pathways that facilitate metastasis, but also identify potential therapeutic options for preventing or reversing this process.

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