Bladder Cancer (CaB) is the fourth most common type of cancer in men, with an index lower than only prostate, lung and bronchial cancer. In Brazil, according to the National Cancer Institute (INCA), for the year 2020, 7,590 new cases in men and 3,050 in women were estimated. The main risk factor is smoking, followed by occupational exposure to amines and organic substances. The most common symptom is painless hematuria and the treatment of CaB depends on its form of presentation, mainly on the histological type, staging and degree. In muscle-invasive tumors, the gold standard of therapy is radical cystectomy associated with pelvic lymphadenectomy, which results in a significant impact on patients' quality of life. In recent years, abnormalities in the expression of microRNAs (miRNAs) have been identified in the progression of various types of cancers and, consequently, have been proposed as potential targets for antitumor therapies. MiR-21 is highly expressed in many tumor types and is associated with the promotion of cell invasion, through direct control of the RECK protein, which is a metalloproteinase (MMP) inhibitor, including MMP-9. This protein has the ability to degrade a wide variety of proteins in the membrane and the extracellular environment, facilitating tumor invasion and angiogenesis. In CaB there is a strong expression of this protein mainly in high grade invasive tumors. The literature does not answer what would be the effect of miR-21 block on MMP9 in this neoplasm. Thus, the present project aims to block the expression of miR-21, in order to increase the expression of RECK, and consequently decrease the expression of MMP9 in the CaB cell line, T24. We will also assess whether the inhibition of miR-21 and the consequent decrease in MMP-9 is capable of reducing migration and the rate of proliferation in this cell line. Methods: For carrying out the experiments, the high-grade CaB cell line T24 (transitional cell carcinoma) will be used. To inhibit miR-21 expression, we will perform transfection with the miR-21 inhibitor. After cell transfection, gene expression analyzes of mir-21, RECK and MMP9 will be performed by real-time PCR. We will also assess the potential for migration and proliferation of cells transfected with the miR-21 inhibitor by wound healing and colony formation assays, respectively.
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