engleski

The miR-200c/TUBB3 Regulatory Axis is Part of the Cellular Stress Response to Carboplatin in Drug- resistant Ovarian Cancer Cell Lines

Acquired drug resistance remains a major problem for successful chemotherapy, contributing to poor long-term prognosis of ovarian cancer (OC) patients. The combination of platinum drugs and taxanes is commonly used to treat patients with OC, due to their different modes of action. Despite the positive initial response to chemotherapy, up to 80% of OC patients will eventually relapse, and become platinum/taxane unresponsive. Moreover, cross-resistance occurs in almost 30% of OC cases. We established two OC cell line models, i.e., MES-OV CBP and SK-OV-3 CBP characterized by clinically relevant acquired resistance to carboplatin (CBP), a mesenchymal- like phenotype, CBP-induced class III β-tubulin (TUBB3) overexpression, and different responsiveness to paclitaxel (TAX) treatment. We showed previously that despite increased TUBB3 protein expression in both CBP resistant variants only MES-OV CBP cells are sensitized to CBP upon TUBB3 silencing. The lack of compensation phenomena with other β-tubulin isotypes noticed in SK-OV-3 CBP, but absent in MES-OV CBP cell line, underlined that pan TUBB should be considered together with TUBB3 for the prediction of treatment efficacy. We noticed further that the presence of compensation phenomena correlated with the expression pattern of miRNA-200 family members, known regulators of TUBB3 expression. We focused on the miR-200c that is predominantly investigated in the context of drug resistance and epithelial-mesenchymal transition. We showed that in MES-OV CBP cells, long-term exposure to CBP induced stable miR-200c downregulation via alterations in epigenetic regulation, and consequently led to the upregulation of TUBB3. Transient transfection of MES-OV CBP cells with mimic miR-200c sensitized them to CBP, while transduction of MES-OV cells with lentiviral particles carrying miR-200c inhibitor rendered them less sensitive to CBP and TAX as well. Most importantly, decreased constitutive expression of miR-200c in MES-OV cells was accompanied by elevated expression of TUBB3 and TUBB. This finding shows for the first time that the miR- 200c/TUBB3 axis is part of the cellular stress response to CBP.

carboplatin resistance ; ovarian cancer ; paclitaxel ; tubulin ; cellular trafficking

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