The present invention concerns methods and compositions regarding one or more microRNAs or variants thereof that are provided to an individual for a variety of medical treatments, including sensitization to cancer therapy or prevention of a cancer to become sensitized to a cancer therapy. In specific embodiments, the microRNAs include miR-520a (including at least miR-520a-3p and miR-520-5p), miR-520g, miR-520h, and functional variants thereof. In some embodiments, the cancer is ovarian cancer, and in particular embodiments, the cancer therapy is platinum-based chemotherapy.