The invention relates to the treatment and prevention of cancer by administering agents that inhibit the activity of microRNAs that modulate tumor suppressor genes, which can include PTEN, p53, and INPP4B, among others. Inhibitors can include oligonucleotides that are at least partially complementary to these miRNAs. In some embodiments, these inhibitors are chemically modified oliognucleotides, including locked nucleic acids (LNAs).