The hypothesis that miRNAs could be involved in the modulation of P-gp expression is supported by suggestive evidence: (i) miR-27a and miR-451 induce an increased P-gp expression in ovarian cancer cells [9,14], (ii) miR-451 also down-regulates MDR1 expression in MCF7/DOX-resistant cells [9]; (iii) changes in miR-381 and miR-495 expression are inversely correlated to MDR1 expression and the development of MDR [19]. The gene discussed is PGP; the disease is ovarian carcinoma.