Because miR-34a can affect p53 expression by multiple mechanisms, we investigated the effect of miR-34a overexpression on p53 levels in a panel of tumor lines of different origin (MCF7 and MDA-MB-231 breast carcinomas, RKO and SW480 colorectal carcinomas, HepG2 hepatocellular carcinoma and LN229 glioblastoma). The gene discussed is TP53; the disease is neoplasm.