For example, loss of specific microRNAs may lead to overexpression of well known oncogenes such as Bcl2, Fos, Igf2, Mycn, and Wnt1. Likewise, microRNA overexpression could effectively downregulate tumor suppressors including Brca1, Fhit, Rb1, Trp53, and Wwox. This finding is particularly important given that a common Adeno-Associated Virus (AAV) insertion site in mice has recently been identified that maps between miR-341 and miR-370 in Meg8 that causes hepatocellular carcinomas, suggesting that perturbed expression of microRNAs may be responsible. This evidence concerns the gene RB1 and hepatocellular carcinoma.