A variety of approaches have been employed in order to identify novel genetic causes of RCC including the mapping and characterisation of RCC-associated constitutional translocations and genetic association studies. The released IFNs can subsequently activate IFN-stimulated genes, resulting in cellular gene expression profile changes that may contribute to adverse sideeffects such as global degradation of mRNA, inhibition of general protein translation or cell death. Moreover, long-term and high-level shRNA expression can result in oversaturation of the endogenous cellular microRNA pathways leading to cytotoxicity and eventually fatality, as reported previously. The amiRNAs represent a type of shRNAs in which a siRNA sequence is embedded into a native microRNA scaffold, most commonly into that of miR-30 or miR-155. In contrast to shRNAs, amiRs are expressed from polymerase II promoters and are processed consecutively into functionally active siRNAs via the nuclear class 2 RNase III enzyme Drosha and the cytoplasmic endoribonuclease Dicer. Several studies have compared shRNAs and amiRs Tris(2-carboxyethyl)phosphine hydrochloride regarding their efficiency and safety. The general trend of these studies is that amiRs substantially reduce the toxicity observed for the shRNAs of the same constructs. The efficiency of gene silencing mediated by amiRNAs has been reported to be higher, comparable or lower in comparison to shRNAs. We demonstrated the first successful treatment of experimental heart failure by RNAi in vivo. An AAV9 vector and adenoviral vector-mediated cardiac expression of rat PLB-specific shRNA resulted in strong cardiac down-regulation of PLB. This led to restoration of the compromised left ventricular contractile function. It also significantly reduced cardiac dilatation, hypertrophy, cardiomyocyte Anlotinib Dihydrochloride diameter and cardiac fibrosis. Importantly, no adverse side effects were observed using this shPLBr gene therapeutic approach in rats. More recently, however, Bish et al. evaluated the efficiency and safety of an adapted shPLB in healthy dogs. They found that AAV6 vector-mediated cardiac shPLB delivery to these animals resulted in the strong knockdown of PLB, accompanied by severe cardiac toxicity. Here, we show that scAAV6-amiR155-PLBr, which expresses a newly engineered small regulatory RNA directed against the negative SERCA2a modulatory protein PLB, improves the SERCA2a-catalyzed Ca2+ transport activity of the SR in CM. The efficiency of scAAV6-amiR155-PLBr was as high as that of an AAV6 vector expressing the conventional shPLBr that was previously used for PLB silencing. Importantly, our data reveal that scAAV6-amiR155-PLBr exhibits an improved cardiac safety compared to the shPLBr-expressing vector. In a previous study, we demonstrated the therapeutic efficacy of shPLBr in a rat heart failure model using AAV9 vectors for cardiac delivery. No negative side effects were detected in this study. Severe cardiac toxicity, however, was observed in healthy canines after AAV6 vector-mediated delivery of shPLB. Reducing the expression of the shRNA by decreasing the vector dose or the use of weaker promoters are potential ways to prevent shRNAinduced side effects. This procedure, however, is not always successful and shRNAs can remain toxic, even when shRNA levels are reduced. Thus, reduction of shRNA toxicity might come at the price of loss of therapeutic efficiency.