siRNA-mediated integrin-linked kinase suppression: nonspecific effects of siRNA/cationic liposome complexes trigger changes in the expression of phosphorylated-AKT and mTOR independently of ILK silencing.

Short interfering RNA targeting ILK (ILK siRNA) could be used to treat patients with cancers where constitutive activation of the AKT/PI3K pathway is prominent (e.g., those cancers lack functional PTEN). It is generally believed that siRNA therapeutics will require the use of delivery systems and lipid-based formulations containing cationic lipids (CLs) are a viable option. However, CLs are known to be toxic and exposure to CLs can influence cell survival pathways. This study characterized how CLs combine with ILK siRNA to influence the AKT/PI3K pathway. Using PTEN-negative cell lines (PC3 castration-insensitive prostate cancer cells and U251 glioma cancer cells), the influence of CLs on the downstream consequences of ILK silencing was determined. When comparing nucleofection (an electroporation method that does not require the use of CLs) and CLs as means to deliver ILK siRNA, a 12- to 30-fold increase in siRNA delivery was achieved when using a CL formulation, yet ILK suppression was less efficient. Importantly, time-dependent signaling consequences associated with ILK silencing, including suppression of phosphorylated (serine 473)-AKT and changes in mTOR expression, were observed independently of ILK suppression when the target cells were exposed to cationic lipids following nucleofection-based delivery of ILK siRNA.