Adhesion- and migration-related side effects of phosphothioated CpG oligodeoxynucleotides.

Nucleic acid oligodeoxynucleotides (ODN) are increasingly used in biological research and in clinics where they are used for both diagnostic and therapeutic purposes. In order to increase the stability and efficacy of ODNs, various chemical modifications have been applied to create nucleic acid derivatives that are not recognized by endogenous nucleic acid cleavage mechanisms. One of the most common and cost-effective modifications is the phosphothioate (PTO) modification. The PTO modification is implemented mainly in antisense ODN, but also in ODN that were shown to activate members of the toll-like receptor (TLR) family such as TLR3 (poly-I:C), TLR8 (ssRNA) and TLR9 (CpG). We recently found that PTO-ODN aimed at activating TLR9 induce a non-TLR9-specific detachment phenotype in a growth-substrate dependent manner. Moreover, we found that unmodified and PTO-modified TLR ligands induce distinct patterns of gene expression in cultured neural cells. These findings suggest that PTO-ODN can cause nonspecific effects on cell adhesion that could compromise interpretation of data from experiments using PTO-ODN.