Modulation of RNA splicing as a potential treatment for cancer

Abstract

Close to 90% of human genes are transcribed into pre-mRNA that undergoes alterative splicing, producing multiple mRNAs and proteins from single genes. This process is largely responsible for human proteome diversity, and about half of genetic disease-causing mutations affect splicing. Splice-switching oligonucleotides (SSOs) comprise an emerging class of antisense therapeutics that modify gene expression by directing pre-mRNA splice site usage. Bauman et al. investigated an SSO that upregulated the expression of an anti-cancer splice variant while simultaneously eliminating an overexpressed cancer-causing splice variant. This was accomplished by targeting pre-mRNA of the apoptotic regulator Bcl-x, which is alternatively spliced to express antiand pro-apoptotic splice variants Bcl-x L and Bcl-x S, respectively. High expression of Bcl-x L is a hallmark of many cancers and is considered a general mechanism used by cancer cells to evade apoptosis. Redirection of Bcl-x pre-mRNA splicing from Bcl-x L to -x S by SSO induced apoptotic and chemosensitizing effects in various cancer cell lines. Importantly, the paper shows that delivery of Bcl-x SSO using a lipid nanoparticle redirected Bcl-x splicing and reduced tumor burden in melanoma lung metastases. This was the first demonstration of SSO efficacy in tumors in vivo. SSOs are not limited to be solely potential anti-cancer drugs. SSOs were first applied to repair aberrant splicing in thalassemia, a genetic disease, they have been used to create novel proteins (e.g., Δe7TNFR1), and they have recently progressed to clinical trials for patients with Duchenne muscular dystrophy. © 2011 Landes Bioscience.