Apoptosis induced by a HIPK2 full-length-specific siRNA is due to off-target effects rather than prevalence of HIPK2-Delta e8 isoform

作者：Di Rocco Giuliana; Verdina Alessandra; Gatti Veronica; Virdia Ilaria; Toietta Gabriele; Todaro Matilde; Stassi Giorgio; Soddu Silvia^*

来源：Oncotarget, 2016, 7(2): 1675-1686.

DOI：10.18632/oncotarget.6423

• HIPK2
• alternative splicing isoforms
• colorectal cancer
• siRNA therapeutic application
• off-target effects

Small interfering RNAs (siRNAs) are widely used to study gene function and extensively exploited for their potential therapeutic applications. HIPK2 is an evolutionary conserved kinase that binds and phosphorylates several proteins directly or indirectly related to apoptosis. Recently, an alternatively spliced isoform skipping 81 nucleotides of exon 8 (Hipk2-Delta e8) has been described. Selective depletion of Hipk2 full-length (Hipk2-FL) with a specific siRNA that spares the Hipk2-Delta e8 isoform has been shown to strongly induce apoptosis, suggesting an unpredicted dominant-negative effect of Hipk2-FL over the Delta e8 isoform. From this observation, we sought to take advantage and assessed the therapeutic potential of generating Hipk2 isoform unbalance in tumor-initiating cells derived from colorectal cancer patients. Strong reduction of cell viability was induced in vitro and in vivo by the originally described exon 8-specific siRNA, supporting a potential therapeutic application. However, validation analyses performed with additional exon8-specific siRNAs with different stabilities showed that all exon8-targeting siRNAs can induce comparable Hipk2 isoform unbalance but only the originally reported e8-siRNA promotes cell death. These data show that loss of viability does not depend on the prevalence of Hipk2-Delta e8 isoform but it is rather due to microRNA-like off-target effects.

• 出版日期2016-1-12