Induction of DISE in ovarian cancer cells in vivo

Abstract

The death receptor CD95/Fas can be activated by immune cells to kill cancer cells. shRNAs and siRNAs derived from CD95 or CD95 ligand (CD95L) are highly toxic to most cancer cells. We recently found that these sh/siRNAs kill cancer cells in the absence of the target by targeting the 3’UTRs of critical survival genes through canonical RNAi. We have named this unique form of off-target effect DISE (for death induced by survival gene elimination). DISE preferentially kills transformed cells and cancer stem cells. We demonstrate that DISE induction occurs in cancer cells in vivo after introducing a lentiviral CD95L derived shRNA (shL3) into HeyA8 ovarian cancer cells grown as i.p. xenografts in mice, when compared to a scrambled shRNA. To demonstrate the possibility of therapeutically inducing DISE, we coupled siRNAs to templated lipoprotein nanoparticles (TLP). In vitro, TLPs loaded with a CD95L derived siRNA (siL3) selectively silenced a biosensor comprised of Venus and CD95L ORF and killed ovarian cancer cells. In vivo, two siRNA-TLPs (siL2-TLP and siL3-TLP) reduced tumor growth similarly as observed for cells expressing the shL3 vector. These data suggest that it is possible to kill ovarian cancer cells in vivo via DISE induction using siRNA-TLPs.

6mer seed toxicity in tumor suppressive microRNAs

“…In humans, miR-34a is highly expressed in many tissues. Consistent with our data that delivering siRNAs with toxic 6mer seeds to mice are not toxic to normal cells 21 miR-34a exhibits low toxicity to normal cells in vitro and in vivo 47 . miR-34a (MRX34) became the first miRNA to be tested in a phase I clinical trial of unresectable primary liver cancer 27 , 48 .…”

“…We called this mechanism DISE (for death induced by SG elimination). Cancer cells have difficulty in developing resistance to this mechanism both in vitro and when treated in vivo 21 . We reported that a 6mer seed sequence in the toxic siRNAs is sufficient for effective killing 20 .…”

Trinucleotide Repeat Expansion Diseases, RNAi, and Cancer

“…This suggests that cancer cells are more sensitive to this form of cell death than normal cells, possibly because normal cells are protected from RNAi-mediated toxicity by miRNAs which are more highly expressed in normal cells than in cancer cells [121]. This interpretation is also supported by our data demonstrating that toxic siRNA derived from the gene FASLG when delivered in vivo affected cancer cells without toxicity to normal cells [122]. Mechanistically we showed that titering in a non toxic siRNA ameliorated toxicity of such a toxic siRNA to cancer cells [123] and as a reverse we demonstrated that when most miRNAs were eliminated by knocking out Drosha or Dicer, cells became hypersensitive to any toxic siRNA [97, 124].…”

DISE: A Seed-Dependent RNAi Off-Target Effect That Kills Cancer Cells

“…Due to its fundamental targeting of survival genes it first seemed unlikely that DISE could be developed into a novel form of cancer therapy. However, we recently demonstrated that DISE can be triggered in vivo by delivering CD95L-derived siRNAs via HDL mimetic bioactive nanoparticles to treat ovarian cancer in mouse xenografts [61]. The CD95L derived siRNA used in our study could also kill a mouse cancer cell line, yet the treatment had no toxic effect on the mice, suggesting that DISE preferentially affects cancer cells.…”