Presenting Author:

Andrea Murmann, Ph.D.

Principal Investigator:

Marcus Peter, Ph.D.

Department:

Medicine

Keywords:

RNAi, Fas, ovarian cancer, TLP nanoparticles, cell death, DICE, DISE

Location:

Third Floor, Feinberg Pavilion, Northwestern Memorial Hospital

B52 - Basic Science Women's Health Research

Induction of DISE in Ovarian Cancer Cells in vivo

The death receptor CD95/Fas can be activated by immune cells to kill cancer cells. siRNAs and shRNAs derived from CD95 or CD95 ligand (CD95L) are highly toxic to most cancer cells. Cell death is preceded by an increase in cell size and production of mitochondrial ROS, which is followed by DNA damage. It resembles a necrotic form of mitotic catastrophe. We recently found that CD95L and CD95 derived si- and shRNAs kill cancer cells in the absence of the target through a unique form of a selective off-target effect. These si- and shRNAs preferentially kill transformed cells and cancer stem cells. They act through canonical RNAi by targeting the 3'UTRs of critical survival genes. We have named this form of cell death DISE (for death induced by survival gene elimination). To determine whether DISE induction occurs in cancer cells in the context of a tumor microenvironment, we introduced a lentiviral shRNA (shL3) into HeyA8 ovarian cancer cells, both constitutively and in a Tet inducible vector, and compared their growth in vivo to cells expressing a scrambled shRNA (shScr). When injected i.p. into immune deficient mice, shL3 expressing tumors grew significantly less and histological analysis revealed large areas of necrosis consistent with ongoing cell death. These data confirmed that in vivo induction of DISE is possible. To demonstrate the possibility of therapeutically inducing DISE, we used a siRNA nanoparticle delivery vehicle called templated lipoprotein particles (TLP). In vitro, siRNA-TLPs selectively silenced a biosensor comprised of Venus and CD95L open reading frame and killed ovarian cancer cells. In vivo, two CD95L derived siRNAs were administered to ovarian cancer cells grown as xenografts in mice. The siL2-TLP and siL3-TLP reduced tumor growth to a similar extent as observed for cells expressing the shL3 vector. The data suggest that it is possible to kill ovarian cancer cells in vivo via DISE induction using locally administered siRNA-TLPs.