Death Induced by CD95 or CD95 Ligand Elimination

Abstract

SUMMARY CD95 (Fas/APO-1), when bound by its cognate ligand CD95L, induces cells to die by apoptosis. We now show that elimination of CD95 or CD95L results in a form of cell death that is independent of caspase-8, RIPK1/MLKL, and p53, is not inhibited by Bcl-xL expression, and preferentially affects cancer cells. All tumors that formed in mouse models of low-grade serous ovarian cancer or chemically induced liver cancer with tissue specific deletion of CD95 still expressed CD95, suggesting that cancer cannot form in the absence of CD95. Death induced by CD95R/L elimination (DICE) is characterized by an increase in cell size and production of mitochondrial ROS, and DNA damage. It resembles a necrotic form of mitotic catastrophe. No single drug was found to completely block this form of cell death, and it could also not be blocked by the knockdown of a single gene, making it a promising new way to kill cancer cells.

Small interfering RNAs based on huntingtin trinucleotide repeats are highly toxic to cancer cells

“…When transfecting siCAG/CUG into various human (Fig 1B) and mouse (Fig 1C) cancer cell lines at 10 nM, all cancer cells stopped growing within hours of transfection and eventually most of the cells died with no outgrowth of recovering cells (Movies EV1-EV10) (Appendix Fig S1A). All cancer cells transfected with siCAG/CUG showed morphological changes similar to the ones we observed in cells undergoing DISE (Appendix Fig S1B, [15,17]). We found that siCAG/CUG killed HCT116 cells even when transfected at 10 pM (Fig 1D).…”

“…DISE (death induced by survival gene elimination) was found to involve simultaneous activation of multiple cell death pathways, and cancer cells have a hard time developing resistance to this form of cell death [17]. DISE was found to preferentially affect transformed cells [17].…”

“…DISE (death induced by survival gene elimination) was found to involve simultaneous activation of multiple cell death pathways, and cancer cells have a hard time developing resistance to this form of cell death [17]. DISE was found to preferentially affect transformed cells [17]. Because the length of the CAG repeats in different CAG repeat diseases has been inversely correlated with cancer incidence in various organs [18][19][20][21], we were wondering whether RNAi active CAG based TNRs might be responsible for this phenomenon and whether they could be used to kill cancer cells.…”

CD95 and CD95L promote and protect cancer stem cells

“…We have subsequently demonstrated that when either CD95 or CD95L are eliminated cancer cells die through a process we have coined DICE (for death induced by CD95R/L elimination) 12 . DICE is a necrotic form of mitotic catastrophe characterized by cell swelling and ROS production followed by DNA damage, activation of caspase-2, and loss of mitochondrial outer membrane potential (MOMP) 12 . DICE appears to be a fundamental mechanism, since it was consistently detected in all cancer cells investigated and in an in vivo mouse model of low-grade ovarian cancer.…”

Basal autophagy is negatively regulated by RIP1

“…Upon perusing the literature, we found this to be consistent with an analysis of multiple genome-wide shRNA lethality screens conducted by the HTS Core Facility at Memorial Sloan-Kettering Cancer Center (MSKCC), which indicated that RIP1 shRNAs were selected against in 9 of 12 cancer cell lines where such screens were conducted. 6 This consistently observed negative selection of RIP1 shRNAs under normal growth conditions underscored to us the significance that the presence of RIP1 shRNAs were selected for when autophagy was artificially limited in 67NR cells (these cells require autophagy for growth) or when these cells were starved in Earle's Balanced Salt Solution (EBSS). Upon further investigation, we found that the acute knockdown of RIP1 led to a large increase in basal autophagic flux in multiple cell types.…”