My lab has made seminal contributions to our understanding of how the death receptor CD95 (Fas) mediates apoptosis. Our discovery of the CD95 death-inducing signaling complex (DISC) has influenced many others, and has laid the groundwork for the study of all death receptors, including TRAIL and TNF receptors. Our discovery of caspase-8 resulted in elucidation of the extrinsic apoptosis pathway, which has had implications for cancer research and beyond. In 2004, my interest began to turn toward nonapoptotic signaling through CD95. We recognized that CD95 was expressed on virtually all cells, including cells that should never undergo apoptosis (e.g., neurons), and was expressed on virtually all cancer cells, many of which were highly sensitive to apoptosis induction through CD95 in vitro. In 2010 these studies led to the break-through discovery that CD95 generally promotes growth of cancer cells. Based largely on this work, a CD95L inhibitor has been successfully used in clinical trials. More recently, we reported that elimination of CD95 or CD95L from cancer cells results in a form of cell death that I have termed DICE (death induced by CD95R/L elimination). Strikingly, we have found that DICE can be induced in all cancer cells tested (in vitro and in vivo), and we have not found a way to block it, suggesting that cancer cells may have a hard time developing resistance to DICE. The data suggest that CD95 acts as a dead man's switch, which ensures low level survival signaling through multiple signaling pathways, and when it is removed multiple cell death pathways are activated. In 2008 we discovered that miR-200 is a key regulator of EMT. Most recently, we found that stimulation of CD95 on cancer cells or reducing miR-200c levels increases the number of cancer stem cells (CSCs), which are more sensitive to induction of DICE than non-CSCs but are less sensitive to CD95 mediated apoptosis. In contrast, induction of DICE or overexpression of miR-200c reduces the number of CSCs. I proposed that DICE is a fundamental mechanism arising during evolution to control neoplastic transformation by eliminating cells that have lost either CD95 or CD95L. DICE strikes me as being a profoundly important cancer surveillance mechanism, and I have decided to focus this proposal on DICE, its mechanisms, related mechanisms, and the development of a novel form of cancer therapy. I am planning to pursue 8 projects over the next 7 years presented here, in no particular order, in the form of 8 questions: 1. What are the signals emanating from CD95 that keep cancer cells alive? 2. What are the signals that mediate the activities of CD95 that promote and maintain CSCs? 3. What cell death pathways comprise DICE? 4. What determines the difference in sensitivity to DICE between normal and cancer cells? 5. What is the role of the immune system in DICE? 6. Can induction of DICE be developed into a novel form of cancer therapy? 7. Are therapy resistant cancers susceptible to DICE? 8. Are there other tumor suppressors that can be targeted? I believe that DICE and related mechanisms can provide a new approach to cancer therapy, and I am deeply committed to bringing this new treatment to the clinic.
My lab has made seminal contributions to our understanding of how the death receptor CD95 (Fas) mediates apoptosis, however, we recently found that elimination of CD95 or CD95L from cancer cells results in a form of cell death that I have termed DICE (death induced by CD95R/L elimination), which is more effective and more cancer cell-specific than induction of apoptosis. This proposal is focused on DICE, its mechanisms, related mechanisms, and the development of a novel form of cancer therapy that could revolutionize the treatment of cancer.
| Patel, Monal; Peter, Marcus E (2018) Identification of DISE-inducing shRNAs by monitoring cellular responses. Cell Cycle 17:506-514 |
| Putzbach, Will; Haluck-Kangas, Ashley; Gao, Quan Q et al. (2018) CD95/Fas ligand mRNA is toxic to cells. Elife 7: |
| Gao, Quan Q; Putzbach, William E; Murmann, Andrea E et al. (2018) 6mer seed toxicity in tumor suppressive microRNAs. Nat Commun 9:4504 |
| Murmann, Andrea E; Gao, Quan Q; Putzbach, William E et al. (2018) Small interfering RNAs based on huntingtin trinucleotide repeats are highly toxic to cancer cells. EMBO Rep 19: |
| Putzbach, William; Gao, Quan Q; Patel, Monal et al. (2018) DISE: A Seed-Dependent RNAi Off-Target Effect That Kills Cancer Cells. Trends Cancer 4:10-19 |
| Qadir, Abdul S; Ceppi, Paolo; Brockway, Sonia et al. (2017) CD95/Fas Increases Stemness in Cancer Cells by Inducing a STAT1-Dependent Type I Interferon Response. Cell Rep 18:2373-2386 |
| Putzbach, William; Gao, Quan Q; Patel, Monal et al. (2017) Many si/shRNAs can kill cancer cells by targeting multiple survival genes through an off-target mechanism. Elife 6: |
| Murmann, Andrea E; McMahon, Kaylin M; Haluck-Kangas, Ashley et al. (2017) Induction of DISE in ovarian cancer cells in vivo. Oncotarget 8:84643-84658 |
