Northwestern University Feinberg School of Medicine

Peter Lab

The function of CD95 as a tumor promotor

CD95 (APO-1/Fas) is an established apoptosis inducing receptor. The Peter lab initially described that upon induction of apoptosis CD95 recruits the DD and DED containing adapter molecule FADD and the DED containing cysteine protease caspase-8, caspase-10 and the caspase-8 regulator c-FLIP to the activated receptor forming the death-inducing signaling complex (DISC) (1-4). The description of the DISC was the first multi-protein signaling complex regulating apoptosis and was identified prior to the identification of the apoptosome. Binding of the proenzyme procaspase-8 to the DISC results in its activation and the release of active caspase-8 into the cytoplasm where it can cleave a number death substrates including caspase-3, BID and proteins of the cytoskeleton such as plectin (5-7).
Model to illustrate the function of CD95 as a tumor promotorWhile the apoptosis inducing activity of CD95 may be important for eliminating certain tumor cells most cancer cells are completely resistant to CD95 induced apoptosis. However, today not a single tumor has been reported that completely lacks CD95 expression. The Peter lab recently showed that on CD95 apoptosis resistant tumor cells stimulation of CD95 results in activation of NF-kB and MAP kinases inducing increased motility and invasiveness of tumor cells (8) (Figure). Two genes, urokinase plasminogen activator and the Ser/Thr kinase SNARK were identified to be critical for this activity of tumor cells (8,9). Subsequently, it was found that the threshold for tumor cells to activate NF-B is much lower than to activate apoptosis providing an explanation for the finding that patients with a mutation in one allele of the CD95 death domain (ALPS type Ia) have an increased risk of developing lymphoma (10). Activation of apoptosis in cells from these patients is blocked while activation of NF-kB and MAP kinases is normal. These findings underscore the novel role of death pathways and their components outside of apoptosis which are studied in the Peterlab (11-20). They study in vivo mouse tumor models in which CD95 acts as a tumor promotor with the goal to understand the nature and relevance of the tumor promoting activities of CD95. In one of these models it could be shown that a mutant CD95 receptor that does not allow apoptosis signaling to occur but still permits nonapoptotic signaling protects mice from developing liver cancer (21). The data support the view that nonapoptotic activities of the "death receptor" CD95 have been widely neglected (22).
To finally test whether CD95 has tumor promoting activities in vivo mice were generated with reconstituted immune systems and mice lacking CD95 expression in different tissues. Focus was on the liver, the organ with the highest constitutive expression of CD95 in the body, the colon (second highest expression) and the ovaries.
When mice expressing a mutant CD95 receptor that can not transduce apoptosis anymore but still nonapoptotic signaling were reconstituted with bone marrow from wild type mice these mice developed spontaneous liver cancer. This activity involved nonapoptotic signaling through CD95 (23). The function of CD95 as an apoptotic inducer in the colon has been widely studied without solid evidence that CD95 is involved in either colitis or colon cancer (24). To test the function of CD95 in both experimental colitis and colon cancer mice were generated lacking CD95 expression in the intestinal epithelial cells (25). These mice were hypersensitive to a form of chemically induced colitis but did not show increase in colon cancer when a carcinogen was administered. To fundamentally test the role of CD95 in cancer the Peterlab knocked down CD95 or its ligand in a number of human cancer cell lines and a primary ovarian cancer (26). This resulted in a severe reduction of cell growth suggesting that CD95 is required for cancer cells to grow. This was then confirmed in vivo. CD95 was required for cancer formation in a model of endometrioid ovarian cancer using Kras/pten mutant mice. Finally when CD95 was knocked out in the liver, livers were severely impaired in their capacity to regenerate. These mice also showed a significant reduction of tumors in a chemically induced form of liver cancer. JNK and JUN were identified as potential downstream signaling components that CD95 engages to mediate its growth promoting activities in cancer cells. In addition Egr1 and Fos were found to be part of this pathway. The lab is currently involved in the study of the signaling pathway that CD95 uses to mediate these growth promoting activities.


  1. Kischkel, F.C., Hellbardt, S., Behrmann, I., Germer, M., Pawlita, M., Krammer, P.H. and Peter, M.E. (1995) Cytotoxicity-dependent APO-1(Fas/CD95)-associated proteins form a death-inducing signalling complex (DISC) with the receptor. EMBO J., 14, 5579-5588.

  2. Muzio, M., Chinnaiyan, A.M., Kischkel, F.C., O' Rourke, K., Shevchenko, A., Scaffidi, C., Zhang, M., Ni, J., Gentz, R., Mann, M., Krammer, P.H., Peter, M.E.* and Dixit, V.M.* (1996) FLICE, a novel FADD-homologous ICE/CED-3-like protease, is recruited to the CD95 (Fas/APO-1) death-inducing signaling complex DISC), Cell, 85, 817-827. * Authors share senior authorship.
    Voted by "Science" to be one of the top 10 discoveries of 1996.
    3rd most cited paper in 1997.

  3. Peter, M.E. and Krammer, P.H. (2003) The CD95 death-inducing signaling complex and beyond. Cell Death Differ, 10, 26-35.

  4. Chang, D.W., Xing,, Z., Pan, Y., Algeciras-Schimnich, A., Barnhart, B.C.,Yaish-Ohad, S., Peter, M. E. and Yang, X. (2002) c-FLIPL is a dual function regulator for caspase-8 activation and CD95 (APO-1/Fas-mediated apoptosis. EMBO J., 21: 3704-3714.

  5. Medema, J.P., Scaffidi, C., Kischkel, F.C., Shevchenko, A., Mann, M., Krammer, P.H. and Peter, M.E. (1997) FLICE is activated by association with the CD95 death-inducing signaling complex (DISC), EMBO J., 16, 2794-2804.

  6. Chang, D.W., Xing, Z., Capacio, V., Peter, M.E and Yang, X. (2003) Interdimer processing mechanism of procaspase-8 activation. EMBO J., 22, 4132-4142.

  7. Stegh, A.H., Herrmann, H., Lampel, S., Weisenberger, D., Andrä, K., Seper, M., Wiche, G., Krammer, P.H. and Peter, M.E. (2000) Identification of the cytolinker plectin as a major early in vivo substrate for caspase-8 during CD95 and TNF-receptor mediated apoptosis. Mol. Cell. Biol., 20, 5665-5679.

  8. Barnhart, B.C., Legembre, P., Pietras, E., Bubici, C., Franzoso, G. and Peter, M.E. (2004) CD95 ligand induces motility and invasiveness of apoptosis resistant tumor cells. EMBO J., 23, 3175-3185.
    Press release by Nature Publishing Group on July 22, 2004, "Clue to Cancer spread".
    Article in New Scientist July 21, 2004, Vol. 183, 2458, "Renegade gene can aid and abet spread of cancer".

  9. Legembre, P., Schickel, R. Barnhart, B.C. and Peter, M.E. (2004) Identification of SNF1/AMPK-related kinase as a NF-kB regulated antiapoptotic kinase involved in CD95-induced motility and invasiveness. J. Biol. Chem., 279, 46742-46747.

  10. Legembre, P., Barnhart, B.C., Zheng, L., Vijayan, S., Straus, S.E., Puck, J., Dale, J.K., Lenardo, M. and Peter, M.E. (2004) Induction of apoptosis and activation of NF-B by CD95 require different signaling thresholds. EMBO Reports, 5, 1084-1089.

  11. Barnhart, B.C. and Peter M.E. (2002) Two faces of caspase-8. Nature Immunol., 3: 896-898.

  12. Algeciras-Schimnich, A., Barnhart, B.C. and Peter, M.E. (2002) Apoptosis-independent functions of killer caspases. Curr. Opin. Cell Biol, 14, 721-726.1.

  13. Park, S.M., Schickel, R. and Peter, M.E. (2005) Nonapoptotic functions of death receptors and their signaling components. Curr. Opin. Cell Biol., 17, 610-616.

  14. Barnhart, B.C., Pietras, E., Algeciras-Schimnich, A., Salmena, L., Hakem, R. and Peter, M.E. (2005) Overcoming CD95 apoptosis resistance in certain cells through noncanonical activation of caspase-8. Cell Death Differ., 12, 25-37.

  15. Alappat, E.C., Feig, C., Boyerinas, B., Volkland, J., Samuels, M., Murmann, A.E., Thorburn, A., Kidd, V.J., Slaughter, C.A., Osborn, S., Winoto, A., Tang, W.-J. and Peter, M.E. (2005) Phosphorylation of FADD at serine 194 by CKIa regulates its nonapoptotic activities. Mol. Cell, 19, 321-332.

  16. Peter, M.E., Budd, R.C., Desbarats, J., Hedrick, S.M., Hueber, A.-O., Newell, M.K., Owen, L.B., Pope, R.M., Tschopp, J., Wajant, H., Wallach, D., Wiltrout, R.H., Zörnig, M. and Lynch, D.H. (2007) The CD95 receptor: Apoptosis revisited. Cell, 129, 447-450.

  17. Scaffidi, C., Volkland, J., Blomberg, I, Hoffmann, I., Krammer, P.H. and Peter, M.E. (2000) Phosphorylation of FADD/Mort1 at serine 194 and association with a 70 kDa cell cycle regulated kinase. J. Immunol., 164, 1236-1242.

  18. Alappat, E.C., Volkland, J. and Peter, M.E. (2003) Growth inhibition by C-FADD depends on its C-terminal phosphorylation site. J. Biol. Chem., 278, 41585-41588.

  19. Lee, JC, Barnhart, BC, Alappat, E. and Peter, M.E. (2003) The family of death effector proteins. Oncogene, 22, 8634-8644.

  20. Peter, M.E., Legembre, P., Barnhart, B.C. (2005) Does CD95 have tumor promoting activities? BBA - Reviews on Cancer, 1755, 25-36.

  21. Park, S.M., Rajapaksha, T.W., Zhang, M., Sattar, H.A., Fichera, A., Ashton-Rickardt, P.G., Peter, M.E. (2008) CD95 signaling deficient mice with a wild-type hematopoietic system are prone to hepatic neoplasia. Apoptosis, 13, 41-51.

  22. Peter, M.E., Budd, R.C., Desbarats, J., Hedrick, S.M., Hueber, A.-O., Newell, M.K., Owen, L.B., Pope, R.M., Tschopp, J., Wajant, H., Wallach, D., Wiltrout, R.H., Zörnig, M. and Lynch, D.H. (2007) The CD95 receptor: Apoptosis revisited. Cell, 129, 447-450.

  23. Park, S.-M., Rajapaksha, T., Zhang, M., Sattar, H.H., Fichera, A., Ashton-Rickardt, P.G. and Peter, M.E. (2008) CD95 signaling deficient mice with a wild-type hematopoietic system are prone to hepatic neoplasia. Apoptosis, 13, 41-51.

  24. Chen, L. Park, S.M., Turner, J.R. and Peter, M.E. (2010) Cell Death in the Colonic Epithelium during Inflammatory Bowel Diseases: CD95/Fas and Beyond. Inflam Bowel Dis., 16, 1071-1076.

  25. Park, S.M., Chen, L. Zhang, M., Ashton-Rickardt, P., Turner, J.R. and Peter, M.E. (2010) CD95 is Cytoprotective for Intestinal Epithelial Cells in Colitis. Inflamm Bowel Dis., 16, 1063-1070.
    Editorial: When expression is not enough: The evolving thoughts on Fas/FasL and epithelial apoptosis. Stadnyk, A.W. (2010) IBD 16, 1061-1062.

  26. Chen, L., Park, S.M., Tumanov, A., Hau, A., Sawada, K., Feig, C., Turner, J., Fu, Y.X., Romeo, I., Lengyel, E. and Peter, M.E. (2010) CD95 promotes tumour growth. Nature, 465, 492-496.
    News and Views: "Wolf in wolf's clothing" by Doug Green, Nature, 465, 433-434. Coverage by NPR and many other news outlets.