Death Receptors at the Molecular Level: Therapeutic Implications

Marion MacFarlane, University of Leicester, Leicester, UK

Published online: December 2009

DOI: 10.1002/9780470015902.a0021998

Since the discovery that activation of a subset of cell surface receptors within the tumour necrosis factor (TNF) receptor superfamily could trigger apoptosis, several members of the TNF superfamily including TNF, CD95L and TNF-related apoptosis-inducing ligand (TRAIL) have been identified as potentially important targets for cancer therapy. Although systemic administration of TNF or CD95L causes severe toxic side effects, thus hampering their potential application in the clinic, the discovery of TRAIL and its cognate death receptors, TRAIL-R1 and TRAIL-R2, have provided an exciting new opportunity for selective targeting of tumour cells. TRAIL receptor activation has emerged as the most promising approach for death receptor-targeted therapy while inducing minimal toxicity in the majority of normal cells. Intensive research, including detailed analysis of death ligand–death receptor pairs at the structural level have enabled the development of several different approaches aimed at selective targeting of TRAIL-R1/TRAIL-R2 in tumour cells.

Key concepts:

  • Death receptor ligands, including CD95L and tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), are potent stimulators of apoptosis.
  • Unlike TNF and CD95L, which on systemic administration exhibit toxicity, TRAIL is selectively toxic to tumour cells while sparing most normal cells.
  • Although the molecular basis for the tumour selective activity of TRAIL remains to be fully defined, the TRAIL pathway is an attractive therapeutic target for the treatment of cancer.
  • Key discoveries at the structural level have revealed several important features of the molecular interaction between TRAIL and its cognate death receptors, TRAIL-R1/ TRAIL-R2, that are critical for TRAIL-receptor triggering of apoptosis.
  • Based on structural and predicted models of TRAIL in complex with TRAIL-R1/ TRAIL-R2, recombinant TRAIL, receptor-selective TRAIL variants, as well as anti-TRAIL receptor antibodies have been developed, thus providing the opportunity to target both receptors or selectively target either TRAIL-R1 or TRAIL-R2 in tumour cells.
  • In preclinical trials, recombinant forms of TRAIL and agonistic anti-TRAIL receptor antibodies can synergise with chemotherapeutic drugs and novel chemotherapeutic agents to effectively kill TRAIL-resistant primary tumour cells.
  • Although early phase clinical trials indicate these agents can be delivered safely and are generally well tolerated as monotherapies, the most attractive use of these agents and their greatest promise for further clinical development will be when used in combination with other cancer treatments.

Keywords: apoptosis; CD95; TRAIL; TRAIL-R1/R2; X-ray crystallography; cancer therapy

Figure 1. Potential Therapeutic approaches to target TRAIL death receptor activation. The main types of TRAIL receptor agonists discussed in this article include ligand- and antibody-based protein agents which induce apoptosis via TRAIL receptor-mediated activation of the caspase cascade. Recombinant human Apo2L/TRAIL interacts with the death receptors, TRAIL-R1 and TRAIL-R2 (as well as the decoy receptors, TRAIL-R3/R4), whereas receptor-selective rhTRAIL variants and the monoclonal agonist antibodies are monospecific for either TRAIL-R1 or TRAIL-R2 (see text and Table 1 for further detail).
Figure 2. Crystal structure of the complex between rhApo2L/TRAIL and the extracellular domain of TRAIL-R2. The rhApo2L/TRAIL trimer is shown as a ribbon rendering in gradations of blue, and the three receptors are rendered as tubes in yellow and orange colours. The zinc atom that coordinates the sulfhydryl groups of three unpaired cysteines, located at position 230 of each subunit, is shown in green. strands and relevant loops are labelled (see text for further detail). (a) Side view. In this orientation, the membrane of the receptor-containing cell is at the bottom of the figure. (b) Axial view. View down the 3-fold axis of the complex, perpendicular to (a) (Hymowitz et al., 1999). Reproduced by permission of Elsevier (Cell Press).
Figure 3. Model of TRAIL/TRAIL-R1 complex and crystal structure of TRAIL/TRAIL-R2 complex. (a) Role of TRAIL Asn-199 in TRAIL (yellow)/TRAIL-R1 (cyan)/TRAIL-R2 (green) interactions. Hydrogen bond present with both TRAIL-R1 and TRAIL-R2 (black dashed line), and that present with only TRAIL-R2 (red dashed line) is indicated. The loss of these hydrogen bonds with the TRAIL substitution N199V is also illustrated. (b) Role of TRAIL Tyr-189 in TRAIL (yellow)/TRAIL-R1/R2 (green) interactions. Hydrogen bond from this tyrosine to the conserved glutamate in TRAIL-R1/R2 (dashed line) is indicated. Residues in TRAIL involved in hydrophobic interactions with Tyr-189, that is, interactions lost in Y189A-substituted TRAIL, are also shown (see text for further detail) (MacFarlane et al., 2005b). Reproduced by permission of American Association for Cancer Research.
Figure 4. Crystal structure of the Apomab Fab fragment in complex with the TRAIL-R2 extracellular domain. (a) Apomab binds at the junction between CRD2 and CRD3. TRAIL-R2 (brown, yellow and orange) and the Apomab Fab (light chain blue and heavy chain red) are shown as molecular interfaces. (b) Apo2L/TRAIL (blue) and Apomab (red) bind to overlapping yet distinct sites on TRAIL-R2 (yellow). The structure of the Apomab Fab/TRAIL-R2 complex is overlaid on the previously solved Apo2L /TRAIL-R2 complex (see Figure 2). For clarity, only one copy of TRAIL-R2 is shown. Additional copies of TRAIL-R2 that would bind at the Apo2L/TRAIL monomer–monomer interfaces are shown as yellow backbone ribbons (Adams et al., 2008). Reproduced by permission of Nature Publishing Group.
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 References
    Adams C, Totpal K, Lawrence D et al. (2008) Structural and functional analysis of the interaction between the agonistic monoclonal antibody Apomab and the proapoptotic receptor DR5. Cell Death and Differentiation 15: 751–761.
    Ashkenazi A (2008) Targeting the extrinsic apoptosis pathway in cancer. Cytokine Growth Factor Review 19: 325–331.
    Ashkenazi A and Dixit VM (1998) Death receptors: signaling and modulation. Science 281: 1305–1308.
    Ashkenazi A and Herbst RS (2008) To kill a tumor cell: the potential of proapoptotic receptor agonists. Journal of Clinical Investigation 118: 1979–1990.
    Ashkenazi A, Holland P and Eckhardt SG (2008) Ligand-based targeting of apoptosis in cancer: the potential of recombinant human apoptosis ligand 2/tumor necrosis factor-related apoptosis-inducing ligand (rhApo2L/TRAIL). Journal of Clinical Oncology 26: 3621–3630.
    Ashkenazi A, Pai RC, Fong S et al. (1999) Safety and antitumor activity of recombinant soluble Apo2 ligand. Journal of Clinical Investigation 104: 155–162.
    Bremer E, ten Cate B, Samplonius DF, de Leij LF and Helfrich W (2006) CD7-restricted activation of Fas-mediated apoptosis: a novel therapeutic approach for acute T-cell leukemia. Blood 107: 2863–2870.
    Bremer E, ten Cate B, Samplonius DF et al. (2008) Superior activity of fusion protein scFvRit:sFasL over cotreatment with rituximab and Fas agonists. Cancer Research 68: 597–604.
    Dyer MJ, MacFarlane M and Cohen GM (2007) Barriers to effective TRAIL-targeted therapy of malignancy. Journal of Clinical Oncology 25: 4505–4506.
    Ganten TM, Koschny R, Sykora J et al. (2006) Preclinical differentiation between apparently safe and potentially hepatotoxic applications of TRAIL either alone or in combination with chemotherapeutic drugs. Clinical Cancer Research 12: 2640–2646.
    Grunhagen DJ, de Wilt JH, Graveland WJ, van Geel AN and Eggermont AM (2006) The palliative value of tumor necrosis factor alpha-based isolated limb perfusion in patients with metastatic sarcoma and melanoma. Cancer 106: 156–162.
    Hanahan D and Weinberg RA (2000) The hallmarks of cancer. Cell 100: 57–70.
    Hymowitz SG, Christinger HW, Fuh G et al. (1999) Triggering cell death: the crystal structure of Apo2L/TRAIL in a complex with death receptor 5. Molecular Cell 4: 563–571.
    Johnstone RW, Frew AJ and Smyth MJ (2008) The TRAIL apoptotic pathway in cancer onset, progression and therapy. Nature Reviews. Cancer 8: 782–798.
    Kelley RF, Totpal K, Lindstrom SH et al. (2005) Receptor-selective mutants of apoptosis-inducing ligand 2/tumor necrosis factor-related apoptosis-inducing ligand reveal a greater contribution of death receptor (DR) 5 than DR4 to apoptosis signaling. Journal of Biological Chemistry 280: 2205–2212.
    Lawrence D, Shahrokh Z, Marsters S et al. (2001) Differential hepatocyte toxicity of recombinant Apo2L/TRAIL versions. Nature Medicine 7: 383–385.
    Lowe SW, Cepero E and Evan G (2004) Intrinsic tumour suppression. Nature 432: 307–315.
    MacFarlane M, Harper N, Snowden RT et al. (2002) Mechanisms of resistance to TRAIL-induced apoptosis in primary B cell chronic lymphocytic leukaemia. Oncogene 21: 6809–6818.
    MacFarlane M, Inoue S, Kohlhaas SL et al. (2005a) Chronic lymphocytic leukemic cells exhibit apoptotic signaling via TRAIL-R1. Cell Death and Differentiation 12: 773–782.
    MacFarlane M, Kohlhaas SL, Sutcliffe MJ, Dyer MJ and Cohen GM (2005b) TRAIL receptor-selective mutants signal to apoptosis via TRAIL-R1 in primary lymphoid malignancies. Cancer Research 65: 11265–11270.
    Mongkolsapaya J, Grimes JM, Chen N et al. (1999) Structure of the TRAIL-DR5 complex reveals mechanisms conferring specificity in apoptotic initiation. Nature Structural Biology 6: 1048–1053.
    Nagata S (1997) Apoptosis by death factor. Cell 88: 355–365.
    Natoni A, MacFarlane M, Inoue S et al. (2007) TRAIL signals to apoptosis in chronic lymphocytic leukaemia cells primarily through TRAIL-R1 whereas cross-linked agonistic TRAIL-R2 antibodies facilitate signalling via TRAIL-R2. British Journal of Haematology 139: 568–577.
    Ogasawara J, Watanabe-Fukunaga R, Adachi M et al. (1993) Lethal effect of the anti-Fas antibody in mice. Nature 364: 806–809.
    Pitti RM, Marsters SA, Ruppert S et al. (1996) Induction of apoptosis by Apo-2 ligand, a new member of the tumor necrosis factor cytokine family. Journal of Biological Chemistry 271: 12687–12690.
    Samel D, Muller D, Gerspach J et al. (2003) Generation of a FasL-based proapoptotic fusion protein devoid of systemic toxicity due to cell-surface antigen-restricted activation. Journal of Biological Chemistry 278: 32077–32082.
    van der Sloot AM, Tur V, Szegezdi E et al. (2006) Designed tumor necrosis factor-related apoptosis-inducing ligand variants initiating apoptosis exclusively via the DR5 receptor. Proceedings of the National Academy of Sciences of the USA 103: 8634–8639.
    Trauth BC, Klas C, Peters AM et al. (1989) Monoclonal antibody-mediated tumor regression by induction of apoptosis. Science 245: 301–305.
    Tur V, van der Sloot AM, Reis CR et al. (2008) DR4-selective tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) variants obtained by structure-based design. Journal of Biological Chemistry 283: 20560–20568.
    Volkmann X, Fischer U, Bahr MJ et al. (2007) Increased hepatotoxicity of tumor necrosis factor-related apoptosis-inducing ligand in diseased human liver. Hepatology 46: 1498–1508.
    Walczak H, Miller RE, Ariail K et al. (1999) Tumoricidal activity of tumor necrosis factor-related apoptosis- inducing ligand in vivo [see comments]. Nature Medicine 5: 157–163.
    Wiley SR, Schooley K, Smolak PJ et al. (1995) Identification and characterization of a new member of the TNF family that induces apoptosis. Immunity 3: 673–682.
    Yonehara S, Ishii A and Yonehara M (1989) A cell-killing monoclonal antibody (anti-Fas) to a cell surface antigen co-downregulated with the receptor of tumor necrosis factor. Journal of Experimental Medicine 169: 1747–1756.
 Further Reading
    Ashkenazi A (2002) Targeting death and decoy receptors of the tumour-necrosis factor superfamily. Nature Reviews. Cancer 2: 420–430.
    Ashkenazi A (2008) Directing cancer cells to self-destruct with pro-apoptotic receptor agonists. Nature Review of Drug Discovery 7: 1001–1012.
    Buchsbaum DJ, Forero-Torres A and LoBuglio AF (2007) TRAIL-receptor antibodies as a potential cancer treatment. Future Oncology 3: 405–409.
    Fesik SW (2005) Promoting apoptosis as a strategy for cancer drug discovery. Nature Reviews. Cancer 5: 876–885.
    Fulda S and Debatin KM (2004) Exploiting death receptor signaling pathways for tumor therapy. Biochimica et Biophysica Acta 1705: 27–41.
    Gajewski TF (2007) On the TRAIL toward death receptor-based cancer therapeutics. Journal of Clinical Oncology 25: 1305–1307.
    Hymowitz SG, O'Connell MP, Ultsch MH et al. (2000) A unique zinc-binding site revealed by a high-resolution X-ray structure of homotrimeric Apo2L/TRAIL. Biochemistry 39: 633–640.
    MacFarlane M (2003) TRAIL-induced signalling and apoptosis. Toxicological Letters 139: 89–97.
    Papenfuss K, Cordier SM and Walczak H (2008) Death receptors as targets for anti-cancer therapy. Journal of Cellular and Molecular Medicine 12: 2566–2585.
    Smyth MJ, Takeda K, Hayakawa Y et al. (2003) Nature's TRAIL – on a path to cancer immunotherapy. Immunity 18: 1–6.

Related Sub-Topics:

Intracellular and Extracellular Signalling | Cell Biology of Cancer | Cell Cycle | Cell Death and Cellular Senescence | Membrane Proteins | Signal Transduction | Protein Structure | Techniques and Tools in Molecular Biology | Mechanisms of Cell Death, Senescence and Metabolism
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Article Title: Death Receptors at the Molecular Level: Therapeutic Implications
 
How to Cite close
MacFarlane, Marion(Dec 2009) Death Receptors at the Molecular Level: Therapeutic Implications. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0021998]