Targeting death receptors: is this trail still hot?

Targeting death receptors: is this trail still hot?

Rajen Mody

Department of Pediatrics, The University of Michigan, Ann Arbor, MI 48109-5718, USA

Correspondence to: Rajen Mody, MD, MS, Director, Pediatric Phase-I Program, Principal Investigator, COG Phase I Consortium, Associate Professor. Department of Pediatrics, The University of Michigan, D4202, Medical Professionals Building, BOX 5718, Ann Arbor, MI 48109-5718, USA. Email:

Submitted Jan 25, 2013. Accepted for publication Feb 26, 2013.

doi: 10.3978/j.issn.2224-4336.2013.02.01

Despite tremendous improvements in the survival of patients with pediatric solid tumors, outcomes for metastatic solid tumors and tumors that fail upfront therapy remains dismal (1,2). Further dose intensification of cytotoxic chemotherapy and radiation has not improved survival and new treatment strategies are desperately needed. Over the last few decades several newer biological agents, which target specific mutations or pathways responsible cancer growth have shown promise in pre-clinical testing (3-5). Many of them are already in clinical trials as a single agent and/or in combination with cytotoxic chemotherapy with mixed results (6,7). In addition, last decade has seen an increasing understanding of apoptosis defects observed in many cancer cell types and its role in promoting relentless cancer cell growth and drug resistance (8). This has generated a great deal of interest in the development of therapeutics to activate cancer cell-death-pathway with the ultimate goal of restoring self-destruction by cancer cells.

Two different pathways initiate Apoptosis: the death receptors-mediated extrinsic pathway and the mitochondria-involved intrinsic pathway (9). Death receptors (DR1-DR6) belong to the tumor necrosis factor receptor (TNFR) family that can engage intracellular apoptotic pathways upon binding of their cognate ligands of the tumor necrosis factor (TNF) family. TRAIL (also known as Apo2L) is a TNF family ligand (10) that binds on the death receptors, DR4 (also known as TRAIL-R1) (11,12) and DR5 (also known as TRAIL-R2) (13) and activates apoptotic pathways selectively in cancer cells.

While the molecular basis for this selectivity by TRAIL is poorly understood, it has certainly made TRAIL pathway an attractive target for cancer treatment, Higher expression of the TRAIL- receptors in tumor cells, relative high level of decoy receptors in normal cells (11), and non-functionality of the pathway at more downstream levels can potentially explain the mechanism (13,14). TRAIL targeting strategies can be divided in two broad categories: recombinant human TRAIL (rh-TRAIL) generated mainly from the extracellular domain (Untagged and tagged) (15) and monoclonal antibodies (MAbs) against DR4 and DR5 (humanized mouse MAb and fully human MAbs) (16-18). MAbs have proven to be effective clinical cancer therapeutics because they can selectively target specific antigens and have a much longer half-life than rh-TRAIL ligands (19,20). Both rh-TRAIL and MAbs have shown excellent activity in pre-clinical studies against adult as well as pediatric tumor models including breast cancer, osteosarcoma, Ewing’s sarcoma and rhabdomyosarcoma (21-23). They have also shown synergy with cytotoxic chemotherapy and radiation in pre-clinical models (24-27). A number of fully human DR4 and DR5 MAbs are now in Phase-I-II clinical trials in adults including HGS-ETR1 (mapatumumab) (20,28) and HGS-ETR2 (lexatumumab) (19,29).

In the Nov 2012 issue of Journal of Clinical Oncology (J Clin Oncol 30:4141-7) Merchant MS and colleagues have published results of the first Pediatric Phase-I Trial and Pharmacokinetic Study of Lexatumumab in Patients with Solid Tumors (30). I want to congratulate the authors on a well designed and nicely executed study. Primary findings of this study were very similar to two other adult Phase-I studies done with this agent previously (19,29). Lexatumumab was tolerated very well in children with relapsed solid tumors, when administered once every 14 days. Despite the fact that pediatric patients in this trial were heavily pre-treated, only one patient experienced DLT, Patients tolerated adult maximum tolerated dose (MTD) of 10 mg/kg every 2 weeks relatively well. In particular, liver and gastrointestinal toxicities seen in pre-clinical models and adult trials, were minimal in this study and no cumulative toxicities were seen in a patient treated for almost 2 years. Pharmacokinetic studies showed a profile similar to that seen in adult studies, with linear increase in drug exposure from dose of 5-10 mg/kg dose levels and adult equivalent accumulation indices validating every 14 days dosing. Overall area under the curve (AUC) was lower in children but was within 1 standard deviation of adult exposure. Mirroring the adult Phase-I trial experience, the agent was found not to be very immunogenic and no antibodies were detected against Lexatumumab (19,29).

Twenty one out of twenty four patients had either soft tissue or bone sarcoma, a disease group most likely to show clinical response based on pre-clinical studies and adult trials. The pediatric trial did show hints of activity although no objective responses were seen. A patient with osteosarcoma showed prolonged improvement in clinical symptoms and disappearance of FDG activity, a patient with Ewing’s sarcoma showed mixed response with disappearance of mass which was irradiated before trial enrollment and a patient with hepatoblastoma showed a dramatic reduction in tumor marker. Correlative studies showed strong staining for TRAIL-R2 in 7/14 of tissue slides and 7/9 had strong caspase-8 staining while none stained strongly for TRAIL-R1. There was no correlation between clinical benefit and strength of TRAIL-R2 or Caspase-8 staining, a finding also seen in adult trials (19,29). However, in this pediatric trial there was a correlation noted between no TRAIL-R2 staining and rapid progression on the study, with all 4 patients with no staining progressing within first 2 cycles.

This pediatric Phase-I trial of Lexatumumab shows that it is an agent, which is nicely tolerated in children and shows a hint of clinical activity as a single agent in a Phase-I clinical setting. Authors made several important observations and raise many intriguing questions as to how best to move forward with this agent in pediatric oncology. First, the trial confirms findings of the two previous adult Phase-I trials, that soft tissue and bone sarcoma patients seem to show some benefit and merits further testing in a Phase-II setting (19,29,30). Second, what is the role of prior radiation therapy in patients receiving lexatumumab? Two out of three cases showing some clinical benefit on a trial had received radiation 4 weeks prior to trial enrolment. This observation was also supported by pre-clinical studies, which suggests that radiation therapy up-regulates TRAIL-R2 expression in tumor tissue without increasing the toxicity in normal tissues (27,31). Third, this pediatric study also showed correlation between lack of TRAIL-R2 expression and rapid progression on trial. However, numbers are very small and majority of patients had their tissue collected at the time of original diagnosis, so the true TRAIL-R1, TRAIL-R2 and caspase-8 expression at the time of enrolment is unknown. This is contrary to majority of available evidence, which suggests that death receptor and caspases expression are not predictive of clinical response (19,29). There is some evidence that O-Glycosyltransferase expression is required for DR4/DR5 clustering and Caspase-8 activation and its levels are predictive of sensitivity to rh-TRAIL in a large number of cancer cell lines (32), but this needs to be confirmed in patient samples in a clinical trial.

So, where do we go from here? There are several questions, which needs to be answered before we move forward. What’s the most likely patient population who might benefit? What’s the best modality for combination therapy? Is it Radiation and/or chemotherapy or with new biologic agents? Based on early clinical experience in pediatrics, testing of lexatumumab in pediatric sarcomas with either sequential or concurrent radiation therapy seems most logical. In addition, several chemotherapeutic agents have also shown ability to modulate the TRAIL receptor expression in pre-clinical settings by inducing DR4/DR5 and Fas expression in human cancer cells (25,33-35) or downregulated c-FLIP (36). Chemotherapy agents most likely to potentiate the effect of TRAIL agonists include etoposide, cytarabine, doxorubicin, cisplatin, methotrexate and bleomycin, which are some of the most commonly used chemotherapeutic agents in pediatric oncology. Also, there is evidence to suggest that when TRAIL therapy is combined with either radiation therapy or chemotherapy, it can overcome resistance to any of these modalities as single agent by upregulating death receptors DR4 or DR5, caspase-3, caspase-8, or bax, or through downregulating Bcl-XL or cFLIP (37). This would have implications in using TRAIL combination therapy in tumors where either of those modalities were known to be ineffective in the past. These finding argues strongly in favor of combination trial between TRAIL receptor agonists and chemotherapy and/or radiation therapy and there are several such Phase-II trials ongoing in adults with solid tumors as well with hematological malignancies (28).

Finally, in addition to chemotherapy, there are several new biologics including HDAC inhibitors and Proteasome inhibitors, which are also known to increase the expression of TRAIL receptors DR5 and/or DR4, reduce the levels of c-FLIP and enhance TRAIL induced apoptosis in both hematopoietic and/or solid tumor models (38-42). A combination of these biologics and TRAIL agonists are in clinical trials in adults with hematological malignancies and solid tumors and certainly merits further testing against pediatric tumors.

In summary, lexatumumab and other TRAIL agonists are very exciting new class of drugs with very favorable toxicity profile, easy schedule of administration and hints of clinical activity in early phase pediatric clinical trials. Their true place in the new treatment paradigm is yet to be defined and their ultimate success will depend on how quickly we can answer some of these remaining questions.




Conflicts of Interest: The author has no conflicts of interest to declare.


  1. Pappo AS, Anderson JR, Crist WM, et al. Survival after relapse in children and adolescents with rhabdomyosarcoma: A report from the Intergroup Rhabdomyosarcoma Study Group. J Clin Oncol 1999;17:3487-93. [PubMed]
  2. Cotterill SJ, Ahrens S, Paulussen M, et al. Prognostic factors in Ewing’s tumor of bone: analysis of 975 patients from the European Intergroup Cooperative Ewing’s Sarcoma Study Group. J Clin Oncol 2000;18:3108-14. [PubMed]
  3. Ferrara N, Hillan KJ, Gerber HP, et al. Discovery and development of bevacizumab, an anti-VEGF antibody for treating cancer. Nat Rev Drug Discov 2004;3:391-400. [PubMed]
  4. Kolb EA, Gorlick R, Maris JM, et al. Combination testing (Stage 2) of the Anti-IGF-1 receptor antibody IMC-A12 with rapamycin by the pediatric preclinical testing program. Pediatr Blood Cancer 2012;58:729-35. [PubMed]
  5. Beltran PJ, Chung YA, Moody G, et al. Efficacy of ganitumab (AMG 479), alone and in combination with rapamycin, in Ewing’s and osteogenic sarcoma models. J Pharmacol Exp Ther 2011;337:644-54. [PubMed]
  6. Malempati S, Weigel B, Ingle AM, et al. Phase I/II trial and pharmacokinetic study of cixutumumab in pediatric patients with refractory solid tumors and Ewing sarcoma: a report from the Children’s Oncology Group. J Clin Oncol 2012;30:256-62. [PubMed]
  7. Klement G, Baruchel S, Rak J, et al. Continuous low-dose therapy with vinblastine and VEGF receptor-2 antibody induces sustained tumor regression without overt toxicity. J Clin Invest 2000;105:R15-24. [PubMed]
  8. Testa U. TRAIL/TRAIL-R in hematologic malignancies. J Cell Biochem 2010;110:21-34. [PubMed]
  9. Ashkenazi A. Targeting death and decoy receptors of the tumour-necrosis factor superfamily. Nat Rev Cancer 2002;2:420-30. [PubMed]
  10. Wiley SR, Schooley K, Smolak PJ, et al. Identification and characterization of a new member of the TNF family that induces apoptosis. Immunity 1995;3:673-82. [PubMed]
  11. Pan G, Ni J, Wei YF, et al. An antagonist decoy receptor and a death domain-containing receptor for TRAIL. Science 1997;277:815-8. [PubMed]
  12. Pan G, O’Rourke K, Chinnaiyan AM, et al. The receptor for the cytotoxic ligand TRAIL. Science 1997;276:111-3. [PubMed]
  13. Eggert A, Grotzer MA, Zuzak TJ, et al. Resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in neuroblastoma cells correlates with a loss of caspase-8 expression. Cancer Res 2001;61:1314-9. [PubMed]
  14. Daniel PT, Wieder T, Sturm I, et al. The kiss of death: promises and failures of death receptors and ligands in cancer therapy. Leukemia 2001;15:1022-32. [PubMed]
  15. Lawrence D, Shahrokh Z, Marsters S, et al. Differential hepatocyte toxicity of recombinant Apo2L/TRAIL versions. Nat Med 2001;7:383-5. [PubMed]
  16. Adams C, Totpal K, Lawrence D, et al. Structural and functional analysis of the interaction between the agonistic monoclonal antibody Apomab and the proapoptotic receptor DR5. Cell Death Differ 2008;15:751-61. [PubMed]
  17. Yada A, Yazawa M, Ishida S, et al. A novel humanized anti-human death receptor 5 antibody CS-1008 induces apoptosis in tumor cells without toxicity in hepatocytes. Ann Oncol 2008;19:1060-7. [PubMed]
  18. Humphreys RC, Halpern W. Trail receptors: targets for cancer therapy. Adv Exp Med Biol 2008;615:127-58. [PubMed]
  19. Plummer R, Attard G, Pacey S, et al. Phase 1 and pharmacokinetic study of lexatumumab in patients with advanced cancers. Clin Cancer Res 2007;13:6187-94. [PubMed]
  20. Tolcher AW, Mita M, Meropol NJ, et al. Phase I pharmacokinetic and biologic correlative study of mapatumumab, a fully human monoclonal antibody with agonist activity to tumor necrosis factor-related apoptosis-inducing ligand receptor-1. J Clin Oncol 2007;25:1390-5. [PubMed]
  21. Zinonos I, Labrinidis A, Lee M, et al. Apomab, a fully human agonistic antibody to DR5, exhibits potent antitumor activity against primary and metastatic breast cancer. Mol Cancer Ther 2009;8:2969-80. [PubMed]
  22. Picarda G, Lamoureux F, Geffroy L, et al. Preclinical evidence that use of TRAIL in Ewing’s sarcoma and osteosarcoma therapy inhibits tumor growth, prevents osteolysis, and increases animal survival. Clin Cancer Res 2010;16:2363-74. [PubMed]
  23. Petak I, Douglas L, Tillman DM, et al. Pediatric rhabdomyosarcoma cell lines are resistant to Fas-induced apoptosis and highly sensitive to TRAIL-induced apoptosis. Clin Cancer Res 2000;6:4119-27. [PubMed]
  24. Lacour S, Hammann A, Wotawa A, et al. Anticancer agents sensitize tumor cells to tumor necrosis factor-related apoptosis-inducing ligand-mediated caspase-8 activation and apoptosis. Cancer Res 2001;61:1645-51. [PubMed]
  25. Gibson SB, Oyer R, Spalding AC, et al. Increased expression of death receptors 4 and 5 synergizes the apoptosis response to combined treatment with etoposide and TRAIL. Mol Cell Biol 2000;20:205-12. [PubMed]
  26. Gong B, Almasan A. Apo2 ligand/TNF-related apoptosis-inducing ligand and death receptor 5 mediate the apoptotic signaling induced by ionizing radiation in leukemic cells. Cancer Res 2000;60:5754-60. [PubMed]
  27. Marini P, Junginger D, Stickl S, et al. Combined treatment with lexatumumab and irradiation leads to strongly increased long term tumour control under normoxic and hypoxic conditions. Radiat Oncol 2009;4:49. [PubMed]
  28. Leong S, Cohen RB, Gustafson DL, et al. Mapatumumab, an antibody targeting TRAIL-R1, in combination with paclitaxel and carboplatin in patients with advanced solid malignancies: results of a phase I and pharmacokinetic study. J Clin Oncol 2009;27:4413-21. [PubMed]
  29. Wakelee HA, Patnaik A, Sikic BI, et al. Phase I and pharmacokinetic study of lexatumumab (HGS-ETR2) given every 2 weeks in patients with advanced solid tumors. Ann Oncol 2010;21:376-81. [PubMed]
  30. Merchant MS, Geller JI, Baird K, et al. Phase I trial and pharmacokinetic study of lexatumumab in pediatric patients with solid tumors. J Clin Oncol 2012;30:4141-7. [PubMed]
  31. Marini P, Denzinger S, Schiller D, et al. Combined treatment of colorectal tumours with agonistic TRAIL receptor antibodies HGS-ETR1 and HGS-ETR2 and radiotherapy: enhanced effects in vitro and dose-dependent growth delay in vivo. Oncogene 2006;25:5145-54. [PubMed]
  32. Wagner KW, Punnoose EA, Januario T, et al. Death-receptor O-glycosylation controls tumor-cell sensitivity to the proapoptotic ligand Apo2L/TRAIL. Nat Med 2007;13:1070-7. [PubMed]
  33. Müller M, Wilder S, Bannasch D, et al. p53 activates the CD95 (APO-1/Fas) gene in response to DNA damage by anticancer drugs. J Exp Med 1998;188:2033-45. [PubMed]
  34. Wu GS, Burns TF, McDonald ER 3rd, et al. KILLER/DR5 is a DNA damage-inducible p53-regulated death receptor gene. Nat Genet 1997;17:141-3. [PubMed]
  35. Nagane M, Pan G, Weddle JJ, et al. Increased death receptor 5 expression by chemotherapeutic agents in human gliomas causes synergistic cytotoxicity with tumor necrosis factor-related apoptosis-inducing ligand in vitro and in vivo. Cancer Res 2000;60:847-53. [PubMed]
  36. Longley DB, Wilson TR, McEwan M, et al. c-FLIP inhibits chemotherapy-induced colorectal cancer cell death. Oncogene 2006;25:838-48. [PubMed]
  37. Bhojani MS, Rossú BD, Rehemtulla A. TRAIL and anti-tumor responses. Cancer Biol Ther 2003;2:S71-8. [PubMed]
  38. Shankar S, Singh TR, Fandy TE, et al. Interactive effects of histone deacetylase inhibitors and TRAIL on apoptosis in human leukemia cells: involvement of both death receptor and mitochondrial pathways. Int J Mol Med 2005;16:1125-38. [PubMed]
  39. Insinga A, Monestiroli S, Ronzoni S, et al. Inhibitors of histone deacetylases induce tumor-selective apoptosis through activation of the death receptor pathway. Nat Med 2005;11:71-6. [PubMed]
  40. Nebbioso A, Clarke N, Voltz E, et al. Tumor-selective action of HDAC inhibitors involves TRAIL induction in acute myeloid leukemia cells. Nat Med 2005;11:77-84. [PubMed]
  41. Liu X, Yue P, Chen S, et al. The proteasome inhibitor PS-341 (bortezomib) up-regulates DR5 expression leading to induction of apoptosis and enhancement of TRAIL-induced apoptosis despite up-regulation of c-FLIP and survivin expression in human NSCLC cells. Cancer Res 2007;67:4981-8. [PubMed]
  42. Johnson TR, Stone K, Nikrad M, et al. The proteasome inhibitor PS-341 overcomes TRAIL resistance in Bax and caspase 9-negative or Bcl-xL overexpressing cells. Oncogene 2003;22:4953-63. [PubMed]
Cite this article as: Mody R. Targeting death receptors: is this trail still hot? Transl Pediatr 2013;2(2):66-69. doi: 10.3978/j.issn.2224-4336.2013.02.01

Download Citation