Enhanced apoptosis and tumor regression induced by a direct agonist antibody to tumor necrosis factor-related apoptosis-inducing ligand receptor 2

Apomab, a fully human agonistic antibody to DR5, exhibits potent antitumor activity against primary and metastatic breast cancer

Apomab, a fully human agonistic DR5 monoclonal antibody, triggers apoptosis through activation of the extrinsic apoptotic signaling pathway. In this study, we assessed the cytotoxic effect of Apomab in vitro and evaluated its antitumor activity in murine models of breast cancer development and progression. MDA-MB-231-TXSA breast cancer cells were transplanted into the mammary fat pad or directly into the tibial marrow cavity of nude mice. Apomab was administered early, postcancer cell transplantation, or after tumors progressed to an advanced stage. Tumor burden was monitored progressively using bioluminescence imaging, and the development of breast cancer-induced osteolysis was measured using microcomputed tomography. In vitro, Apomab treatment induced apoptosis in a panel of breast cancer cell lines but was without effect on normal human primary osteoblasts, fibroblasts, or mammary epithelial cells. In vivo, Apomab exerted remarkable tumor suppressive activity leading to complete regression of well-advanced mammary tumors. All animals transplanted with breast cancer cells directly into their tibiae developed large osteolytic lesions that eroded the cortical bone. In contrast, treatment with Apomab following an early treatment protocol inhibited both intraosseous and extraosseous tumor growth and prevented breast cancer-induced osteolysis. In the delayed treatment protocol, Apomab treatment resulted in the complete regression of advanced tibial tumors with progressive restoration of both trabecular and cortical bone leading to full resolution of osteolytic lesions. Apomab represents a potent immunotherapeutic agent with strong activity against the development and progression of breast cancer and should be evaluated in patients with primary and metastatic disease.

Combination of the pro-apoptotic TRAIL-receptor antibody mapatumumab with ionizing radiation strongly increases long-term tumor control under ambient and hypoxic conditions

PURPOSE

Mapatumumab, an agonistic tumor necrosis factor-related apoptosis inducing ligand-receptor antibody, exerts highly synergistic apoptotic effects in vitro and in short-term growth delay assays when combined with irradiation. Because it remained unclear in how far these effects influence local tumor control, long-term experiments using a colorectal xenograft model were undertaken.

MATERIAL AND METHODS

Experiments were performed with irradiation (5 x 3 Gy, d1-5) and mapatumumab (10 mg/kg) in Colo205-xenograft-bearing NMRI (nu/nu) nude mice. Graded top up doses were delivered on the tumor-bearing hind leg under ambient and hypoxic conditions; follow-up was 270 days. Growth delay and local tumor control were end points of the study. Statistical analysis of the experiments included calculation of tumor regrowth and local tumor control.

RESULTS

After combined treatment, a pronounced tumor regrowth-delay was observed when compared with irradiation alone. Long-term experiments revealed a highly significant increase in local tumor control for ambient (p = 0.00076) and hypoxic treatment (p = 0.000069).

CONCLUSIONS

The present data demonstrate for the first time that combination of a pro-apoptotic antibody with irradiation results in evidently reduced tumor regrowth times and subsequently highly increased local tumor control under normoxic and hypoxic conditions in a xenograft mouse model.

Induction of apoptosis by cross-linking antibodies bound to human B-lymphoma cells: expression of Annexin V binding sites on the antibody cap

There are many reports that cross-linking antibodies (Abs) bound to the surface of B-lymphoma cells can induce apoptosis and/or cell death, especially with anti-CD20 Abs. This study was intended to extend our understanding of these effects. To determine if CD20 is a unique target in this respect, or whether Abs to other antigens would have similar effects, six Abs were tested, with and without cross-linking with a secondary Ab, on three target cell lines. We utilized assays that distinguish between apoptotic, dead, and viable cells. Two assays were used: Annexin V plus propidium iodide, and JC-1 plus SYTOX green (Molecular Probes, Eugene, OR). Most of the Abs tested induced a low level of apoptosis and cell death in Ramos cells, but not in the other two cell lines (Raji and RL). In general, the level of toxicity was correlated with the level of antigen expression, with Abs to high-density antigens having the strongest effects. However, since the majority of Ramos cells continued to multiply, it is questionable whether toxicity at this level can provide a significant clinical benefit. Unexpectedly, there was also a population of cells that stained weakly with Annexin V. These cells were distinct from classical apoptotic cells, and appeared to belong to the viable cell population. In these cells, Annexin V stained the region of the Ab cap, in contrast to the ringed staining of classical apoptotic cells.

IN CONCLUSION

1) Low-level induction of apoptosis was not unique for anti-CD20 Abs, but occurred similarly with other Abs, and 2) results of Annexin V staining experiments may need to be reevaluated. Further studies are required to explain why Annexin V binding sites are exposed in the region of an Ab cap.

The Biology of TRAIL and the Role of TRAIL-Based Therapeutics in Infectious Diseases

TNF-related apoptosis inducing ligand (TRAIL) is a key mediator of the innate immune response to infection. While TRAIL-mediated apoptosis plays an essential role in the clearance of virus-infected cells, its physiologic role also includes immunosurveilance for cancer cells. Therapeutics that induce TRAIL-mediated apoptosis in cancer cells remain a focus of ongoing investigation in clinical trials, and much has been learned from these studies regarding the efficacy and toxicity of these interventions. These data, combined with data from numerous preclinical studies that detail the important and multifaceted role of TRAIL during infection with human immunodeficiency virus and other viruses, suggest that therapeutic exploitation of TRAIL signaling offers a novel and efficacious strategy for the management of infectious diseases.

Cooperation of the agonistic DR5 antibody apomab with chemotherapy to inhibit orthotopic lung tumor growth and improve survival

PURPOSE

Apomab is a fully human monoclonal antibody that induces programmed cell death through the proapoptotic receptor DR5 in various cancer cells but not in normal cells. Several lung cancer cell lines express DR5 and exhibit apoptosis in response to apomab in vitro.

EXPERIMENTAL DESIGN

We investigated the efficacy of apomab and its interaction with chemotherapy in xenograft models based on human NCI-H460 non-small-cell lung carcinoma cells. In an established model of s.c. tumor xenografts, apomab or Taxol plus carboplatin chemotherapy delayed tumor progression, whereas combined treatment caused tumor regression and a substantially longer growth delay. To test apomab activity in a setting that may more closely mimic lung cancer pathology in patients, we developed a lung orthotopic model.

RESULTS

In this model, microcomputed tomography imaging showed that apomab, chemotherapy, or combination treatment significantly inhibited tumor growth compared with vehicle, whereas the combination caused greater inhibition in tumor growth relative to chemotherapy or apomab. Similarly, histologic analysis revealed that apomab, chemotherapy, or the combination significantly reduced tumor size compared with vehicle, whereas the combination induced significantly greater reduction in tumor size than did chemotherapy or apomab. Furthermore, combined treatment improved 105-day survival relative to vehicle (P = 0.0023) as well as to apomab (P = 0.0445) or chemotherapy (P = 0.0415).

CONCLUSION

These results show a positive interaction of apomab with chemotherapy, evidenced by significant inhibition of tumor growth as well as improved survival, thus supporting further investigation of this therapeutic approach in lung cancer patients.

The TRAIL apoptotic pathway in cancer onset, progression and therapy

Triggering of tumour cell apoptosis is the foundation of many cancer therapies. Death receptors of the tumour necrosis factor (TNF) superfamily have been largely characterized, as have the signals that are generated when these receptors are activated. TNF-related apoptosis-inducing ligand (TRAIL) receptors (TRAILR1 and TRAILR2) are promising targets for cancer therapy. Herein we review what is known about the molecular control of TRAIL-mediated apoptosis, the role of TRAIL in carcinogenesis and the potential therapeutic utility of recombinant TRAIL and agonistic antibodies against TRAILR1 and TRAILR2.

Treating metastatic solid tumors with bortezomib and a tumor necrosis factor-related apoptosis-inducing ligand receptor agonist antibody

BACKGROUND

Resistance of tumors to cell death signals poses a complex clinical problem. We explored the therapeutic potential and in vivo toxicity of a combination of bortezomib, a proteasome inhibitor, and MD5-1, a tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor (DR5) agonist monoclonal antibody, in mouse carcinomas. METHODS; Mice bearing Renca-FLAG (renal) or 4T1 (mammary) tumors were treated with bortezomib and/or MD5-1 and examined for lung metastases (Renca-FLAG: n = 93; 4T1: n = 40) or monitored for survival (Renca-FLAG: n = 143). Toxicity was assessed by histopathology and hematology. Viability and apoptotic signaling in Renca-FLAG and 4T1 cells treated with bortezomib alone or in combination with TRAIL were analyzed using 3-[4,5-dimethyiazol-2-yl-5]-[3-carboxymethyloxyphenyl]-2-[4-sulfophenyl]-2H tetrazolium assay and by measuring mitochondrial membrane depolarization and caspase-8 and caspase-3 activation. All statistical tests were two-sided.

RESULTS

Bortezomib (20 nM) sensitized Renca-FLAG and 4T1 cells to TRAIL-mediated apoptosis (mean percent decrease in numbers of viable cells, bortezomib + TRAIL vs TRAIL: Renca-FLAG, 95% vs 34%, difference = 61%, 95% confidence interval [CI] = 52% to 69%, P < .001; 4T1, 85% vs 20%, difference = 65%, 95% CI = 62% to 69%, P < .001). Sensitization involved activation of caspase-8 and caspase-3 but not mitochondrial membrane depolarization, suggesting an amplified signaling of the extrinsic cell death pathway. Treatment with bortezomib and MD5-1 reduced lung metastases in mice carrying Renca and 4T1 tumors (mean number of metastases, bortezomib + MD5-1 vs MD5-1: Renca-FLAG, 1 vs 8, difference = 7, 95% CI = 5 to 9, P < .001; 4T1, 1 vs 12, difference = 11, 95% CI = 9 to 12, P < .001) and increased median survival of mice bearing Renca-FLAG tumors (bortezomib + MD5-1 vs bortezomib + control isotype antibody: 22 of 30 [73%] were still alive at day 180 vs median survival of 42 days [95% CI = 41 to 44 days, P < .001]) in the absence of obvious toxicity.

CONCLUSION

Bortezomib combined with DR5 agonist monoclonal antibody may be a useful treatment for metastatic solid tumors.

P53-mediated upregulation of DcR1 impairs oxaliplatin/TRAIL-induced synergistic anti-tumour potential in colon cancer cells

Oxaliplatin has emerged as a major chemotherapeutic drug in the treatment of advanced colorectal cancer, yet like most conventional cancer therapeutics, its efficacy is often compromised due to p53 mutations. Unlike oxaliplatin, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers apoptosis in a p53-independent manner, and chemotherapy is known to overcome tumour resistance to TRAIL-induced cell death in most cancer cells. Using a panel of colon cancer cell lines, we assessed the ability of oxaliplatin to sensitize to TRAIL-induced apoptosis. We demonstrate that while both drugs additively or synergistically induced apoptosis in almost all cell lines tested, p53 wild-type colon cancer cells such as HCT116, LS513 or LS174T remained resistant. Impaired TRAIL-induced cell death resulted from a strong p53 dependent, oxaliplatin-mediated, DcR1 receptor expression increase. According to our finding, downregulation of DcR1 using siRNA, in p53 wild-type colon cancer cells, restored oxaliplatin/TRAIL synergistic apoptotic activity. On the contrary, exogenous DcR1 overexpression in SW480, a p53-mutated cell line, abolished the synergy between the two drugs. Altogether we demonstrate for the first time that p53 negatively regulates oxaliplatin-mediated TRAIL-induced apoptotic activity through DcR1 upregulation. Our findings could have important implications for future therapeutic strategies, and suggest that the association oxaliplatin/TRAIL should be restricted to patients harbouring a non-functional p53 protein.

Structural and functional analysis of the interaction between the agonistic monoclonal antibody Apomab and the proapoptotic receptor DR5

Activation of the proapoptotic receptor death receptor5 (DR5) in various cancer cells triggers programmed cell death through the extrinsic pathway. We have generated a fully human monoclonal antibody (Apomab) that induces tumor cell apoptosis through DR5 and investigated the structural features of its interaction with DR5. Biochemical studies showed that Apomab binds DR5 tightly and selectively. X-ray crystallographic analysis of the complex between the Apomab Fab fragment and the DR5 ectodomain revealed an interaction epitope that partially overlaps with both regions of the Apo2 ligand/tumor necrosis factor-related apoptosis-inducing ligand binding site. Apomab induced DR5 clustering at the cell surface and stimulated a death-inducing signaling complex containing the adaptor molecule Fas-associated death domain and the apoptosis-initiating protease caspase-8. Fc crosslinking further augmented Apomab's proapoptotic activity. In vitro, Apomab triggered apoptosis in cancer cells, while sparing normal hepatocytes even upon anti-Fc crosslinking. In vivo, Apomab exerted potent antitumor activity as a single agent or in combination with chemotherapy in xenograft models, including those based on colorectal, non-small cell lung and pancreatic cancer cell lines. These results provide structural and functional insight into the interaction of Apomab with DR5 and support further investigation of this antibody for cancer therapy.

TRAIL in cancer therapy: present and future challenges

Since its identification in 1995, TNF-related apoptosis-inducing ligand (TRAIL) has sparked growing interest in oncology due to its reported ability to selectively trigger cancer cell death. In contrast to other members of the TNF superfamily, TRAIL administration in vivo is safe. The relative absence of toxic side effects of this naturally occurring cytokine, in addition to its antitumoural properties, has led to its preclinical evaluation. However, despite intensive investigations, little is known in regards to the mechanisms underlying TRAIL selectivity or efficiency. An appropriate understanding of its physiological relevance, and of the mechanisms controlling cancer cells escape from TRAIL-induced cell death, will be required to optimally use the cytokine in clinics. The present review focuses on recent advances in the understanding of TRAIL signal transduction and discusses the existing and future challenges of TRAIL-based cancer therapy development.

Augmented antitumor activity against B-cell lymphoma by a combination of monoclonal antibodies targeting TRAIL-R1 and CD20

PURPOSE

Mapatumumab and lexatumumab are fully humanized, high-affinity immunoglobulin G(1 lambda) monoclonal antibodies (mAb) that target/activate the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor 1 (TRAIL-R1) and receptor 2 (TRAIL-R2), respectively, triggering the extrinsic apoptotic pathway. Theoretically, synergistic antitumor activity should be observed by combining TRAIL-R mAbs with agents (e.g., rituximab) that activate the intrinsic apoptotic pathway.

EXPERIMENTAL DESIGN

To this end, targeted antigen expression in a NHL-cell panel was evaluated by flow cytometry. NHL cells were exposed to mapatumumab or lexatumumab followed by rituximab, isotype, or RPMI. DNA synthesis was quantified by [(3)H]-thymidine incorporation assays. Induction of apoptosis was detected by flow-cytometric analysis. For antibody-dependent cellular cytotoxicity (ADCC) and complement-mediated cytotoxicity (CMC) studies, standardized (51)Cr-release assays were done. We inoculated severe combined immunodeficiency (SCID) mouse with Raji cells i.v. The animals then were treated with various combinations of rituximab, mapatumumab, lexatumumab, and isotype alone or in combination.

RESULTS

In vitro exposure to mapatumumab resulted in significant apoptosis (30-50%) and decreased DNA synthesis in sensitive lymphoma cells. Mapatumumab/rituximab combination resulted in a significant inhibition of cell proliferation (90% reduction) when compared with mapatumumab (60% reduction) or rituximab (5% reduction). In vivo, the median survival time of animals treated with mapatumumab and rituximab was longer (not reached) than those treated with rituximab monotherapy [33 days (95% confidence interval, 29-37), log-rank test, P = 0.05].

CONCLUSIONS

Mapatumumab induces apoptosis, cell growth arrest, ADCC, and CMC. The combination of mapatumumab plus rituximab is more effective in controlling lymphoma growth in vivo than either antibody. Rituximab and mapatumumab warrant further evaluation against B-cell lymphoma.

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

Tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF family, which is being developed as an anti-tumour agent due to its selective toxicity to tumour cells, induces apoptosis by binding to two membrane-bound receptors, TRAIL-R1 and TRAIL-R2. Clinical trials have been initiated with various preparations of TRAIL as well as agonistic monoclonal antibodies to TRAIL-R1 and TRAIL-R2. Previously we reported that prior treatment of primary chronic lymphocytic leukaemia (CLL) cells with histone deacetylase inhibitors was required to sensitize CLL cells to TRAIL and, using various receptor-selective TRAIL mutant ligands, we demonstrated that CLL cells signalled to apoptosis primarily through TRAIL-R1. Some, but not all, agonistic TRAIL-receptor antibodies require cross-linking in order to induce apoptosis. The present study demonstrated that CLL cells can signal to apoptosis through the TRAIL-R2 receptor, but only after cross-linking of the agonistic TRAIL-R2 antibodies, LBY135 and lexatumumab (HGS-ETR2). In contrast, signalling through TRAIL-R1 by receptor-selective ligands or certain agonistic antibodies, such as mapatumumab (HGS-ETR1), occurs in the absence of cross-linking. These results further highlight important differences in apoptotic signalling triggered through TRAIL-R1 and TRAIL-R2 in primary tumour cells. Such information is clearly important for the rational optimisation of TRAIL therapy in primary lymphoid malignancies, such as CLL.

A human scFv antibody against TRAIL receptor 2 induces autophagic cell death in both TRAIL-sensitive and TRAIL-resistant cancer cells

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptotic cell death in a variety of tumor cells without significant cytotoxicity on normal cells. However, many cancer cells with apoptotic defects are resistant to treatment with TRAIL alone, limiting its potential as an anticancer therapeutic. Here, we report on the tumoricidal activity of a human single-chain fragment variable, HW1, which specifically binds to TRAIL receptor 2 (TR2) without competing with TRAIL for the binding. HW1 treatment as a single agent induces autophagic cell death in a variety of both TRAIL-sensitive and TRAIL-resistant cancer cells, but exhibits much less cytotoxicity on normal cells. The HW1-induced autophagic cell death was inhibited by an autophagy inhibitor, 3-methyladenine, or by RNA interference knockdown of Beclin-1 and Atg7. We also show that the HW1-mediated autophagic cell death occurs predominantly via the c-Jun NH(2)-terminal kinase pathway in a caspase-independent manner. Analysis of the death-inducing signaling complex induced by HW1 binding to TR2 exhibits the recruitment of TNF receptor-associated death domain and TNF receptor-associated factor 2, but not Fas-associated death domain, caspase-8, or receptor-interacting protein, which is distinct from that induced by TRAIL. Our results reveal a novel TR2-mediated signaling pathway triggering autophagic cell death and provides a new strategy for the elimination of cancer cells, including TRAIL-resistant tumors, through nonapoptotic cell death.

Targeting death-inducing receptors in cancer therapy

Deregulated cell death pathways may lead to the development of cancer, and induction of tumor cell apoptosis is the basis of many cancer therapies. Knowledge accumulated concerning the molecular mechanisms of apoptotic cell death has aided the development of new therapeutic strategies to treat cancer. Signals through death receptors of the tumor necrosis factor (TNF) superfamily have been well elucidated, and death receptors are now one of the most attractive therapeutic targets in cancer. In particular, DR5 and DR4, death receptors of TNF-related apoptosis-inducing ligand (TRAIL or Apo2L), are interesting targets of antibody-based therapy, since TRAIL may also bind decoy receptors that may prevent TRAIL-mediated apoptosis, whereas TRAIL ligand itself selectively induces apoptosis in cancer cells. Here, we review the potential therapeutic utility of agonistic antibodies against DR5 and DR4 and discuss the possible extension of this single-antibody-based strategy when combined with additional modalities that either synergizes to cause enhanced apoptosis or further engage the cellular immune response. Rational design of antibody-based therapies combining the induction of tumor cell apoptosis and activation of tumor-specific adaptive immunity enables promotion of distinct steps of the antitumor immune response, thereby enhancing tumor-specific lymphocytes that can eradicate TRAIL/DR5-resistant mutating, large established and heterogeneous tumors in a manner that does not require the definition of individual tumor-specific antigens.

High-resolution single-photon emission computed tomography and X-ray computed tomography imaging of Tc-99m-labeled anti-DR5 antibody in breast tumor xenografts

A murine, apoptosis-inducing monoclonal antibody (mTRA-8) targeting human DR5 was radiolabeled with Tc-99m. The binding affinity (K(d)) and the number of DR5 receptors were measured in MD MBA-231-derived 2LMP cell lines that were "sensitive" or "resistant" to mTRA-8 killing. Single-photon emission computed tomography and X-ray computed tomography (SPECT/CT) evaluated the Tc-99m-mTRA-8 retention and distribution within xenograft tumors; biodistribution analyses confirmed the levels. Scatchard assays showed specific and high binding affinity of Tc-99m-mTRA-8 to DR5; the killing efficacy of mTRA-8 was unchanged by Tc-99m labeling. There was no significant difference between sensitive and resistant 2LMP cells for K(d) values (1.5 +/- 0.3 nmol/L = acid labile), or DR5 receptors (mean/cell = 11,000). SPECT/CT imaging analyses at 6 h after injection of Tc-99m-mTRA-8 revealed the second 1.5 mm shell from the surface of the mammary fat pad tumors (n = 5; 5,627 mm(3)) retained 12.7 +/- 1.4%ID/g, higher than the other shells, with no difference between the sensitive and resistant 2LMP tumors. Binding of Tc-99m-labeled mTRA-8 in tumor was specific; excess unlabeled mTRA-8 blocked Tc-99m-mTRA-8 retention in tumor by 45%. Retention of Tc-99m-labeled isotype antibody in tumor was consistent with the blocking study, and 30% lower. These studies show that SPECT/CT imaging provided detailed distribution information of Tc-99m-labeled mTRA-8 within breast tumor xenografts. Imaging could provide a mechanism to assess DR5 modulation when DR5 therapy is combined with chemotherapy and radiation, and thereby aid in optimizing the dosing schedule.

The promise of TRAIL—potential and risks of a novel anticancer therapy

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising new anticancer biotherapeutic. As shown by many preclinical studies, TRAIL efficiently induces apoptosis in numerous tumor cell lines but not in the majority of normal cells. However, an increasing number of publications report on a predominance of TRAIL resistance in primary human tumor cells, which require sensitization for TRAIL-induced apoptosis. Sensitization of cancer cells by treatment with chemotherapeutic drugs and irradiation has been shown to restore TRAIL sensitivity in many TRAIL-resistant tumor cells. Accordingly TRAIL treatment has been successfully used in different in vivo models for the treatment of tumors also in combination with chemotherapeutics without significant toxicity. However, some reports demonstrated toxicity of TRAIL alone or in combination with chemotherapeutic drugs in normal cells. This review summarizes data concerning the apoptosis-inducing pathways and efficacy of TRAIL, alone or in combination with chemotherapeutic drugs, in primary cancer cells compared to the unwanted effects of TRAIL treatment on normal tissue. We discuss the different in vitro tumor cell models and the potential of different recombinant forms of TRAIL or agonistic antibodies to TRAIL death receptors. Most preclinical studies show a high efficiency of a combinatorial TRAIL-based therapy in animal models and in primary human ex vivo tumor cells with a low toxicity in normal cells. Accordingly clinical phase I/II studies have begun and will be developed further with caution.

Prognostic significance of tumor necrosis factor-related apoptosis-inducing ligand and its receptors in adjuvantly treated stage III colon cancer patients

PURPOSE

In preclinical models, there is synergism between chemotherapy and recombinant human tumor necrosis factor (TNF) -related apoptosis-inducing ligand (TRAIL) on apoptosis induction in tumor cells. Therefore, the prognostic relevance was analyzed of the expression of TRAIL and its death receptors DR4 and DR5 on disease-free survival and overall survival in stage III colon cancer patients treated with adjuvant chemotherapy.

METHODS

Tissue microarrays were constructed of primary tumor tissue from 376 stage III colon cancer patients treated in a randomized adjuvant chemotherapy study (fluorouracil/levamisole v fluorouracil/levamisole/leucovorin) and stained immunohistochemically for TRAIL, DR4, and DR5. Log-rank tests and Cox proportional hazard analysis, with adjustment for treatment arm, sex, age, N stage, microsatellite instability status, and p53 mutation status, were performed.

RESULTS

The majority of tumors showed high expression of TRAIL (83%), DR4 (92%), and DR5 (87%). Median follow-up was 43 months. High DR4 expression was associated with worse disease-free survival (odds ratio [OR] = 2.19; 95% CI, 1.06 to 4.53; P = .03), worse overall survival (OR = 2.22; 95% CI,1.03 to 4.81; P = .04) and shorter time to recurrence (P = .02) compared with those with low DR4 expression. TRAIL or DR5 expression had no prognostic value.

CONCLUSION

High DR4 expression is associated with worse disease-free and overall survival in stage III adjuvant-treated colon cancer patients. Evaluation of DR4 expression in stage III colon cancer patients may identify a subset requiring more aggressive adjuvant treatment.

Expression of tumor necrosis factor--related apoptosis-inducing ligand receptors 1 and 2 in melanoma

PURPOSE

The proapoptotic receptors tumor necrosis factor--related apoptosis-inducing ligand receptor 1 (TRAIL-R1) and TRAIL-R2 are targets of drugs in clinical development, and receptor expression levels may be important determinants of sensitivity to receptor agonists. We assessed TRAIL-R1 and TRAIL-R2 expression patterns in a large cohort of melanomas and benign nevi.

EXPERIMENTAL DESIGN

We analyzed tissue microarrays containing 546 melanomas and 540 nevi using our automated quantitative method to measure protein levels in situ (AQUA). The system uses S100 to define pixels as melanoma (tumor mask) within the array spot and measures intensity of TRAIL-receptor expression using Cy5-conjugated antibodies within the mask. AQUA scores were correlated with clinical and pathologic variables.

RESULTS

TRAIL-R1 and TRAIL-R2 expression was higher in melanomas than in nevi (P < 0.0001), and higher in primary than in metastatic specimens (P = 0.0031 and P < 0.0001, respectively). TRAIL-R1 and TRAIL-R2 expression exceeding the 95th percentile for nevi was found in 19% and 74% of melanoma specimens, respectively. Although on univariate analysis, high TRAIL-R2 expression correlated with increased survival (P = 0.0439), it was not associated with survival within the primary or metastatic subcohorts. TRAIL-R1 expression was not associated with survival.

CONCLUSIONS

TRAIL-R1 and TRAIL-R2 expression is higher in malignant melanocytes than in their benign counterparts, suggesting that these receptors might be effective therapeutic targets in melanoma. Expression is higher in early-stage disease than in metastatic specimens, and expression exceeding that found in nevi is found in a substantially larger fraction of melanomas for TRAIL-R2 compared with TRAIL-R1. Assessment of baseline tumor TRAIL receptor expression may be important in analysis of clinical trials involving TRAIL receptor agonists.

The clinical trail of TRAIL

The naturally occurring tumour necrosis factor related apoptosis-inducing ligand (TRAIL) induces apoptosis through two death receptors, death receptor 4 (DR4) and death receptor 5 (DR5), that are expressed on the cell membrane. Binding of the ligand to the death receptors leads to activation of the extrinsic apoptosis pathway. Chemotherapy on the other hand stimulates the intrinsic apoptosis pathway via activation of p53 in response to cellular damage. Many cancer cells have mutations in p53 causing resistance to chemotherapy-induced apoptosis. Concomitant signalling through the extrinsic pathway may overcome this resistance. Moreover, enthusiasm for TRAIL as an anticancer agent is based on the demonstration of rhTRAIL-induced selective cell death in tumour cells and not in normal cells. In this review, we provide an overview of the TRAIL pathway, the physiological role of TRAIL and the factors regulating TRAIL sensitivity. We also discuss the clinical development of novel agents, i.e. rhTRAIL and agonistic antibodies, that activate the death receptors.

Transduction of tumor necrosis factor-related apoptosis-inducing ligand into hematopoietic cells leads to inhibition of syngeneic tumor growth in vivo

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family of cytokines and has been shown to induce cell death in many types of tumor and transformed cells but not in normal cells. This tumor-selective property has made TRAIL a promising candidate for the development of cancer therapy. However, safety issues are a concern because certain preparations of recombinant TRAIL protein were reported to induce toxicity in normal human hepatocytes in culture. In addition, previous studies on tumor selectivity of exogenous TRAIL protein were carried out in xenograft models, which do not directly address the tumor selectivity issue. It was not known whether exogenous or overexpression of TRAIL in a syngeneic system could induce tumor cell death while leaving normal tissue cells unharmed. Thus, the tumor selectivity of TRAIL-induced apoptosis remains to be further characterized. In our study, we established mice that overexpress TRAIL by retroviral-mediated gene transfer in bone marrow cells followed by bone marrow transplantation. Our results show that TRAIL overexpression is not toxic to normal tissues, as analyzed by hematologic and histologic analyses of tissue samples from TRAIL-transduced mice. We show for the first time that TRAIL overexpression in hematopoietic cells leads to significant inhibition of syngeneic tumor growth in certain tumor lines. This approach may be used further to identify important molecules that regulate the sensitivity of tumor cells to TRAIL-induced cell death in vivo.

Engineering of therapeutic antibodies to minimize immunogenicity and optimize function

One of the first difficulties in developing monoclonal antibody therapeutics was the recognition that human anti-mouse antibody (HAMA) response limited the administration of murine antibodies. Creative science has lead to a number of ways to counter the immunogenicity of non-human antibodies, primarily through chimeric, humanized, de-immunized, and most recently, human-sequence therapeutic antibodies. Once therapeutic antibodies of low or no immunogenicity were available, the creativity then turned to engineering both the antigen-binding domains (e.g., affinity maturation, stability) and altering the effector functions (e.g. antibody-dependent cellular cytotoxicity, complement-dependent cellular cytotoxicity, and clearance rate).

TNF-related apoptosis-inducing ligand as a therapeutic agent in autoimmunity and cancer

Recombinant, soluble TNF-related apoptosis-inducing ligand (TRAIL) is currently being developed as a promising natural immune molecule for trial in cancer patients because it selectively induces apoptosis in transformed or stressed cells but not in most normal cells. In cancer patients, phase 1 and 2 clinical trials using agonistic mAbs that engage the human TRAIL receptors DR4 and DR5 have also provided encouraging results. It is now evident that TRAIL suppresses autoimmune disease in various experimental animal models, suggesting that the therapeutic value of recombinant TRAIL and agonistic DR4 and DR5 mAbs might also extend to the suppression of autoimmune disease. This review provides an insight into our current understanding of the role(s) of TRAIL in disease, with a specific focus on cancer and autoimmunity. We also emphasize biological agents and drugs that sensitize tumour cells to TRAIL-mediated apoptosis and discuss the potential molecular basis for their sensitization.