Enhanced apoptosis following treatment with TRA-8 anti-human DR5 monoclonal antibody and overexpression of exogenous Bax in human glioma cells

Harnessing the apoptotic programs in cancer stem-like cells

Elimination of malignant cells is an unmet challenge for most human cancer types even with therapies targeting specific driver mutations. Therefore, a multi-pronged strategy to alter cancer cell biology on multiple levels is increasingly recognized as essential for cancer cure. One such aspect of cancer cell biology is the relative apoptosis resistance of tumor-initiating cells. Here, we provide an overview of the mechanisms affecting the apoptotic process in tumor cells emphasizing the differences in the tumor-initiating or stem-like cells of cancer. Further, we summarize efforts to exploit these differences to design therapies targeting that important cancer cell population.

Dovitinib sensitizes hepatocellular carcinoma cells to TRAIL and tigatuzumab, a novel anti-DR5 antibody, through SHP-1-dependent inhibition of STAT3

Hepatocellular carcinoma (HCC) often displays resistance to recombinant tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Dovitinib, a multiple tyrosine kinase inhibitor, and tigatuzumab, a novel humanized anti-human death receptor 5 (DR5) agonistic antibody, are both under clinical investigations in HCC. Here, we report that dovitinib sensitizes resistant HCC cells to TRAIL- and tigatuzumab-induced apoptosis through inhibition of signal transducers and activators of transcription 3 (STAT3). Our data indicate that HCC cells showed significant resistance to TRAIL- and tigatuzumab-induced apoptosis. The combination of dovitinib and tigatuzumab restored the sensitivity of HCC cells to TRAIL- and tigatuzumab-induced apoptosis. Dovitinib down-regulated phospho-STAT3 (Tyr705) (p-STAT3) and subsequently reduced the protein levels of STAT3-regulated proteins, Mcl-1, survivin and cylcin D1, in TRAIL-treated HCC cells. Knockdown of STAT3 by RNA-interference overcame apoptotic resistance to TRAIL in HCC cells, and ectopic expression of STAT3 in HCC cells abolished the sensitizing effect of dovitinib on TRAIL-induced apoptosis. Importantly, silencing SHP-1 by RNA-interference reduced the effects of dovitinib and TRAIL on p-STAT3 and apoptosis, whereas co-treatment of TRAIL and dovitinib increased the activity of SHP-1. Moreover, in vivo the combination of tigatuzumab and dovitinib inhibited Huh-7 xenograft tumor growth. In conclusion, dovitinib sensitizes resistant HCC cells to TRAIL- and tigatuzumab-induced apoptosis through a novel machinery: SHP-1 dependent STAT3 inhibition.

Phase I trial of weekly tigatuzumab, an agonistic humanized monoclonal antibody targeting death receptor 5 (DR5)

BACKGROUND

TRA-8 is a murine agonist monoclonal antibody to death receptor 5 (DR5), which is able to trigger apoptosis in DR5 positive human tumor cells without the aid of crosslinking. It has demonstrated cytotoxicity in vitro and in vivo antitumor efficacy to a wide range of solid tumors in murine xenograft models. Tigatuzumab is a humanized IgG1 monoclonal antibody derived from TRA-8.

METHODS

A phase I trial of tigatuzumab in patients with relapsed/refractory carcinomas (n = 16) or lymphoma (n = 1) was designed to determine the maximal tolerated dose (MTD), pharmacokinetics, immunogenicity, and safety. Three to six (3-6) patients were enrolled in successive escalating cohorts at doses ranging from 1 to 8 mg/kg weekly.

RESULTS

Seventeen (17) patients enrolled, 9 in the 1-, 2-, and 4-mg/kg dose cohorts (3 in each cohort) and 8 in the 8-mg/kg dose cohort. Tigatuzumab was well tolerated with no DLTs observed, and the MTD was not reached. There were no study-drug-related grade 3 or 4, renal, hepatic, or hematologic toxicities. Plasma half-life was 6-10 days, and no anti-tigatuzumab responses were detected. Seven (7) patients had stable disease, with the duration of response ranging from 81 to 798 days.

CONCLUSIONS

Tigatuzumab is well tolerated, and the MTD was not reached. The high number of patients with stable disease suggests antitumor activity.

A combination of DR5 agonistic monoclonal antibody with gemcitabine targets pancreatic cancer stem cells and results in long-term disease control in human pancreatic cancer model

Pancreatic ductal adenocarcinoma (PDA) is an aggressive malignancy with one of the worst outcomes among all cancers. PDA often recurs after initial treatment to result in patient death despite the use of chemotherapy or radiation therapy. PDA contains a subset of tumor-initiating cells capable of extensive self-renewal known as cancer stem cells (CSC), which may contribute to therapeutic resistance and metastasis. At present, conventional chemotherapy and radiotherapy are largely ineffective in depleting CSC pool, suggesting the need for novel therapies that specifically target the cancer-sustaining stem cells for tumor eradication and to improve the poor prognosis of PDA patients. In this study, we report that death receptor 5 (DR5) is enriched in pancreatic CSCs compared with the bulk of the tumor cells. Treating a collection of freshly generated patient-derived PDA xenografts with gemcitabine, the first-line chemotherapeutic agent for PDA, is initially effective in reducing tumor size, but largely ineffective in diminishing the CSC populations, and eventually culminated in tumor relapse. However, a combination of tigatuzumab, a fully humanized DR5 agonist monoclonal antibody, with gemcitabine proved to be more efficacious by providing a double hit to kill both CSCs and bulk tumor cells. The combination therapy produced remarkable reduction in pancreatic CSCs, tumor remissions, and significant improvements in time to tumor progression in a model that is considered more difficult to treat. These data provide the rationale to explore the DR5-directed therapies in combination with chemotherapy as a therapeutic option to improve the current standard of care for pancreatic cancer patients.

Enhancement of glioma radiotherapy and chemotherapy response with targeted antibody therapy against death receptor 5

PURPOSE

TRA-8 is an agonistic mouse monoclonal antibody that binds to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) death receptor 5, which induces apoptosis in cancer cells through a caspase-8-dependent mechanism. We investigated the ability of TRA-8 to augment the radiotherapy (RT) and chemotherapy response of human glioma cells in vitro and in vivo.

METHODS AND MATERIALS

The in vitro cytotoxicity of TRA-8 and temozolomide (Tmz) or RT was examined using adenosine triphosphate-dependent viability and clonogenic survival assays with five glioma cell lines. Death receptor 5 expression was determined by flow cytometry. In vivo studies included subcutaneous and intracranial xenograft models testing various combination treatments, including RT, Tmz, and TRA-8.

RESULTS

TRA-8, combined with Tmz or RT, produced enhanced cytotoxicity against five glioma cell lines compared with the use of the individual agents alone. Death receptor 5 upregulation occurred in response to RT. Complete tumor regression in the subcutaneous experiments was the most common in animals that received combination therapy with TRA-8/Tmz/RT. TRA-8 enhanced tumor growth delay in combination with RT or Tmz. TRA-8 alone had limited activity against intracranial tumors. In contrast, the median survival of mice treated with TRA-8/Tmz/RT was significantly greater than the control or TRA-8-alone-treated mice. The median survival of the mice treated with TRA-8/Tmz/RT or chemoradiotherapy only was significantly greater than the control or TRA-8-treated mice. A trend toward improved survival was observed between TRA-8/Tmz/RT-treated and Tmz/RT-treated mice.

CONCLUSIONS

These preliminary findings support the hypothesis that TRA-8 will augment the RT and chemotherapy response in gliomas. A humanized version of TRA-8 is being evaluated in a Phase II clinical trial.

DR5 activation of caspase-8 induces DC maturation and immune enhancement in vivo

Non-homeostatic tissue apoptosis in vivo has been shown to induce inflammatory responses and facilitate the cross-presentation of proteins within apoptotic bodies. We hypothesize that in the presence of foreign antigens, the apoptotic-inflammatory process improves immune priming; further, molecules that trigger apoptosis may be adapted for use as immune adjuvants. One very attractive molecule in this context is the tumor necrosis factor receptor (TNFR) family molecule DR5/TRAIL-receptor 2. We show a significant improvement in CD8(+) T-cell mediated vaccine immunity with the use of death receptor-5 (DR5) as an immune adjuvant, a property that is correlated with the activation of caspases-8 (casp8) and dependent on its ability to induce apoptosis in vivo.

Combination of cytosine deaminase suicide gene expression with DR5 antibody treatment increases cancer cell cytotoxicity

Combined treatment using adenoviral-directed enzyme/prodrug therapy and immunotherapy has the potential to become a powerful alternative method of cancer therapy. We have developed adenoviral vectors encoding the cytosine deaminase gene (Ad-CD) and cytosine deaminase:uracil phosphoribosyltransferase fusion gene (Ad-CD:UPRT). A monoclonal antibody, TRA-8, specifically binds to death receptor 5, one of two death receptors bound by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). The purpose of this study was to evaluate cytotoxicity in vitro and therapeutic efficacy in vivo of the combination of Ad-CD:UPRT and TRA-8 against human pancreatic cancer and glioma cell lines. The present study demonstrates that Ad-CD:UPRT infection resulted in increased 5-FC-mediated cell killing, compared with Ad-CD. Furthermore, a significant increase of cytotoxicity following Ad-CD:UPRT/5-FC and TRA-8 treatment of cancer cells in vitro was demonstrated. Animal studies showed significant inhibition of tumor growth of MIA PaCa-2 pancreatic and D54MG glioma xenografts by the combination of Ad-CD:UPRT/5-FC plus TRA-8 as compared with either agent alone or no treatment. The results suggest that the combination of Ad-CD:UPRT/5-FC with TRA-8 produces an additive cytotoxic effect in cancer cells in vitro and in vivo. These data indicate that combined treatment with enzyme/prodrug therapy and TRAIL immunotherapy provides a promising approach for cancer therapy.

HGS-ETR1, a fully human TRAIL-receptor 1 monoclonal antibody, induces cell death in multiple tumour types in vitro and in vivo

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a variety of tumour cells through activation of TRAIL-R1 and TRAIL-R2 death signalling receptors. Here, we describe the characterisation and activity of HGS-ETR1, the first fully human, agonistic TRAIL-R1 mAb that is being developed as an antitumour therapeutic agent. HGS-ETR1 showed specific binding to TRAIL-R1 receptor. HGS-ETR1 reduced the viability of multiple types of tumour cells in vitro, and induced activation of caspase 8, Bid, caspase 9, caspase 3, and cleavage of PARP, indicating activation of TRAIL-R1 alone was sufficient to induce both extrinsic and intrinsic apoptotic pathways. Treatment of cell lines in vitro with HGS-ETR1 enhanced the cytotoxicity of chemotherapeutic agents (camptothecin, cisplatin, carboplatin, or 5-fluorouracil) even in tumour cell lines that were not sensitive to HGS-ETR1 alone. In vivo administration of HGS-ETR1 resulted in rapid tumour regression or repression of tumour growth in pre-established colon, non-small-cell lung, and renal tumours in xenograft models. Combination of HGS-ETR1 with chemotherapeutic agents (topotecan, 5-fluorouracil, and irinotecan) in three independent colon cancer xenograft models resulted in an enhanced antitumour efficacy compared to either agent alone. Pharmacokinetic studies in the mouse following intravenous injection showed that HGS-ETR1 serum concentrations were biphasic with a terminal half-life of 6.9–8.7 days and a steady-state volume of distribution of approximately 60 ml kg⁻¹. Clearance was 3.6–5.7 ml⁻¹ day⁻¹ kg⁻¹. These data suggest that HGS-ETR1 is a specific and potent antitumour agent with favourable pharmacokinetic characteristics and the potential to provide therapeutic benefit for a broad range of human malignancies.

Plattenepithelkarzinome des Kopf-Hals-Bereichs

Biologic therapies able to induce or up-regulate anti-tumor immune responses could represent a complementary approach to improve the conventional treatment of squamous cell carcinomas of the head and neck (SCCHN). Patients with SCCHN are frequently immunocompromised due to the elimination and dysfunction of critical immune effector cells. Therefore, it might be necessary to restore these immune functions to allow for the generation of effective anti-tumor host responses. Simultaneously, to prevent tumor escape from immunological recognition and destruction, it might also be necessary to alter antigenic and immunogenic attributes of the malignant cells. The present overview summarizes general aspects, historical data, and recent advances in the field of immunotherapy of SCCHN, including non-specific immune stimulation, transfer of immunocompetent cells, gene therapy, use of monoclonal antibodies, and anti-cancer vaccines.

Enhancement of therapeutic potential of TRAIL by cancer chemotherapy and irradiation: mechanisms and clinical implications

Activation of cell surface death receptors by their cognate ligands triggers apoptosis. Several human death receptors (Fas, TNF-R1, TRAMP, DR4, DR5, DR6, EDA-R and NGF-R) have been identified. The most promising cytokine for anticancer therapy is TRAIL/APO-2L, which induces apoptosis in cancer cells by binding to death receptors TRAIL-R1/DR4 and TRAIL-R2/DR5. The cytotoxic activity of TRAIL is relatively selective to cancer cells compared to normal cells. Signaling by TRAIL and its receptors is tightly regulated process essential for key physiological functions in a variety of organs, as well as the maintenance of immune homeostasis. Despite early promising results, recent studies have identified several TRAIL-resistant cancer cells of various origins. Based on molecular analysis of death-receptor signaling pathways several new approaches have been developed to increase the efficacy of TRAIL. Resistance of cancer cells to TRAIL appears to occur through the modulation of various molecular targets. They may include differential expression of death receptors, constitutively active Akt and NFkappaB, overexpression of cFLIP and IAPs, mutations in Bax and Bak genes, and defects in the release of mitochondrial proteins in resistant cells. Conventional chemotherapeutic and chemopreventive drugs, and irradiation can sensitize TRAIL-resistant cells to undergo apoptosis. Thus, these agents enhance the therapeutic potential of TRAIL in TRAIL-sensitive cells and sensitize TRAIL-resistant cells. TRAIL and TRAIL-receptor antibodies may prove to be useful for cancer therapy, either alone or in association with conventional approaches such as chemotherapy or radiation therapy. This review discusses intracellular mechanisms of TRAIL resistance and various approaches that can be taken to sensitize TRAIL-resistant cancer cells.

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Fast response temperature measurement and highly reproducible heating methods for 96-well plates

Hyperthermia, the procedure of exposing cells to a temperature between 42° and 49°C, has been shown to be a promising approach for cancer treatment. To understand the underlying mechanisms of hyperthermic killing of cancer cells, it is critical to have an accurate temperature measurement technique and a heating method with high reproducibility. To this end, we have developed a method using fine thermocouples with fast response time to measure the temperatures in multiple wells of a 96-well plate. The accuracy of temperature measurement was ±0.2°C. Such a capability allows a complete record of the time and temperature of the treatment procedure and helps define an accurate thermal dose. We have also compared several methods for heating 96-well plates and found that use of copper blocks in contact with the lower surface of the 96-well plate in an incubator provides a highly reproducible heating method. The common method of using water bath to heat cells in vitro resulted in a decrease of cell viability even at the control temperature of 37°C and a decrease in the reproducibility of certain biological assays. In summary, using these improved techniques, proposed thermal dose can be defined more precisely, and highly reproducible heating in vitro can be achieved.