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

Abstract

We and others have demonstrated already that TRAIL (TNF-related apoptosis-inducing ligand) is a very promising candidate for molecular targeted anticancer therapy, especially when combined with ionizing radiation or other DNA-damaging agents. Agonist monoclonal antibodies that activate and are specific for the death signaling TRAIL receptors are an alternative method to stimulate the programmed cell death pathway. Phase 1 clinical trials have subsequently been conducted and shown a very good tolerability of these antibodies. In order to assess the efficacy of TRAIL receptor stimulation to induce cell death by this alternate method, we studied the combination of the agonistic-TRAIL receptor antibodies HGS-ETR1 and HGS-ETR2 with radiation in vitro and in vivo. Induction of apoptosis after combined treatment with TRAIL receptor antibodies HGS-ETR1 and/or HGS-ETR2 (0.01, 0.1, 1.0 mg/ml) and irradiation with 2, 5 or 10 Gy was determined by fluorescence microscopy and Western blot analysis of caspase-8 and PARP. The colorectal tumour cell lines Colo 205, HCT 116 and HCT-15 were used for in vitro experiments. Growth delay experiments were performed with combined treatment with fractionated irradiation (days 1-5 and 3 Gy single dose/day) and the receptor antibodies (intraperitonially, three different concentrations, application on days 1, 4 and 8) on Colo 205 xenograft-bearing NMRI (nu/nu) nude mice. HGS-ETR1 and HGS-ETR2 induced apoptotic cell death in a dose-dependent fashion and significantly increased cell death in combination with irradiation in vitro when compared to either irradiation or antibody treatment alone. The efficacy of the combined treatment seems to be at least partially Bax-dependent. Similar to the results from cell culture experiments, in vivo experiments demonstrated a dose-dependent delay in tumour growth after combined treatment. In vivo, in the Colo205 xenograft model, HGS-ETR2 revealed a higher activity than HGS-ETR1. This is the first study to demonstrate significant efficacy of combined treatment with the monoclonal agonistic TRAIL receptor antibodies HGS-ETR1 and HGS-ETR2 and ionising radiation in in vitro and in vivo models. We postulate that HGS-ETR1 and HGS-ETR2 will be very promising new agents in the field of molecular targeted multi-modality anticancer therapy.

Enhanced susceptibility to tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis in oral squamous cell carcinoma cells treated with phosphatidylinositol 3-kinase inhibitors

“…As such, pharmacological inhibitors of the PI 3-K/Akt signaling pathway might achieve this aim: recent studies have demonstrated that agonistic mAbs against DR4 and DR5 can induce apoptosis in a variety of cultured and primary cancer cells (53). Other studies have shown that the combination of anti-human DR4 and DR5 mAbs with chemotherapeutic drugs or radiotherapy synergistically enhanced anti-tumor effects (54,55). Given the inherent difficulties of using wortmannin and LY294002 (stability, solubility and toxicity), efforts are underway to develop new PI 3-K pathway inhibitors; recently, a novel candidate has been reported that exhibits strong anti-tumor activity against human cancers without concomitant toxic effects on organs (56).…”

Targeting death-inducing receptors in cancer therapy

“…Sensitivity to rTRAIL-induced apoptosis was reported in cell lines derived from human colon, lung, breast, kidney, brain and skin cancer (Ashkenazi et al, 1999). Till date, effective apoptosis induction by rTRAIL has been reported in human melanoma, leukemia, multiple myeloma, breast, bladder, prostate, renal or colon cancer in single treatments and/or combination therapy with chemotherapeutic agents (Chawla-Sarkar et al, 2002;An et al, 2003;Buchsbaum et al, 2003;van Geelen et al, 2003;VoelkelJohnson, 2003;Merchant et al, 2004;Georgakis et al, 2005;Kaufmann and Steensma, 2005;Kurbanov et al, 2005;Pukac et al, 2005;Bucur et al, 2006;Marini et al, 2006;O'Kane et al, 2006;Zeng et al, 2006). Thus, these cancers are the most promising indications for clinical trials of TRAIL and anti-DR5/DR4 mAb.…”

TRAIL receptor upregulation and the implication of KRAS/BRAF mutations in human colon cancer tumors

“…3,[7][8][9] In addition, TRAIL acts synergistically with chemotherapeutic drugs and can overcome drug resistance in tumor cell lines and animal models. [10][11][12] Immunohistochemical studies have demonstrated that the proapoptotic DR4 and DR5 are expressed in normal colon mucosa as well as colorectal adenomas and carcinomas, and their expression was increased in malignant versus normal cells. In comparison, there is a marked increase in sensitivity to TRAIL-induced apoptosis associated with progression from benign to malignant tumor with the assumption that sensitivity to TRAIL could be acquired early in colorectal tumorigenesis during the formation of adenoma.…”