Modulation of TRAIL resistance in colon carcinoma cells: Different contributions of DR4 and DR5

<p>Abstract</p> <p>Background</p> <p>rhTRAIL is a therapeutic agent, derived from the TRAIL cytokine, which induces apoptosis in cancer cells by activating the membrane death receptors 4 and 5 (DR4 and DR5). Here, we investigated each receptor's contribution to rhTRAIL sensitivity and rhTRAIL resistance. We assessed whether agonistic DR4 or DR5 antibodies could be used to circumvent rhTRAIL resistance, alone or in combination with various chemotherapies.</p> <p>Methods</p> <p>Our study was performed in an isogenic model comprised of the SW948 human colon carcinoma cell line and its rhTRAIL resistant sub-line SW948-TR. Effects of rhTRAIL and agonistic DR4/DR5 antibodies on cell viability were measured using MTT assays and identification of morphological changes characteristic of apoptosis, after acridine orange staining. Sensitivity to the different death receptor ligands was stimulated using pretreatment with the cytokine IFN-gamma and the proteasome inhibitor MG-132. To investigate the mechanisms underlying the changes in rhTRAIL sensitivity, alterations in expression levels of targets of interest were measured by Western blot analysis. Co-immunoprecipitation was used to determine the composition of the death-inducing signalling complex at the cell membrane.</p> <p>Results</p> <p>SW948 cells were sensitive to all three of the DR-targeting agents tested, although the agonistic DR5 antibody induced only weak caspase 8 cleavage and limited apoptosis. Surprisingly, agonistic DR4 and DR5 antibodies induced equivalent DISC formation and caspase 8 cleavage at the level of their individual receptors, suggesting impairment of further caspase 8 processing upon DR5 stimulation. SW948-TR cells were cross-resistant to all DR-targeting agents as a result of decreased caspase 8 expression levels. Caspase 8 protein expression was restored by MG-132 and IFN-gamma pretreatment, which also re-established sensitivity to rhTRAIL and agonistic DR4 antibody in SW948-TR. Surprisingly, MG-132 but not IFN-gamma could also increase DR5-mediated apoptosis in SW948-TR.</p> <p>Conclusions</p> <p>These results highlight a critical difference between DR4- and DR5-mediated apoptotic signaling modulation, with possible implications for future combinatorial regimens.</p

Mapatumumab, a Fully Human Agonistic Monoclonal Antibody That Targets TRAIL-R1, in Combination with Gemcitabine and Cisplatin: a Phase I Study

Purpose: To evaluate the safety, tolerability, pharmacokinetics, and antitumor activity of mapatumumab, a fully human monoclonal antibody targeting tumor necrosis factor-related apoptosis-inducing ligand receptor 1 (TRAIL-R1), in combination with gemcitabine and cisplatin. Experimental Design: Patients with advanced solid tumors received gemcitabine 1,250 mg/m(2) i.V. on days 1 and 8 and cisplatin 80 mg/m(2) i.V. on day 1 of each 21-day cycle. Escalating mapatumumab doses were administered i.v. every 21 days. Toxicity was evaluated and pharmacokinetic analysis of plasma mapatumumab, gemcitabine, 2-difluoro-2-deoxyuridine, and unbound and total platinum was done. TRAIL-R1 tumor expression was determined immunohistochemically. Results: Forty-nine patients received mapatumumab (1 mg/kg, n = 4; 3 mg/kg, n = 7; 10 mg/kg, n = 12; 20 mg/kg, n = 13; or 30 mg/kg, n = 13). A median of six cycles (range, 1-48) was administered. The adverse events most commonly observed reflect the toxicity profile of gemcitabine and cisplatin. Dose-limiting toxicities were seen in 3 of 12 patients at 10 mg/kg, consisting of grade 3 transaminitis, neutropenic fever, and grade 4 thrombocytopenia. At 20 mg/kg, 2 of 12 patients had dose-limiting toxicities, including grade 4 thrombocytopenia and grade 4 fatigue. The maximum tolerated dose was not reached. Pharmacokinetic interactions have not been observed. Twelve patients had a partial response, and 25 patients showed stable disease with a median duration of 6 months. Conclusions: Mapatumumab in combination with gemcitabine and cisplatin is safe and well tolerated at doses up to 30 mg/kg. Further studies on this combination are warranted. (Clin Cancer Res 2009;15(17):5584-90

Sulindac inhibits beta-catenin expression in normal-appearing colon of hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis patients

Sulindac reduces colorectal cancer risk in genetically susceptible humans and animals. The molecular mechanisms underlying these effects are incompletely understood. Many studies suggest an important role for induction of apoptosis involving the mitochondrial pathway and the death receptor pathway. Alternatively, mechanisms involving the APC-beta-catenin-Wnt pathway have been suggested, possibly mediated by p21. We determined the effects of sulindac on apoptosis and expression of death receptor (DR)4 and DR5, beta-catenin, and p21 in normal-appearing colorectal epithelium. Biopsies were obtained before and after sulindac treatment during two chemoprevention studies. Patients (n = 18) with hereditary nonpolyposis colorectal cancer (HNPCC) received 150 mg sulindac bd for 4 weeks in a placebo-controlled crossover design. Patients (n = 6) with familial adenomatous polyposis (FAP) received 150 mg sulindac bd for 6 months. Apoptosis was assessed by M30 staining and expression patterns of DR4, DR5, beta-catenin, and p21 were studied immunohistochemically. In HNPCC patients, apoptotic indices were similar following placebo and sulindac. Also in FAP patients, apoptotic indices were not different after sulindac compared with pretreatment values. Expression of DR4 and DR5 was observed in all samples with no consistent differences between placebo/baseline and sulindac. Intensity of membranous beta-catenin staining was lower in HNPCC samples following sulindac compared with placebo (P <0.001). Similar results were obtained in FAP samples (P <0.01). p21 expressions before and after sulindac treatment were similar in both patient groups. In conclusion, sulindac inhibits beta-catenin expression in normal colorectal epithelium from HNPCC and FAP patients without affecting apoptotic indices and DR4, DR5, and p21 expression