High TRAIL-R3 expression on leukemic blasts is associated with poor outcome and induces apoptosis-resistance which can be overcome by targeting TRAIL-R2.
ABSTRACT Activation of the TNF-related apoptosis-inducing ligand (TRAIL) pathway can induce apoptosis in a broad range of human cancer cells. Four membrane-bound receptors have been identified. TRAIL-R1 and TRAIL-R2 contain a functional death domain; TRAIL-R3 and TRAIL-R4 lack a functional death domain and function as decoy receptors. Flow-cytometric analysis revealed that acute myeloid leukemic (AML) blasts expressed significantly more pro-apoptotic receptors compared to normal blasts. However, about 20% of AML patients highly expressed decoy receptor TRAIL-R3, which was strongly correlated to a shortened overall survival. TRAIL-R3 expression was also high on CD34+/CD38- cells, the compartment that harbors the leukemia initiating stem cell. Expression levels of pro-apoptotic TRAIL receptors were not correlated to the susceptibility for soluble TRAIL, which was generally low (mean level of cell death induction 14%). Cell death could be enhanced by down-modulation of TRAIL-R3, confirming its decoy function on AML blasts. Bypassing of TRAIL-R3 by treatment with antibodies directly targeting TRAIL-R2 resulted in higher rates of induced cell death (max. 80%). In conclusion, AML blasts do express pro-apoptotic TRAIL receptors. However, co-expression of decoy receptor TRAIL-R3 results in significant shortened overall survival. AML blasts could be targeted by anti-TRAIL-R2 antibodies, yielding a new therapeutic option for AML patients.
- SourceAvailable from: Alex A Philchenkov[show abstract] [hide abstract]
ABSTRACT: The review considers the current knowledge on molecular mechanisms of apoptosis. Particular emphasis is given to the key elements of the extrinsic death receptor pathway and the intrinsic mitochondrial pathway. Dysregulation of apoptotic pathways is considered as a key factor in the survival of cancer cells in response to conventional chemotherapeutic drugs or radiation therapy. Substances that selectively reactivate apoptosis in malignant cells are considered as the promising candidate anticancer drugs, which have now entered various phases of clinical trials. The modern techniques allowing non�invasive visualization of apoptotic cells with special reference to therapy�induced cell death are briefly surveyed.Biochemistry (Moscow) Supplement Series B Biomedical Chemistry 01/2012; 6(4):343-358.
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ABSTRACT: Apo 2 ligand/tumor necrosis factor (TNF)-related apoptosis-inducing ligand (Apo2L/TRAIL), is a member of the TNF family of cytokines, which can induce apoptotic cell death in cells expressing at least one of their specific death receptors, DR4 (TRAIL-R1) or DR5 (TRAIL-R2). In the last decade, the Apo2L/TRAIL system of apoptosis has attracted significant interest as a potential drug-targeting pathway for human therapy, due to the ability of that cytokine to trigger apoptosis in various types of cancer cells while displaying low or no toxicity to normal cells. Recent results suggest that manipulating the Apo2L/TRAIL system may be also useful for the treatment of inflammatory disorders such as rheumatoid arthritis. For its possible therapeutic use, a number of receptor-specific Apo2L/TRAIL molecular variants and agonistic monoclonal antibodies have been developed, and some of them are in clinical trials. In addition, Apo2L/TRAIL-resistant tumors can be sensitized to Apo2L/TRAIL by selected novel or classical chemotherapeutic agents, opening new possibilities for combined therapies. We will briefly review the current status of Apo2L/TRAIL-based therapies for human disease, their promises and limitations.Biochemical pharmacology 01/2012; 83(11):1475-83. · 4.25 Impact Factor