Tumor-necrosis-factor-related apoptosis-inducing ligand and the regulation of hematopoiesis

Non-canonical role for the TRAIL receptor DR5/FADD/caspase pathway in the regulation of MyoD expression and skeletal myoblast differentiation

We report herein that the TRAIL receptor DR5/FADD/caspase pathway plays a role in skeletal myoblast differentiation through modulation of the expression of the muscle regulatory transcription factor MyoD. Specifically, treatment with the selective caspase 3 inhibitor DEVD-fmk or the selective caspase 8 inhibitor IETD-fmk in growth media (GM), prior to culture in differentiation media (DM), inhibited differentiation. Further, this treatment resulted in decreased levels of MyoD message and protein. We next explored a role for the TRAIL receptor DR5/FADD pathway. We found that expression of either dominant negative (dn) FADD or dominant negative (dn) DR5 also resulted in decreased levels of MyoD mRNA and protein and blocked differentiation. This decreased level of MyoD mRNA was not a consequence of altered stability. Treatment with TSA, an inhibitor of histone deacetylases (HDACs), allowed MyoD expression in myoblasts expressing dnDR5. Finally, acetylation of histones associated with the distal regulatory region (DRR) enhancer of MyoD was decreased in myoblasts expressing dnDR5. Thus, our data suggests a non-canonical role for the TRAIL receptor/FADD pathway in the regulation of MyoD expression and skeletal myoblast differentiation.

Transient severe pancytopenia due to elevated tumor necrosis factor-alpha in overwhelming infection

A 66-year-old woman complained of fever, sore throat, and neck pain due to pharyngitis and painful lymph node swelling. CBC revealed severe pancytopenia and markedly hypocellular marrow. The administration of antibiotics and granulocyte-colony stimulating factor (G-CSF) successfully ameliorated the inflammatory lesions, and hematopoiesis recovered. Causes for pancytopnenia was unlikely to be virus infection or drugs, and aplastic anemia was also unlikely since only the plasma levels of tumor necrosis factor-alpha (TNF-alpha) was markedly elevated, erythropoietin (EPO) was slightly elevated, interferon-gamma (IFN-gamma) was normal, and flow cytometric analysis for paroxysmal nocturnal hemoglobinuria (PNH)-type cells was negative. These results suggested that the cause of impaired hematopoiesis in the present patient might have been due to elevated TNF-alpha in overwhelming infection, although the pathogen was not identified.

Selection and Characterization of a Novel Agonistic Human Recombinant Anti-Trail-R2 Minibody with Antileukemic Activity

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising natural anticancer therapeutic agent because through its “death receptors”, TRAIL-R1 and TRAIL-R2, it induces apoptosis in many transformed tumor cells, but not in the majority of normal cells. Hence, agonistic compounds directed against TRAIL death receptors have the potential of being excellent cancer therapeutic agents, with minimal cytotoxicity in normal tissues. Here, we report the selection and characterization of a new single-chain fragment variable (scFv) to TRAIL-R2 receptor isolated from a human phage-display library, produced as minibody (MB), and characterized for the in vitro anti-leukemic tumoricidal activity. The anti-TRAIL-R2 MB2.23 efficiently and specifically bound to membrane-associated TRAIL-R2 on different leukemic cell lines and could act as a direct agonist in vitro, initiating apoptotic signaling as well as complement-dependent cytotoxicity and antibody-dependent cell cytotoxicity, providing a rationale for further investigations of MB2.23 in anticancer therapy.

Stroma-dependent apoptosis in clonal hematopoietic precursors correlates with expression of PYCARD

The role of the marrow microenvironment in the pathophysiology of myelodysplastic syndromes (MDSs) remains controversial. Using stromal/hematopoietic cell cocultures, we investigated the effects of stroma-derived signals on apoptosis sensitivity in hematopoietic precursors. The leukemia-derived cell line KG1a is resistant to proapoptotic ligands. However, when cocultured with the human stromal cell line HS5 (derived from normal marrow) and exposed to tumor necrosis factor-alpha (TNF-alpha), KG1a cells showed caspase-3 activation and induction of apoptosis. Apoptosis was contact dependent. Identical results were obtained in coculture with primary stroma. Gene-expression profiling of KG1a cells identified coculture-induced up-regulation of various genes involved in apoptosis, including PYCARD. Suppression of PYCARD expression in KG1a by miRNA interfered with apoptosis. Knockdown of the TNF receptor 1 (TNFR1) or TNFR2 in HS5 cells had no effect. However, knockdown of R1 in KG1a cells prevented TNF-alpha-induced apoptosis, while apoptosis was still induced by TNF-alpha-related apoptosis-inducing ligand. Primary CD34(+) cells from MDS marrow, when cocultured with HS5 and TNF-alpha, also underwent apoptosis. In contrast, no apoptosis was observed in CD34(+) cells from the marrow of healthy donors. These data indicate that stroma may convey not only protective effects on hematopoietic cells, but, dependent upon the milieu, may also facilitate apoptosis.

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.

Tumor necrosis factor-related apoptosis-inducing ligand promotes migration of human bone marrow multipotent stromal cells

Adult multipotent stromal cells (MSCs), also known as mesenchymal stem cells, represent an important source of cells for the repair of a number of damaged tissues. Both bone marrow (BM)-derived and amniotic MSCs expressed detectable surface levels of two (tumor necrosis factor-related apoptosis-inducing ligand receptor 2 [TRAIL-R2] and TRAIL-R4) of four transmembrane TRAIL receptors. Although the best-characterized activity of TRAIL-R2 is the transduction of apoptotic signals, neither recombinant TRAIL (rTRAIL) nor infection with an adenovirus-expressing TRAIL induced cytotoxic effects on MSCs. Moreover, whereas rTRAIL did not affect proliferation or differentiation of MSCs along the osteogenic and adipogenic lineages, it significantly promoted the migration of human MSCs in range of concentrations comparable to that of soluble TRAIL in human plasma (100 pg/ml). Since rTRAIL induced the rapid phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in MSC cultures and pretreatment with pharmacological inhibitors of the ERK1/2 pathway efficiently counteracted the rTRAIL-induced human MSC migration, these data indicate that ERK1/2 is involved in mediating the ability of rTRAIL to stimulate MSC migration. Taking into consideration that the soluble factors able to induce MSC migration have not been extensively characterized, our current data indicate that the TRAIL/TRAIL-R system might play an important role in the biology of MSCs. Disclosure of potential conflicts of interest is found at the end of this article.

Apoptosis by dietary agents for prevention and treatment of cancer

The role of apoptosis or programmed cell death in the regulation of development and maintenance of homeostasis in multicellular organisms is well established. During the last decade, naturally occurring dietary agents known to produce chemopreventive effects in experimental models have been shown to target signaling intermediates in apoptosis-inducing pathways. Apoptosis is triggered by two different signals, one extrinsic, which responds mainly to extracellular stimuli, and the other intrinsic, activated by modulators within the cell itself. Proapoptotic compounds could protect against cancer by enhancing elimination of initiated, precancerous cells, and antiapoptotic compounds could promote tumor formation by inhibiting apoptosis in genetically damaged cells. In this brief review, we explore the potential mechanistic interactions of various dietary cancer chemopreventive components within the context of apoptosis.