TRAIL, the tumor necrosis factor-related apoptosis-inducing ligand, selectively induces apoptosis of tumor cells, but not most normal cells. Its role in normal, nontransformed tissues is not clear. We report here that mice deficient in TRAIL have a severe defect in thymocyte apoptosis-thus, thymic deletion induced by T cell receptor ligation is severely impaired. TRAIL-deficient mice are also hypersensitive to collagen-induced arthritis and streptozotocin-induced diabetes and develop heightened autoimmune responses. Thus, TRAIL mediates thymocyte apoptosis and is important in the induction of autoimmune diseases.

The pronounced biological influence of the tumor microenvironment on cancer progression and metastasis has gained increased recognition over the past decade, yet most preclinical antineoplastic drug testing is still reliant on conventional 2D cell culture systems. Although monolayer cultures recapitulate some of the phenotypic traits observed clinically, they are limited in their ability to model the full range of microenvironmental cues, such as ones elicited by 3D cell-cell and cell-extracellular matrix interactions. To address these shortcomings, we established an ex vivo 3D Ewing sarcoma model that closely mimics the morphology, growth kinetics, and protein expression profile of human tumors. We observed that Ewing sarcoma cells cultured in porous 3D electrospun poly(e-caprolactone) scaffolds not only were more resistant to traditional cytotoxic drugs than were cells in 2D monolayer culture but also exhibited remarkable differences in the expression pattern of the insulin-like growth factor-1 receptor/mammalian target of rapamycin pathway. This 3D model of the bone microenvironment may have broad applicability for mechanistic studies of bone sarcomas and exhibits the potential to augment preclinical evaluation of antineoplastic drug candidates for these malignancies.tissue engineering | tumor model | biological therapy | connective tissue D espite the primacy of the cancer cell's dysregulated genotype [e.g., a near universal translocation of the Ewing sarcoma (EWS) breakpoint region 1 gene in EWS cells] as the initial step in malignant transformation, it has become increasingly apparent that the overall tumor phenotype is also dictated by the 3D tumor microenvironment (1-4). Nonetheless, studies of cancer biology and evaluation of antineoplastic drug efficacy remain heavily dependent on conventional 2D cell culture systems despite their limited ability to reflect the 3D tumor architecture, extracellular matrix (ECM), and surrounding cell types that comprise the in vivo tumor milieu.To overcome some of these constraints, 3D in vitro models such as spheroid and gel systems have been extensively studied and, compared with 2D monolayer culture, appear to better mimic the profound effects that the in vivo 3D environment has upon the human tumor phenotype (5-9). For example, malignant cells cultured in 3D exhibit increased chemoresistance (10, 11) and decreased cell proliferation (12), and assume specific phenotypes inducible only under a 3D context, such as angiogenic capability (13-15). Furthermore, striking differences in signaling pathways targeted by proven and experimental therapies have been observed in 3D tumor models (16-18). Accordingly, heightened awareness of the importance of 3D culture for cancer cells has resulted in the increasing use of spheroid culture systems for cancer research. However, these non-adhesion-mediated systems provide poor control over the tumor architecture and cell-cell interactions; as a result of culture conditions that prohibit cellular attachment onto surrounding surfaces, ce...

The tumor suppressor p53 regulates apoptosis, cell cycle, and oncogenesis. To explore the roles of p53 in autoimmunity, we studied type 1 diabetes and innate immune responses using C57BL/6 mice deficient in p53. We found that p53-deficient mice were more susceptible to streptozotocin-induced diabetes than control mice, and they produced higher levels of interleukin-1, -6, and -12. The innate immune response of p53 ؊/؊ macrophages to lipopolysaccharides and ␥-interferon was significantly enhanced compared with p53 ؉/؉ cells. p53 ؊/؊ macrophages produced more proinflammatory cytokines and higher levels of total and phosphorylated signal transducer and activator of transcription (STAT)-1. These results indicate that p53 inhibits autoimmune diabetes and innate immune responses through downregulating STAT-1 and proinflammatory cytokines.

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Three-dimensional tumor models accurately describe different aspects of the tumor microenvironment and are readily available for mechanistic studies of tumor biology and for drug screening. Nevertheless, these systems often overlook biomechanical stimulation, another fundamental driver of tumor progression. To address this issue, we cultured Ewing sarcoma (ES) cells on electrospun poly(e-caprolactone) 3D scaffolds within a flow perfusion bioreactor. Flow-derived shear stress provided a physiologically relevant mechanical stimulation that significantly promoted insulin-like growth factor-1 (IGF1) production and elicited a superadditive release in the presence of exogenous IGF1. This finding is particularly relevant, given the central role of the IGF1/IGF-1 receptor (IGF-1R) pathway in ES tumorigenesis and as a promising clinical target. Additionally, flow perfusion enhanced in a rate-dependent manner the sensitivity of ES cells to IGF-1R inhibitor dalotuzumab (MK-0646) and showed shear stress-dependent resistance to the IGF-1R blockade. This study demonstrates shear stressdependent ES cell sensitivity to dalotuzumab, highlighting the importance of biomechanical stimulation on ES-acquired drug resistance to IGF-1R inhibition. Furthermore, flow perfusion increased nutrient supply throughout the scaffold, enriching ES culture over static conditions. Our use of a tissue-engineered model, rather than human tumors or xenografts, enabled precise control of the forces experienced by ES cells, and therefore provided at least one explanation for the remarkable antineoplastic effects observed by some ES tumor patients from IGF-1R targeted therapies, in contrast to the lackluster effect observed in cells grown in conventional monolayer culture. T he ability to treat cancer patients is critically dependent upon a robust drug discovery pipeline and an efficient method to select the most promising drug candidates for clinical trial advancement. Preclinical drug screening typically relies on the use of 2D culture systems, which are reproducible, fast, and inexpensive. Nevertheless, tumor phenotype is dictated by its interaction with the surrounding 3D microenvironment (1). The inability of 2D systems to mimic this key element has generally resulted in preclinical findings that overstate drug activity when subsequently tested in human clinical trials, therefore undermining the drug discovery process in cancer therapies (2).To overcome these issues, several 3D tumor models have been proposed, including tumor spheroids and hydrogel systems, which attempt to recapitulate heterotypic interactions either between tumor and stroma or tumor and extracellular matrix (ECM), respectively (3, 4). These systems have begun to bridge the gap between in vitro and in vivo testing in several aspects, such as cell growth (5), gene expression pattern (6), and chemoresistance (7). However, these models are still unable to recapitulate and adequately examine the effects of other cues present in the tumor microenvironment, such as heterotypic cell−cell...