Abstract 5007: Role of the interferon-gamma response pathway in immune escape of colorectal carcinoma

The presence of an interferon-dominated Th1 immune response in colorectal carcinoma (CRC) has been associated with improved clinical outcome. We have previously identified the guanylate-binding protein 1 (GBP-1), one of the major IFN-γ-induced proteins, as a marker for the Th1 immune response and an independent positive prognostic factor in CRC. We also found that GBP-1 is a necessary mediator of the anti-tumorigenic effects of IFNγ. Interestingly, the expression of GBP-1 in CRC was observed more frequently in the desmoplastic stroma than in the directly adjacent tumor cells, suggesting that CRC tumor cells might become resistant to IFN-γ in the course of tumorigenesis. Indeed, we found that several colorectal carcinoma cell lines failed to express GBP-1 or other interferon-stimulated genes after treatment with IFN-γ, and were resistant to IFN-γ-induced apoptosis or proliferation inhibition. In these cell lines, the loss of IFN-γresponsiveness correlated either with the down-regulation of the IFN-γ receptor alpha chain (IFNγRα) or with the presence of a mis-glycosylated form of IFNγRα, which displayed an aberrant intracellular localization. We further validated these findings at the clinical level by showing that the expression of IFNγRα is decreased in CRC compared to normal tissue. In addition, the down-regulation of IFNγRα expression in CRC correlated with a reduced cancer-related survival together with a higher rate of distant metastasis. In addition, in-vivo colon tumorigenesis models using conditional knock-out mice revealed that the absence of IFNγRα expression by intestinal epithelial cells fosters tumor growth. Altogether, our data suggest that the loss of IFN-γ responsiveness is a common event in CRC and protects tumor cells against the anti-tumorigenic effects of IFN-γ.

Citation Format: Nathalie Britzen-Laurent, Julia Straube, Philipp Tripal, Maximilian Waldner, Christoph Becker, Susanne Merkel, Roland S. Croner, Michael Sturzl. Role of the interferon-gamma response pathway in immune escape of colorectal carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5007. doi:10.1158/1538-7445.AM2017-5007

Abstract 1255: A novel chip-based parallel transfection assay to evaluate paracrine cell interactions

Introduction: The analysis of how genes are regulating interactions between different cell types is of highest importance for the understanding of physiologic and pathologic processes in multi-cellular organisms. We present a novel method for the highly parallel analysis of gene functions in paracrine interactions between different cell types at the microarray level on a chip. The basic idea was to apply a mixture of two different cell types to the technique of reverse transfection with expression plasmids spotted in an ordered array on chips. The goal was to establish conditions that exclusively result in the transfection of one cell type (effector cells) and to use the other cell type as the indicator cells to determine paracrine gene effects (either directly exerted by the secreted product of the transfected gene or induced by the transfected gene). Methods: Reverse transfection was carried out spotting plasmid DNA in Lipofectamine 2000 and 0.2% gelatin on a slide. Subsequently, HEK 293T cells (effector cells) alone or in a mixture with different indicator cells (human fibroblasts, HUVEC, HaCaT, HT29, WiDr) were seeded. After 5 h a pre-warmed diffusion restricting matrix was gently poured onto the slides. The slides were further incubated for 43 h at 37 °C. Then, the matrix was removed, and the slides were washed gently and subjected to immunofluorescence analysis. Results: We successfully solved the two key problems required for this approach: (1) exclusive, differential transfection of the effector cells and not the indicator cells and (2) restriction of diffusion to localize gene effects to the specific transfection area. With the established methodology presented in our study, 192 parallel tests of paracrine gene activations can be conducted on a single chip. Demonstrating the broad applicability of the method, we used different indicator cells such as human primary fibroblasts (of relevance for inflammatory tissue reconstruction and invasion), endothelial cells (of relevance for angiogenesis research), keratinocytes (of relevance for wound healing research) and two different colorectal cancer cell lines (of relevance for cancer research). In addition, we used different indicator genes such as GBP-1 (indicates IFN-gamma like activation), COX-2 (of relevance for tumor research), ICAM-1 and VCAM-1 (of relevance for angiogenesis and inflammation research) and different paracrine inducers by including IFN-γ, TNF-α and IFN-γ. Discussion: Our method provides a significant improvement over current methodologies for the analysis of paracrine gene functions. It is highly relevant to systematically investigate single and combination effects of disease-associated gene clusters in intercellular communication in many different research applications including cancer, inflammation, angiogenesis and infectious diseases research.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1255. doi:1538-7445.AM2012-1255

Axial prevascularization of porous matrices using an arteriovenous loop promotes survival and differentiation of transplanted autologous osteoblasts

Generation of axially vascularized bioartificial bone might be performed using matrix neovascularization in connection with osteoblast injection. We sought to evaluate whether prevascularization of porous hard matrices using an arteriovenous (AV) loop promotes survival of transplanted osteoblasts. A processed bovine cancellous bone matrix was inserted into the AV loop. Six weeks later, 5 x 10(6) carboxyfluorescein diacetate-stained osteoblasts were injected into the matrix (group A, n = 34). Osteoblast-seeded matrices without prevascularization were implanted subcutaneously as controls (group B, n = 32). Specimens were subjected to histologic, morphometric, and molecular-biological analysis after 1, 4, 8, and 16 weeks. Upon cell injection, matrices were completely vascularized. An intense foreign body reaction was observed in matrices from both groups. Group A was significantly superior to group B in terms of osteoblast survival at any time point. Expression of bone-specific genes was detected in the AV loop group but not in the subcutaneous control. Bone formation was only detectable in 1 long-term animal of group A. This study demonstrates for the first time that axial prevascularization increases the survival of implanted osteoblasts in porous matrices. Matrices with optimized biocompatibility might eventually facilitate generation of axially vascularized bone tissue after injection of osteogenic cells in the AV loop model.

Interferon-alpha prevents apoptosis of endothelial cells after short-term exposure but induces replicative senescence after continuous stimulation

Although the antiangiogenic activity of type I interferons (IFN) is well known, the mechanism by which it occurs is unclear. In the present study, we have investigated effects of short-term and long-term IFN-alpha exposure on different types of endothelial cells (EC). Short-term IFN-alpha treatment resulted in a distinct reduction of apoptosis of serum and growth factor starved HUVEC and HDMEC. This was accompanied by a strong upregulation of the IFN inducible guanylate binding protein-1 (GBP-1) whereas no consistent regulation of several known antiapoptotic proteins was evident. Stable transfection of HUVEC with an expression vector for GBP-1 mimicked the protective effect of IFN-alpha, suggesting that GBP-1 may contribute to the inhibition of apoptosis. When IFN-alpha, together with serum and EC growth factors, was present continuously a decrease of population doublings by more than 40% was observed in both HDMEC and HCAEC. In addition, the cells displayed a senescent phenotype significantly earlier than control cells and showed an increased adherence for monocytes. Our findings suggest that the antiangiogenic effect of IFN-alpha is mediated by inducing EC senescence rather than EC apoptosis. Furthermore IFN-alpha released in chronic inflammatory conditions might contribute via its prosenescent activity to the pathogenesis of atherosclerosis.

Big but weak: how many pathogenic genes does human herpesvirus-8 need to cause Kaposi's sarcoma? (Review)

Human herpesvirus-8 (HHV-8) is implicated in the pathogenesis of Kaposi's sarcoma (KS). In the last two years several HHV-8 gene products were heralded to 'cause KS' without any evidence that the respective gene is expressed in the tumor cells of KS lesions. In this framework it is of interest that almost 10% of the genes encoded by HHV-8 have been suggested to promote KS development due to either mitogenic, anti-apoptotic, chemoattractive, angiogenic or transforming activities. The rapidly growing number of HHV-8-encoded genes with 'KS causing' activities raises the question of why HHV-8 may need so many genes to trigger growth of KS that appears to be more closely related to a hyperplasia than to a real sarcoma. In this review an overview of the current knowledge of HHV-8 gene expressions in KS lesions in vivo is presented.

Oncogenesis in HIV-infection

The presence of human Kaposi's sarcoma associated herpesvirus-like sequences (KSHV) was examined in different epidemiological variants of Kaposi's sarcoma (KS) and in KS-derived cell cultures by polymerase chain reaction (PCR). KSHV DNA was present in all tumor biopsies of AIDS-associated KS (59 biopsies), endemic KS (26 biopsies; 21 African endemic KS, 5 Greek endemic KS), sporadic/classical KS (28 biopsies) and post-transplant/iatrogenic KS (6 of 7 biopsies). On the contrary, these sequences were only detected rarely in non-involved skin of KS patients (3 positive specimens of 12), in the peripheral blood mononuclear cells of HIV-infected patients (3 positive specimens of 54) and in lymphoma-biopsies (3 positive specimens of 47). Cell cultures derived from KS skin lesions were positive for KSHV DNA only in the first two passages. However, two longer-term positive cultures from a biopsy of a patient affected with sporadic KS and a biopsy of a patient affected with epidemic KS was identified. A strong association of KSHV with KS tissue was observed in all the different epidemiological variants of KS. Long-term positive KS-derived cell cultures will be an important tool to study the herpesvirus-like agent and to investigate its functional role in the initiation and progression of KS.