Peritumoral administration of GPI-anchored TIMP-1 inhibits colon carcinoma growth in Rag-2 gamma chain-deficient mice

Exogenous application of recombinant TIMP-1 protein modified by addition of a glycosylphosphatidylinositol (GPI) anchor allows efficient insertion of the fusion protein into cell membranes. This `cell surface engineering' leads to changes in the proteolytic environment. TIMP-1-GPI shows enhanced as well as novel in vitro biological activities including suppression of proliferation, reduced migration, and inhibition of invasion of the colon carcinoma cell line SW480. Treatment of SW480 tumors implanted in Rag (-/-) common gamma chain (-/-) C57BL/6 mice with peritumorally applied TIMP-1-GPI, control rhTIMP-1 protein, or vehicle shows that TIMP-1-GPI leads to a significant reduction in tumor growth

Composition of CXCL10-mucin-GPI as an example for a novel class of GPI-anchored chemokine fusion proteins.

<p>The mucin domain of CX3CL1 was combined with a GPI anchor and a CXCL10 chemokine head to generate a flexible tool for the modification of tumor micromilieus capable of selectively stimulating the recruitment of CXCR3⁺ leukocytes. The chemokine head directs the specificity towards CXCR3⁺ leukocytes, while the mucin domain assists in the recruitment process and lowers the requirement for other adhesion molecules. Inclusion of a GPI anchor allows the protein to integrate into the cell membranes of tumor, stromal and endothelial cells when applied exogenously, thus superseding the transfer of genetic material into the tumor.</p

Subcutaneously implanted 291 tumors are well vascularized and show a pronounced infiltration with T cells.

<p>Tumor cells were injected subcutaneously into the flanks of C57BL/6 mice. Grown tumors were excised, fixed and analyzed by hematoxylin/eosin (H/E) staining or immunohistology using antibodies against CD3 or NKp46. <b>A–F</b>: The respective magnifications are indicated at the top of each image. Panels A and B show the presence of numerous blood vessels (arrows) throughout the tumors in H/E staining. Panels D, E and F represent serial sections of the same position within a tumor. Various blood vessels are visible in H/E staining and the CD3 staining shows infiltration of the tumor with CD3⁺ cells (dark grey/black staining). Less NKp46⁺ cells could be detected in the respective staining of the same position (dark grey/black staining; one cell is marked by an arrow). Panel C depicts a cluster of NKp46⁺ cells, which was sometimes found at the margins of tumors (margin: upper part of the picture). <b>G</b>: Injection of CXCL10-mucin-GPI tends to increase endogenous NK cell infiltration of subcutaneous tumors. Purified CXCL10-mucin-GPI was injected into established 291 tumors. As controls, either the same or a 500×higher molar quantity of commercially available human CXCL10 (rhCXCL10) were injected. As additional controls, the same volume of identically purified sEGFP-GPI was injected or the tumors were left completely untreated. The animals were sacrificed 4 h after injection and infiltration of the tumors was assessed by FACS analysis. The figure shows the percentage of CD3^- NK1.1⁺ cells among the total lymphocyte count with each symbol representing one individual tumor and horizontal bars the average values. Statistical significance was calculated using the Kruskal-Wallis-test (P = 0.19) followed by Dunńs post test (not significant, N.S.).</p

Purified GPI-anchored proteins incorporate into cell membranes.

<p><b>A</b>: In order to test the capacity of the purified recombinant fusion proteins to reincorporate into cell membranes, non-transfected CHO cells were incubated with the purified GPI-anchored proteins (0.9 nM) for 1 h at 37°C. As controls, two samples were treated either with identically diluted chromatography buffer (buffer) or MEM alpha medium (medium). The soluble CXCL10-mucin-Stop protein served as an additional control as it lacks a GPI anchor. All samples except the medium control contained the same percentage of chromatography buffer and detergent. Following incubation, the cells were washed and tested for the presence of the proteins on their surface by FACS staining. Dead cells were identified by 7-AAD staining and the histograms shown are gated on viable cells. The black lines indicate staining with isotype-matched control antibodies, blue lines staining with anti c-myc antibodies. Mean fluorescence intensities (MFIs) are given for each sample. This experiment was performed routinely to monitor protein quality after purification and the data shown here therefore stand representative for over 20 independent experiments. <b>B</b>: To verify the subcellular localization of the incorporated proteins, immunofluorescence microscopy was performed. Primary microvascular endothelial cells were treated with purified CXCL10-GPI, CXCL10-mucin-GPI or a buffer control diluted in culture medium, with all samples containing the same percentage of buffer to exclude artifacts. After treatment, the cells were washed, fixed with Paraformaldehyde and incorporated proteins were detected using anti c-myc primary and biotinylated secondary antibodies followed by RPE-labeled streptavidin. The figure shows fluorescence images and corresponding bright field images from a representative experiment, which was performed three times. All images within each row were acquired using the same exposure time. The black bars indicate 50 µm.</p

CXCL10-mucin-GPI induces rolling and tight adhesion of CXCR3⁺ NK cells under conditions of physiologic flow.

<p>Laminar flow assays were performed to test if resting primary human microvascular endothelial cells treated with the GPI-anchored CXCL10 fusion proteins could recruit freely flowing CXCR3⁺ NK cells (YT) under conditions of physiologic flow. <b>A</b>: Resting primary human endothelial cells from fetal foreskin, selected for blood vessel endothelial cells, were treated with 0.34 nM of GPI-anchored CXCL10 fusion proteins or with identically diluted sEGFP-GPI protein for 1 h. Other slides were treated with commercially available CXCL10 at 1000-fold higher concentration as additional control (rhCXCL10). All samples contained the same percentage of chromatography buffer and detergent. Subsequently, YT cells were perfused over the endothelial cells with 1 dyn/cm² and the number of cells accumulating on the endothelial cells was counted. Data shown here are derived from six independent experiments, each performed using independent protein preparations and separate batches of cells. Bars represent the average numbers of cells adhering to the endothelium, +/− SEM. Statistical significance was calculated using the Kruskal-Wallis test (P = 0.0022) followed by Dunńs post test; ** = P<0.01. <b>B</b>: Experiments were performed as detailed in A. Tight adhesion was defined as an event in which a particular NK cell adhered to the endothelium and did not move further than one cell diameter within 30 sec. Rolling adhesion was defined as an event in which the NK cell adhered to the endothelium, but was dragged along the endothelium by the shear forces exerted by the buffer at a higher speed than one cell diameter per 30 sec or detached again. Cells displaying both rolling and tight adhesion were counted only as tightly adherent. Bars represent averaged values derived from four independent experiments +/− SEM. Statistical significance was calculated using the Kruskal-Wallis test (P = 0.0038 for rolling adhesion and 0.0021 for tight adhesion) followed by Dunńs post test; * = P<0.05, ** = P<0.01.</p

A novel CXCL10-based GPI-anchored fusion protein as adjuvant in NK-based tumor therapy

BACKGROUND: Cellular therapy is a promising therapeutic strategy for malignant diseases. The efficacy of this therapy can be limited by poor infiltration of the tumor by immune effector cells. In particular, NK cell infiltration is often reduced relative to T cells. A novel class of fusion proteins was designed to enhance the recruitment of specific leukocyte subsets based on their expression of a given chemokine receptor. The proteins are composed of an N-terminal chemokine head, the mucin domain taken from the membrane-anchored chemokine CX3CL1, and a C-terminal glycosylphosphatidylinositol (GPI) membrane anchor replacing the normal transmembrane domain allowing integration of the proteins into cell membranes when injected into a solid tumor. The mucin domain in conjunction with the chemokine head acts to specifically recruit leukocytes expressing the corresponding chemokine receptor. METHODOLOGY/PRINCIPAL FINDINGS: A fusion protein comprising a CXCL10 chemokine head (CXCL10-mucin-GPI) was used for proof of concept for this approach and expressed constitutively in Chinese Hamster Ovary cells. FPLC was used to purify proteins. The recombinant proteins efficiently integrated into cell membranes in a process dependent upon the GPI anchor and were able to activate the CXCR3 receptor on lymphocytes. Endothelial cells incubated with CXCL10-mucin-GPI efficiently recruited NK cells in vitro under conditions of physiologic flow, which was shown to be dependent on the presence of the mucin domain. Experiments conducted in vivo using established tumors in mice suggested a positive effect of CXCL10-mucin-GPI on the recruitment of NK cells. CONCLUSIONS: The results suggest enhanced recruitment of NK cells by CXCL10-mucin-GPI. This class of fusion proteins represents a novel adjuvant in cellular immunotherapy. The underlying concept of a chemokine head fused to the mucin domain and a GPI anchor signal sequence may be expanded into a broader family of reagents that will allow targeted recruitment of cells in various settings

Human Renal Cell Carcinoma Induces a Dendritic Cell Subset That Uses T-Cell Crosstalk for Tumor-Permissive Milieu Alterations

Tissue dendritic cells (DCs) may influence the progression of renal cell carcinoma (RCC) by regulating the functional capacity of antitumor effector cells. DCs and their interaction with T cells were analyzed in human RCC and control kidney tissues. The frequency of CD209+ DCs in RCCs was found to be associated with an unfavorable TH1 cell balance in the tissue and advanced tumor stages. The CD209+ DCs in RCC were unusual because most of them co-expressed macrophage markers (CD14, CD163). The phenotype of these enriched-in-renal-carcinoma DCs (ercDCs) could be reiterated in vitro by carcinoma-secreted factors (CXCL8/IL-8, IL-6, and vascular endothelial growth factor). ErcDCs resembled conventional DCs in costimulatory molecule expression and antigen cross-presentation. They did not suppress cognate cytotoxic T-lymphocyte function and did not cause CD3ζ down-regulation, FOXP3 induction, or T-cell apoptosis in situ or in vitro; thus, they are different from classic myeloid-derived suppressor cells. ErcDCs secreted high levels of metalloproteinase 9 and used T-cell crosstalk to increase tumor-promoting tumor necrosis factor α and reduce chemokines relevant for TH1-polarized lymphocyte recruitment. This modulation of the tumor environment exerted by ercDCs suggests an immunologic mechanism by which tumor control can fail without involving cytotoxic T-lymphocyte inhibition. Pharmacologic targeting of the deviated DC differentiation could improve the efficacy of immunotherapy against RCC