Many tumor cells shed specialized membrane vesicles known as exosomes. In this study, we show that pretreatment of mice with exosomes produced by TS/A or 4T.1 murine mammary tumor cells resulted in accelerated growth of implanted tumor cells in both syngeneic BALB/c mice and nude mice. As implanted TS/A tumor cells grew more rapidly in mice that had been depleted of NK cells, we analyzed the effects of the tumor-derived exosomes on NK cells. The tumor-derived exosomes inhibit NK cell cytotoxic activity ex vivo and in vitro as demonstrated by chromium release assays. The treatment of mice with TS/A tumor exosomes also led to a reduction in the percentages of NK cells, as determined by FACS analysis, in the lungs and spleens. Key features of NK cell activity were inhibited, including release of perforin but not granzyme B, as well as the expression of cyclin D3 and activation of the Jak3-mediated pathways. Human tumor cell lines also were found to produce exosomes that were capable of inhibiting IL-2-stimulated NK cell proliferation. Exosomes produced by dendritic cells or B cells did not. The presentation of tumor Ags by exosomes is under consideration as a cancer vaccine strategy; however, we found that pretreatment of mice with tumor exosomes blunted the protective effect of syngeneic dendritic cells pulsed ex vivo with tumor exosomes. We propose that tumor exosomes contribute to the growth of tumors by blocking IL-2-mediated activation of NK cells and their cytotoxic response to tumor cells.

There has been a rapid growth of bioluminescence imaging applications in small animal models in recent years, propelled by the availability of instruments, analysis software, reagents, and creative approaches to apply the technology in molecular imaging. Advantages include the sensitivity of the technique as well as its efficiency, relatively low cost, and versatility. Bioluminescence imaging is accomplished by sensitive detection of light emitted following chemical reaction of the luciferase enzyme with its substrate. Most imaging systems provide 2-dimensional (2D) information in rodents, showing the locations and intensity of light emitted from the animal in pseudo-color scaling. A 3-dimensional (3D) capability for bioluminescence imaging is now available, but is more expensive and less efficient; other disadvantages include the requirement for genetically encoded luciferase, the injection of the substrate to enable light emission, and the dependence of light signal on tissue depth. All of these problems make it unlikely that the method will be extended to human studies. However, in small animal models, bioluminescence imaging is now routinely applied to serially detect the location and burden of xenografted tumors, or identify and measure the number of immune or stem cells after an adoptive transfer. Bioluminescence imaging also makes it possible to track the relative amounts and locations of bacteria, viruses, and other pathogens over time. Specialized applications of bioluminescence also follow tissue-specific luciferase expression in transgenic mice, and monitor biological processes such as signaling or protein interactions in real time. In summary, bioluminescence imaging has become an important component of biomedical research that will continue in the future.

Purpose Comprehensive cervical lymphadenectomy can be associated with significant morbidity and poor quality of life. This study evaluated the sensitivity and specificity of cetuximab-IRDye800CW to identify metastatic disease in patients with head and neck cancer. Experimental Design Consenting patients scheduled for curative resection were enrolled in a clinical trial to evaluate the safety and specificity of cetuximab-IRDye800CW. Patients (n=12) received escalating doses of the study drug. Where indicated, cervical lymphadenectomy accompanied primary tumor resection, which occurred 3–7days following intravenous infusion of cetuximab-IRDye800CW. All 471 dissected lymph nodes were imaged with a closed-field, near-infrared imaging device during gross processing of the fresh specimens. Intraoperative imaging of exposed neck levels was performed with an open-field fluorescence-imaging device. Blinded assessments of the fluorescence data were compared to histopathology to calculate sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV). Results Of the 35 nodes diagnosed pathologically positive, 34 were correctly identified with fluorescence imaging, yielding a sensitivity of 97.2%. Of the 435 pathologically negative nodes, 401 were correctly assessed using fluorescence imaging, yielding a specificity of 92.7%. The NPV was determined to be 99.7%, and the PPV was 50.7%. When 37 fluorescently false-positive nodes were sectioned deeper (1mm) into their respective blocks, metastatic cancer was found in 8.1% of the re-cut nodal specimens, which altered staging in two of those cases. Conclusions Fluorescence imaging of lymph nodes after systemic cetuximab-IRDye800CW administration demonstrated high sensitivity and was capable of identifying additional positive nodes on deep sectioning.

Development of anti-Fas Abs to treat diseases with insufficient Fas-mediated apoptosis has been limited by concern about hepatotoxicity. We report here that hepatotoxicity elicited by anti-Fas Ab Jo2 is dependent on FcγRIIB. Thus, following Jo2 treatment, all FcγRIIB−/− mice survived while 80% of wild-type and all FcR-γ−/− mice died from acute liver failure. Microscopic examination suggests that FcγRIIB deficiency protects the hepatic sinusoidal endothelium, a cell type that normally coexpresses Fas and FcγRIIB. In vitro studies showed that FcγRIIB, but not FcγRI and FcγRIII, on neighboring macrophages substantially enhanced Jo2 mediated apoptosis of Fas expressing target cells. However, FcγRI and FcγRIII appeared essential for apoptosis-inducing activity of a non-hepatotoxic anti-Fas mAb HFE7A. These findings imply that by interacting with the Fc region of agonistic Abs, FcγRs can modulate both the desired and undesired consequences of Ab-based therapy. Recognizing this fact should facilitate development of safer and more efficacious agonistic Abs.

ABSTRACT67Cu (tl2 = 62 h) has demonstrated potential as a radionuclide for radioimmunotherapy, but limited availability severely restricts its widespread use. 6"Cu (t1l2 = 12.8 h)has been shown to have comparable effectiveness in vitro and in vivo. The present study was undertaken to examine the therapeutic potential of 64Cu-and 67Cu-bromoacetamidobenzyl-1,4,8,1 1-tetraazacyclotetradecane-N,N',N",N'"-tetraacetic acid (BAT)-2-iminothiolane (2IT)-1A3 (1A3 is a mouse anti-human colorectal cancer mAb) for treatment of GW39 human colon carcinoma carried in hamster thighs. Hamsters were injected with 64Cu-or 67Cu-BAT-21T-1A3 or Cu-labeled nonspecific IgG (MOPC) or saline. Hamsters were killed 6-7 months after therapy or when tumors were 210 g. Of the hamsters with small tumors (mean weight 0.43 ± 0.25 g), 87.5% were disease-free 7 months after treatment with 2 mCi (1 Ci = 37 GBq) of 64Cu-BAT-21T-1A3 or 0.4 mCi of 67Cu-BAT-2IT-1A3. The mean tumor doses at these activities of 64Cu-and 67Cu-BAT-21T-lA3 were 586 and 1269 rad (1 rad = 0.01 Gy), respectively. In contrast, 76% of hamsters treated with 2 mCi of 64Cu-BAT-21T-MOPC or 0.4 mCi of 67Cu-BAT-2IT-MOPC had to be killed before 6 months because of tumor regrowth. When hamsters with larger tumors (mean weight 0.66 + 0.11 g) were treated with 64Cu-or 67Cu-BAT-21T-lA3, survival was extended compared with controls, but only one animal remained tumor-free to 6 months. These results demonstrate that 64Cu-and 67Cu-BAT-21T-1A3 given in a single administered dose can eradicate small tumors without significant host toxicity, but additional strategies to deliver higher tumor doses will be needed for larger tumors.