Bioluminescence-based visualization of CD4 T cell dynamics using a T lineage-specific luciferase transgenic model.

BACKGROUND: Rapid clonal expansion of T cells occurs in response to antigenic challenges. The kinetics of the T cell response has previously been described using tissue-based studies performed at defined time points. Luciferase bioluminescence has recently been utilized for non-invasive analysis of in vivo biologic processes in real-time. RESULTS: We have created a novel transgenic mouse model (T-Lux) using a human CD2 mini-gene to direct luciferase expression specifically to the T cell compartment. T-Lux T cells demonstrated normal homing patterns within the intact mouse and following adoptive transfer. Bioluminescent signal correlated with T cell numbers in the whole body images as well as within specific organ regions of interest. Following transfer into lymphopenic (RAG2-/-) recipients, homeostatic proliferation of T-Lux T cells was visualized using bioluminescent imaging. Real-time bioluminescent analysis of CD4+ T cell antigen-specific responses enabled real-time comparison of the kinetics and magnitude of clonal expansion and contraction in the inductive lymph node and tissue site of antigen injection. T cell expansion was dose-dependent despite the presence of supraphysiologic numbers of OVA-specific OT-II transgenic TCR T-Lux T cells. CD4+ T cells subsequently underwent a rapid (3-4 day) contraction phase in the draining lymph node, with a delayed contraction in the antigen delivery site, with bioluminescent signal diminished below initial levels, representing TCR clonal frequency control. CONCLUSION: The T-Lux mouse provides a novel, efficient model for tracking in vivo aspects of the CD4+ T cell response to antigen, providing an attractive approach for studies directed at immunotherapy or vaccine design.

Noninvasive bioluminescence imaging in small animals.

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.

High-resolution single-photon emission computed tomography and X-ray computed tomography imaging of Tc-99m-labeled anti-DR5 antibody in breast tumor xenografts.

A murine, apoptosis-inducing monoclonal antibody (mTRA-8) targeting human DR5 was radiolabeled with Tc-99m. The binding affinity (K(d)) and the number of DR5 receptors were measured in MD MBA-231-derived 2LMP cell lines that were "sensitive" or "resistant" to mTRA-8 killing. Single-photon emission computed tomography and X-ray computed tomography (SPECT/CT) evaluated the Tc-99m-mTRA-8 retention and distribution within xenograft tumors; biodistribution analyses confirmed the levels. Scatchard assays showed specific and high binding affinity of Tc-99m-mTRA-8 to DR5; the killing efficacy of mTRA-8 was unchanged by Tc-99m labeling. There was no significant difference between sensitive and resistant 2LMP cells for K(d) values (1.5 +/- 0.3 nmol/L = acid labile), or DR5 receptors (mean/cell = 11,000). SPECT/CT imaging analyses at 6 h after injection of Tc-99m-mTRA-8 revealed the second 1.5 mm shell from the surface of the mammary fat pad tumors (n = 5; 5,627 mm(3)) retained 12.7 +/- 1.4%ID/g, higher than the other shells, with no difference between the sensitive and resistant 2LMP tumors. Binding of Tc-99m-labeled mTRA-8 in tumor was specific; excess unlabeled mTRA-8 blocked Tc-99m-mTRA-8 retention in tumor by 45%. Retention of Tc-99m-labeled isotype antibody in tumor was consistent with the blocking study, and 30% lower. These studies show that SPECT/CT imaging provided detailed distribution information of Tc-99m-labeled mTRA-8 within breast tumor xenografts. Imaging could provide a mechanism to assess DR5 modulation when DR5 therapy is combined with chemotherapy and radiation, and thereby aid in optimizing the dosing schedule.

Use of fluorescent labeled anti-epidermal growth factor receptor antibody to image head and neck squamous cell carcinoma xenografts.

Physicians and surgeons rely on subtle tissue changes to detect the extent of tumors and the presence of residual disease in the clinical setting. The development of a cancer-specific fluorescent contrast agent has the potential to provide real-time tumor imaging in the clinic or operating room. Because epidermal growth factor receptor (EGFR) is highly overexpressed on the surface of head and neck squamous cell carcinoma (HNSCC), we sought to determine if fluorescently labeled anti-EGFR antibody could be used to image HNSCC xenografts in vivo. Cetuximab or control isotype-matched IgG1 was conjugated with the Cy5.5 fluorochrome and systemically injected into mice bearing human split thickness skin grafts, tumor cell line xenografts, transplanted human tumor xenografts, or mouse mesothelioma tumors. Xenografts were imaged by time-domain fluorescence imaging or fluorescence stereomicroscopy. Both imaging modalities detected specific uptake of cetuximab-Cy5.5 in HNSCC xenografts with significantly higher fluorescence levels relative to control IgG1-Cy5.5. Tumor xenograft fluorescence was higher compared with background (before injection), human split thickness skin grafts, or mouse mesothelioma tumors at 24, 48, and 72 h. Fluorescence was detected in multiple HNSCC tumor cell lines with variable EGFR expression levels. Mock resections of flank tumors using fluorescence stereomicroscopy showed that small (2 mm) specimens could be detected in the surgical wound bed. These results show the feasibility of using fluorescently labeled anti-EGFR antibody to detect human tumors in the surgical setting.

In vivo imaging of hepatic growth hormone signaling.

We developed a system to noninvasively and repeatedly image in vivo hepatic GH signaling. GH regulates postnatal growth and metabolism. It affects numerous tissues, but has major effects in liver. We used nude mice for adenoviral-mediated delivery of a signal transducer and activator of transcription 5-dependent GH response element, a luciferase reporter to detect GH signaling pathway activation. We detected by noninvasive bioluminescence imaging GH-induced hepatic GH signaling serially within intact mice. Statistically significant effects of GH dose and time dependence were detected in the liver luciferase signal that peaked 3 h after GH injection. Codelivery of GH receptor significantly enhanced GH response, an effect that was further augmented by fasting. Our imaging system allows detailed in vivo analysis of GH signaling and action and may be a paradigm for studies of additional signaling pathways in liver and other tissues.

Intraperitoneal pretarget radioimmunotherapy with CC49 fusion protein.

PURPOSE: This study examined a pretarget radioimmunotherapy strategy for treatment of an i.p. tumor model (LS174T). EXPERIMENTAL DESIGN: The strategy used regional administration (i.p.) of a novel targeting molecule composed of four CC49 anti-tumor-associated glycoprotein 72 (TAG-72) single-chain antibodies linked to streptavidin as a fusion protein (CC49 fusion protein); 24 hours later, a synthetic clearing agent was administered i.v. to produce hepatic clearance of unbound CC49 fusion protein/synthetic clearing agent complexes. Four hours later, a low molecular weight radiolabeled reagent composed of biotin conjugated to the chelating agent 7,10-tetra-azacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) complexed with (111)In-, (90)Y-, or (177)Lu-DOTA-biotin was injected. RESULTS: Radiolocalization to tumor sites was superior with i.p. administration of radiolabeled DOTA-biotin as compared with i.v. administration. Imaging and biodistribution studies showed excellent tumor localization of radioactivity with (111)In- or (177)Lu-DOTA-biotin. Tumor localization of (111)In-DOTA-biotin was 43% ID/g and 44% ID/g at 4 and 24 hours with the highest normal tissue localization in the kidney with 6% ID/g at 48 and 72 hours. Therapy studies with (90)Y-DOTA-biotin at doses of 400 to 600 microCi or (177)Lu-DOTA-biotin at doses of 600 to 800 microCi produced significant prolongation of survival compared with controls (P = 0.03 and P < 0.01). CONCLUSIONS: Pretarget radioimmunotherapy using regional administration of CC49 fusion protein and i.p. (90)Y- or (177)Lu-DOTA-biotin represents a successful therapeutic strategy in the LS174T i.p. tumor model and this strategy may be applicable to human trials in patients with i.p. ovarian cancer.

In vivo molecular chemotherapy and noninvasive imaging with an infectivity-enhanced adenovirus.

BACKGROUND: Adenovirus-based gene therapy is a promising approach to treat advanced cancers that are resistant to other treatments. However, many primary cells lack the requisite coxsackie-adenovirus receptor (CAR), limiting the in vivo efficacy of gene therapy. Recently, a modified adenovirus that is not dependent on CAR expression for infectivity was developed. We used noninvasive imaging to investigate the in vivo antitumor efficacy of gene therapy using this adenovirus in an animal model of ovarian cancer. METHODS: The adenoviral vectors RGDTKSSTR (CAR-independent) and AdTKSSTR (CAR-dependent) express herpes simplex virus thymidine kinase (TK) for molecular chemotherapy and the human somatostatin receptor subtype 2 (SSTR) for noninvasive nuclear imaging. Subcutaneous or peritoneal human xenograft ovarian cancers were established from highly aggressive SKOV3.ip1 cells in immune-deficient mice. Adenoviral constructs were infected intratumorally or intraperitoneally once a day for 3 days. Control mice received three injections, one per day, of Ad5Luc1, a CAR-dependent adenoviral vector that includes a luciferase marker gene. The somatostatin analogue (99m)Tc-P2045 was used for noninvasive in vivo imaging of RGDTKSSTR that was injected into subcutaneous tumors. For mice with peritoneal tumors, survival was compared among the different treatment groups using Kaplan-Meier analysis with the log-rank statistic. All statistical tests were two-sided. RESULTS: Tumor-associated RGDTKSSTR could be detected 15 days after introduction of the vector. In the subcutaneous model, tumors injected with RGDTKSSTR were statistically significantly smaller than those injected with AdTKSSTR (P<.001). In the intraperitoneal model, mice treated with RGDTKSSTR lived longer (survival at day 45 = 63.6%; 95% confidence interval [CI] = 35.2% to 92.0%) than those treated with AdTKSSTR (survival at day 45 = 0%) or Ad5Luc1 (survival at day 45 = 18.1%; 95% CI = 0.0% to 41.0%). DISCUSSION: RGDTKSSTR shows antitumor efficacy against ovarian cancer in vivo in animal models. The virus can be imaged noninvasively and may have the potential to be a useful agent for treating ovarian cancer.

Radiotargeted gene therapy.

The radiotargeted gene therapy approach to localizing radionuclides at tumor sites involves inducing tumor cells to synthesize a membrane-expressed receptor with a high affinity for injected radiolabeled ligands. A second strategy involves transduction of the sodium iodide symporter (NIS) and free radionuclide therapy. Using the first strategy, induction of high levels of human somatostatin receptor subtype 2 expression and selective tumor uptake, imaging, or growth inhibition with radiolabeled somatostatin analogs has been achieved in human tumor xenograft models. Therapy studies have been performed on several tumor xenograft models with various radionuclides using the NIS radiotargeted gene therapy approach. The use of gene transfer technology to induce expression of high-affinity membrane receptors or transporters can enhance the specificity and extent of radioligand or radionuclide localization in tumors, and the use of radionuclides with appropriate emissions can deliver radiation-absorbed cytotoxic doses across several cell diameters to compensate for limited transduction efficiency. Clinical studies are needed to determine the most promising of these new therapeutic approaches.

Glomerular targeting of acidic fibroblast growth factor-1 in renal transplanted rats.

BACKGROUND: Acidic fibroblast growth factor (FGF-1) functions as a potent hormonal inducer of wound repair mechanisms in vivo. In addition, the involvement of FGF-1 in a number of pathophysiological conditions, including chronic human renal allograft rejection, has been described. Consequently, there is an increasing need to monitor FGF-1 pharmacokinetics and distribution for both therapeutic and diagnostic opportunities. We now describe in vivo imaging and targeting of FGF-1 in renal transplanted rats. METHODS: Sham-operated, syngeneic renal transplanted, and allogeneic renal transplanted rats were imaged using an Anger gamma camera. Renal function was evaluated first by dynamic 99mTc-MAG3 imaging, and subsequently, 99mTc-labeled FGF-1 (99mTc-FGF-1) was imaged after i.v. injection. Microautoradiography of harvested kidneys determined the compartmental localization of 99mTc-FGF-1. RESULTS: 99mTc-MAG3 renal scans were grossly abnormal in the allogeneic renal transplanted rats. In this group, a significant reduction in 99mTc-FGF-1 renal binding was measured by imaging analyses, as compared with renal binding in the sham-operated and syngeneic renal transplanted groups, which were not significantly different. Both groups of renal transplanted rats showed a redistribution of FGF-1 to the glomerular compartment. CONCLUSIONS: 99mTc-FGF-1 serves as a new radiotracer to measure in vivo targeting of the growth factor. Reduced renal binding of 99mTc-FGF-1 in the allogeneic transplanted kidney was consistent with decreased blood flow. Unique glomerular targeting of 99mTc-FGF-1 in the transplanted kidney provides additional evidence supporting a role for this growth factor in the pathogenesis of chronic rejection.

Sinusoidal endothelium in mouse liver show rapid and saturable binding of Jo2 anti-Fas antibody.

PURPOSE: To evaluate liver binding of Jo2, a Fas agonist antibody known to induce death in mice. PROCEDURES: Jo2 was labeled with 99mTc and separately conjugated with Cy5.5. Following dosing in normal and Fas deficient mice, the in vivo distribution of 99mTc-Jo2 was imaged. Biodistribution studies were conducted, and liver sections from mice injected with Cy5.5-Jo2 were immunostained with endothelial-specific antibodies and examined by confocal microscopy. RESULTS: 99mTc-Jo2 injected intravenously (i.v.) was rapidly bound in the mouse liver. Fas dependence was confirmed by reduced liver binding in Fas deficient mice. For intraperitoneal (i.p.) dosing, the liver binding was delayed. However, tissue distributions were similar for both routes of injection. 99mTc-Jo2 liver binding was saturated at greater than 10 microg. For Cy5.5-Jo2 doses less than 10 microg, binding within the liver was confirmed to be sinusoidal endothelium. CONCLUSIONS: Rapid binding of Jo2 to liver endothelium is the initial event of Jo2-induced death.

Blood-based screening and light based imaging for the early detection and monitoring of ovarian cancer xenografts.

We report a novel technology for in vivo early detection, identification, and monitoring of ovarian cancer in live mice leading to better treatment outcome. A genetic dualistic reporter system that uses an adenoviral (Ad) vector to transfer the genetic reporters to the ovarian cancer is described. Infection of the cancer cells leads to expression of one reporter that is detected in blood, namely, secreted human placental alkaline phosphatase (SEAP). A second reporter, namely, enhanced green fluorescent protein (GFP) is also delivered by the Ad, leading to expression at the site of ovarian cancer. The SEAP gene under control of the cytomegalovirus (CMV) promoter element is linked to the GFP gene with an IRES element. A diagnostic adenoviral vector (Ad) encoding the SEAP and GFP (Ad5-SEAP-GFP) is produced. Efficacy of newly developed diagnostic vector is tested in cell culture and animal models. SKOV3ip.1 cells are infected with Ad5-SEAP-GFP. Over time the cells are monitored for fluorescence and SEAP is also measured in the growth media supernatant. For animal experiments, SKOV3ip.1 cells are implanted first in nude mice either subcutaneously (SC) or intraperitoneally (IP) separately. After 4-7 days, the Ad5-SEAP-GFP is administered. Control mice do not receive any Ad vector. All mice are imaged with a fluorescent stereomicroscope after 24 h, and blood is collected for SEAP analyses. Increasing green fluorescence is detected in all SKOV3ip.1 cells infected with Ad5-SEAP-GFP, while SEAP levels in growth media increase over monitoring period. Expression of GFP in both SC and IP tumors is detected by 24 h in the live mice. At this time, the SEAP blood levels are more than 2-3 fold greater than blood levels of control group. GFP fluorescence and SEAP levels continue to increase in all mice that are injected with Ad5-SEAP-GFP until termination. Control mice (both SC and IP) do not express GFP or SEAP throughout the experiment. GFP contrast is necessary to differentiate between micro-sized early stage non-palpable ovarian tumor nodules and surrounding normal tissue. While the studies are conducted in mice, it is envisioned that the dual-based approach will eventually be translated into human applications for routine diagnosis and monitoring of ovarian cancer when an ovarian cancer specific promoter will be available. Due to the thickness of the abdominal wall in human laparoscopy or laparotomy will be necessary. This system will provide gynecologic oncologists with a more effective tool for treating patients. The blood-based screening assay provides a quick test to determine the presence of the ovarian cancer at its earliest stage. The location of the ovarian cancer is afforded by the light-based imaging component, which represents a new and improving technology with tremendous advantages of sensitivity and spatial resolution to localize micro-sized tumor nodules. The novelty of the dualistic system is the linkage of blood-based reporter screening as a selection criteria for subsequent light-based imaging procedures. This combination will lead to an accurate and widely applicable method for the early detection and monitoring of ovarian cancer, especially in high-risk women

A non-invasive approach for monitoring breast tumor cells during therapeutic intervention.

OBJECTIVE: This study was performed to develop a non-invasive imaging method to evaluate non-palpable tumors in a breast xenograft model undergoing therapy. METHODS: Human breast cancer cells were infected with an adenoviral (Ad) vector encoding enhanced Green Fluorescent Protein (GFP). GFP-positive breast cancer cells were treated with doxorubicin 12 h after plating cells and sequentially imaged. Nude mice were implanted with GFP-positive tumor cells, treated with doxorubicin 24 h after implantation, and imaged at 1, 3, and 5 days after treatment. In vitro and in vivo images of the GFP-positive cells were collected using an inverted microscope and a fluorescent stereomicroscope, respectively. The fluorescence of GFP and of doxorubicin was simultaneously detected using two different GFP filters. RESULTS: Over 99% of tumor cells were GFP-positive following Ad-GFP infection. Doxorubicin therapy killed GFP-positive cancer cells and gradually eliminated GFP fluorescence in vitro and in vivo. Loss of GFP fluorescence was verified as cell death. Incorporation of doxorubicin into tumor cells and detection of single GFP-positive cells was observed in vivo through light-based imaging. CONCLUSION: The response of GFP-positive breast tumor cells to doxorubicin treatment was non-invasively imaged using light-based microscopy. This approach provides many useful applications for the evaluation of new anti-tumor drugs.

Gene expression imaging with radiolabeled peptides.

An approach to image radiolabeled peptide localization at tumor sites by inducing tumor cells to synthesize membrane expressed human somatostatin receptor subtype 2 (hSSTr2) with a high affinity for radiolabeled somatostatin analogues is described. The use of gene transfer technology to induce expression of high affinity membrane hSSTr2 can enhance the specificity and degree of radiolabeled peptide localization in tumors. Employing this strategy, induction of high levels of hSSTr2 expression with selective tumor uptake of radiolabeled peptides was achieved in both subcutaneous non-small cell lung cancer and intraperitoneal ovarian cancer mouse human tumor xenograft models. The features of this genetic transduction imaging approach are: (1) constitutive expression of a tumor-associated receptor is not required; (2) tumor cells are altered to express a new target receptor or increased quantities of a constitutive receptor at levels which may significantly increase tumor targeting of radiolabeled peptides compared to uptake in normal tissues; (3) gene transfer can be accomplished by local or regional injection of adenoviral vectors; (4) it is feasible to target adenovirus vectors to tumor cells by modifying adenoviral tropism (binding) or by the use of tumor-specific promoters such that the hSSTr2 will be specifically expressed in the desired tumor; and (5) this technique can be used to image expression of a second therapeutic gene.

The type 2 human somatostatin receptor as a platform for reporter gene imaging.

The human somatostatin receptor subtype 2A (hSSTr2) is under evaluation as a reporter gene for molecular imaging applications. Two approved somatostatin analogues are already available for imaging expression of the reporter gene following delivery with adenoviral (Ad) vectors or other genetic targeting strategies. In animal models, Ad-mediated expression of hSSTr2 in subcutaneous and intraperitoneal tumors was detected by non-invasive gamma camera imaging. This review discusses the rationale and strategy for using the hSSTr2 reporter gene as a platform for imaging applications.

Targeted radiotherapy with [(90)Y]-SMT 487 in mice bearing human nonsmall cell lung tumor xenografts induced to express human somatostatin receptor subtype 2 with an adenoviral vector.

BACKGROUND: Novel approaches to increasing the therapeutic efficacy of targeted radiotherapy of cancer are required. One strategy to achieve this goal is to induce high-level expression of a receptor on the surface of tumor cells that can be targeted with a radiolabeled peptide. The objectives of this study were to 1) induce somatostatin receptor (SSTr2) expression in tumor cells using an adenovirus encoding the SSTr2 gene (AdSSTr2), 2) demonstrate tumor localization of [(111)In]-DTPA-D-Phe(1)-octreotide in AdSSTr2-injected tumors, and 3) show therapeutic efficacy with [(90)Y]-DOTA-D-Phe(1)-Tyr(3)-octreotide ([(90)Y]-SMT 487). METHODS: SSTr2 expression was validated in vitro by the binding and subsequent internalization of [(111)In]-DTPA-D-Phe(1)-octreotide (21.3% per mg of total protein) in A-427 cells infected with AdSSTr2. In vivo imaging confirmed 5- to 10-fold greater uptake 5.5 hours after intravenous administration of [(111)In]-DTPA-D-Phe(1)-octreotide in AdSSTr2-injected tumors relative to control tumors. For therapy studies, mice bearing established subcutaneous A-427 tumors were given two intratumoral injections of AdSSTr2 1 week apart, followed by an intravenous injection of 400 microCi or 500 microCi [(90)Y]-SMT 487 at 2 and 4 days after each adenoviral administration. Control animals either were not treated or were administered 500 microCi [(90)Y]-SMT 487 with no AdSSTr2 injection. RESULTS: These studies showed that untreated animals and animals treated with no virus and 500 microCi [(90)Y]-SMT 487 had median tumor quadrupling times of 16 and 25 days, respectively. Mice administered AdSSTr2 and either 400 microCi or 500 microCi of [(90)Y]-SMT 487 demonstrated significantly longer median tumor quadrupling times of 40 and 44 days, respectively (P < 0.02). CONCLUSIONS: These studies are the first to demonstrate in vivo therapeutic efficacy using a radiolabeled peptide targeted to a receptor expressed on the surface of tumor cells following gene transfer. Future studies will focus on the optimization of this approach.

Gamma camera dual imaging with a somatostatin receptor and thymidine kinase after gene transfer with a bicistronic adenovirus in mice.

PURPOSE: To compare two systems for assessing gene transfer to cancer cells and xenograft tumors with noninvasive gamma camera imaging. MATERIALS AND METHODS: A replication-incompetent adenovirus encoding the human type 2 somatostatin receptor (hSSTr2) and the herpes simplex virus thymidine kinase (TK) enzyme (Ad-hSSTr2-TK) was constructed. A-427 human lung cancer cells were infected in vitro and mixed with uninfected cells at different ratios. A-427 tumors in nude mice (n = 23) were injected with 1 x 10(6) to 5 x 10(8) plaque-forming units (pfu) of Ad-hSSTr2-TK. The expressed hSSTr2 and TK proteins were imaged owing to internally bound, or trapped, technetium 99m ((99m)Tc)-labeled hSSTr2-binding peptide (P2045) and radioiodinated 2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl-5-iodouracil (FIAU), respectively. Iodine 125 ((125)I)-labeled FIAU was used in vitro and iodine 131 ((131)I)-labeled FIAU, in vivo. The (99m)Tc-labeled P2045 and (125)I- or (131)I-labeled FIAU were imaged simultaneously with different window settings with an Anger gamma camera. Treatment effects were tested with analysis of variance. RESULTS: Infected cells in culture trapped (125)I-labeled FIAU and (99m)Tc-labeled P2045; uptake correlated with the percentage of Ad-hSSTr2-TK-positive cells. For 100% of infected cells, 24% +/- 0.4 (mean +/- SD) of the added (99m)Tc-labeled P2045 was trapped, which is significantly lower (P <.05) than the 40% +/- 2 of (125)I-labeled FIAU that was trapped. For the highest Ad-hSSTr2-TK tumor dose (5 x 10(8) pfu), the uptake of (99m)Tc-labeled P2045 was 11.1% +/- 2.9 of injected dose per gram of tumor (thereafter, dose per gram), significantly higher (P <.05) than the uptake of (131)I-labeled FIAU at 1.6% +/- 0.4 dose per gram. (99m)Tc-labeled P2045 imaging consistently depicted hSSTr2 gene transfer in tumors at all adenovirus doses. Tumor uptake of (99m)Tc-labeled P2045 positively correlated with Ad-hSSTr2-TK dose; (131)I-labeled FIAU tumor uptake did not correlate with vector dose. CONCLUSION: The hSSTr2 and TK proteins were simultaneously imaged following dual gene transfer with an adenovirus vector.

Fc gamma Rs modulate cytotoxicity of anti-Fas antibodies: implications for agonistic antibody-based therapeutics.

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 FcgammaRIIB. Thus, following Jo2 treatment, all FcgammaRIIB(-/-) mice survived while 80% of wild-type and all FcR-gamma(-/-) mice died from acute liver failure. Microscopic examination suggests that FcgammaRIIB deficiency protects the hepatic sinusoidal endothelium, a cell type that normally coexpresses Fas and FcgammaRIIB. In vitro studies showed that FcgammaRIIB, but not FcgammaRI and FcgammaRIII, on neighboring macrophages substantially enhanced Jo2 mediated apoptosis of Fas expressing target cells. However, FcgammaRI and FcgammaRIII 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, FcgammaRs 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.

Enhanced therapeutic efficacy for ovarian cancer with a serotype 3 receptor-targeted oncolytic adenovirus.

Oncolytic viruses that are replication competent in tumor but not in normal cells represent a novel approach for treating neoplastic diseases. However, the oncolytic potency of replicating agents is determined directly by their capability of infecting target cells. Most adenoviruses used for gene therapy or virotherapy have been based on serotype 5 (Ad5). Unfortunately, expression of the primary receptor for Ad5 (the coxsackie-adenovirus receptor, or CAR) is highly variable on ovarian and other cancer cells. By performing genetic fiber pseudotyping, we created Ad5/3-Delta24, a conditionally replicating adenovirus that does not bind CAR but facilitates entry into and killing of ovarian cancer cells. We show replication of Ad5/3-Delta24 and subsequent oncolysis of ovarian adenocarcinoma lines. Replication was also analyzed with quantitative PCR on three-dimensional primary tumor cell spheroids purified from patient samples. Moreover, in a therapeutic orthotopic model of peritoneal carcinomatosis, dramatically enhanced survival was noted. Finally, Ad5/3-Delta24 achieved a significant antitumor effect as assessed by noninvasive, in vivo bioluminescence imaging. Therefore, the preclinical therapeutic efficacy of Ad5/3-Delta24 is improved over the respective CAR- and integrin-binding controls. Taken together with promising biodistribution and toxicity data, this approach could translate into successful clinical interventions for ovarian cancer patients.