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Chimeric antigen receptor (CAR) T cell therapy in hematologic malignancies has shown remarkable responses, but the same level of success has not been observed in solid tumors. A new prostate cancer model (Myc-CaP:PSMA(+)) and a second-generation anti-hPSMA human CAR T cells expressing a Click Beetle Red luciferase reporter) were used to study hPSMA targeting and assess CAR T cell trafficking and persistence by bioluminescence imaging (BLI). We investigated the antitumor efficacy of human CAR T cells targeting human prostate-specific membrane antigen (hPSMA), in the presence and absence of the target antigen; first alone and then combined with a monoclonal antibody targeting the human programmed death receptor 1 (anti-hPD1 mAb). PDL-1 expression was detected in Myc-CaP murine prostate tumors growing in immune competent FVB/N and immune-deficient SCID mice. Endogenous CD3+ T cells were restricted from the centers of Myc-CaP tumor nodules growing in FVB/N mice. Following anti-programmed cell death protein 1 (PD-1) treatment, the restriction of CD3+ T cells was reversed, and a tumor-treatment response was observed. Adoptive hPSMA-CAR T cell immunotherapy was enhanced when combined with PD-1 blockade, but the treatment response was of comparatively short duration, suggesting other immune modulation mechanisms exist and restrict CAR T cell targeting, function, and persistence in hPSMA expressing Myc-CaP tumors. Interestingly, an “inverse pattern” of CAR T cell BLI intensity was observed in control and test tumors, which suggests CAR T cells undergo changes leading to a loss of signal and/or number following hPSMA-specific activation. The lower BLI signal intensity in the hPSMA test tumors (compared with controls) is due in part to a decrease in T cell mitochondrial function following T cell activation, which may limit the intensity of the ATP-dependent Luciferin-luciferase bioluminescence signal.

Secondary lymphedema is a common condition among cancer survivors, and treatment strategies to prevent or treat lymphedema are in high demand. The development of novel strategies to diagnose or treat lymphedema would benefit from a robust experimental animal model of secondary lymphedema. The purpose of this methods paper is to describe and summarize our experience in developing and characterizing a rat hindlimb model of lymphedema. Here we describe a protocol to induce secondary lymphedema that takes advantage of micro computed tomography imaging for limb volume measurements and visualization of lymph drainage with near infrared imaging. To demonstrate the utility of this preclinical model for studying the therapeutic benefit of novel devices, we apply this animal model to test the efficacy of a biomaterials-based implantable medical device.

Purpose Radionuclide-based reporter gene imaging has the sensitivity to monitor gene- and cell-based therapies in human subjects. Potential immunogenicity of current viral transgenes warrants development of human-based reporter systems. We compared human nucleoside kinase reporters to a panel of nucleoside analogs of FEAU, FMAU, and FIAU, including the first in vivo assessment of l -[ 18 F]FEAU. Procedures Human isogenic U87 cell lines were transduced to express different human reporter genes including dCK-R104M/D133A (dCKDM), dCK-R104Q/D133N (dCKep16A), dCK-A100V/R104M/D133A (dCK3M), and TK2-N93D/L109F (TK2DM), and wild-type dCK (dCK) and herpes simplex virus type-1 (HSVTK) reporter gene as references. In vitro cell uptake assays were performed with [ 18 F]FEAU, l -[ 18 F]FEAU, [ 14 C]FMAU, l -[ 18 F]FMAU, and [ 124 I]FIAU. Micro-positron emission tomography/X-ray computed tomography imaging of xenograft-bearing nu/nu mice was conducted with [ 18 F]FEAU, l -[ 18 F]FEAU, l -[ 18 F]FMAU, and [ 124 I]FIAU on consecutive days. A cell viability assay was also performed to assess sensitivities to gemcitabine and bromovinyldeoxyuridine (BVdU). Results In vitro , dCKep16A and dCKDM with [ 18 F]FEAU exhibited the highest sensitivity and selectivity of the human reporters, second only to HSVTK/[ 18 F]FEAU. l -[ 18 F]FEAU biodistribution in mice was on par with [ 18 F]FEAU and l -[ 18 F]FMAU. l -[ 18 F]FMAU uptake in isogenic xenografts was highest for all human reporter genes. However, [ 18 F]FEAU was the most selective of the short half-life reporter probes due to its minimal recognition by human dCK and relative sensitivity, whereas [ 124 I]FIAU permitted imaging at a later time point, improving signal-to-background ratio. Of the human reporter genes, dCKep16A consistently outperformed the other tested reporters. Reporter genes of interest increased potency to the nucleoside analog prodrugs gemcitabine and BVdU. Conclusions We demonstrate that human nucleoside kinase reporter systems vary significantly in their sensitivity and selectivity for in vivo imaging. The sufficiently high signal-to-background ratios and enhanced suicide gene potential support clinical translation.

The human somatostatin receptor subtype 2 (hSSTr2)-68Ga-DOTATOC reporter system has several attractive features for potential translation to human studies. These include a low expression of hSSTr2 in most organs, a rapid internalized accumulation of 68Ga-DOTATOC in the SSTr2-expressing cells, and a rapid excretion of unbound radioligand by the renal system. We performed a series of in vitro and in vivo validation studies of this reporter system. A retroviral vector containing a dual reporter, pQCXhSSTr2-IRES-GFP (IRES: internal ribosome entry site; GFP: green fluorescent protein), was constructed and transduced into Jurkat, C6, and U87 cells. Stably transduced reporter cells were characterized in vitro using optical and radiometric methods. Multiple tumor-bearing mice were evaluated with 68Ga-DOTATOC PET studies. The dual-reporter genes were incorporated into all tumor cell lines, and their expression levels were confirmed by fluorescence-activated cell sorting (FACS), GFP visualization, and reverse-transcriptase polymerase chain reaction (RT-PCR) analysis for hSSTr2. In vitro, hSSTr2 cell membrane expression was 36,000, 280,000, and 1,250,000 copies per cell for the SSTR2-transfected Jurkat, U87, and C6 cell lines. Small-animal PET of 68Ga-DOTATOC in tumor-bearing mice demonstrated that the in vivo uptake of this radioligand was directly proportional to the in vitro expression of hSSTr2. The in vivo uptake of 68Ga-DOTATOC, at 2 h after injection, was low in all organs except the kidneys (7.8 percentage of injected dose per gram [%ID/g]) and as high as 15.2 %ID/g in transduced C6 tumors. The corresponding transduced-to-nontransduced tumor uptake ratio was 64, and the tumor-to-muscle uptake ratio was around 500. 68Ga-DOTATOC is an excellent specific ligand for this hSSTr2 reporter system and for hSSTr2 reporter gene PET. Because DOTATOC has undergone extensive clinical testing, this human reporter system has the potential for translation to human studies.

Current strategies to suppress graft-versus-host disease (GVHD) also compromise graft-versus-tumor (GVT) responses. Furthermore, most experimental strategies to separate GVHD and GVT responses merely spare GVT function without actually enhancing it. We have previously shown that endogenously expressed TNF-related apoptosis-inducing ligand (TRAIL) is required for optimal GVT activity against certain malignancies in recipients of allogeneic hematopoietic stem cell transplantation (allo-HSCT). In order to model a donor-derived cellular therapy, we genetically engineered T cells to overexpress TRAIL and adoptively transferred donor-type unsorted TRAIL+ T cells into mouse models of allo-HSCT. We found that murine TRAIL+ T cells induced apoptosis of alloreactive T cells, thereby reducing GVHD in a DR5-dependent manner. Furthermore, murine TRAIL+ T cells mediated enhanced in vitro and in vivo antilymphoma GVT response. Moreover, human TRAIL+ T cells mediated enhanced in vitro cytotoxicity against both human leukemia cell lines and against freshly isolated chronic lymphocytic leukemia (CLL) cells. Finally, as a model of off-the-shelf, donor-unrestricted antitumor cellular therapy, in vitro-generated TRAIL+ precursor T cells from third-party donors also mediated enhanced GVT response in the absence of GVHD. These data indicate that TRAIL-overexpressing donor T cells could potentially enhance the curative potential of allo-HSCT by increasing GVT response and suppressing GVHD.

Current strategies to suppress graft-versus-host disease (GVHD) also compromise graft-versus-tumor (GVT) responses. Furthermore, most experimental strategies to separate GVHD and GVT responses merely spare GVT function without actually enhancing it. We have previously shown that endogenously expressed TNF-related apoptosis-inducing ligand (TRAIL) is required for optimal GVT activity against certain malignancies in recipients of allogeneic hematopoietic stem cell transplantation (allo-HSCT). In order to model a donor-derived cellular therapy, we genetically engineered T cells to overexpress TRAIL and adoptively transferred donor-type unsorted TRAIL super( +) T cells into mouse models of allo-HSCT. We found that murine TRAIL super( +) T cells induced apoptosis of alloreactive T cells, thereby reducing GVHD in a DR5-dependent manner. Furthermore, murine TRAIL super( +) T cells mediated enhanced in vitro and in vivo antilymphoma GVT response. Moreover, human TRAIL super( +) T cells mediated enhanced in vitro cytotoxicity against both human leukemia cell lines and against freshly isolated chronic lymphocytic leukemia (CLL) cells. Finally, as a model of off-the-shelf, donor-unrestricted antitumor cellular therapy, in vitro-generated TRAIL super( +) precursor T cells from third-party donors also mediated enhanced GVT response in the absence of GVHD. These data indicate that TRAIL-over-expressing donor T cells could potentially enhance the curative potential of allo-HSCT by increasing GVT response and suppressing GVHD.

Current strategies to suppress graft-versus-host disease (GVHD) also compromise graft-versus-tumor (GVT) responses. Furthermore, most experimental strategies to separate GVHD and GVT responses merely spare GVT function without actually enhancing it. We have previously shown that endogenously expressed TNF-related apoptosis-inducing ligand (TRAIL) is required for optimal GVT activity against certain malignancies in recipients of allogeneic hematopoietic stem cell transplantation (allo-HSCT). In order to model a donor-derived cellular therapy, we genetically engineered T cells to overexpress TRAIL and adoptively transferred donor-type unsorted TRAIL^sup +^ T cells into mouse models of allo-HSCT. We found that murine TRAIL^sup +^ T cells induced apoptosis of alloreactive T cells, thereby reducing GVHD in a DR5-dependent manner. Furthermore, murine TRAIL^sup +^ T cells mediated enhanced in vitro and in vivo antilymphoma GVT response. Moreover, human TRAIL^sup +^ T cells mediated enhanced in vitro cytotoxicity against both human leukemia cell lines and against freshly isolated chronic lymphocytic leukemia (CLL) cells. Finally, as a model of off-the-shelf, donor-unrestricted antitumor cellular therapy, in vitro-generated TRAIL^sup +^ precursor T cells from third-party donors also mediated enhanced GVT response in the absence of GVHD. These data indicate that TRAIL-over-expressing donor T cells could potentially enhance the curative potential of allo-HSCT by increasing GVT response and suppressing GVHD. [PUBLICATION ABSTRACT]

The human somatostatin receptor subtype 2 (hSSTr2)-^sup 68^Ga-DOTATOC reporter system has several attractive features for potential translation to human studies. These include a low expression of hSSTr2 in most organs, a rapid internalized accumulation of ^sup 68^Ga-DOTATOC in the SSTr2-expressing cells, and a rapid excretion of unbound radioligand by the renal system. We performed a series of in vitro and in vivo validation studies of this reporter system. Methods: A retroviral vector containing a dual reporter, pQCXhSSTr2-IRES-GFP (IRES: internal ribosome entry site; GFP: green fluorescent protein), was constructed and transduced into Jurkat, C6, and U87 cells. Stably transduced reporter cells were characterized in vitro using optical and radiometric methods. Multiple tumor-bearing mice were evaluated with ^sup 68^Ga-DOTATOC PET studies. Results: The dual-reporter genes were incorporated into all tumor cell lines, and their expression levels were confirmed by fluorescence-activated cell sorting (FACS), GFP visualization, and reverse-transcriptase polymerase chain reaction (RT-PCR) analysis for hSSTr2. In vitro, hSSTr2 cell membrane expression was 36,000, 280,000, and 1,250,000 copies per cell for the SSTR2-transfected Jurkat, U87, and C6 cell lines. Small-animal PET of ^sup 68^Ga-DOTATOC in tumor-bearing mice demonstrated that the in vivo uptake of this radioligand was directly proportional to the in vitro expression of hSSTr2. The in vivo uptake of ^sup 68^Ga-DOTATOC, at 2 h after injection, was low in all organs except the kidneys (7.8 percentage of injected dose per gram [%ID/g]) and as high as 15.2 %ID/g in transduced C6 tumors. The corresponding transduced-to-nontransduced tumor uptake ratio was 64, and the tumor-to-muscle uptake ratio was around 500. Conclusion: ^sup 68^Ga-DOTATOC is an excellent specific ligand for this hSSTr2 reporter system and for hSSTr2 reporter gene PET. Because DOTATOC has undergone extensive clinical testing, this human reporter system has the potential for translation to human studies. [PUBLICATION ABSTRACT]

The norepinephrine transporter (NET) has recently been suggested as a useful reporter gene. We have extended this effort by constructing an internal ribosomal entry site (IRES)-linked hNET-green fluorescent protein (GFP) hybrid reporter gene for both nuclear and optical imaging. Methods: A retroviral vector pQCXhNET-IRES-GFP was constructed and used to generate several reporter cell lines and xenografts. Transduced cells were sorted by fluorescence-activated cell sorting based on GFP expression and used for both in vitro and in vivo imaging studies. Results: The transduced reporter cells accumulated ^sup 123^I- or ^sup 124^I-labeled metaiodobenzylguanidine (MIBG) to high levels compared with the wild-type parent cell lines. Differences in MIBG accumulation between cell lines were primarily due to differences in influx (K^sub 1^) rather than efflux (k^sub 2^). The estimated MIBG distribution volumes (V^sub d^) for transduced Jurkat, C6, and COS-7 cells were 572 ± 13, 754 ± 25, and 1,556 ± 38 mL/g, respectively. A correlation between radiotracer accumulation (K^sub 1^) and GFP fluorescence intensity was also demonstrated. Sequential imaging studies of mice bearing pQCXhNET-IRES-GFP transduced and wild-type C6 xenografts demonstrated several advantages of ^sup 124^I-MIBG small-animal PET compared with ^sup 123^I-MIBG γ-camera/SPECT. This was primarily due to the longer half-life of ^sup 124^I and to the retention and slow clearance (half-time, 63 ± 6 h) of MIBG from transduced xenografts compared with that from wild-type xenografts (half-time, 12 ± 1 h) and other organs (half-time, 2.6-21 h). Very high radioactivity ratios were observed at later imaging times; at 73 h after ^sup 124^I-MIBG injection, the C6/hNET-IRES-GFP xenograft-to-muscle ratio was 293 ± 48 whereas the C6 xenograft-to-muscle ratio was 0.71 ± 0.19. Conclusion: These studies demonstrate the potential for a wider application of hNET reporter imaging and the future translation to patient studies using radiopharmaceuticals that are currently available for both SPECT and PET. [PUBLICATION ABSTRACT]

The norepinephrine transporter (NET) has recently been suggested as a useful reporter gene. We have extended this effort by constructing an internal ribosomal entry site (IRES)-linked hNET-green fluorescent protein (GFP) hybrid reporter gene for both nuclear and optical imaging. A retroviral vector pQCXhNET-IRES-GFP was constructed and used to generate several reporter cell lines and xenografts. Transduced cells were sorted by fluorescence-activated cell sorting based on GFP expression and used for both in vitro and in vivo imaging studies. The transduced reporter cells accumulated (123)I- or (124)I-labeled metaiodobenzylguanidine (MIBG) to high levels compared with the wild-type parent cell lines. Differences in MIBG accumulation between cell lines were primarily due to differences in influx (K(1)) rather than efflux (k(2)). The estimated MIBG distribution volumes (V(d)) for transduced Jurkat, C6, and COS-7 cells were 572 +/- 13, 754 +/- 25, and 1,556 +/- 38 mL/g, respectively. A correlation between radiotracer accumulation (K(1)) and GFP fluorescence intensity was also demonstrated. Sequential imaging studies of mice bearing pQCXhNET-IRES-GFP transduced and wild-type C6 xenografts demonstrated several advantages of (124)I-MIBG small-animal PET compared with (123)I-MIBG gamma-camera/SPECT. This was primarily due to the longer half-life of (124)I and to the retention and slow clearance (half-time, 63 +/- 6 h) of MIBG from transduced xenografts compared with that from wild-type xenografts (half-time, 12 +/- 1 h) and other organs (half-time, 2.6-21 h). Very high radioactivity ratios were observed at later imaging times; at 73 h after (124)I-MIBG injection, the C6/hNET-IRES-GFP xenograft-to-muscle ratio was 293 +/- 48 whereas the C6 xenograft-to-muscle ratio was 0.71 +/- 0.19. These studies demonstrate the potential for a wider application of hNET reporter imaging and the future translation to patient studies using radiopharmaceuticals that are currently available for both SPECT and PET.