Fibroblast Growth Factor Receptor 1 Drives the Metastatic Progression of Prostate Cancer.

BACKGROUND: No curative therapy is currently available for metastatic prostate cancer (PCa). The diverse mechanisms of progression include fibroblast growth factor (FGF) axis activation. OBJECTIVE: To investigate the molecular and clinical implications of fibroblast growth factor receptor 1 (FGFR1) and its isoforms (α/ß) in the pathogenesis of PCa bone metastases. DESIGN, SETTING, AND PARTICIPANTS: In silico, in vitro, and in vivo preclinical approaches were used. RNA-sequencing and immunohistochemical (IHC) studies in human samples were conducted. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: In mice, bone metastases (chi-square/Fisher's test) and survival (Mantel-Cox) were assessed. In human samples, FGFR1 and ladinin 1 (LAD1) analysis associated with PCa progression were evaluated (IHC studies, Fisher's test). RESULTS AND LIMITATIONS: FGFR1 isoform expression varied among PCa subtypes. Intracardiac injection of mice with FGFR1-expressing PC3 cells reduced mouse survival (α, p < 0.0001; ß, p = 0.032) and increased the incidence of bone metastases (α, p < 0.0001; ß, p = 0.02). Accordingly, IHC studies of human castration-resistant PCa (CRPC) bone metastases revealed significant enrichment of FGFR1 expression compared with treatment-naïve, nonmetastatic primary tumors (p = 0.0007). Expression of anchoring filament protein LAD1 increased in FGFR1-expressing PC3 cells and was enriched in human CRPC bone metastases (p = 0.005). CONCLUSIONS: FGFR1 expression induces bone metastases experimentally and is significantly enriched in human CRPC bone metastases, supporting its prometastatic effect in PCa. LAD1 expression, found in the prometastatic PCa cells expressing FGFR1, was also enriched in CRPC bone metastases. Our studies support and provide a roadmap for the development of FGFR blockade for advanced PCa. PATIENT SUMMARY: We studied the role of fibroblast growth factor receptor 1 (FGFR1) in prostate cancer (PCa) progression. We found that PCa cells with high FGFR1 expression increase metastases and that FGFR1 expression is increased in human PCa bone metastases, and identified genes that could participate in the metastases induced by FGFR1. These studies will help pinpoint PCa patients who use fibroblast growth factor to progress and will benefit by the inhibition of this pathway.

Bempegaldesleukin (BEMPEG; NKTR-214) efficacy as a single agent and in combination with checkpoint-inhibitor therapy in mouse models of osteosarcoma.

Survival of patients with relapsed/refractory osteosarcoma has not improved in the last 30 years. Several immunotherapeutic approaches have shown benefit in murine osteosarcoma models, including the anti-programmed death-1 (anti-PD-1) and anti-cytotoxic T-lymphocyte antigen-4 (anti-CTLA-4) immune checkpoint inhibitors. Treatment with the T-cell growth factor interleukin-2 (IL-2) has shown some clinical benefit but has limitations due to poor tolerability. Therefore, we evaluated the efficacy of bempegaldesleukin (BEMPEG; NKTR-214), a first-in-class CD122-preferential IL-2 pathway agonist, alone and in combination with anti-PD-1 or anti-CTLA-4 immune checkpoint inhibitors in metastatic and orthotopic murine models of osteosarcoma. Treatment with BEMPEG delayed tumor growth and increased overall survival of mice with K7M2-WT osteosarcoma pulmonary metastases. BEMPEG also inhibited primary tumor growth and metastatic relapse in lungs and bone in the K7M3 orthotopic osteosarcoma mouse model. In addition, it enhanced therapeutic activity of anti-CTLA-4 and anti-PD-1 checkpoint blockade in the DLM8 subcutaneous murine osteosarcoma model. Finally, BEMPEG strongly increased accumulation of intratumoral effector T cells and natural killer cells, but not T-regulatory cells, resulting in improved effector:inhibitory cell ratios. Collectively, these data in multiple murine models of osteosarcoma provide a path toward clinical evaluation of BEMPEG-based regimens in human osteosarcoma.

Virus-Mimicking Nanoparticles for Targeted Near Infrared Fluorescence Imaging of Intraperitoneal Ovarian Tumors in Mice.

Ovarian cancer is the most lethal malignancy affecting the female reproductive system. Identification and removal of all ovarian intraperitoneal tumor deposits during the intraoperative surgery is important towards preventing cancer recurrence and ultimately improving patient survival. Herein, we investigate the effectiveness of virus mimicking nanoparticles, derived from genome-depleted plant-infecting brome mosaic virus, and doped with near infrared (NIR) brominated cyanine dye BrCy106-NHS, for targeted NIR fluorescence imaging of intraperitoneal ovarian tumors. We refer to these nanoparticles as optical viral ghosts (OVGs). We functionalized the OVGs with antibodies against HER2 receptor, a biomarker over-expressed in ovarian cancers. We injected functionalized OVGs, non-functionalized OVGs, and non-encapsulated BrCy106-NHS intravenously in mice implanted with ovarian intraperitoneal tumors. Tumors were extracted at 2, 6, and 24 h post-injection, and quantitatively analyzed using NIR fluorescence imaging. Fluorescence emission from tumors associated with the injection of the functionalized OVGs continued to increase between 2 and 24 h post-injection. At 24 h timepoint, the average spectrally-integrated fluorescence emission from homogenized tumors containing functionalized-OVGs was about 3.5 and 19.5 times higher than those containing non-functionalized OVGs or non-encapsulated BrCy106-NHS, respectively. Similarly, by using the functionalized-OVGs, the imaging signal-to-noise ratio at 24 h timepoint was enhanced by approximately threefold and sevenfold as compared to non-functionalized OVGs and the non-encapsulated dye, respectively. These functionalized virus-mimicking NIR nano-constructs could potentially be used for intraoperative visualization of ovarian tumors implants.

The MD Anderson Prostate Cancer Patient-derived Xenograft Series (MDA PCa PDX) Captures the Molecular Landscape of Prostate Cancer and Facilitates Marker-driven Therapy Development.

PURPOSE: Advances in prostate cancer lag behind other tumor types partly due to the paucity of models reflecting key milestones in prostate cancer progression. Therefore, we develop clinically relevant prostate cancer models. EXPERIMENTAL DESIGN: Since 1996, we have generated clinically annotated patient-derived xenografts (PDXs; the MDA PCa PDX series) linked to specific phenotypes reflecting all aspects of clinical prostate cancer. RESULTS: We studied two cell line-derived xenografts and the first 80 PDXs derived from 47 human prostate cancer donors. Of these, 47 PDXs derived from 22 donors are working models and can be expanded either as cell lines (MDA PCa 2a and 2b) or PDXs. The histopathologic, genomic, and molecular characteristics (androgen receptor, ERG, and PTEN loss) maintain fidelity with the human tumor and correlate with published findings. PDX growth response to mouse castration and targeted therapy illustrate their clinical utility. Comparative genomic hybridization and sequencing show significant differences in oncogenic pathways in pairs of PDXs derived from different areas of the same tumor. We also identified a recurrent focal deletion in an area that includes the speckle-type POZ protein-like (SPOPL) gene in PDXs derived from seven human donors of 28 studied (25%). SPOPL is a SPOP paralog, and SPOP mutations define a molecular subclass of prostate cancer. SPOPL deletions are found in 7% of The Cancer Genome Atlas prostate cancers, which suggests that our cohort is a reliable platform for targeted drug development. CONCLUSIONS: The MDA PCa PDX series is a dynamic resource that captures the molecular landscape of prostate cancers progressing under novel treatments and enables optimization of prostate cancer-specific, marker-driven therapy.

In vivo magnetic resonance imaging of orthotopic prostate cancer.

Methods for imaging orthotopic prostate tumors within the prostate or small tumors with extension outside the prostate are needed to more closely model human prostate tumors, which are most commonly located within the gland or may extend just through the gland. By comparing MR sequences, we found that the T2-based Dixon 'water only' sequence best visualized tumors within the prostate of mouse models in both young and old mice and that tumor weight derived from this sequence correlated highly with ex vivo tumor weight (r2 = 0.98, p < 0.001, n = 12). This should aid tumor detection, margin delineation and evaluation of tumor burden to enable studies including, but not limited to, evaluating the natural history of the disease, the mechanisms of action and the efficacy of therapeutic interventions.

Metformin Reduces Renal Uptake of Radiotracers and Protects Kidneys from Radiation-Induced Damage.

Metformin is the most widely prescribed drug for type 2 diabetes. Chemically, metformin is a hydrophilic base that functions as an organic cation, suggesting that it may have the capacity to inhibit the tubular reabsorption of peptide radiotracers. The purpose of this study was to investigate whether metformin could reduce renal uptake of peptidyl radiotracers and serve as a radioprotective agent for peptide receptor radionuclide therapy (PRRT). METHODS: We used two radiolabeled peptides: a 68Ga-labeled cyclic (TNYL-RAW) peptide (68Ga-NOTA-c(TNYL-RAW) (NOTA: 1,4,7 triazacyclononane-1,4,7-trisacetic acid) targeting EphB4 receptors and an 111In- or 64Cu-labeled octreotide (111In/64Cu-DOTA-octreotide) (DOTA: 1,4,7,10 triazacyclododecane-1,4,7,10-tetraacetic acid) targeting somatostatin receptors. Each radiotracer was injected intravenously into normal Swiss mice or tumor-bearing nude mice in the presence or absence of metformin administered intravenously or orally. Micropositron emission tomography or microsingle-photon emission computed tomography images were acquired at different times after radiotracer injection, and biodistribution studies were performed at the end of the imaging session. To assess the radioprotective effect of metformin on the kidneys, normal Swiss mice received two doses of 111In-DOTA-octreotidein the presence or absence of metformin, and renal function was analyzed via blood chemistry and histology. RESULTS: Intravenous injection of metformin with 68Ga-NOTA-c(TNYL-RAW) or 111In-DOTA-octreotide reduced the renal uptake of the radiotracer by 60% and 35%, respectively, compared to uptake without metformin. These reductions were accompanied by greater uptake in the tumors for both radiolabeled peptides. Moreover, the renal uptake of 111In-DOTA-octreotide was significantly reduced when metformin was administered via oral gavage. Significantly more radioactivity was recovered in the urine collected over a period of 24 h after intravenous injection of 64Cu-DOTA-octreotide in mice that received oral metformin than in mice that received vehicle. Finally, coadministration of 111In-DOTA-octreotide with metformin mitigated radio-nephrotoxicity. CONCLUSION: Metformin inhibits kidney uptake of peptidyl radiotracers, protecting the kidney from nephrotoxicity. Further studies are needed to elucidate the mechanisms of these finding and to optimize mitigation of radiation-induced damage to kidney in PRRT.

Routes to Potentially Safer T1 Magnetic Resonance Imaging Contrast in a Compact Plasmonic Nanoparticle with Enhanced Fluorescence.

Engineering a compact, near-infrared plasmonic nanostructure with integrated image-enhancing agents for combined imaging and therapy is an important nanomedical challenge. Recently, we showed that Au@SiO2@Au nanomatryoshkas (NM) are a highly promising nanostructure for hosting either T1 MRI or fluorescent contrast agents with a photothermal therapeutic response in a compact geometry. Here, we show that a near-infrared-resonant NM can provide simultaneous contrast enhancement for both T1 magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI) by encapsulating both types of contrast agents in the internal silica layer between the Au core and shell. We also show that this method of T1 enhancement is even more effective for Fe(III), a potentially safer contrast agent compared to Gd(III). Fe-NM-based contrast agents are found to have relaxivities 2× greater than those found in the widely used gadolinium chelate, Gd(III) DOTA, providing a practical alternative that would eliminate Gd(III) patient exposure entirely. This dual-modality nanostructure can enable not only tissue visualization with MRI but also fluorescence-based nanoparticle tracking for quantifying nanoparticle distributions in vivo, in addition to a near-infrared photothermal therapeutic response.

In Vivo Assessment of Ovarian Tumor Response to Tyrosine Kinase Inhibitor Pazopanib by Using Hyperpolarized 13C-Pyruvate MR Spectroscopy and 18F-FDG PET/CT Imaging in a Mouse Model.

Purpose To assess in a mouse model whether early or late components of glucose metabolism, exemplified by fluorine 18 (18F) fluorodeoxyglucose (FDG) positron emission tomography (PET) and hyperpolarized carbon 13 (13C)-pyruvate magnetic resonance (MR) spectroscopy, can serve as indicators of response in ovarian cancer to multityrosine kinase inhibitor pazopanib. Materials and Methods In this Animal Care and Use Committee approved study, 17 days after the injection of 2 × 106 human ovarian SKOV3 tumors cells into 14 female nude mice, treatment with vehicle or pazopanib (2.5 mg per mouse peroral every other day) was initiated. Longitudinal T2-weighted MR imaging, dynamic MR spectroscopy of hyperpolarized pyruvate, and 18F-FDG PET/computed tomographic (CT) imaging were performed before treatment, 2 days after treatment, and 2 weeks after treatment. Results Pazopanib inhibited ovarian tumor growth compared with control (0.054 g ± 0.041 vs 0.223 g ± 0.112, respectively; six mice were treated with pazopanib and seven were control mice; P < .05). Significantly higher pyruvate-to-lactate conversion (lactate/pyruvate + lactate ratio) was found 2 days after treatment with pazopanib than before treatment (0.46 ± 0.07 vs 0.31 ± 0.14, respectively; P < .05; six tumors after treatment, seven tumors before treatment). This was not observed with the control group or with 18F-FDG PET/CT imaging. Conclusion The findings suggest that hyperpolarized 13C-pyruvate MR spectroscopy may serve as an early indicator of response to tyrosine kinase (angiogenesis) inhibitors such as pazopanib in ovarian cancer even when 18F-FDG PET/CT does not indicate a response. © RSNA, 2017 Online supplemental material is available for this article.

Angiotensin II increases gene expression after selective intra-arterial adenovirus delivery in a rabbit model assessed using in vivo SSTR2-based reporter imaging.

BACKGROUND: Gene therapy has been hampered by low expression upon in vivo delivery. Using a somatostatin receptor type 2 (SSTR2)-based reporter, we assessed whether angiotensin II (AII) can improve gene expression by adenovirus upon intra-arterial (IA) delivery in a large animal model. METHODS: A SSTR2-based reporter that can be imaged by a clinically approved radiopharmaceutical was used to assess gene expression. Eight rabbits bearing VX2 tumors in each thigh were randomly injected IA with adenovirus containing a human SSTR2 (Ad-CMV-HA-SSTR2) gene chimera ± AII or control adenovirus containing green fluorescent protein (Ad-CMV-GFP). Three days later, (111)In-octreotide was given IV after computed tomography (CT) imaging using a clinical CT scanner and intravenous contrast. Tumor uptake of (111)In-octreotide was evaluated the next day using a clinical gamma camera. Gene expression was normalized to tumor weight and morphology from CT to obtain in vivo biodistribution. RESULTS: SSTR2-based expression was readily visualized. VX2 tumors infected with Ad-CMV-HA-SSTR2 upon intra-arterial delivery with AII had greater in vivo biodistribution, thus greater gene expression, than those without AII (p < 0.01, n = 6). VX2 tumors infected with Ad-CMV-HA-SSTR2 upon IA delivery had greater biodistribution, thus greater gene expression, than those with the negative control Ad-CMV-GFP (p < 0.02). Similarly, VX2 tumors infected with Ad-CMV-HA-SSTR2 upon IA delivery with AII had greater biodistribution, thus greater gene expression, than those with the negative control Ad-CMV-GFP (p < 0.01). CONCLUSIONS: Angiotensin II improves in vivo gene expression by adenovirus upon intra-arterial delivery and thus may improve gene therapy efficacy. In vivo SSTR2-based reporter imaging can be used to compare methodologies for improving gene expression.

Deletion of cyclooxygenase-2 inhibits K-ras-induced lung carcinogenesis.

The purpose of this study was to identify the role COX-2 plays in K-ras-induced lung carcinogenesis. We crossed COX-2-homozygous knockout mice with K-rasLA1 (G12D) expressing mice to obtain COX-2-deficient mice with K-ras expression (K-ras/COX-2(-/-) mice) and COX-2 wild type mice with K-ras expression (K-ras mice). At 3.5 months of age, the K-ras/COX-2(-/-) mice had significantly fewer lung adenocarcinomas and substantially smaller tumors than K-ras mice. K-ras/COX-2(-/-) mice also had significantly fewer bronchioalveolar hyperplasias than K-ras mice. Compared with lung tumors from K-Ras mice, the levels of prostaglandin E2 (PGE2) were significantly lower, whereas levels of the PGE2 metabolite 13,14-dihydro-15-keto-PGE2 were significantly higher, in lung tumors from K-ras/COX-2(-/-) mice. In addition, K-ras/COX-2(-/-) mice had strikingly lower rates of tumor cell proliferation and expressed less MEK and p-Erk1/2 protein than K-ras mice did. In line with this, knocking down COX-2 in mutant K-ras non-small cell lung cancer A549 cells reduced colony formation, PGE2 synthesis and ERK phosphorylation compared to that of vector control cells. Taken together, these findings suggest that COX-2 deletion contributes to the repression of K-ras-induced lung tumorigenesis by reducing tumor cell proliferation, decreasing the production of PGE2, and increasing the production of 13,14-dihydro-15-keto-PGE2, possibly via the MAPK pathway. Thus, COX-2 is likely important in lung tumorigenesis, and COX-2 and its product, PGE2, are potential targets for lung cancer prevention.

Dependence of DCE-MRI biomarker values on analysis algorithm.

BACKGROUND: Dynamic contrast-enhanced MRI (DCE-MRI) biomarkers have proven utility in tumors in evaluating microvascular perfusion and permeability, but it is unclear whether measurements made in different centers are comparable due to methodological differences. PURPOSE: To evaluate how commonly utilized analytical methods for DCE-MRI biomarkers affect both the absolute parameter values and repeatability. MATERIALS AND METHODS: DCE-MRI was performed on three consecutive days in twelve rats bearing C6 xenografts. Endothelial transfer constant (Ktrans), extracellular extravascular space volume fraction (ve), and contrast agent reflux rate constant (kep) measures were computed using: 2-parameter ("Tofts" or "standard Kety") vs. 3-parameter ("General Kinetic" or "extended Kety") compartmental models (including blood plasma volume fraction (vp) with 3-parameter models); individual- vs. population-based vascular input functions (VIFs); and pixel-by-pixel vs. whole tumor-ROI. Variability was evaluated by within-subject coefficient of variation (wCV) and variance components analyses. RESULTS: DCE-MRI absolute parameter values and wCVs varied widely by analytical method. Absolute parameter values ranged, as follows, median Ktrans, 0.09-0.18 min-1; kep, 0.51-0.92 min-1; ve, 0.17-0.23; and vp, 0.02-0.04. wCVs also varied widely by analytical method, as follows: mean Ktrans, 32.9-61.9%; kep, 11.6-41.9%; ve, 16.1-54.9%; and vp, 53.9-77.2%. Ktrans and kep values were lower with 3- than 2-parameter modeling (p<0.0001); kep and vp were lower with pixel- than whole-ROI analyses (p<0.0006). wCVs were significantly smaller for ve, and larger for kep, with individual- than population-based VIFs. CONCLUSIONS: DCE-MRI parameter values and repeatability can vary widely by analytical methodology. Absolute values of DCE-MRI biomarkers are unlikely to be comparable between different studies unless analyses are carefully standardized.

Tumor T1 Relaxation Time for Assessing Response to Bevacizumab Anti-Angiogenic Therapy in a Mouse Ovarian Cancer Model.

PURPOSE: To assess whether T1 relaxation time of tumors may be used to assess response to bevacizumab anti-angiogenic therapy. PROCEDURES: 12 female nude mice bearing subcutaneous SKOV3ip1-LC ovarian tumors were administered bevacizumab (6.25ug/g, n=6) or PBS (control, n=6) therapy twice a week for two weeks. T1 maps of tumors were generated before, two days, and 2 weeks after initiating therapy. Tumor weight was assessed by MR and at necropsy. Histology for microvessel density, proliferation, and apoptosis was performed. RESULTS: Bevacizumab treatment resulted in tumor growth inhibition (p<0.04, n=6), confirming therapeutic efficacy. Tumor T1 relaxation times increased in bevacizumab treated mice 2 days and 2 weeks after initiating therapy (p<.05, n=6). Microvessel density decreased 59% and cell proliferation (Ki67+) decreased 50% in the bevacizumab treatment group (p<.001, n=6), but not apoptosis. CONCLUSIONS: Findings suggest that increased tumor T1 relaxation time is associated with response to bevacizumab therapy in ovarian cancer model and might serve as an early indicator of response.

PBI-05204, a supercritical CO2 extract of Nerium oleander, inhibits growth of human pancreatic cancer via targeting the PI3K/mTOR pathway.

Introduction Oleandrin, a cardiac glycoside, exerts strong anti-proliferative activity against various human malignancies in in vitro cells. Here, we report the antitumor efficacy of PBI-05204, a supercritical C02 extract of Nerium oleander containing oleandrin, in a human pancreatic cancer Panc-1 orthotopic model. Results While all the control mice exhibited tumors by the end of treatment, only 2 of 8 mice (25%) treated for 6 weeks with PBI-05204 (40 mg/kg) showed dissectible tumor at the end of the treatment period. The average tumor weight (222.9 ± 116.9 mg) in mice treated with PBI-05204 (20 mg/kg) was significantly reduced from that in controls (920.0 ± 430.0 mg) (p < 0.05). Histopathologic examination of serial sections from each pancreas with no dissectible tumor in the PBI-05204 (40 mg/kg) treated group showed that the pancreatic tissues of 5/6 mice were normal while the remaining mouse had a tumor the largest diameter of which was less than 2.3 mm. In contrast, while gemcitabine alone did not significantly reduce tumor growth, PBI-05204 markedly enhanced the antitumor efficacy of gemcitabine in this particular model. Ki-67 staining was reduced in pancreatic tumors from mice treated with PBI-05204 (20 mg/kg) compared to that of control, suggesting that PBI-05204 inhibited the proliferation of the Panc-1 tumor cells. PBI-05204 suppressed expression of pAkt, pS6, and p4EPB1 in a concentration-dependent manner in both Panc-1 tumor tissues and human pancreatic cancer cell lines, implying that this novel botanical drug exerts its potent antitumor activity, at least in part, through down-regulation of PI3k/Akt and mTOR pathways.

Prostate cancer cell-stromal cell crosstalk via FGFR1 mediates antitumor activity of dovitinib in bone metastases.

Bone is the most common site of prostate cancer (PCa) progression to a therapy-resistant, lethal phenotype. We found that blockade of fibroblast growth factor receptors (FGFRs) with the receptor tyrosine kinase inhibitor dovitinib has clinical activity in a subset of men with castration-resistant PCa and bone metastases. Our integrated analyses suggest that FGF signaling mediates a positive feedback loop between PCa cells and bone cells and that blockade of FGFR1 in osteoblasts partially mediates the antitumor activity of dovitinib by improving bone quality and by blocking PCa cell-bone cell interaction. These findings account for clinical observations such as reductions in lesion size and intensity on bone scans, lymph node size, and tumor-specific symptoms without proportional declines in serum prostate-specific antigen concentration. Our findings suggest that targeting FGFR has therapeutic activity in advanced PCa and provide direction for the development of therapies with FGFR inhibitors.

Tumour angiogenesis regulation by the miR-200 family.

The miR-200 family is well known to inhibit the epithelial-mesenchymal transition, suggesting it may therapeutically inhibit metastatic biology. However, conflicting reports regarding the role of miR-200 in suppressing or promoting metastasis in different cancer types have left unanswered questions. Here we demonstrate a difference in clinical outcome based on miR-200's role in blocking tumour angiogenesis. We demonstrate that miR-200 inhibits angiogenesis through direct and indirect mechanisms by targeting interleukin-8 and CXCL1 secreted by the tumour endothelial and cancer cells. Using several experimental models, we demonstrate the therapeutic potential of miR-200 delivery in ovarian, lung, renal and basal-like breast cancers by inhibiting angiogenesis. Delivery of miR-200 members into the tumour endothelium resulted in marked reductions in metastasis and angiogenesis, and induced vascular normalization. The role of miR-200 in blocking cancer angiogenesis in a cancer-dependent context defines its utility as a potential therapeutic agent.

Somatostatin receptor type 2-based reporter expression after plasmid-based in vivo gene delivery to non-small cell lung cancer.

Plasmids tend to have much lower expression than viruses. Gene expression after systemic administration of plasmid vectors has not been assessed using somatostatin receptor type 2 (SSTR2)-based reporters. The purpose of this work was to identify gene expression in non-small cell lung cancer (NSCLC) after systemic liposomal nanoparticle delivery of plasmid containing SSTR2-based reporter gene. In vitro, Western blotting was performed after transient transfection with the plasmid cytomegalovirus (CMV)-SSTR2, CMV-TUSC2-IRES-SSTR2, or CMV-TUSC2. SSTR2 is the reporter gene, and TUSC2 is a therapeutic gene. Mice with A549 NSCLC lung tumors were injected intravenously with CMV-SSTR2, CMV-TUSC2-IRES-SSTR2, or CMV-TUSC2 plasmids in DOTAP:cholesterol-liposomal nanoparticles. Two days later, mice were injected intravenously with 111In-octreotide. The next day, biodistribution was performed. The experiment was repeated including single-photon emission computed tomography/computed tomography (SPECT/CT). Immunohistochemistry was performed. In vitro, SSTR2 expression was similar in cells transfected with CMV-SSTR2 or CMV-TUSC2-IRES-SSTR2. TUSC2 expression was similar in cells transfected with CMV-TUSC2 or CMV-TUSC2-SSTR2. Biodistribution demonstrated significantly greater 111In-octreotide uptake in tumors from mice injected with CMV-TUSC2-IRES-SSTR2 or CMV-SSTR2 than the control plasmid, CMV-TUSC2 (p < .05). Gamma-camera and SPECT/CT imaging illustrated SSTR2 expression in tumors in mice injected with CMV-TUSC2-IRES-SSTR2 or CMV-SSTR2 versus background with control plasmid. Immunohistochemistry corresponded with imaging. SSTR2-based reporter imaging can visualize gene expression in lung tumors after systemic liposomal nanoparticle delivery of plasmid containing SSTR2-based reporter gene or SSTR2 linked to a second therapeutic gene, such as TUSC2.

Noninvasive assessment of gene transfer and expression by in vivo functional and morphologic imaging in a rabbit tumor model.

PURPOSE: To evaluate the importance of morphology in quantifying expression after in vivo gene transfer and to compare gene expression after intra-arterial (IA) and intra-tumoral (IT) delivery of adenovirus expressing a SSTR2-based reporter gene in a large animal tumor model. MATERIALS AND METHODS: Tumor directed IA or IT delivery of adenovirus containing a human somatostatin receptor type 2A (Ad-CMV-HA-SSTR2A) gene chimera or control adenovirus (Ad-CMV-GFP) was performed in VX2 tumors growing in both rabbit thighs. Three days later, ¹¹¹In-octreotide was administered intravenously after CT imaging using a clinical scanner. ¹¹¹In-octreotide uptake in tumors was evaluated the following day using a clinical gamma-camera. Gene expression was normalized to tumor weight with and without necrosis. This procedure was repeated on nine additional rabbits to investigate longitudinal gene expression both 5 days and 2 weeks after adenovirus delivery. CT images were used to evaluate tumor morphology and excised tissue samples were analyzed to determine ¹¹¹In-octreotide biodistribution ex vivo. RESULTS: VX2 tumors infected with Ad-CMV-HA-SSTR2 had greater ¹¹¹In-octreotide uptake than with control virus (P<0.05). Intra-arterial and intra-tumoral routes resulted in similar levels of gene expression. Longitudinally, expression appeared to wane at 2 weeks versus 5 days after delivery. Areas of necrosis did not demonstrate significant uptake ex vivo. Morphology identified areas of necrosis on contrast enhanced CT and upon excluding necrosis, in vivo biodistribution analysis resulted in greater percent injected dose per gram (P<0.01) and corresponded better with ex vivo biodistribution(r = 0.72, P<0.01, Coefficient of the x-variable = .72) at 2 weeks than without excluding necrosis (P<0.01). CONCLUSION: Tumor specificity and high transgene expression can be achieved in tumors via both tumor directed intra-arterial and intra-tumoral delivery in a large animal tumor model. Using clinical machines, morphologic imaging contributes to functional imaging for quantifying SSTR2-based reporter expression in vivo.

Visualizing the prostate gland by MR imaging in young and old mice.

PURPOSE: Prostate imaging requires optimization in young and old mouse models. We tested which MR sequences and field strengths best depict the prostate gland in young and old mice; and, whether prostate MR signal, size, and architecture change with age. TECHNIQUE: Magnetic resonance imaging (MRI) of the prostate of young (2 months) and old (18 months) male nude mice (n = 6) was performed at 4.7 and 7 T and SCID mice (n = 6) at 7 T field strengths, using T1, fat suppressed T1, DWI, T2, fat suppressed T2, as well as T2-based- and proton density-based Dixon "water only" sequences. Images were ranked for best overall sequence for prostate visualization, prostate delineation, and quality of fat suppression. Prostate volume and signal characteristics were compared and histology was performed. RESULTS: T2-based-Dixon "water only" images ranked best overall for prostate visualization and delineation as well as fat suppression (n = 6, P<0.001) at both 4.7 T and 7 T in nude and 7T in SCID mice. Evaluated in nude mice, T2-based Dixon "water only" had greater prostate CNR and lower fat SNR at 7 T than 4.7 T (P<0.001). Prostate volume was less in older than younger mice (n = 6, P<0.02 nude mice; n = 6, P<0.002 SCID mice). Prostate T2 FSE as well as proton density-based and T2-based-Dixon "water only" signal intensity was higher in younger than older mice (P<0.001 nude mice; P<0.01 SCID mice) both at 4.7 and 7 T. This corresponded to an increase in glandular hyperplasia in older mice by histology (P<0.01, n = 6). CONCLUSION: T2-based Dixon "water only" images best depict the mouse prostate in young and old nude mice at 4.7 and 7 T. The mouse prostate decreases in size with age. The decrease in T2 and T2-based Dixon "water only" signal with age corresponds with glandular hyperplasia. Findings suggest age should be an important determinant when choosing models of prostate biology and disease.

Reproducibility and comparison of DCE-MRI and DCE-CT perfusion parameters in a rat tumor model.

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and computed tomography (DCE-CT) provide independent measures of biomarkers related to tumor perfusion. We compared the reproducibilities and absolute values of DCE-MRI and DCE-CT biomarkers in the same tumors in an animal model, to investigate the physiologic validity of both approaches. DCE-MRI and DCE-CT were each performed sequentially on three consecutive days in each of twelve rats bearing C6 glioma xenografts. DCE-MRI yielded endothelial transfer constant (K(trans)), extracellular, extravascular space volume fraction (v(e)), and contrast agent reflux rate constant (k(ep)); and DCE-CT, blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability-surface area product (PS) using Tofts and deconvolution physiological models, with 6.6 and 0.4 seconds temporal resolutions, respectively. Variability in DCE-CT and DCE-MRI were evaluated by variance components analysis. Intra-rat coefficients of variation for DCE-CT parameters BF, BV, MTT and PS were 25%, 22%, 18% and 23%; and for DCE-MRI parameters K(trans), k(ep) and v(e) were 23%, 16% and 20%, respectively. Mean (±SD) BF, BV, MTT and PS were: 44.6 (±13.7) ml min(-1) 100 g(-1), 5.7 (±1.5) ml 100 g(-1), 10.8 (±2.3) seconds, and 14.6 (±4.7) ml min(-1) 100 g(-1), respectively. Mean (±SD) K(trans), k(ep) and v(e) were: 0.21 (±0.05) min(-1), 0.68 (±0.14) min(-1), and 0.29 (±0.06), respectively. Permeability estimates from DCE-MRI (K(trans)) were 44% higher than from DCE-CT (PS), despite application of appropriate corrections. DCE-MRI and DCE-CT biomarkers of tumor perfusion have similar reproducibilities suggesting that they may have comparable utility, but their derived parameter values are not equivalent.