Echo-planar imaging for MRI evaluation of intrathoracic tumors in murine models of lung cancer

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.

Magnetic Resonance Imaging and Bioluminescence Imaging for Evaluating Tumor Burden in Orthotopic Colon Cancer

Quantifying tumor burden is important for following the natural history of orthotopic colon cancer and therapeutic efficacy. Bioluminescence imaging (BLI) is commonly used for such assessment and has both advantages and limitations. We compared BLI and magnetic resonance imaging (MRI) for quantifying orthotopic tumors in a mouse model of colon cancer. Among sequences tested, T2-based MRI imaging ranked best overall for colon cancer border delineation, contrast, and conspicuity. Longitudinal MRI detected tumor outside the colon, indistinguished by BLI. Colon tumor weights calculated from MRI in vivo correlated highly with tumor weights measured ex vivo whereas the BLI signal intensities correlated relatively poorly and this difference in correlations was highly significant. This suggests that MRI may more accurately assess tumor burden in longitudinal monitoring of orthotopic colon cancer in this model as well as in other models.

Cardio-Respiratory synchronized bSSFP MRI for high throughput in vivo lung tumour quantification

The identification and measurement of tumours is a key requirement in the study of tumour development in mouse models of human cancer. Disease burden in autochthonous tumours, such as those arising in the lung, can be seen with non-invasive imaging, but cannot be accurately measured using standard tools such as callipers. Lung imaging is further complicated in the mouse due to instabilities arising from the rapid but cyclic cardio-respiratory motions, and the desire to use free-breathing animals. Female A/JOlaHsd mice were either injected (i.p.) with PBS 0.1ml/10g body weight (n = 6), or 10% urethane/PBS 0.1ml/10g body weight (n = 12) to induce autochthonous lung tumours. Cardio-respiratory synchronised bSSFP MRI, at 200 μm isotropic resolution was performed at 8, 13 and 18 weeks post induction. Images from the same mouse at different time points were aligned using threshold-based segmented masks of the lungs (ITK-SNAP and MATLAB) and tumour volumes were determined via threshold-based segmentation (ITK-SNAP).Scan times were routinely below 10 minutes and tumours were readily identifiable. Image registration allowed serial measurement of tumour volumes as small as 0.056 mm³. Repetitive imaging did not lead to mouse welfare issues. We have developed a motion desensitised scan that enables high sensitivity MRI to be performed with high throughput capability of greater than 4 mice/hour. Image segmentation and registration allows serial measurement of individual, small tumours. This allows fast and highly efficient volumetric lung tumour monitoring in cohorts of 30 mice per imaging time point. As a result, adaptive trial study designs can be achieved, optimizing experimental and welfare outcomes.

A spontaneous model of spondyloarthropathies that develops bone loss and pathological bone formation: A process regulated by IL27RA-/- and mutant-p53

Spondyloarthropathies, the second most frequently occurring form of chronic inflammatory arthritis, affects young adults in particular. However, a proper model with which to study the biology of this disease and to develop therapeutics is lacking. One of the most accepted animal models for this disease uses HLA-B27/Hu-β2m transgenic rats; however, only 30%-50% of male HLA-B27/Hu-β2m rats develop spontaneous, clinically apparent spondylitis and have a variable time until disease onset. Here, we report a high-incidence, low-variation spontaneous mouse model that delineates how the combination of inflammatory cytokine interleukin-27 (IL-27) signaling deficiency and mitogenic signaling (mutant p53^R172H) in vivo, leads to bone loss in the vertebral bodies and ossification of the cartilage in the intervertebral discs. In this human disease–like mouse model, bone loss and pathogenic bone development are seen as early as 4 months of age in the absence of inflammatory aggregates in the enthesis or intervertebral disc.

Lack of Immunomodulatory Interleukin-27 Enhances Oncogenic Properties of Mutant p53 In Vivo

PURPOSE

p53 is mutated in about 50% of human cancers, mostly through missense mutations. Expression of mutant p53 is associated with poor clinical outcomes or metastasis. Although mutant p53 is inherently instable, various stressors such as DNA damage or expression of the oncogenic Kras or c-myc affect the oncogenic properties of mutant p53. However, the effects of inflammation on mutant p53 are largely unknown. IL27 is an important immunomodulatory cytokine, but its impact on mutant p53-driven tumorigenesis has not been reported.

EXPERIMENTAL DESIGN

IL27RA(-/-) mice were bred with mutant p53 heterozygous (p53(R172H/+)) mice to obtain IL27RA(-/-)p53(H/+) and IL27RA(-/-)p53(H/H) mice. Mouse survival and tumor spectra for the cohort were analyzed. Stability of p53 protein was analyzed via IHC and Western blot analysis.

RESULTS

This study unraveled that lack of IL27 signaling significantly shortened the survival duration of mice with tumors expressing both copies of the mutant p53 gene (Li-Fraumeni mouse model). Interestingly, in mice that were heterozygous for mutant p53, lack of IL27 signaling not only significantly shortened survival time but also doubled the incidence of osteosarcomas. Furthermore, lack of IL27 signaling is closely associated with increased mutant p53 stability in vivo from early age.

CONCLUSIONS

These results suggest that IL27 signaling modulates the oncogenic properties of mutant p53 in vivo Clin Cancer Res; 22(15); 3876-83. ©2016 AACR.

Detection of lung tumors in mice using a 1-tesla compact magnetic resonance imaging system

Due to their small size, lung tumors in rodents are typically investigated using high-field magnetic resonance (MR) systems (4.7 T or higher) to achieve higher signal-to-noise ratios, although low-field MR systems are less sensitive to susceptibility artifacts caused by air in the lung. We investigated the feasibility of detecting lung tumors in living, freely breathing mice with a 1-T compact permanent magnet MR system. In total, 4 mice were used, and MR images of mouse lungs were acquired using a T1-weighted three-dimensional fast low-angle shot sequence without cardiac or respiratory gating. The delineation and size of lung tumors were assessed and compared with histopathological findings. Submillimeter lesions were demonstrated as hyperintense, relative to the surrounding lung parenchyma, and were delineated clearly. Among the 13 lesions validated in histopathological sections, 11 were detected in MR images; the MR detection rate was thus 84.6%. A strong correlation was obtained in size measurements between MR images and histological sections. Thus, a dedicated low-field MR system can be used to detect lung tumors in living mice noninvasively without gating.

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.

Photodynamic therapy of disseminated non-small cell lung carcinoma in a murine model

BACKGROUND AND OBJECTIVE

Photodynamic therapy (PDT) of thoracic malignancies involving the pleural surfaces is an active area of clinical investigation. The present report aims to characterize a model for PDT of disseminated non-small cell lung carcinoma (NSCLC) grown orthotopically in nude mice, and to evaluate the effect of PDT on tumor and normal tissues.

STUDY DESIGN

H460 human NSCLC cells were injected percutaneously into the thoracic cavity of nude mice. HPPH-PDT (1 mg/kg, 24 hours) was performed via the interstitial delivery (150 mW/cm) of 661 nm light to the thoracic cavity at fluences of 25-200 J/cm.

RESULTS

H460 tumors exhibited exponential growth within the thoracic cavity consisting of diffuse, gross nodular disease within 9 days after intrathoracic injection. Tumor volume, measured by magnetic resonance imaging (MRI), was highly correlated with the aggregate tumor mass extracted from the corresponding animal. Intrathoracic PDT at fluences of ≥50 J/cm produced significant decreases in tumor burden as compared to untreated controls, however, mortality increased with rising fluence. Accordingly, 50 J/cm was selected for MRI studies to measure intra-animal PDT effects. Tumor distribution favored the ventral (vs. dorsal), caudal (vs. cranial), and right (vs. left) sides of the thoracic cavity by MRI; PDT did not change this spatial pattern despite an overall effect on tumor burden. Histopathology revealed edema and fibrin deposition within the pulmonary interstitium and alveoli of the PDT-treated thoracic cavity, as well as occasional evidence of vascular disruption. Prominent neutrophil infiltration with a concomitant decline in the lymphocyte compartment was also noted in the lung parenchyma within 24 hours after PDT.

CONCLUSION

HPPH-PDT of an orthotopic model of disseminated NSCLC is both feasible and effective using intracavitary light delivery. We establish this animal model, together with the treatment and monitoring approaches, as novel and valuable methods for the pre-clinical investigation of intrathoracic PDT of disseminated pleural malignancies.

SSTR2-based reporters for assessing gene transfer into non-small cell lung cancer: evaluation using an intrathoracic mouse model

The most common cause of cancer-related deaths in North America is lung cancer, 85% of which is non-small cell lung cancer (NSCLC). Gene therapy is a promising approach, but has been hindered by lack of methods for localizing and quantifying gene expression in vivo. Human somatostatin receptor subtype-2 (SSTR2)-based reporters can be used to follow gene expression in vivo using ligands with greater affinity for this subtype. NSCLCs can express SSTR subtypes, which may interfere with SSTR2-based reporters. We assessed whether a SSTR2-based reporter can serve as a reporter of gene transfer into NSCLCs. SSTR subtype expression was assessed in NSCLC cell lines A549, H460, and H1299 using RT-PCR. After infection with an adenovirus containing hemagglutinin-A-tagged-SSTR2 (Ad-HA-SSTR2) or control insert, expression was assessed by immunologic techniques and binding to clinically-approved (111)In-octreotide. In vivo, after magnetic resonance (MR) imaging, intrathoracic H460 tumors were injected with Ad-HA-SSTR2 or control virus (n = 6 mice/group) under ultrasound guidance. Intravenous injection of (111)In-octreotide 2 days later was followed by planar and single-photon emission computed tomography (SPECT) imaging. Biodistribution into tumors was assessed in vivo using anatomic MR and functional gamma-camera images and ex vivo using excised organs/tumors. In human lung tumor samples (n = 70), SSTR2 expression was assessed using immunohistochemistry. All three NSCLC cell lines expressed different SSTR subtypes, but none expressed SSTR2. Upon Ad-HA-SSTR2 infection, HA-SSTR2 expression was seen in all three cell lines using antibodies targeting the HA domain or (111)In-octreotide targeting the receptor domain (p < 0.05). Intrathoracic tumors infected with Ad-HA-SSTR2 were clearly visible by gamma-camera imaging; expression was quantified by both in vivo and ex vivo biodistribution analysis and demonstrated greater uptake in tumors infected with Ad-HA-SSTR2 compared with control virus (p < 0.05). Immunohistochemistry found that 78% of NSCLCs are negative for and 13% have low levels of SSTR2 expression. It is concluded that SSTR2-based reporters can serve as reporters of gene transfer into NSCLCs.

Efficacy of PHA-848125, a cyclin-dependent kinase inhibitor, on the K-Ras(G12D)LA2 lung adenocarcinoma transgenic mouse model: evaluation by multimodality imaging

K-ras is the most frequently mutated oncogene in non-small cell lung cancer (NSCLC), the most common form of lung cancer. Recent studies indicate that NSCLC patients with mutant K-ras do not respond to epidermal growth factor receptor inhibitors. In the attempt to find alternative therapeutic regimes for such patients, we tested PHA-848125, an oral pan cyclin-dependent kinase inhibitor currently under evaluation in phase II clinical trial, on a transgenic mouse model, K-Ras(G12D)LA2, which develops pulmonary cancerous lesions reminiscent of human lung adenocarcinomas. We used magnetic resonance imaging and positron emission tomography to follow longitudinally disease progression and evaluate therapeutic efficacy in this model. Treatment of K-Ras(G12D)LA2 mice with 40 mg/kg twice daily for 10 days with PHA-848125 induced a significant tumor growth inhibition at the end of treatment (P < 0.005) and this was accompanied by a reduction in the cell membrane turnover, as seen by 11C-Choline-positron emission tomography (P < 0.05). Magnetic resonance imaging data were validated versus histology and the mechanism of action of the compound was verified by immunohistochemistry, using cyclin-dependent kinase-related biomarkers phospho-Retinoblastoma and cyclin A. In this study, multimodality imaging was successfully used for the preclinical assessment of PHA-848125 therapeutic efficacy on a lung adenocarcinoma mouse model. This compound induced a volumetric and metabolic anticancer effect and could represent a valid therapeutic approach for NSCLC patients with mutant K-ras.

In vivo functional and anatomic imaging for assessment of in vivo gene transfer

PURPOSE

To assess whether a combination of in vivo anatomic and functional imaging can help quantify expression of somatostatin receptor type 2 (SSTR2)-based reporters after in vivo gene transfer.

MATERIALS AND METHODS

All animal experiments were approved by an institutional animal care and use committee. Six nude mice bearing two subcutaneous L3.6pl (human pancreatic cancer) tumors were injected intratumorally with an adenovirus containing a human somatostatin receptor type 2 gene chimera (Ad-HA-SSTR2) or a control adenovirus containing green fluorescent protein (Ad-GFP). Two days later, magnetic resonance (MR) imaging was performed to derive tumor weight and analyze morphology. Intravenous injection of Food and Drug Administration-approved indium 111 octreotide was followed by gamma camera imaging (planar imaging and single photon emission computed tomography [SPECT]) the next day. Region-of-interest analysis followed. The procedure was also performed in six nude mice with slow-growing MDA-MB-435 (human breast carcinoma) tumors, which allowed serial imaging 3 days and 2 weeks after adenovirus injection. After imaging, excised tumor weight and biodistribution were assessed. Statistical analyses included a Student t test and linear regression.

RESULTS

With both tumor types, ex vivo and image-based in vivo biodistribution demonstrated greater uptake (percentage of injected dose per gram) in tumors infected with Ad-HA-SSTR2 than in those infected with Ad-GFP (P < .05). Furthermore, in vivo and ex vivo biodistribution analysis correlated (ex vivo vs planar and MR imaging: r = 0.87, P < .05, n = 24; ex vivo vs SPECT and MR imaging: r = 0.84, P < .05, n = 24). Moreover, in vivo biodistribution distinguished greater expression at the earlier time point in MDA-MB-435 tumors infected with Ad-HA-SSTR2 from waning expression at the later time point (P < .05).

CONCLUSION

A combination of in vivo functional and anatomic imaging methods can help quantify gene expression after in vivo gene transfer.