Skeletal metastases models typically use parameters such as radiographic analysis, tumor volume, tumor weight, and histological analysis to assess tumor burden. With the exception of radiographic analysis, each of these parameters requires sacrifice of the animal - an undesirable practice both for the numerous animals required as well as the necessary termination of study of the particular animal. We hypothesized that bioluminescence imaging would offer a novel, sensitive, non-invasive means to follow the progression of tumors in vivo. A cooled charge coupled device (CCD) camera captures photons emitted from the enzyme luciferase after exposure to its substrate, luciferin, and integrates them over a period of time.
Materials and Methods
The luciferase gene was delivered to human osteolytic prostate cancer (PC-3) cells through in vitro retroviral gene therapy. To determine in vitro correlation, increasing numbers of luciferase expressing PC-3 cells were placed in a 96 well culture plate. At 24 hours, the cells were lysed and a luciferase assay was performed. A correlation coefficient was determined by linear regression. To induce bone lesions in SCID mice, 1 × 105 cells of luciferase expressing PC-3 cells were implanted into the proximal tibias of 8 week old mice. A 3 mm medial parapatellar incision was made, and cells were injected with a 27 1/2 ga needle. Radiographs and CCD images were obtained every 10 days. Photons emitted from PC-3 cells were collected and integrated. Images were obtained by superimposing gray-scale photographic images and luciferase color images. Tumor alone was compared to two different tumor suppression treatments previously shown to be effective for treating osteolytic prostate cancer. Animals were sacrificed at 50 days.
Results
A correlation of R2 = 0.95 was found between luciferase activity and cell number in vitro. CCD imaging detected an increase in signal intensity at 10 days, whereas radiographs were unable to detect a lesion until 20 days. Tumor suppression was so significant in one treatment that no lesion was detectable on radiograph, though tumor progression could still be followed with CCD imaging.
Conclusion
CCD imaging is a novel, safe and effective means to follow tumor progression in vivo in a skeletal metastasis model. It was more sensitive than radiograph for showing small lesions, and it was able to demonstrate the effectiveness of two previously validated treatments of osteolytic prostate cancer lesions more effectively than conventional radiographs.
It is standard practice to closely monitor distal radial fractures treated nonoperatively to ensure that there is no fracture displacement. Patients are often asked to initially return weekly for radiographs. To our knowledge, nondisplaced distal radial fractures in adults have not been specifically evaluated to determine if this level of vigilance is required. If this subset of fractures is unlikely to displace, the cost, radiation exposure, and inconvenience of weekly office visits could be spared.Using our billing database, we identified 642 closed distal radial fractures among the patients who presented to our institution during the four-year period from the beginning of 2006 to the end of 2009. Radiographs of the injuries were reviewed to identify fractures for which radiographic measurements were within predefined radiographic norms. Only those fractures that were believed to be nondisplaced by all reviewers were classified as nondisplaced for the purposes of this study. Radiographic measurements were made at the time of injury and at the time of fracture union to evaluate for displacement over time. The total number of clinic visits and radiographs that were received were calculated from the longitudinal medical record for each patient.Eighty-two fractures were identified as nondisplaced. None displaced or required operative intervention. The largest measured difference from injury to fracture union for radial inclination was 3.6° (average 0.8°); for radial height, 2.1 mm (average 0.5 mm); and for palmar tilt, 3.1° (average 1.0°). These numbers are all within the error of measurement.Nondisplaced distal radial fractures in adults appear to be inherently stable, and it may be appropriate to treat this subset of distal radial fractures with cast immobilization (when swelling allows) and a single follow-up visit with radiographs to document union at the time of cast removal.Prognostic level III. See Instructions for authors for a complete description of levels of evidence.
Lung cancer metastases to bone produce a primarily mixed osteolytic/osteoblastic lesion. The purpose of this study was to determine if blockade of both pathways would inhibit the formation these lesions in bone. Inhibition of the osteoblastic lesion with noggin and the osteolytic lesion with RANK:Fc was a successful treatment strategy to inhibit progression of mixed lung cancer lesions in bone.Approximately 9-30% of patients with lung cancer develop bone metastases, leading to significant morbidity and mortality. A549 is a non-small-cell lung cancer (NSCLC) line that produces a mixed metastatic lesion in bone. We sought to determine if blockade of key components in both osteolytic and osteoblastic pathways would result in a reduction of a NSCLC tumor progression in a murine model of bony metastasis.The study used a retroviral vector overexpressing noggin (RN), a specific inhibitor of BMP, and RANK:Fc, a chimeric protein that inhibits the RANK-RANKL interaction. A549 cells were transduced with RN before implantation in SCID mice. Cells were implanted in a subcutaneous model and tibial injection model. RANK:Fc was administered twice weekly at 15 mg/kg. There were five treatment groups: A549; A549 + RN; A549 + RANK:Fc; A549 + empty vector; and A549 + RN + RANK:Fc (n = 10/group).In SCID mice who underwent subcutaneous A549 tumor cell injection, animals treated with A549 + RN had significantly smaller subcutaneous tumor size at 8 weeks. In an intratibial model of bony metastasis, animals injected with A549 cells developed a mixed lytic/blastic lesion with cortical destruction at 8 weeks. Treatment with RANK:Fc inhibited the formation of osteoclasts, led to a smaller tumor volume in bone, and inhibited the lytic component of the mixed lesion. Animals treated with A549 + RN had a decreased number of osteoblasts in bone lesions, smaller tumor volume, and inhibition of the blastic component of the mixed lesions. Combination treatment inhibited both the lytic and blastic components of the lesion.The NSCLC cell line A549 forms a mixed osteolytic/osteoblastic lesion in vivo. Noggin overexpression inhibited the formation of the osteoblastic aspect of the lesion in bone and the tumor growth in vivo. Treatment with RANK:Fc limited the formation of the lytic aspect of the mixed lesion and also inhibited the rate of in vivo tumor growth. Inhibition of both pathways is necessary to effectively inhibit the progression of mixed metastatic lesions in bone.
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