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1.  Lower-Limb Power cannot be Estimated Accurately from Vertical Jump Tests 
The countermovement jump test is often adopted to monitor lower-limb power of an individual. Despite several studies on the validity of this test, there is still a need to determine the minimal difference needed to be confident that a difference in power between two individuals is present or that a true change in the performance of an individual has occurred. In this study, power was measured from ground reaction forces and compared to that obtained from predictive equations for two groups of subjects (67 trained and 20 highly trained individuals). The height of each jump was determined with kinematic techniques. The main outcome is a large discrepancy between power calculated from ground reaction forces and that calculated from predictive equations. For the trained group, the R-square value between power and predicted power was 0.53 and the minimal difference to consider that two individuals were different was 821.7 W. For the highly trained individuals, a much larger R-square value was obtained (0.94). Despite this, the minimal difference to consider that two individuals were different was still large (689.3 W). The large minimal differences obtained raise serious concerns about using countermovement jumps for appraisal and monitoring of lower-limb power of an individual.
PMCID: PMC3827754  PMID: 24235979
Countermovement jump; force; validity; minimal difference
2.  [18 F]FDG-PET imaging is an early non-invasive pharmacodynamic biomarker for a first-in-class dual MEK/Raf inhibitor, RO5126766 (CH5126766), in preclinical xenograft models 
EJNMMI Research  2013;3:67.
Positron emission tomography (PET) with [2-18 F]-2-fluoro-2-deoxy-D-glucose ([18 F]FDG-PET) was acquired at multiple time-points a) to monitor the early response to RO5126766 (CH5126766) in xenograft models b) to evaluate non-invasive small animal [18 F]FDG-PET imaging as a biomarker for MEK inhibitors for translation into dose-finding studies in cancer patients and c) to explore the underlying mechanism related to FDG uptake in tumors treated with RO5126766.
[18 F]FDG uptake was studied in HCT116 (K-ras), COLO205 (B-raf) mutants and COLO320DM (wild type) xenografts from day 0 to 3 of RO5126766 treatment using a microPET Focus 120 and complemented with in vitro incubations, ex-vivo phosphor imaging and immunohistochemical (IHC) analyses.
In the HCT116 (K-ras) and COLO205 (B-raf) mutant xenografts, significant decreases in [18 F]FDG uptake were detected in vivo on day 1 with 0.3 mg/kg and ex vivo on day 3 with 0.1 mg/kg RO5126766. [18 F]FDG changes correlated with decreases in tumor cells proliferation (Ki-67) and with changes in expression levels of GLUT1. No effects were observed in drug resistant COLO320DM cells. The cellular fractionation and Western blotting analyses suggested that the change of [18 F]FDG uptake associated with RO5126766 is due to translocation of GLUT1 from membrane to cytosol, similar to the results reported in the literature with EGFR tyrosine kinase inhibitors, which also target the MAPK pathway.
RO5126766 inhibition resulted in a rapid time - and dose - dependent decline in [18 F]FDG uptake in both mutant xenografts. These results strongly resemble the clinical observations obtained with MEK/Raf inhibitors support the use of preclinical [18 F]FDG-PET as a translational tool for decision support in preclinical and early clinical development of MEK inhibitors.
PMCID: PMC3848680  PMID: 24041012
Positron emission tomography; RO5126766; MEK inhibitor; Translational imaging
3.  [125I]FIAU imaging in a preclinical model of lung infection: quantification of bacterial load 
2'-Fluoro-2'-deoxy-1β-D-arabinofuranosyl-5-[125I]iodouracil ([125I]FIAU), a substrate for the thymidine kinase (TK) present in most bacteria, has been used as an imaging agent for single photon emission computed tomography (SPECT) in an experimental model of lung infection. Using SPECT-CT we show that [125I]FIAU is specific for bacterial infection rather than sterile inflammation. We report [125I]FIAU lung uptake values of 1.26 ± 0.20 percent injected dose per gram (%ID/g) in normal controls, 1.69 ± 0.32 %ID/g in lung inflammation and up to 7.14 ± 1.09 %ID/g in lung infection in ex vivo biodistribution studies at 24 h after intranasal administration of bacteria. Images of [125I]FIAU signal within lung can be used to estimate the number of bacteria present, with a limit of detection of 109 colony forming units per mL on the X-SPECT scanner. [125I]FIAU-Based bacterial imaging may be useful in preclinical models to facilitate the development of new antibiotics, particularly in cases where a corresponding human trial is planned.
PMCID: PMC3477740  PMID: 23133816
Inflammation; thymidine kinase; nucleoside; SPECT; PET; molecular imaging
4.  Assessment of Acute Antivascular Effects of Vandetanib with High-Resolution Dynamic Contrast-Enhanced Computed Tomographic Imaging in a Human Colon Tumor Xenograft Model in the Nude Rat1 
Neoplasia (New York, N.Y.)  2010;12(9):697-707.
Tumor size is not a reliable marker for the assessment of early antivascular effects of antiangiogenics. In the present study, we used 200-µm in-plane high-resolution dynamic contrast-enhanced computed tomography (DCE-CT) to noninvasively assess the immediate antivascular effects of vandetanib in a subcutaneous human colon cancer (LoVo) xenograft model in nude rats and to investigate correlation between changes in CT perfusion parameters and tumor volume or immunohistochemical end points. At 3 to 4 weeks after LoVo cell implantation, the animal was gavaged with either vandetanib (50 mg/kg) or vehicle twice (22 hours apart) and scanned with a preclinical DCE-CT scanner before (0 hour) and after treatment (24 hours). Quantitative maps of blood flow (BF) and volume (BV) of the tumor were calculated from the acquired DCE-CT images. The rats were divided into nonhypovascular, hypovascular, and combined (regardless of vascularity) groups. In the nonhypovascular group, significant decreases in both tumor BF and BV were observed in the vandetanib-treated rats compared with increases in the vehicle-treated rats. A significant decrease in BV was detected in the vandetanib-treated rats in the combined group as well. No differences in tumor growth, vascular endothelial growth factor expression, microvessel density, or apoptosis were observed between vandetanib- and vehicle-treated rats in all three groups. These results demonstrate that BF and BV imaging biomarkers from DCE-CT imaging can be used for rapid monitoring of immediate (24 hours after) antimicrovascular effects of vandetanib on tumors, even in the absence of significant changes of tumor volume or clinically relevant immunohistochemical end points.
PMCID: PMC2933690  PMID: 20824046
5.  DCE-MRI assessment of the effect of vandetanib on tumor vasculature in patients with advanced colorectal cancer and liver metastases: a randomized phase I study 
Vandetanib is a once-daily oral inhibitor of VEGFR, EGFR and RET signaling pathways. In patients with advanced colorectal cancer and liver metastases, the effect of vandetanib on tumor vasculature was assessed using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).
Eligible patients received vandetanib 100 or 300 mg/day. DCE-MRI (iAUC60 and Ktrans) was used to quantify the primary endpoints of tumor perfusion and vascular permeability. An exploratory assessment of tumor oxygenation was performed using MRI/T2*. All MRI parameters were measured at baseline (twice) and on days 2, 8, 29 and 57.
Twenty-two patients received vandetanib (n = 10, 100 mg; n = 12, 300 mg). Baseline measurements of iAUC60 and Ktrans were reproducible, with low intrapatient coefficients of variation (11% and 24%, respectively). Estimates of mean % changes from baseline were -3.4% (100 mg) and -4.6% (300 mg) for iAUC60, and -4.6% (100 mg) and -2.7% (300 mg) for Ktrans; these changes were not significantly different between doses. The exploratory T2* measurement showed a significant increase at 300 mg versus 100 mg (P = 0.006). Both doses of vandetanib were generally well tolerated; common toxicities were fatigue, rash and diarrhea (majority CTC grade 1 or 2). The pharmacokinetic profile of vandetanib was similar to that observed previously. There were no RECIST-defined objective responses; five patients experienced stable disease ≥8 weeks.
In this study in patients with advanced colorectal cancer, vandetanib did not modulate gadolinium uptake in tumor vasculature and tissue measured by the DCE-MRI parameters iAUC60 and Ktrans.
Trial registration
NCT00496509 (; D4200C00050 (AstraZeneca)
PMCID: PMC2776237  PMID: 19946413
6.  Correlation of MRI Biomarkers with Tumor Necrosis in Hras5 Tumor Xenograft in Athymic Rats 
Neoplasia (New York, N.Y.)  2007;9(5):382-391.
Magnetic resonance imaging (MRI) can measure the effects of therapies targeting the tumor vasculature and has demonstrated that vascular-damaging agents (VDA) induce acute vascular shutdown in tumors in human and animal models. However, at subtherapeutic doses, blood flow may recover before the induction of significant levels of necrosis. We present the relationship between changes in MRI biomarkers and tumor necrosis. Multiple MRI measurements were taken at 4.7 T in athymic rats (n = 24) bearing 1.94 ± 0.2-cm3 subcutaneous Hras5 tumors (ATCC 41000) before and 24 hours after clinically relevant doses of the VDA, ZD6126 (0–10 mg/kg, i.v.). We measured effective transverse relaxation rate (R2*), initial area under the gadolinium concentration-time curve (IAUGC60/150), equivalent enhancing fractions (EHF60/150), time constant (Ktrans), proportion of hypoperfused voxels as estimated from fit failures in Ktrans analysis, and signal intensity (SI) in T2-weighted MRI (T2W). ZD6126 treatment induced > 90% dose-dependent tumor necrosis at 10 mg/kg; correspondingly, SI changes were evident from T2W MRI. Although R2* did not correlate, other MRI biomarkers significantly correlated with necrosis at doses of ≥ 5 mg/kg ZD6126. These data on Hras5 tumors suggest that the quantification of hypoperfused voxels might provide a useful biomarker of tumor necrosis.
PMCID: PMC1877977  PMID: 17534443
ZD6126; vascular-damaging agent; magnetic resonance imaging; necrosis; xenograft

Results 1-6 (6)