A dual-inhibition study on vascular smooth muscle cells with meclofenamic acid and ß-irradiation for the prevention of restenosis.

PURPOSE: Restenosis is still one of the major limitations after angioplasty. A therapeutic treatment combining ß-irradiation and pharmacologic cyclooxygenase-2 inhibition was employed to study the impact on vascular smooth muscle cells (SMCs). MATERIALS AND METHODS: The effects of meclofenamic acid in combination with yttrium-90 ((90)Y) on cell growth, clonogenic activity, cell migration, and cell cycle distribution of human aortic SMCs were investigated. Treatment was sustained over a period of 4 days and recovery of cells was determined until day 20 after initiation. The hypothesis was that there is no difference between control and treated groups. RESULTS: A dose-dependent growth inhibition was observed in single and combined treatment groups for meclofenamic acid and ß-irradiation. Cumulative radiation dosage of 8 Gy completely inhibited colony formation. This was also observed for 200 µM meclofenamic acid alone or in combination with minor ß-irradiation dosages. Results of the migration tests showed also a dose dependency with additive effects of combined therapy. Meclofenamic acid 200 µM alone and with cumulative ß-irradiation dosages resulted in an increased G2/M-phase share. CONCLUSIONS: Incubating human SMCs with meclofenamic acid and (90)Y for a period of 4 d (ie, 1.5 half-life times) resulted in an effective inhibition of smooth muscle cell proliferation, colony formation, and migration.

The Prognostic Value of Quantitative Bone SPECT/CT Before 223Ra Treatment in Metastatic Castration-Resistant Prostate Cancer.

Radiolabeled bisphosphonates such as 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) typically show intense uptake in skeletal metastases from metastatic castration-resistant prostate cancer (mCRPC). Extensive bone involvement is regarded as a risk factor for mCRPC patients treated with 223Ra-dichloride (223Ra). The aim of this study was to quantify 99mTc-DPD uptake by means of SPECT/CT before 223Ra and compare the results with the feasibility of treatment and overall survival (OS). Methods: Sixty consecutive mCRPC patients were prospectively included in this study. SPECT/CT of the central skeleton covering the skull to the mid-femoral level was performed before the first cycle of 223Ra. The bone compartment was defined by means of low-dose CT. Emission data were corrected for scatter, attenuation, and decay supplemented by resolution recovery using dedicated software. The Kaplan-Meier estimator, U test, and Cox regression analysis were used for statistics. Results: Total 99mTc-DPD uptake of the central skeleton varied between 11% and 56% of injected dose (%ID) or between 1.8 and 10.5 %ID/1,000 mL of bone volume (%ID/L). SUVmean ranged from 1.9 to 7.4, whereas the SUVmax range was 18-248. Patients unable to complete 223Ra treatment because of progression and/or cytopenia (n = 23) showed significantly higher uptake (31.9 vs. 25.4 %ID and 6.0 vs. 4.7 %ID/L; P < 0.02). OS after 223Ra (median, 15.2 mo) was reduced to 7.3 mo in cases of skeletal uptake that was 26 %ID or higher, as compared with 30.8 mo if lower than 26 %ID (P = 0.008). Similar results were obtained for %ID/L and SUVmean SUVmax did not correlate with survival. %ID/L was identified as an independent prognostic factor for OS (hazard ratio, 1.381 per unit), along with number of previous treatment lines. Conclusion: Quantitative SPECT/CT of bone scans performed at baseline is prognostic for survival in mCRPC patients treated with 223Ra.

3'-Deoxy-3'-[(18)F]fluorothymidine (FLT) uptake in breast cancer cells as a measure of proliferation after doxorubicin and docetaxel treatment.

INTRODUCTION: The nucleoside analogue [(18)F]fluorothymidine (FLT) has been designed as a marker of cell proliferation that can be imaged in vivo by positron emission tomography. Clinical pilot studies have demonstrated decreasing FLT uptake following antiproliferative chemotherapy of breast cancer. However, the significance of posttreatment FLT uptake has not been evaluated at the cell level. The aim of this study was to investigate whether FLT uptake detects proliferation inhibition induced by docetaxel or doxorubicin treatment in an in vitro breast cancer model. METHODS: Breast cancer cells (MCF-7) were treated with docetaxel or doxorubicin for 24 h at drug doses inducing 25-99% inhibition of clonogenic survival (IC(25) to IC(99)). Cellular FLT uptake was estimated at 4 h and at 1, 3 and 5 days interval from chemotherapy. [(3)H]Thymidine incorporation and S-phase fraction were measured for comparison. Analysis of variance and the Bland-Altman difference plot were employed for statistical analysis. RESULTS: After treatment, FLT uptake was declined in dependence of the proliferation inhibition mediated by both chemotherapeutic agents (all P<.0001). The decrease of FLT was greater after doxorubicin treatment than after the corresponding docetaxel dose. With doxorubicin (IC(99)), FLT accumulation was reduced by 70% as early as 4 h after treatment. FLT uptake was closely correlated to [(3)H]thymidine incorporation and S-phase fraction (r=.84 to .93). CONCLUSIONS: Right after docetaxel or doxorubicin treatment, FLT uptake corresponds to the reduction of tumor cell proliferation induced. [(18)F]FLT appears promising for monitoring chemosensitivity in breast cancer.

In vitro comparison of the antiproliferative effects of rhenium-186 and rhenium-188 on human aortic endothelial cells.

PURPOSE: Rhenium-186 ((186)Re) and rhenium-188 ((188)Re) are promising radionuclides for the inhibition of restenosis after percutaneous transluminal angioplasty or other vascular interventions. Until now the maximal dose tolerance of endothelial cells has not been clearly known. MATERIALS AND METHODS: To characterize the effects of local irradiation treatment, human aortic endothelial cells (ECs) were incubated with different doses of (186)Re and (188)Re. Two days after plating, ECs received treatment for a period of 5 days. The total radiation doses applied were 1, 4, 8, 16, and 32 Gy. On days 1, 3, 5, 7, and 12 after initial rhenium incubation, cell growth, clonogenic activity, cell-cycle distribution, and cytoskeletal architecture were evaluated. RESULTS: From the first day on, a dose-dependent growth inhibition was observed. Cumulative doses of ≥32 Gy caused a weak colony formation and significant alterations in the cytoskeletal architecture. An increased fraction of cells in G2/M phase was seen for cumulative radiation doses of ≥16 Gy. Interestingly, there were no significant differences between (186)Re and (188)Re. CONCLUSION: Even for low dose rates of ß particles a dose-dependent proliferation inhibition of ECs is seen. Doses beyond 32 Gy alter the cytoskeletal architecture with possibly endothelial dysfunction and late thrombosis.

Early changes in [18F]FLT uptake after chemotherapy: an experimental study.

This study evaluated the use of 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT) for monitoring of the early effects of anticancer chemotherapy on tumour cell proliferation. Cells derived from human oesophageal squamous cell carcinoma (OSC-1) were grown for 2 days and incubated with cisplatin (CDDP), 5-fluorouracil (5-FU), methotrexate (MTX) or gemcitabine (GEM) for 4 h. Cultures were incubated with drug doses (CDDP: 0.67, 6.7, 67 micro M; 5-FU 15.4, 154, 1,540 micro M; MTX: 4.4, 44, 440 micro M; GEM: 0.0067, 0.067, 0.67 micro M) corresponding to approximately 10%-95% proliferation inhibition (MTX: 10%-75%). Treatment was stopped and cells were allowed to recover for 4, 24 or 72 h. [(18)F]FLT was added for 10-180 min. Control cultures were incubated with [(18)F]fluorodeoxyglucose (FDG). Cell counts, viability, clonogenic activity and cell cycle distribution estimated by flow cytometry were used to evaluate the cytotoxic effects of chemotherapy. Strikingly, FLT uptake per 10(5) viable cells was increased seven- to tenfold 24 h after treatment with 5-FU or MTX irrespective of dose. Thus, total FLT uptake per tissue culture exceeded that of controls despite a considerable decrease in overall cell counts due to cytostasis up to 72 h after treatment. 5-FU-treated cells showed accumulation in early S phase (overall S phase: 88% vs 42%). GEM treatment resulted in a more moderate increase in total FLT accumulation, to a maximum of fivefold at the dose close to the IC(50). In contrast, FLT accumulation was significantly reduced at cytostatic concentrations of CDDP and was still decreasing in a dose-related manner at 72 h despite considerable S phase arrest. With 5-FU or CDDP, the uptake of FDG did not differ significantly from control values 24 h after treatment. These findings demonstrate that tumour cell uptake of FLT - in contrast to that of FDG - reveals specific changes depending on the cytostatic drug used for treatment. The antimetabolites 5-FU and MTX massively increase FLT accumulation per cell independent of dose, i.e. cytotoxicity. Early after treatment, this increase is not predictive of proliferation inhibition but reflects activated salvage pathway of DNA synthesis. By contrast, CDDP results in an early decline in FLT but not in FDG uptake. This drug-specific modulation of FLT uptake has to be taken into account in positron emission tomography studies using FLT for treatment monitoring.