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Title:Evaluation of carboplatin-impregnated calcium sulfate hemihydrate beads as a local treatment option for feline injection site-associated sarcomas
Author(s):Maxwell, Elizabeth A.
Advisor(s):Phillips, Heidi
Contributor(s):Selmic, Laura; Fan, Tim
Department / Program:Vet Clinical Medicine
Discipline:VMS-Veterinary Clinical Medcne
Degree Granting Institution:University of Illinois at Urbana-Champaign
calcium sulfate hemihydrate beads
Abstract:Experiment 1: Objective: To determine the in vitro chemosensitivity of feline injection site-associated sarcoma (FISAS) cells to carboplatin concentrations generated by elution of carboplatin-impregnated calcium sulfate hemihydrate (C-I CSH) beads. Sample: Five immortalized cell lines from histologically confirmed, primary FISASs. Procedures: For each cell line, one 96-well microplate was used for each time point (24, 48, 72 hours). In each microplate, 3 wells were seeded with ~7.5 x 103 cells per well for every carboplatin treatment added, ranging from 5 to 450 µM. Microculture plates were incubated for 24, 48, or 72 hours. Drug efficacy was assessed via a bioreductive fluorometric assay. For apoptosis analysis, 3 wells were seeded with~5 x 104 cells per well for every carboplatin treatment added, ranging from 5 to 450 µM. Flow cytometry was performed and the relative percentages of viable, apoptotic, and late apoptotic/necrotic cells were reported. All experiments were run in triplicates. Results: Carboplatin exerted dose-dependent and time-dependent effects on FISAS cell viability. The IC50 values were within the range of carboplatin concentrations eluted from C-I CSH beads. Conclusion and Clinical Relevance: Elution of carboplatin from C-I CSH beads generate concentrations sufficient to result in 50% growth inhibition of FISAS cells in vitro. Local tumor control might be achieved by implantation of C-I CSH beads immediately following radical or marginal excision of the primary tumor or by implantation without tumor resection. Experiment 2: Objective: To characterize spatial release of platinum from carboplatin-impregnated calcium sulfate hemihydrate (C-I CSH) beads using an agarose tissue phantom. Sample: 3-mm-diameter beads (n = 60) containing 4.6 mg carboplatin (2.4 mg platinum)/bead. Procedures: 18 L of 1% agarose were prepared and poured into 36 containers, each of which was 10 X 10 X 10 cm and filled half full (0.5 L/container). After the agarose solidified, 1, 3, 6, or 10 C-I CSH beads were placed on the agar in defined patterns. An additional 36 blocks of agar (0.5 L/block) were placed atop the beads, positioning the beads in the center of 1 L of agar. The experiment was replicated 3 times for each bead pattern for 24, 48, and 72 hours, respectively. At these times, representative agarose blocks were sectioned in the x-, y-, and z-planes and labeled in accordance with their positions in shells radiating 1, 2, 3, 4, and 5 cm from the center of the blocks. Agarose from each shell was homogenized, and a sample was submitted for platinum analysis by use of inductively coupled plasma-mass spectroscopy. Results: Platinum diffused from C-I CSH beads at predicted anticancer cytotoxic concentrations for 2-5 cm radial source length. Conclusions and Clinical Relevance: Results of this study provided information regarding the spatial distribution of platinum expected to occur in vivo. Agarose may be used as a diffusion model, mimicking the characteristics of subcutaneous tissues. Measured platinum concentrations might be useful to guide patterns for implantation of C-I CSH beads in animals with susceptible neoplasms. Experiment 3: Objectives: To evaluate the pharmacokinetics and safety of carboplatin-impregnated calcium sulfate hemihydrate (C-I CSH) beads after implantation in healthy cats Sample: Six healthy adult research cats Procedure: Three C-I CSH beads were implanted into individual muscle pockets in specific patterns over both the right and left hemithoraces of all cats. Clinical laboratory testing was performed prior to the beginning of the study and at 3, 7, 14, and 21 days, and serum was analyzed for platinum content at specific times from 1 hour to 21 days. Tissue samples were obtained for histopathology and analysis of platinum at 3, 7, 14, and 21 days at specific distances from the sites of bead implantation. Results: At all time points and distances, tissue concentrations of platinum were sustained over 21 days but below levels reported to be cytotoxic for FISAS cells in vitro. Serum concentrations of platinum increased to 3 hours and then decreased sharply, and mild abnormalities in serum calcium were noted. Some subcutaneous tissue samples were found to contain muscle which resulted in significantly higher platinum concentrations than in samples containing only subcutaneous fat. Minimal tissue changes were noted on histopathology. Conclusions and Clinical Significance: Implantation of C-I CSH beads was well-tolerated by healthy adult cats. C-I CSH beads implanted into muscle pockets did not release platinum into the subcutis at levels cytotoxic to FISAS cells in vitro. Use of muscle pockets should be reevaluated for C-I CSH bead placement in animals with dermal or subcutaneous tumors.
Issue Date:2018-04-27
Rights Information:Copyright 2018 Elizabeth A Maxwell
Date Available in IDEALS:2018-09-04
Date Deposited:2018-05

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