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Chris Himes, Evan B Stubbs, Tim Fulghum, Shawn Bairstow, Simon Kaja, Jawed Fareed; Subconjunctival Chemotherapeutic Delivery by Fibrin Sealant in the Treatment of Retinoblastoma. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2815.
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© ARVO (1962-2015); The Authors (2016-present)
To establish vincristine, etoposide, and carboplatin (VEC) combinations as an effective means of tumor cell suppression in addition to determining the effects of admixed VEC in fibrin sealants (FS) on fibrin structure and drug release kinetics with the ultimate goal of developing a method for transscleral delivery for retinoblastoma.
Cytotoxicities of VEC (0.1-1000 µM) were determined in retinoblastoma Y79 and WERI lines after 24/48/72 h using Alamar Blue assay. Dose-response curves were generated and IC50 values extrapolated. Combination studies were completed in WERI cells using a fixed-ratio paradigm. Fibrin formation analyses were performed in VEC-supplemented plasma or FS using adapted densitometry or thromboelastography. Fibrin monomer formation, clot time, amplitude, and shear modulus were determined following clot generation. Network analysis of VEC-embedded FS electron microscope (EM) images were processed by FIJI software and branch lengths, numbers, and junctions were quantified.
Estimated IC50 values for vincristine, etoposide, and carboplatin were 2.9 mM, 2.7 mM, 1.0 mM, respectively, in WERI cells and 0.1 mM, 6.0 mM, and 1.1 mM, respectively, in Y79 cells. Fixed-ratio VEC combination treatments in WERI cells suggest synergistic effects at sub-micromolar concentrations, but antagonistic at therapeutic concentrations based on single-drug IC50 values. Fibrin polymerization was impeded by vincristine, but unaffected by incorporation of etoposide or carboplatin. Network analysis of FS by electron microscopy revealed a lower branch/junction ratio for vincristine-embedded fibrin matrices (55.7) vs. saline (71.0).
Our results are consistent with established VEC inhibitory concentrations of Y79 and WERI cell lines. However, combined treatments performed antagonistically at levels needed to effectively inhibit tumor growth. Deviations in FS characteristics may affect release rates and clot breakdown both in vitro and in vivo, requiring careful dose optimization prior to successful translation. Current work is investigating VEC release kinetics and transscleral permeability.
This is a 2020 ARVO Annual Meeting abstract.
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