Multimodality Imaging Methods for Assessing Retinoblastoma Orthotopic Xenograft Growth and Development

Abstract

Genomic studies of the pediatric ocular tumor retinoblastoma are paving the way for development of targeted therapies. Robust model systems such as orthotopic xenografts are necessary for testing such therapeutics. One system involves bioluminescence imaging of luciferase-expressing human retinoblastoma cells injected into the vitreous of newborn rat eyes. Although used for several drug studies, the spatial and temporal development of tumors in this model has not been documented. Here, we present a new model to allow analysis of average luciferin flux () through the tumor, a more biologically relevant parameter than peak bioluminescence as traditionally measured. Moreover, we monitored the spatial development of xenografts in the living eye. We engineered Y79 retinoblastoma cells to express a lentivirally-delivered enhanced green fluorescent protein-luciferase fusion protein. In intravitreal xenografts, we assayed bioluminescence and computed , as well as documented tumor growth by intraocular optical coherence tomography (OCT), brightfield, and fluorescence imaging. In vivo bioluminescence, ex vivo tumor size, and ex vivo fluorescent signal were all highly correlated in orthotopic xenografts. By OCT, xenografts were dense and highly vascularized, with well-defined edges. Small tumors preferentially sat atop the optic nerve head; this morphology was confirmed on histological examination. In vivo, in xenografts showed a plateau effect as tumors became bounded by the dimensions of the eye. The combination of modeling and in vivo intraocular imaging allows both quantitative and high-resolution, non-invasive spatial analysis of this retinoblastoma model. This technique will be applied to other cell lines and experimental therapeutic trials in the future.

Kif14 overexpression accelerates murine retinoblastoma development

“…To further support our findings, further backcrosses followed by future investigation of Kif14 overexpression in other transgenic retinoblastoma models, and in human cell xenograft models of the disease is warranted. 25 Future high-resolution analyses of multiple human and murine retinoblastoma genomes, and correlation with gene expression, will also help to completely define KIF14's importance in retinoblastomagenesis.…”

A Simple Optical Coherence Tomography Quantification Method for Choroidal Neovascularization

“…15 The technique has found extensive use in ophthalmology 15,16 providing detailed images for both the anterior and posterior segments of the eye 17 and has become an essential tool for the clinical evaluation of ocular pathologies, such as wet AMD, 18 retinal tumors, [19][20][21] and retinal detachment. 22 Paralleling its rise to clinical prominence, OCT has been used preclinically to monitor disease progression, and OCT images have been shown to be comparable to histological characteristics in disease models, [23][24][25][26] including L-CNV. 12,27 However, to our knowledge, 3D quantification of lesions in OCT images has previously used specialized software that is not readily available or compatible with different systems.…”

Retinoblastoma, the visible CNS tumor: A review

“…The advent of small‐animal intraocular imagers enabled documentation of intraocular tumors in both transgenic and orthotopic xenograft models of the cancer. In particular, coupling fluorescence and brightfield imaging of GFP‐expressing xenografts allowed qualitative assessment of tumor growth and (importantly) dissemination within the eye (Corson et al, ). Similarly, a number of preclinical therapeutic studies have included qualitative fundus and fluorescein angiography images (Brennan et al, ; McEvoy et al, ; Zhang et al, ).…”

“…Similarly, a number of preclinical therapeutic studies have included qualitative fundus and fluorescein angiography images (Brennan et al, ; McEvoy et al, ; Zhang et al, ). In the future, quantification of fluorescence should allow volumetric analysis of tumor growth, as is currently done using bioluminescence of luciferase‐expressing xenografts (Corson et al, ; Ji et al, ; Laurie et al, ).…”

“…OCT has proven useful for xenografts: intravitreal xenografts could be monitored (Corson et al, ; Tschulakow, Schraermeyer, Rodemann, & Julien‐Schraermeyer, ) and subretinal xenografts could be rapidly assessed by a combination of OCT and funduscopy (Lemaitre et al, ). Of course, OCT assessment of morphology of xenografts is less clinically relevant than the morphology of tumors arising intraretinally as in genetic retinoblastoma models.…”