TRANSPLANTATION OF Y79 CELLS INTO RAT EYES - AN IN-VIVO MODEL OF HUMAN RETINOBLASTOMAS

Purpose. To develop an in vivo model of human retinoblastoma by return ing cultured Y79 retinoblastoma cells to the retinal environment of a widely available laboratory animal. In so doing, to study the survival , integration, and invasive characteristics expressed by tumoral cells grafted into an intraocular milieu from which these progenitor cells originated more than 20 years ago. Methods. Using the retinal grafting method of Lazar and del Cerro, Y79 cells were injected under direct v isualization into the subretinal space of Fischer 344 rats. The host r ats included 36 animals that received daily injections of cyclosporin A and 4 that did not. All hosts were sacrificed 30 to 60 days after tr ansplantation. Results. Clinical examination showed vitreal invasion b y masses of flocculent white material or the intravitreal formation of solid tumors. Histologic examination showed these formations to be ou tgrowths of grafted tumoral cells into the host retina and vitreal cav ity. Highly anaplastic tumoral cells were also found lodged in subreti nal and intraretinal locations. There were signs of continued and inte nse cell division within the grafts, with no indication of cell-mediat ed host reaction against the grafted cells. Conclusions. After intrare tinal xenografting, human Y79 retinoblastoma cells retain a highly tum oral nature despite many years of in vitro propagation. When xenograft ed, these cells survive, grow, and express their malignancy within the retina of the common laboratory rat protected by a moderate immunosup pressive regimen. This partial immunosuppression is a requirement for the xenografts to prosper. This model offers a valuable opportunity to study in vivo the cellular and molecular biology of this and other hu man retinoblastomas, and it may facilitate the evaluation of antitumor al treatments.