Topotecan,CarboplatinandVincristineTreatmentofRetinoblastomainMice

Abstract

Abstract: : At St. Jude Children's Research Hospital, children with bilateral retinoblastoma are treated with a combination of chemotherapy, laser therapy and cryotherapy.Purpose: To test new chemotherapeutic drugs and drug combinations for the treatment of retinoblastoma, we have developed three new mouse models of retinoblastoma. Methods: We have used an orthotopic, developmentally accurate xenograft model, an in vivo retroviral model that leads to focal clonal tumors and a genetic model using conditional gene inactivation in the retina. Using these three models combined with cell culture experiements, we have tested the efficacy of topotecan, carboplatin and vincristine and all combinations as chemotherapeutic agents for the treatment of retinoblastoma. In culture we determined their effects on cell viability (live/dead assay), apoptosis (TUNEL assay), proliferation (BrdU), cell cycle arrest (FACS) and gene expression (microarray). We then tested different combiations of drugs and different orders of addition to determine the ideal protocol for treatment of retinoblastoma in our animal models. Moreover, we performed a timecourse experiment to test how long tumor cells must be exposed to drug for the observed effects to become irreversible. Prior to testeing each drug in our animal models, we tested drug penetration to the retina and vitreous of rats at different times after i.v. injection. Finallly the rat and mouse model of retinoblastoma were given each drug alone or in combiation and the effects on viability, apoptosis, proliferation, cell cycle arrest and gene expression were assayed in vivo and correlated with the culture data and the pharmacology data. Results: We have found that all three drugs have dramatically different effects on retinoblastoma cells in culture and in vivo. Conclusions: By using a combination of culture experiments, xenograft models and genetic models we can rapidly test new chemotherapeutic treatments for retinoblastoma.  

Keywords: retinoblastoma • drug toxicity/drug effects • genetics