Inhibition of Retinoblastoma In Vitro and In Vivo with Conditionally Replicating Oncolytic Adenovirus H101

PURPOSE. To determine the therapeutic effect of oncolytic adenovirus H101 on retinoblastoma in vitro and in vivo. METHODS. The expression of coxsackievirus-adenovirus receptor (CAR) in human retinoblastoma cell line HXO-RB44 was determined by RT-PCR, Western blot, immunofluorescence, and immunocytochemistry staining. Appropriate multiplicity of infection was determined using flow cytometry in retinoblastoma cells with green fluorescent protein-expressing adenovirus (AdGFP). The viability of HXO-RB44 cells treated with H101 or AdGFP was measured using a cell counting kit-8-based procedure. Viral proliferation in vitro was measured by end point dilution titration and real-time PCR. Cell cycle and apoptotic activity of HXO-RB44 were analyzed by flow cytometry. NOD-SCID mice bearing retinoblastoma xenografts were treated with intratumoral injection of H101, AdGFP, or PBS. Tumor volume and survival time were recorded. Immunohistochemistry for adenoviral fiber protein and Western blot for adenoviral Hexon protein of retinoblastoma xenografts were performed to evaluate H101 virus replication in vivo. RESULTS. HXO-RB44 cells expressed CAR and were sensitive to adenoviral infection. HXO-RB44 cells treated with H101 had reduced cell viability compared with AdGFP-treated cells (P < 0.01). Abundant replication of H101 in HXO-RB44 cells resulted in G(2)/M-phase arrest and finally tumor cell lysis, but the apoptosis pathway was not activated. Tumor-bearing mice treated with H101 had reduced tumor burdens and prolonged survival times compared with PBS and AdGFP controls (both P < 0.01). Immunohistochemical and Western blot examination revealed widespread replication of H101 within the tumor. CONCLUSIONS. These results suggest that H101 effectively inhibits the growth of retinoblastoma cells in vitro and in mice and may serve as a novel therapy for retinoblastoma. (Invest Ophthalmol Vis Sci. 2010;51:2626-2635) DOI:10.1167/iovs.09-3516