Radiation-inducible HtrA2 gene enhances radiosensitivity of uveal melanoma OCM-1 cellsin vitroandin vivo

Abstract

To explore an effective approach for the treatment of patients with uveal melanomas, we designed a strategy that combines HtrA2 gene therapy and radiation therapy. pIRES-Egr1-Omi/HtrA2 (pEgr1-HtrA2) recombinant plasmids were constructed and transfected into human uveal melanoma cells (OCM-1) in vitro. The transfected cells were exposed to irradiation. HtrA2 messenger RNA and protein level was detected by quantitative reverse transcription polymerase chain reaction and Western blot, respectively. Combined with radiation, assays that evaluated the apoptotic inducibility caused by HtrA2 gene therapy was performed by flow cytometry. Followingly, the effects of HtrA2 overexpression on the in vitro radiosensitivity of uveal melanoma cells were investigated by clonogenic formation assay. The in vivo effects of HtrA2 gene therapy combined with radiation therapy were evaluated in different groups. The recombinant plasmids could be successfully transferred into OCM-1 cells, and transfection of pEgr1-HtrA2 plasmids combined with radiotherapy caused dramatically elevation of HtrA2 compared with non-irradiated cells in messenger RNA and protein levels, which was associated with increased apoptosis. Furthermore, we observed that the transfection of pEgr1-HtrA2 could significantly enhance radiosensitivity of OCM-1 cell in vitro. In mice bearing xenograft tumours, pEgr1-HtrA2 combined with radiation therapy significantly inhibited tumour growth compared with the other treatment groups (P < 0.01). Our findings indicate that radiation-inducible gene therapy may have potential to be a more effective and specific therapy for uveal melanoma because the therapeutic gene can be spatially or temporally controlled by exogenous radiation.