In vivo testing of Renilla luciferase substrate analogs in an orthotopic murine model of human glioblastoma.

In vivo bioluminescent imaging using cells expressing Renilla luciferase is becoming increasingly common. Hindrances to the more widespread use of Renilla luciferase are the high autoluminescence of its natural substrate, coelenterazine, in plasma; the relatively high absorbance by tissue of the light emitted by the enzyme - substrate reaction; rapid clearance of the substrate; and significant cost. These factors, save for the cost, which has its own limiting effect on use, can combine to reduce the sensitivity of in vivo assays utilizing this reporter system, and methods of increasing tight output or decreasing autoluminescence could be of great benefit. A number of analogs of coelenterazine are being investigated that may accomplish one or both of these goals. In this study, we report on the testing of two new substrate analogs, EnduRen(TM) and ViviRen(TM), manufactured by Promega Corporation, in an orthotopic murine model of human glioblastoma expressing Renilla luciferase. We have tested these analogs in this cell line, both in vitro and in vivo, and find that the substrate ViviRen results in significantly greater light output than the natural substrate or the other analog EnduRen. This new substrate could be valuable for studies where greater sensitivity is important.