MODULATION OF LUCEFERASE PRODUCTIONBY MELANOMA CELLS in vitro
Reporter proteins find increasing application in biomedical studies in vitro and in vivo, but for the correct interpretation of results based on their use it is important to take into account possible modulation of production of reporter proteins by cells and conditions, under which this may occur. In the present study, the reporter activity of Mel IL melanoma cells transiently transfected with pCpG vector-based plasmid construct expressing firefly luciferase was investigated. After initial fast drop of luciferase expression during the first two culture passages, a quasi-stable period was observed, during which only a relatively small decline in expression of luciferase occured with time. Under a multicycle periodic regime of culturing (batch culture), phases of maximal and minimal production of luciferase that corresponded to exponential and stationary phases of growth, respectively, were detected. After medium change, stimulation of luciferase production during the stationary but not exponential cell growth phase occured. Under severe hypoxia (0.1% O<sub>2</sub>) conditions, suppression of luciferase production was observed, indicating substantial modulation of cell metabolism in whole, and luciferase production in particular, by oxygen deficiency. In the presence of targeted drug Vemurafenib, suppression of luciferase production in Mel IL cells was detected, whereas DMSO, frequently used as drug solvent in experiments with cells, stimulated luciferase production. We hypothesize that modulation of reporter protein production in mammalian cells reflects the adaptation of intracellular metabolism to external conditions and may be a source of incorrect interpretations of experiments using reporter proteins.