We studied in chimeric EGFP-Photinus luciferase HeLa cells the expression of fluorescence and luminescence in different cell culture conditions (medium with or without Serum, static or dynamic conditions, in suspension or on microcarriers) as a model to follow the productivity of a recombinant protein. By studying the effect of Butyrate known as general but unpredictable stimulating agent for protein expression, we were able to establish the optimal conditions for efficacy ( concentration, time of addition, ...)