Dissecting the Mechanism of Action of BHRF1 for the Protection Against Apoptosis in MAb-Producing Cell Lines

Abstract

Cell death by apoptosis limits growth and productivity in most bioprocesses based on the culture of animal cells. It is therefore desirable to define genetic interventions to generate robust cell lines with superior performance in bioreactors, either by increasing specific productivity, life-span of the cultures or both. In this context, forced expression of BHRF1, an Epstein–Barr virus-encoded early protein with structural and functional homology with the anti-apoptotic protein Bcl-2, effectively protected hybridomas in culture and delayed cell death under conditions of glutamine starvation and in different biotechnological process designs (including batch and continuous bioreactor settings). By Q-RT-PCR, we found that BHRF1 operates as a regulator of Bcl-2 mRNA levels, increasing Bcl-2 expression under apoptosis-inducing conditions. In order to further investigate the mechanism of action of BHRF1, we used small molecule inhibitors specific for Bcl-2 and analysed their effect on the survival of the cultures.