Prolongation of murine hybridoma cell survival in stationary batch culture by Bcl-xL expression

While the ectopic expression of the anti-apoptotic protein Bcl-2 has been shown to significantly increase both cell viability and antibody production in batch culture, some cell lines are refractory to these manipulations. For example, the NS/O and the P3x63Ag8.653 murine myelomas, which express high endogenous levels of the Bcl-2 homologue Bcl-xL, are both resistant to the anti-apoptotic effect of Bcl-2. This indicates that, in these cells, Bcl-2 and Bcl-xL may be functionally redundant. In order to define the role which Bcl-xL plays in hybridoma cultures, we used the Sp2/0-Ag14 cell line. This murine hybridoma expresses low levels of Bcl-xL and is highly sensitive to apoptosis induction by cycloheximide (CHX) and by amino acid depletion. Bcl-xL-transfected Sp2/0-Ag14 cells were more resistant than the wild type and the plasmid-containing cells to apoptosis induced by CHX and by glutamine depletion. Moreover, when compared to the vector-transfected control, Bcl-xL-Sp2/0 cells exhibited a substantial increase in viability in stationary batch culture. Interestingly, Sp2/0-Ag14 cells overexpressing Bcl-xL showed a growth behaviour that was similar to the parent myeloma cell line P3x63Ag8.653. Our results suggest that Bcl-xL expression levels are sufficient to account for the relative robustness of some hybridoma cell lines in stationary batch cultures.