Apoptosis-resistant E1B-19K-expressing NS/0 myeloma cells exhibit increased viability and chimeric antibody productivity under perfusion culture conditions

We have shown previously that recombinant NS/0 myelomas expressing sufficie nt amounts of E1B-19K were resistant to apoptosis occurring in the late pha se of batch culture and under stressful conditions such as cultivation in g lutamine-free medium or following heat shock. However, no significant incre ase in monoclonal antibodies (MAb) was observed during the prolonged statio nary phase of these batch cultures. Here, we show that E1B-19K can enhance cell survival and improve MAb productivity in high cell density perfusion c ulture. Typically, lymphoid cells grown under steady state in perfusion exh ibit decreasing viabilities with concomitant accumulation of apoptotic cell s. By modulating the ability of these cells to resist to induction of apopt osis in low nutrient environment, a 3-fold decrease in specific death rate from 0.22 day(-1) for NS/0 control to 0.07 day(-1) for E1B-19K cells was ac hieved, resulting in a significant improvement in cell viability throughout perfusion. E1B-19K cells at the perfusion plateau phase also exhibited a 3 -fold reduction in specific growth rate concomitant with a lower percentage of S and higher percentage of G(1) phase cells. This was associated with a 40% decrease in specific oxygen consumption rate, likely related to a redu ction in the specific consumption rates of limiting nutrient(s). Expression of E1B-19K consequently had a significant impact on the steady-state viabl e cell density, allowing maintenance of 11.5 x 10(6) E1B-19K cells/ml versu s 5.9 x 10(6) control NS/0 cells/mL. for the same amount of fresh medium br ought into the system (half a volume per day). Whereas MAb concentrations f ound in perfusion culture of control NS/0 myelomas were almost 3-fold highe r than those found in batch culture; in the case of E1B-19K-expressing myel omas, the MAb concentration in perfusion was more than 7-fold higher than i n batch. This was attributable to the 2-fold increase in viable cell platea u and to a 40% increase in the perfusion to batch ratio of specific MAb pro ductivity (2.2-fold for E1B-19K myelomas versus 1.6-fold for NS/0 control). (C) 1999 John Wiley & Sons, Inc.