Overexpression of bcl-2 inhibits sodium butyrate-induced apoptosis in Chinese hamster ovary cells resulting in enhanced humanized antibody production

Sodium butyrate (NaBu) can enhance the expression of genes from some of the mammalian promoters including cytomegalovirus (CMV) and simian virus 40 (S V40), but it can also inhibit cell growth and induce cellular apoptosis. Th us, the beneficial effect of using a higher concentration of NaBu on a fore ign protein expression is compromised by its cytotoxic effect on cell growt h. To overcome this cytotoxic effect of NaBu, a survival protein, human Bcl -2, was overexpressed in recombinant Chinese hamster ovary (CHO) cells (SH2 -0.32), producing a humanized antibody directed against the S surface antig en of hepatitis B virus. When batch cultures of both control cells transfec ted with bcl-2-deficient plasmid (SH2-0.32-Delta bcl-2) and cells transfect ed with bcl-2 expression plasmid (14C6-bcl-2) were performed in the absence of NaBu, both cells showed similar profiles of cell viability and antibody production Compared with the SH2-0.32-Delta bcl-2 culture, under the condi tion of NaBu addition at the exponential growth phase, overexpression of th e bcl-2 gene considerably suppressed the NaBu-induced apoptosis of 14C6-bcl -2 by inhibiting caspase 3 activity and extending culture longevity by >2 d ays. As a result, the final antibody concentration of 14C6-bcl-2 culture wa s twofold higher than that of SH2-0.32-Delta bcl-2 culture in the presence of NaBu and threefold higher than that of SH2-0.32-Delta bcl-2 and 14C6-bcl -2 cultures in the absence of NaBu. (C) 2001 John Wiley & Sons, Inc.