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The growth factor inhibitor suramin reduces apoptosis and cell aggregation in protein-free CHO cell batch cultures
J A Zanghi1, W A Renner, J E Bailey
1Institute of Biotechnology, Swiss Federal Institute of Technology, ETH Hönggerberg, HPT, CH-8093 Zürich, Switzerland. zanghi@sciosinc.com
Abstract:
We have previously shown that Chinese hamster ovary (CHO) cells capable of growing in medium free of exogenous proteins die by apoptosis during all stages of a batch culture (Zanghi et al., 1999). On the basis of the hypothesis that extracellular death factors might be important in apoptosis under these conditions, we examined the effect of the growth factor inhibitor and antitumor agent suramin on CHO cell growth and apoptosis in serum-free culture. Suramin protected against apoptosis during exponential growth, as indicated by the absence of DNA laddering and an increase in cell viability from roughly 70% to above 95%. Suramin also effectively dispersed cell aggregates so that single-cell suspension culture was possible. However, suramin did not protect against apoptosis during the death phase, in contrast to serum, suggesting that antiapoptotic factors in the serum remain to be discovered. The increased viable cell yield following suramin supplementation resulted in a 40% increase in product yield, based on results with cells expressing recombinant secreted alkaline phosphatase. Polysulfated compounds dextran sulfate and polyvinyl sulfate worked nearly as well as suramin in dispersing cell clumps and increasing viable cell yield, which implies that suramin's high sulfate group density may be responsible for its effects in cell culture. In addition, suramin was beneficial for long-term adaptation of CHO cells to protein-free media suspension culture, and the compound was synergistic with insulin in accelerating this adaptation time.
Insights
Suramin prevents apoptosis and cell clumping in Chinese hamster ovary (CHO) cells during protein-free culture, enhancing cell viability and product yield. However, it does not prevent cell death during the final culture phase.
Area of Science:
- Biotechnology
- Cell Biology
- Bioprocessing
Background:
- Chinese hamster ovary (CHO) cells grown in protein-free media are susceptible to apoptosis throughout batch culture.
- Extracellular death factors are hypothesized to play a role in this apoptosis.
Purpose of the Study:
- To investigate the effect of suramin, a growth factor inhibitor and antitumor agent, on CHO cell growth and apoptosis in serum-free culture.
- To explore suramin's potential to improve cell viability and product yield in bioprocessing.
Main Methods:
- Culturing CHO cells in serum-free medium supplemented with suramin.
- Assessing cell viability and apoptosis using DNA laddering assays.
- Evaluating the impact of suramin on cell aggregation and product yield (recombinant secreted alkaline phosphatase).
- Comparing suramin's effects with other polysulfated compounds (dextran sulfate, polyvinyl sulfate) and insulin.
Main Results:
- Suramin significantly protected CHO cells against apoptosis during exponential growth, increasing viability from ~70% to >95%.
- Suramin effectively dispersed cell aggregates, enabling single-cell suspension culture.
- Unlike serum, suramin did not prevent apoptosis during the death phase.
- Suramin supplementation increased viable cell yield by 40%, boosting product yield.
- Polysulfated compounds showed similar effects on cell dispersion and viability.
- Suramin demonstrated synergistic effects with insulin for long-term adaptation to protein-free suspension culture.
Conclusions:
- Suramin is a potent agent for mitigating apoptosis and improving cell viability in CHO cells during early-stage protein-free suspension culture.
- The high sulfate group density of suramin may be responsible for its cell-dispersing and viability-enhancing properties.
- Further research is needed to identify serum-derived antiapoptotic factors effective during the death phase of CHO cell cultures.