The growth factor inhibitor suramin reduces apoptosis and cell aggregationin protein-free CHO cell batch cultures

We have previously shown that Chinese hamster ovary (CHO) cells capable of growing in medium free of exogenous proteins die by apoptosis during all st ages of a batch culture (Zanghi et al., 1999). On the basis of the hypothes is that extracellular death factors might be important in apoptosis under t hese conditions, we examined the effect of the growth factor inhibitor and antitumor agent suramin on CHO cell growth and apoptosis in serum-free cult ure. Suramin protected against apoptosis during exponential growth, as indi cated by the absence of DNA laddering and an increase in cell viability fro m roughly 70% to above 95%. Suramin also effectively dispersed cell aggrega tes so that single-cell suspension culture was possible. However, suramin d id not protect; against apoptosis during the death phase, in contrast to se rum, suggesting that antiapoptotic factors in the serum remain to be discov ered. The increased viable cell yield following suramin supplementation res ulted in a 40% increase in product yield, based on results with cells expre ssing recombinant secreted alkaline phosphatase. Polysulfated compounds dex tran sulfate and polyvinyl sulfate worked nearly as well as suramin in disp ersing cell clumps and increasing viable cell yield, which implies that sur amin's high sulfate group density may be responsible for its effects in cel l culture. In addition, suramin was beneficial for long-term adaptation of CHO cells to protein-free media suspension culture, and the compound was sy nergistic with insulin in accelerating this adaptation time.