The role of hydrodynamics and mass transfer in suspension cultures of DU145 human prostate carcinoma cells

Nucleolin, an abundant cellular protein, has been recognized as a therapeutic target in gene therapy treatments for cancer. Structural studies to facilitate rational design of small molecule inhibitors of nucleolin require sufficient quantities of the protein. Since cellular levels of nucleolin are related to the levels of cell proliferation, nucleolin can be obtained most efficiently through large-scale cultivation of human carcinoma cells. Therefore, the purpose of this investigation was to characterize the bioreactor conditions for suspension cultures of DU145 human prostate carcinoma cells for production of nucleolin.; The feasibility of adaptation of attachment-dependent DU145 cells to suspension growth using roller bottles, spinner flasks, and petri dishes was examined. Adaptation using petri dishes proved to be the most successful approach resulting in growth of DU145 cells as natural aggregates in suspension cultures. These cultures exhibited viabilities above 80 to 85% and cell densities reaching more than 2.0 to 3.0 × 105 cells/mL. When these cultures were used as inoculum, it was possible to maintain fed-batch spinner flask suspension cultures for 15 days while keeping cell growth and viability.; Initial process scale-up of DU145 suspension cultures in 0.5-L spinner flasks began with characterization of power consumption and oxygen transfer. Oxygen consumption rates for both monolayer and spinner flask suspension cultures were also evaluated. The feasibility of DU145 spinner flask suspension cultures inoculated directly from monolayer cultures was examined. In these cultures, although cell density and viability decreased without any aggregate formation, the metabolic activity of these cultures was not suppressed. The inhibition of cell growth could be attributed to a combination of both microscale turbulent eddies and presence of vortex formation and hydrodynamic damage from bubble bursting. Although the impact of these factors on a molecular level requires further investigation, the mechanical stress imposed by these factors on the cellular cytoskeleton could in turn play a role in inhibiting cellular proliferation. It was concluded that in establishing suspension cultures of DU145 cells they must be weaned from surface attachment by gradual adaptation to suspension growth before proceeding to larger scales of operation and more intense agitation.