Overexpression of heat shock proteins (HSPs) in CHO cells for extended culture viability and improved recombinant protein production

Abstract

It has been widely reported that CHO cells undergo apoptosis in culture, despite supplementation of nutrients through fed-batch strategies. Improvement of cell viability in culture can effectively improve recombinant protein yield through extension of the culture's production lifespan, especially at high cell densities. Heat shock proteins (HSPs) have been reported to demonstrate anti-apoptotic effects against a wide range of physical and chemical stimuli through their ability to bind and act as antagonists to critical apoptotic molecules. CHO-IFN-gamma cells, expressing recombinant human interferon-gamma (IFN-gamma), were engineered to overexpress two HSPs (HSP27 and HSP70) either individually or in combination. In fed-batch bioreactor cultures, the engineered cell lines exhibited a more gradual viability loss and extension of culture times of 36-72h, with corresponding delays in escalation of caspases 2, 3, 8 and 9 activities, compared to the control cultures utilizing cells transfected with the vector backbone. The extension in culture times translated to a 2.5-fold improvement in IFN-gamma production over controls in fed-batch cultures. These results suggest that overexpression of HSPs represents a promising generic strategy for the development of robust CHO cell lines resistant to apoptotic insults and possessing improved culture characteristics to enhance recombinant glycoprotein yields.