Over Expression of the CMP-sialic Acid Transporter in Chinese Hamster Ovary Cells Leads to Increased Sialylation

Most glyco-engineering approaches used to improve quality of recombinant glycoproteins involve the manipulation of glycosyltransferase and/or glycosidase expression. We investigated whether the over expression of nucleotide sugar transporters, particularly the CMP-sialic acid transporter (CMP-SAT), would be a means to improve the sialylation process in CHO cells. We hypothesized that increasing the expression of the CMP-SAT in the cells would increase the transport of the CMP-sialic acid in the Golgi lumen, hence increasing the intra-lumenal CMP-sialic acid pool, and resulting in a possible increase in sialylation extent of proteins being produced. We report the construction of a CMP-SAT expression vector which was used for transfection into CHO-IFNγ, a CHO cell line producing human IFNγ. This resulted in approximately 2 to 5 times increase in total CMP-SAT expression in some of the positive clones as compared to untransfected CHO-IFNγ, as determined using real-time PCR analysis. This in turn concurred with a 9.6% to 16.3% percent increase in site sialylation. This engineering approach has thus been identified as a novel means of improving sialylation in recombinant glycoprotein therapeutics. This strategy can be utilized feasibly on its own, or in combination with existing sialylation improvement strategies. It is believed that such multi-prong approaches are required to effectively manipulate the complex sialylation process, so as to bring us closer to the goal of producing recombinant glycoproteins of high and consistent sialylation from mammalian cells.

Strategies for Lean Product Development

The essence of lean is very simple, but from a research and implementation point of view overwhelming. Lean is the search for perfection through the elimination of waste and the insertion of practices that contribute to reduction in cost and schedule while improving performance of products. This concept of lean has wide applicability to a large range of processes, people and organizations, from concept design to the factory floor, from the laborer to the upper management, from the customer to the developer. Progress has been made in implementing and raising the awareness of lean practices at the factory floor. However, the level of implementation and education in other areas, like product development, is very low.

Risk Aversion in Inventory Management

Traditional inventory models focus on risk-neutral decision makers, i.e., characterizing replenishment strategies that maximize expected total profit, or equivalently, minimize expected total cost over a planning horizon. In this paper, we propose a framework for incorporating risk aversion in multi-period inventory models as well as multi-period models that coordinate inventory and pricing strategies. In each case, we characterize the optimal policy for various measures of risk that have been commonly used in the finance literature. In particular, we show that the structure of the optimal policy for a decision maker with exponential utility functions is almost identical to the structure of the optimal risk-neutral inventory (and pricing) policies. Computational results demonstrate the importance of this approach not only to risk-averse decision makers, but also to risk-neutral decision makers with limited information on the demand distribution.