03/04/2022
By Sokny Long

The Francis College of Engineering, Department of Chemical Engineering, invites you to attend a doctoral dissertation defense by Ashli Polanco on “Elucidating the combined metabolic effects of zinc and copper supplementation on CHO cell culture.”

Ph.D. Candidate: Ashli Polanco
Defense Date: Friday, March 18, 2022
Time : 10 a.m. - noon EST
Location: This will be in-person defense (UCC-490), and a virtual option via Zoom will be provided. Those interested in attending should contact Ashli_Polanco@student.uml.edu and committee advisor, seongkyu_yoon@uml.edu, at least 24 hours prior to the defense to request access to the meeting.

Committee Chair (Advisor): Seongkyu Yoon, Professor, Chemical Eng, UMass Lowell

Committee Members:

  • Peter Gaines, Professor, Biological Sciences, UMass Lowell
  • Jeffrey Swanberg, Senior Manager, Bristol-Myers Squibb
  • Valmor de Almeida, Associate Professor, Chemical Engineering, UMass Lowell
  • Shannon L. Kelleher, Professor, Biomedical Sciences, UMass Lowell

Brief Abstract:

Metals, such as iron, zinc, copper, and manganese can influence various cellular functions in Chinese hamster ovary (CHO) cells, the primary workhorses for monoclonal antibody (mAb) production. Trace amounts of these metals present in a cell’s microenvironment can influence metabolite and energy metabolism, protein production, and product quality attributes. Thus, understanding the effects of metal supplements on a production cell line is useful as the concentration and time added can be leveraged to improve the bioprocess. Here, a two-level factorial experimental design was performed in fed-batch shake flasks to evaluate the impact of timewise addition of individual and combined trace metals on CHO cell growth, antibody titer, and resulting galactosylation patterns. The study focused on two metal supplements – zinc and copper – each individually recognized for their effects on CHO cell growth, mAb production, and cellular metabolism to different degrees. Cell culture data revealed that delayed zinc supplementation rescued the reduced cell growth exhibited during early growth stage supplementation, however did not improve antibody titer during the production phase. Copper supplementation showed no impact on cell growth profile, and similar to zinc, early copper supplements led to higher antibody titer. Combined zinc and copper supplementation at each time point variably decreased CHO-K1 peak cell growth, with high dependence on zinc concentration and time added. Multivariate regression models confirmed that zinc and time added were the most significant factors contributing to specific productivity and peak VCD. Unlike single metals, combined metal addition enhances antibody titer at every time point and modulates galactosylation to a greater extent when supplemented early. The enhanced mAb productivity under combined-metal supplements derives from enhanced reduction of ROS activity (oxidative stress) and cellular redox ratio observed in CHO-K1 cells. LDH enzyme activity confirms reduced cellular redox status and demonstrates a high dependence on zinc supplementation, with additional enzyme activity and lactate consumption rate when supplemented with copper. As a result, glycolytic flux is reduced during the production phase, and cells can utilize energy resources toward producing antibody instead of oxidative damage control. A validation experiment which tested the optimized setpoints which maximize specific productivity while maintaining a high target peak viable cell density confirmed that combined zinc and copper supplement enhance titer by 20% compared to no metals added.

All interested students and faculty members are invited to attend the online defense via remote access.